diff --git a/adb/Android.mk b/adb/Android.mk
index 0eeafb6..e52f0cb 100644
--- a/adb/Android.mk
+++ b/adb/Android.mk
@@ -11,6 +11,7 @@
 adb_target_sanitize :=
 
 ADB_COMMON_CFLAGS := \
+    -frtti \
     -Wall -Wextra -Werror \
     -Wno-unused-parameter \
     -Wno-missing-field-initializers \
diff --git a/adb/adb.h b/adb/adb.h
index 21e5d4b..b5d6bcb 100644
--- a/adb/adb.h
+++ b/adb/adb.h
@@ -136,9 +136,6 @@
 int adb_server_main(int is_daemon, const std::string& socket_spec, int ack_reply_fd);
 
 /* initialize a transport object's func pointers and state */
-#if ADB_HOST
-int get_available_local_transport_index();
-#endif
 int init_socket_transport(atransport* t, int s, int port, int local);
 void init_usb_transport(atransport* t, usb_handle* usb);
 
diff --git a/adb/services.cpp b/adb/services.cpp
index aff7012..6dc71cf 100644
--- a/adb/services.cpp
+++ b/adb/services.cpp
@@ -407,14 +407,6 @@
         return;
     }
 
-    // Check if more emulators can be registered. Similar unproblematic
-    // race condition as above.
-    int candidate_slot = get_available_local_transport_index();
-    if (candidate_slot < 0) {
-        *response = "Cannot accept more emulators";
-        return;
-    }
-
     // Preconditions met, try to connect to the emulator.
     std::string error;
     if (!local_connect_arbitrary_ports(console_port, adb_port, &error)) {
diff --git a/adb/transport.cpp b/adb/transport.cpp
index f221785..5acaaec 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -41,6 +41,7 @@
 
 #include "adb.h"
 #include "adb_auth.h"
+#include "adb_io.h"
 #include "adb_trace.h"
 #include "adb_utils.h"
 #include "diagnose_usb.h"
@@ -65,6 +66,36 @@
     return next++;
 }
 
+bool FdConnection::Read(apacket* packet) {
+    if (!ReadFdExactly(fd_.get(), &packet->msg, sizeof(amessage))) {
+        D("remote local: read terminated (message)");
+        return false;
+    }
+
+    if (!ReadFdExactly(fd_.get(), &packet->data, packet->msg.data_length)) {
+        D("remote local: terminated (data)");
+        return false;
+    }
+
+    return true;
+}
+
+bool FdConnection::Write(apacket* packet) {
+    uint32_t length = packet->msg.data_length;
+
+    if (!WriteFdExactly(fd_.get(), &packet->msg, sizeof(amessage) + length)) {
+        D("remote local: write terminated");
+        return false;
+    }
+
+    return true;
+}
+
+void FdConnection::Close() {
+    adb_shutdown(fd_.get());
+    fd_.reset();
+}
+
 static std::string dump_packet(const char* name, const char* func, apacket* p) {
     unsigned command = p->msg.command;
     int len = p->msg.data_length;
@@ -220,13 +251,21 @@
 
         {
             ATRACE_NAME("read_transport read_remote");
-            if (t->read_from_remote(p, t) != 0) {
+            if (!t->connection->Read(p)) {
                 D("%s: remote read failed for transport", t->serial);
                 put_apacket(p);
                 break;
             }
+
+            if (!check_header(p, t)) {
+                D("%s: remote read: bad header", t->serial);
+                put_apacket(p);
+                break;
+            }
+
 #if ADB_HOST
             if (p->msg.command == 0) {
+                put_apacket(p);
                 continue;
             }
 #endif
@@ -625,7 +664,7 @@
     t->ref_count--;
     if (t->ref_count == 0) {
         D("transport: %s unref (kicking and closing)", t->serial);
-        t->close(t);
+        t->connection->Close();
         remove_transport(t);
     } else {
         D("transport: %s unref (count=%zu)", t->serial, t->ref_count);
@@ -753,14 +792,14 @@
 }
 
 int atransport::Write(apacket* p) {
-    return write_func_(p, this);
+    return this->connection->Write(p) ? 0 : -1;
 }
 
 void atransport::Kick() {
     if (!kicked_) {
+        D("kicking transport %s", this->serial);
         kicked_ = true;
-        CHECK(kick_func_ != nullptr);
-        kick_func_(this);
+        this->connection->Close();
     }
 }
 
@@ -1082,8 +1121,12 @@
 // This should only be used for transports with connection_state == kCsNoPerm.
 void unregister_usb_transport(usb_handle* usb) {
     std::lock_guard<std::recursive_mutex> lock(transport_lock);
-    transport_list.remove_if(
-        [usb](atransport* t) { return t->usb == usb && t->GetConnectionState() == kCsNoPerm; });
+    transport_list.remove_if([usb](atransport* t) {
+        if (auto connection = dynamic_cast<UsbConnection*>(t->connection.get())) {
+            return connection->handle_ == usb && t->GetConnectionState() == kCsNoPerm;
+        }
+        return false;
+    });
 }
 
 bool check_header(apacket* p, atransport* t) {
diff --git a/adb/transport.h b/adb/transport.h
index 86cd992..9700f44 100644
--- a/adb/transport.h
+++ b/adb/transport.h
@@ -28,10 +28,11 @@
 #include <string>
 #include <unordered_set>
 
-#include "adb.h"
-
 #include <openssl/rsa.h>
 
+#include "adb.h"
+#include "adb_unique_fd.h"
+
 typedef std::unordered_set<std::string> FeatureSet;
 
 const FeatureSet& supported_features();
@@ -56,6 +57,50 @@
 
 TransportId NextTransportId();
 
+// Abstraction for a blocking packet transport.
+struct Connection {
+    Connection() = default;
+    Connection(const Connection& copy) = delete;
+    Connection(Connection&& move) = delete;
+
+    // Destroy a Connection. Formerly known as 'Close' in atransport.
+    virtual ~Connection() = default;
+
+    // Read/Write a packet. These functions are concurrently called from a transport's reader/writer
+    // threads.
+    virtual bool Read(apacket* packet) = 0;
+    virtual bool Write(apacket* packet) = 0;
+
+    // Terminate a connection.
+    // This method must be thread-safe, and must cause concurrent Reads/Writes to terminate.
+    // Formerly known as 'Kick' in atransport.
+    virtual void Close() = 0;
+};
+
+struct FdConnection : public Connection {
+    explicit FdConnection(unique_fd fd) : fd_(std::move(fd)) {}
+
+    bool Read(apacket* packet) override final;
+    bool Write(apacket* packet) override final;
+
+    void Close() override;
+
+  private:
+    unique_fd fd_;
+};
+
+struct UsbConnection : public Connection {
+    explicit UsbConnection(usb_handle* handle) : handle_(handle) {}
+    ~UsbConnection();
+
+    bool Read(apacket* packet) override final;
+    bool Write(apacket* packet) override final;
+
+    void Close() override final;
+
+    usb_handle* handle_;
+};
+
 class atransport {
   public:
     // TODO(danalbert): We expose waaaaaaay too much stuff because this was
@@ -73,12 +118,6 @@
     }
     virtual ~atransport() {}
 
-    int (*read_from_remote)(apacket* p, atransport* t) = nullptr;
-    void (*close)(atransport* t) = nullptr;
-
-    void SetWriteFunction(int (*write_func)(apacket*, atransport*)) { write_func_ = write_func; }
-    void SetKickFunction(void (*kick_func)(atransport*)) { kick_func_ = kick_func; }
-    bool IsKicked() { return kicked_; }
     int Write(apacket* p);
     void Kick();
 
@@ -95,9 +134,7 @@
     bool online = false;
     TransportType type = kTransportAny;
 
-    // USB handle or socket fd as needed.
-    usb_handle* usb = nullptr;
-    int sfd = -1;
+    std::unique_ptr<Connection> connection;
 
     // Used to identify transports for clients.
     char* serial = nullptr;
@@ -105,22 +142,8 @@
     char* model = nullptr;
     char* device = nullptr;
     char* devpath = nullptr;
-    void SetLocalPortForEmulator(int port) {
-        CHECK_EQ(local_port_for_emulator_, -1);
-        local_port_for_emulator_ = port;
-    }
 
-    bool GetLocalPortForEmulator(int* port) const {
-        if (type == kTransportLocal && local_port_for_emulator_ != -1) {
-            *port = local_port_for_emulator_;
-            return true;
-        }
-        return false;
-    }
-
-    bool IsTcpDevice() const {
-        return type == kTransportLocal && local_port_for_emulator_ == -1;
-    }
+    bool IsTcpDevice() const { return type == kTransportLocal; }
 
 #if ADB_HOST
     std::shared_ptr<RSA> NextKey();
@@ -165,10 +188,7 @@
     bool MatchesTarget(const std::string& target) const;
 
 private:
-    int local_port_for_emulator_ = -1;
     bool kicked_ = false;
-    void (*kick_func_)(atransport*) = nullptr;
-    int (*write_func_)(apacket*, atransport*) = nullptr;
 
     // A set of features transmitted in the banner with the initial connection.
     // This is stored in the banner as 'features=feature0,feature1,etc'.
diff --git a/adb/transport_local.cpp b/adb/transport_local.cpp
index d6c84da..560a031 100644
--- a/adb/transport_local.cpp
+++ b/adb/transport_local.cpp
@@ -28,10 +28,12 @@
 #include <condition_variable>
 #include <mutex>
 #include <thread>
+#include <unordered_map>
 #include <vector>
 
 #include <android-base/parsenetaddress.h>
 #include <android-base/stringprintf.h>
+#include <android-base/thread_annotations.h>
 #include <cutils/sockets.h>
 
 #if !ADB_HOST
@@ -40,6 +42,7 @@
 
 #include "adb.h"
 #include "adb_io.h"
+#include "adb_unique_fd.h"
 #include "adb_utils.h"
 #include "sysdeps/chrono.h"
 
@@ -53,48 +56,15 @@
 
 static std::mutex& local_transports_lock = *new std::mutex();
 
-/* we keep a list of opened transports. The atransport struct knows to which
- * local transport it is connected. The list is used to detect when we're
- * trying to connect twice to a given local transport.
- */
-static atransport*  local_transports[ ADB_LOCAL_TRANSPORT_MAX ];
+// We keep a map from emulator port to transport.
+// TODO: weak_ptr?
+static auto& local_transports GUARDED_BY(local_transports_lock) =
+    *new std::unordered_map<int, atransport*>();
 #endif /* ADB_HOST */
 
-static int remote_read(apacket *p, atransport *t)
-{
-    if (!ReadFdExactly(t->sfd, &p->msg, sizeof(amessage))) {
-        D("remote local: read terminated (message)");
-        return -1;
-    }
-
-    if (!check_header(p, t)) {
-        D("bad header: terminated (data)");
-        return -1;
-    }
-
-    if (!ReadFdExactly(t->sfd, p->data, p->msg.data_length)) {
-        D("remote local: terminated (data)");
-        return -1;
-    }
-
-    return 0;
-}
-
-static int remote_write(apacket *p, atransport *t)
-{
-    int   length = p->msg.data_length;
-
-    if(!WriteFdExactly(t->sfd, &p->msg, sizeof(amessage) + length)) {
-        D("remote local: write terminated");
-        return -1;
-    }
-
-    return 0;
-}
-
 bool local_connect(int port) {
     std::string dummy;
-    return local_connect_arbitrary_ports(port-1, port, &dummy) == 0;
+    return local_connect_arbitrary_ports(port - 1, port, &dummy) == 0;
 }
 
 void connect_device(const std::string& address, std::string* response) {
@@ -423,130 +393,83 @@
     std::thread(func, port).detach();
 }
 
-static void remote_kick(atransport *t)
-{
-    int fd = t->sfd;
-    t->sfd = -1;
-    adb_shutdown(fd);
-    adb_close(fd);
-
 #if ADB_HOST
-    int  nn;
-    std::lock_guard<std::mutex> lock(local_transports_lock);
-    for (nn = 0; nn < ADB_LOCAL_TRANSPORT_MAX; nn++) {
-        if (local_transports[nn] == t) {
-            local_transports[nn] = NULL;
-            break;
-        }
-    }
-#endif
-}
+struct EmulatorConnection : public FdConnection {
+    EmulatorConnection(unique_fd fd, int local_port)
+        : FdConnection(std::move(fd)), local_port_(local_port) {}
 
-static void remote_close(atransport *t)
-{
-    int fd = t->sfd;
-    if (fd != -1) {
-        t->sfd = -1;
-        adb_close(fd);
-    }
-#if ADB_HOST
-    int local_port;
-    if (t->GetLocalPortForEmulator(&local_port)) {
-        VLOG(TRANSPORT) << "remote_close, local_port = " << local_port;
+    ~EmulatorConnection() {
+        VLOG(TRANSPORT) << "remote_close, local_port = " << local_port_;
         std::unique_lock<std::mutex> lock(retry_ports_lock);
         RetryPort port;
-        port.port = local_port;
+        port.port = local_port_;
         port.retry_count = LOCAL_PORT_RETRY_COUNT;
         retry_ports.push_back(port);
         retry_ports_cond.notify_one();
     }
-#endif
-}
 
+    void Close() override {
+        std::lock_guard<std::mutex> lock(local_transports_lock);
+        local_transports.erase(local_port_);
+        FdConnection::Close();
+    }
 
-#if ADB_HOST
+    int local_port_;
+};
+
 /* Only call this function if you already hold local_transports_lock. */
 static atransport* find_emulator_transport_by_adb_port_locked(int adb_port)
-{
-    int i;
-    for (i = 0; i < ADB_LOCAL_TRANSPORT_MAX; i++) {
-        int local_port;
-        if (local_transports[i] && local_transports[i]->GetLocalPortForEmulator(&local_port)) {
-            if (local_port == adb_port) {
-                return local_transports[i];
-            }
-        }
+    REQUIRES(local_transports_lock) {
+    auto it = local_transports.find(adb_port);
+    if (it == local_transports.end()) {
+        return nullptr;
     }
-    return NULL;
+    return it->second;
 }
 
-std::string getEmulatorSerialString(int console_port)
-{
+std::string getEmulatorSerialString(int console_port) {
     return android::base::StringPrintf("emulator-%d", console_port);
 }
 
-atransport* find_emulator_transport_by_adb_port(int adb_port)
-{
+atransport* find_emulator_transport_by_adb_port(int adb_port) {
     std::lock_guard<std::mutex> lock(local_transports_lock);
-    atransport* result = find_emulator_transport_by_adb_port_locked(adb_port);
-    return result;
+    return find_emulator_transport_by_adb_port_locked(adb_port);
 }
 
-atransport* find_emulator_transport_by_console_port(int console_port)
-{
+atransport* find_emulator_transport_by_console_port(int console_port) {
     return find_transport(getEmulatorSerialString(console_port).c_str());
 }
-
-
-/* Only call this function if you already hold local_transports_lock. */
-int get_available_local_transport_index_locked()
-{
-    int i;
-    for (i = 0; i < ADB_LOCAL_TRANSPORT_MAX; i++) {
-        if (local_transports[i] == NULL) {
-            return i;
-        }
-    }
-    return -1;
-}
-
-int get_available_local_transport_index()
-{
-    std::lock_guard<std::mutex> lock(local_transports_lock);
-    int result = get_available_local_transport_index_locked();
-    return result;
-}
 #endif
 
-int init_socket_transport(atransport *t, int s, int adb_port, int local)
-{
-    int  fail = 0;
+int init_socket_transport(atransport* t, int s, int adb_port, int local) {
+    int fail = 0;
 
-    t->SetKickFunction(remote_kick);
-    t->SetWriteFunction(remote_write);
-    t->close = remote_close;
-    t->read_from_remote = remote_read;
-    t->sfd = s;
+    unique_fd fd(s);
     t->sync_token = 1;
     t->type = kTransportLocal;
 
 #if ADB_HOST
+    // Emulator connection.
     if (local) {
+        t->connection.reset(new EmulatorConnection(std::move(fd), adb_port));
         std::lock_guard<std::mutex> lock(local_transports_lock);
-        t->SetLocalPortForEmulator(adb_port);
         atransport* existing_transport = find_emulator_transport_by_adb_port_locked(adb_port);
-        int index = get_available_local_transport_index_locked();
         if (existing_transport != NULL) {
             D("local transport for port %d already registered (%p)?", adb_port, existing_transport);
             fail = -1;
-        } else if (index < 0) {
+        } else if (local_transports.size() >= ADB_LOCAL_TRANSPORT_MAX) {
             // Too many emulators.
             D("cannot register more emulators. Maximum is %d", ADB_LOCAL_TRANSPORT_MAX);
             fail = -1;
         } else {
-            local_transports[index] = t;
+            local_transports[adb_port] = t;
         }
+
+        return fail;
     }
 #endif
+
+    // Regular tcp connection.
+    t->connection.reset(new FdConnection(std::move(fd)));
     return fail;
 }
diff --git a/adb/transport_test.cpp b/adb/transport_test.cpp
index 68689d4..d987d4f 100644
--- a/adb/transport_test.cpp
+++ b/adb/transport_test.cpp
@@ -20,22 +20,6 @@
 
 #include "adb.h"
 
-TEST(transport, kick_transport) {
-  atransport t;
-  static size_t kick_count;
-  kick_count = 0;
-  // Mutate some member so we can test that the function is run.
-  t.SetKickFunction([](atransport* trans) { kick_count++; });
-  ASSERT_FALSE(t.IsKicked());
-  t.Kick();
-  ASSERT_TRUE(t.IsKicked());
-  ASSERT_EQ(1u, kick_count);
-  // A transport can only be kicked once.
-  t.Kick();
-  ASSERT_TRUE(t.IsKicked());
-  ASSERT_EQ(1u, kick_count);
-}
-
 static void DisconnectFunc(void* arg, atransport*) {
     int* count = reinterpret_cast<int*>(arg);
     ++*count;
diff --git a/adb/transport_usb.cpp b/adb/transport_usb.cpp
index 3474820..73e8e15 100644
--- a/adb/transport_usb.cpp
+++ b/adb/transport_usb.cpp
@@ -80,25 +80,18 @@
 #endif
 }
 
-static int remote_read(apacket* p, atransport* t) {
-    int n = UsbReadMessage(t->usb, &p->msg);
+static int remote_read(apacket* p, usb_handle* usb) {
+    int n = UsbReadMessage(usb, &p->msg);
     if (n < 0) {
         D("remote usb: read terminated (message)");
         return -1;
     }
-    if (static_cast<size_t>(n) != sizeof(p->msg) || !check_header(p, t)) {
-        D("remote usb: check_header failed, skip it");
-        goto err_msg;
-    }
-    if (t->GetConnectionState() == kCsOffline) {
-        // If we read a wrong msg header declaring a large message payload, don't read its payload.
-        // Otherwise we may miss true messages from the device.
-        if (p->msg.command != A_CNXN && p->msg.command != A_AUTH) {
-            goto err_msg;
-        }
+    if (static_cast<size_t>(n) != sizeof(p->msg)) {
+        D("remote usb: read received unexpected header length %d", n);
+        return -1;
     }
     if (p->msg.data_length) {
-        n = UsbReadPayload(t->usb, p);
+        n = UsbReadPayload(usb, p);
         if (n < 0) {
             D("remote usb: terminated (data)");
             return -1;
@@ -106,34 +99,24 @@
         if (static_cast<uint32_t>(n) != p->msg.data_length) {
             D("remote usb: read payload failed (need %u bytes, give %d bytes), skip it",
               p->msg.data_length, n);
-            goto err_msg;
+            return -1;
         }
     }
     return 0;
-
-err_msg:
-    p->msg.command = 0;
-    return 0;
 }
 
 #else
 
 // On Android devices, we rely on the kernel to provide buffered read.
 // So we can recover automatically from EOVERFLOW.
-static int remote_read(apacket *p, atransport *t)
-{
-    if (usb_read(t->usb, &p->msg, sizeof(amessage))) {
+static int remote_read(apacket* p, usb_handle* usb) {
+    if (usb_read(usb, &p->msg, sizeof(amessage))) {
         PLOG(ERROR) << "remote usb: read terminated (message)";
         return -1;
     }
 
-    if (!check_header(p, t)) {
-        LOG(ERROR) << "remote usb: check_header failed";
-        return -1;
-    }
-
     if (p->msg.data_length) {
-        if (usb_read(t->usb, p->data, p->msg.data_length)) {
+        if (usb_read(usb, p->data, p->msg.data_length)) {
             PLOG(ERROR) << "remote usb: terminated (data)";
             return -1;
         }
@@ -143,45 +126,43 @@
 }
 #endif
 
-static int remote_write(apacket *p, atransport *t)
-{
-    unsigned size = p->msg.data_length;
+UsbConnection::~UsbConnection() {
+    usb_close(handle_);
+}
 
-    if (usb_write(t->usb, &p->msg, sizeof(amessage))) {
+bool UsbConnection::Read(apacket* packet) {
+    int rc = remote_read(packet, handle_);
+    return rc == 0;
+}
+
+bool UsbConnection::Write(apacket* packet) {
+    unsigned size = packet->msg.data_length;
+
+    if (usb_write(handle_, &packet->msg, sizeof(packet->msg)) != 0) {
         PLOG(ERROR) << "remote usb: 1 - write terminated";
-        return -1;
+        return false;
     }
-    if (p->msg.data_length == 0) return 0;
-    if (usb_write(t->usb, &p->data, size)) {
+
+    if (packet->msg.data_length != 0 && usb_write(handle_, &packet->data, size) != 0) {
         PLOG(ERROR) << "remote usb: 2 - write terminated";
-        return -1;
+        return false;
     }
 
-    return 0;
+    return true;
 }
 
-static void remote_close(atransport* t) {
-    usb_close(t->usb);
-    t->usb = 0;
-}
-
-static void remote_kick(atransport* t) {
-    usb_kick(t->usb);
+void UsbConnection::Close() {
+    usb_kick(handle_);
 }
 
 void init_usb_transport(atransport* t, usb_handle* h) {
     D("transport: usb");
-    t->close = remote_close;
-    t->SetKickFunction(remote_kick);
-    t->SetWriteFunction(remote_write);
-    t->read_from_remote = remote_read;
+    t->connection.reset(new UsbConnection(h));
     t->sync_token = 1;
     t->type = kTransportUsb;
-    t->usb = h;
 }
 
-int is_adb_interface(int usb_class, int usb_subclass, int usb_protocol)
-{
+int is_adb_interface(int usb_class, int usb_subclass, int usb_protocol) {
     return (usb_class == ADB_CLASS && usb_subclass == ADB_SUBCLASS && usb_protocol == ADB_PROTOCOL);
 }
 
diff --git a/libbacktrace/Android.bp b/libbacktrace/Android.bp
index 94b1935..14ae445 100644
--- a/libbacktrace/Android.bp
+++ b/libbacktrace/Android.bp
@@ -128,39 +128,8 @@
     cflags: ["-O0"],
     srcs: ["backtrace_testlib.cpp"],
 
-    target: {
-        linux: {
-            shared_libs: [
-                "libunwind",
-                "libunwindstack",
-            ],
-        },
-    }
-}
-
-//-------------------------------------------------------------------------
-// The libbacktrace_offline static library.
-//-------------------------------------------------------------------------
-cc_library_static {
-    name: "libbacktrace_offline",
-    defaults: ["libbacktrace_common"],
-    host_supported: true,
-    srcs: ["BacktraceOffline.cpp"],
-
-    cflags: [
-        "-D__STDC_CONSTANT_MACROS",
-        "-D__STDC_LIMIT_MACROS",
-        "-D__STDC_FORMAT_MACROS",
-    ],
-
-    header_libs: ["llvm-headers"],
-
-    // Use shared libraries so their headers get included during build.
-    shared_libs = [
-        "libbase",
-        "libunwind",
-        "libunwindstack",
-        "libziparchive",
+    shared_libs: [
+      "libunwindstack",
     ],
 }
 
@@ -193,28 +162,11 @@
         "libbase",
         "libcutils",
         "liblog",
-        "libunwind",
         "libunwindstack",
     ],
 
     group_static_libs: true,
 
-    // Statically link LLVMlibraries to remove dependency on llvm shared library.
-    static_libs = [
-        "libbacktrace_offline",
-        "libLLVMObject",
-        "libLLVMBitReader",
-        "libLLVMMC",
-        "libLLVMMCParser",
-        "libLLVMCore",
-        "libLLVMSupport",
-
-        "libziparchive",
-        "libz",
-    ],
-
-    header_libs: ["llvm-headers"],
-
     target: {
         android: {
             cflags: ["-DENABLE_PSS_TESTS"],
@@ -223,9 +175,6 @@
             ],
         },
         linux_glibc: {
-            host_ldlibs: [
-                "-lncurses",
-            ],
             static_libs: ["libutils"],
         },
     },
diff --git a/libbacktrace/Backtrace.cpp b/libbacktrace/Backtrace.cpp
index 1195e5f..dec241c 100644
--- a/libbacktrace/Backtrace.cpp
+++ b/libbacktrace/Backtrace.cpp
@@ -168,5 +168,9 @@
       return "Failed to find a function in debug sections";
     case BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED:
       return "Failed to execute dwarf instructions in debug sections";
+    case BACKTRACE_UNWIND_ERROR_UNWIND_INFO:
+      return "Failed to unwind due to invalid unwind information";
+    case BACKTRACE_UNWIND_ERROR_REPEATED_FRAME:
+      return "Failed to unwind due to same sp/pc repeating";
   }
 }
diff --git a/libbacktrace/BacktraceCurrent.cpp b/libbacktrace/BacktraceCurrent.cpp
index d61b281..f6f4423 100644
--- a/libbacktrace/BacktraceCurrent.cpp
+++ b/libbacktrace/BacktraceCurrent.cpp
@@ -64,7 +64,7 @@
   return bytes;
 }
 
-bool BacktraceCurrent::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
+bool BacktraceCurrent::Unwind(size_t num_ignore_frames, void* ucontext) {
   if (GetMap() == nullptr) {
     // Without a map object, we can't do anything.
     error_.error_code = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
diff --git a/libbacktrace/BacktraceCurrent.h b/libbacktrace/BacktraceCurrent.h
index 60a9117..48c14ea 100644
--- a/libbacktrace/BacktraceCurrent.h
+++ b/libbacktrace/BacktraceCurrent.h
@@ -19,7 +19,6 @@
 
 #include <stdint.h>
 #include <sys/types.h>
-#include <ucontext.h>
 
 #include <backtrace/Backtrace.h>
 
@@ -44,7 +43,7 @@
 
   bool ReadWord(uint64_t ptr, word_t* out_value) override;
 
-  bool Unwind(size_t num_ignore_frames, ucontext_t* ucontext) override;
+  bool Unwind(size_t num_ignore_frames, void* ucontext) override;
 
  protected:
   bool DiscardFrame(const backtrace_frame_data_t& frame);
@@ -52,7 +51,7 @@
  private:
   bool UnwindThread(size_t num_ignore_frames);
 
-  virtual bool UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) = 0;
+  virtual bool UnwindFromContext(size_t num_ignore_frames, void* ucontext) = 0;
 };
 
 #endif // _LIBBACKTRACE_BACKTRACE_CURRENT_H
diff --git a/libbacktrace/BacktraceMap.cpp b/libbacktrace/BacktraceMap.cpp
index 2a657b8..c8a500c 100644
--- a/libbacktrace/BacktraceMap.cpp
+++ b/libbacktrace/BacktraceMap.cpp
@@ -146,13 +146,3 @@
   return map;
 }
 #endif
-
-BacktraceMap* BacktraceMap::Create(pid_t pid, const std::vector<backtrace_map_t>& maps) {
-    BacktraceMap* backtrace_map = new BacktraceMap(pid);
-    backtrace_map->maps_.insert(backtrace_map->maps_.begin(), maps.begin(), maps.end());
-    std::sort(backtrace_map->maps_.begin(), backtrace_map->maps_.end(),
-            [](const backtrace_map_t& map1, const backtrace_map_t& map2) {
-              return map1.start < map2.start;
-            });
-    return backtrace_map;
-}
diff --git a/libbacktrace/BacktraceOffline.cpp b/libbacktrace/BacktraceOffline.cpp
deleted file mode 100644
index a056716..0000000
--- a/libbacktrace/BacktraceOffline.cpp
+++ /dev/null
@@ -1,1145 +0,0 @@
-/*
- * Copyright (C) 2015 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include "BacktraceOffline.h"
-
-extern "C" {
-#define UNW_REMOTE_ONLY
-#include <dwarf.h>
-}
-
-#include <pthread.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <ucontext.h>
-#include <unistd.h>
-
-#include <memory>
-#include <mutex>
-#include <string>
-#include <vector>
-
-#include <android-base/file.h>
-#include <android-base/macros.h>
-#include <backtrace/Backtrace.h>
-#include <backtrace/BacktraceMap.h>
-#include <ziparchive/zip_archive.h>
-
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wunused-parameter"
-
-#include <llvm/ADT/StringRef.h>
-#include <llvm/Object/Binary.h>
-#include <llvm/Object/ELFObjectFile.h>
-#include <llvm/Object/ObjectFile.h>
-
-#pragma clang diagnostic pop
-
-#include "BacktraceLog.h"
-
-struct EhFrame {
-  uint64_t hdr_vaddr;
-  uint64_t vaddr;
-  uint64_t fde_table_offset;
-  uint64_t min_func_vaddr;
-  std::vector<uint8_t> hdr_data;
-  std::vector<uint8_t> data;
-};
-
-struct ArmIdxEntry {
-  uint32_t func_offset;
-  uint32_t value;
-};
-
-struct ArmExidx {
-  uint64_t exidx_vaddr;
-  uint64_t extab_vaddr;
-  std::vector<ArmIdxEntry> exidx_data;
-  std::vector<uint8_t> extab_data;
-  // There is a one-to-one map from exidx_data.func_offset to func_vaddr_array.
-  std::vector<uint32_t> func_vaddr_array;
-};
-
-struct DebugFrameInfo {
-  bool has_arm_exidx;
-  bool has_eh_frame;
-  bool has_debug_frame;
-  bool has_gnu_debugdata;
-
-  EhFrame eh_frame;
-  ArmExidx arm_exidx;
-
-  uint64_t min_vaddr;
-  uint64_t text_end_vaddr;
-
-  DebugFrameInfo() : has_arm_exidx(false), has_eh_frame(false),
-      has_debug_frame(false), has_gnu_debugdata(false) { }
-};
-
-void Space::Clear() {
-  start = 0;
-  end = 0;
-  data = nullptr;
-}
-
-size_t Space::Read(uint64_t addr, uint8_t* buffer, size_t size) {
-  if (addr >= start && addr < end) {
-    size_t read_size = std::min(size, static_cast<size_t>(end - addr));
-    memcpy(buffer, data + (addr - start), read_size);
-    return read_size;
-  }
-  return 0;
-}
-
-static int FindProcInfo(unw_addr_space_t addr_space, unw_word_t ip, unw_proc_info* proc_info,
-                        int need_unwind_info, void* arg) {
-  BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
-  bool result = backtrace->FindProcInfo(addr_space, ip, proc_info, need_unwind_info);
-  return result ? 0 : -UNW_EINVAL;
-}
-
-static void PutUnwindInfo(unw_addr_space_t, unw_proc_info_t*, void*) {
-}
-
-static int GetDynInfoListAddr(unw_addr_space_t, unw_word_t*, void*) {
-  return -UNW_ENOINFO;
-}
-
-static int AccessMem(unw_addr_space_t, unw_word_t addr, unw_word_t* value, int write, void* arg) {
-  if (write == 1) {
-    return -UNW_EINVAL;
-  }
-  BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
-  *value = 0;
-  size_t read_size = backtrace->Read(addr, reinterpret_cast<uint8_t*>(value), sizeof(unw_word_t));
-  // Strictly we should check if read_size matches sizeof(unw_word_t), but it is possible in
-  // .eh_frame_hdr that the section can end at a position not aligned in sizeof(unw_word_t), and
-  // we should permit the read at the end of the section.
-  return (read_size > 0u ? 0 : -UNW_EINVAL);
-}
-
-static int AccessReg(unw_addr_space_t, unw_regnum_t unwind_reg, unw_word_t* value, int write,
-                     void* arg) {
-  if (write == 1) {
-    return -UNW_EINVAL;
-  }
-  BacktraceOffline* backtrace = reinterpret_cast<BacktraceOffline*>(arg);
-  uint64_t reg_value;
-  bool result = backtrace->ReadReg(unwind_reg, &reg_value);
-  if (result) {
-    *value = static_cast<unw_word_t>(reg_value);
-  }
-  return result ? 0 : -UNW_EINVAL;
-}
-
-static int AccessFpReg(unw_addr_space_t, unw_regnum_t, unw_fpreg_t*, int, void*) {
-  return -UNW_EINVAL;
-}
-
-static int Resume(unw_addr_space_t, unw_cursor_t*, void*) {
-  return -UNW_EINVAL;
-}
-
-static int GetProcName(unw_addr_space_t, unw_word_t, char*, size_t, unw_word_t*, void*) {
-  return -UNW_EINVAL;
-}
-
-static unw_accessors_t accessors = {
-    .find_proc_info = FindProcInfo,
-    .put_unwind_info = PutUnwindInfo,
-    .get_dyn_info_list_addr = GetDynInfoListAddr,
-    .access_mem = AccessMem,
-    .access_reg = AccessReg,
-    .access_fpreg = AccessFpReg,
-    .resume = Resume,
-    .get_proc_name = GetProcName,
-};
-
-bool BacktraceOffline::Unwind(size_t num_ignore_frames, ucontext_t* context) {
-  if (context == nullptr) {
-    BACK_LOGW("The context is needed for offline backtracing.");
-    error_.error_code = BACKTRACE_UNWIND_ERROR_NO_CONTEXT;
-    return false;
-  }
-  context_ = context;
-  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;
-
-  unw_addr_space_t addr_space = unw_create_addr_space(&accessors, 0);
-  unw_cursor_t cursor;
-  int ret = unw_init_remote(&cursor, addr_space, this);
-  if (ret != 0) {
-    BACK_LOGW("unw_init_remote failed %d", ret);
-    unw_destroy_addr_space(addr_space);
-    error_.error_code = BACKTRACE_UNWIND_ERROR_SETUP_FAILED;
-    return false;
-  }
-  size_t num_frames = 0;
-  while (true) {
-    unw_word_t pc;
-    ret = unw_get_reg(&cursor, UNW_REG_IP, &pc);
-    if (ret < 0) {
-      BACK_LOGW("Failed to read IP %d", ret);
-      error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;
-      error_.error_info.regno = UNW_REG_IP;
-      break;
-    }
-    unw_word_t sp;
-    ret = unw_get_reg(&cursor, UNW_REG_SP, &sp);
-    if (ret < 0) {
-      BACK_LOGW("Failed to read SP %d", ret);
-      error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;
-      error_.error_info.regno = UNW_REG_SP;
-      break;
-    }
-
-    if (num_ignore_frames == 0) {
-      backtrace_map_t map;
-      FillInMap(pc, &map);
-      if (map.start == 0 || (map.flags & PROT_EXEC) == 0) {
-        // .eh_frame and .ARM.exidx doesn't know how to unwind from instructions setting up or
-        // destroying stack frames. It can lead to wrong callchains, which may contain pcs outside
-        // executable mapping areas. Stop unwinding once this is detected.
-        error_.error_code = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
-        break;
-      }
-      frames_.resize(num_frames + 1);
-      backtrace_frame_data_t* frame = &frames_[num_frames];
-      frame->num = num_frames;
-      frame->pc = static_cast<uint64_t>(pc);
-      frame->sp = static_cast<uint64_t>(sp);
-      frame->stack_size = 0;
-
-      if (num_frames > 0) {
-        backtrace_frame_data_t* prev = &frames_[num_frames - 1];
-        prev->stack_size = frame->sp - prev->sp;
-      }
-      frame->func_name = GetFunctionName(frame->pc, &frame->func_offset);
-      frame->map = map;
-      num_frames++;
-    } else {
-      num_ignore_frames--;
-    }
-    is_debug_frame_used_ = false;
-    ret = unw_step(&cursor);
-    if (ret <= 0) {
-      if (error_.error_code == BACKTRACE_UNWIND_NO_ERROR) {
-        error_.error_code = BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED;
-      }
-      break;
-    }
-    if (num_frames == MAX_BACKTRACE_FRAMES) {
-      error_.error_code = BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT;
-      break;
-    }
-  }
-  unw_destroy_addr_space(addr_space);
-  context_ = nullptr;
-  return true;
-}
-
-bool BacktraceOffline::ReadWord(uint64_t ptr, word_t* out_value) {
-  size_t bytes_read = Read(ptr, reinterpret_cast<uint8_t*>(out_value), sizeof(word_t));
-  return bytes_read == sizeof(word_t);
-}
-
-size_t BacktraceOffline::Read(uint64_t addr, uint8_t* buffer, size_t bytes) {
-  // Normally, libunwind needs stack information and call frame information to do remote unwinding.
-  // If call frame information is stored in .debug_frame, libunwind can read it from file
-  // by itself. If call frame information is stored in .eh_frame, we need to provide data in
-  // .eh_frame/.eh_frame_hdr sections.
-  // The order of readings below doesn't matter, as the spaces don't overlap with each other.
-  size_t read_size = eh_frame_hdr_space_.Read(addr, buffer, bytes);
-  if (read_size != 0) {
-    return read_size;
-  }
-  read_size = eh_frame_space_.Read(addr, buffer, bytes);
-  if (read_size != 0) {
-    return read_size;
-  }
-  read_size = arm_exidx_space_.Read(addr, buffer, bytes);
-  if (read_size != 0) {
-    return read_size;
-  }
-  read_size = arm_extab_space_.Read(addr, buffer, bytes);
-  if (read_size != 0) {
-    return read_size;
-  }
-  read_size = stack_space_.Read(addr, buffer, bytes);
-  if (read_size != 0) {
-    return read_size;
-  }
-  // In some libraries (like /system/lib64/libskia.so), some CIE entries in .eh_frame use
-  // augmentation "P", which makes libunwind/libunwindstack try to read personality routine in
-  // memory. However, that is not available in offline unwinding. Work around this by returning
-  // all zero data.
-  error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED;
-  error_.error_info.addr = addr;
-  memset(buffer, 0, bytes);
-  return bytes;
-}
-
-bool BacktraceOffline::FindProcInfo(unw_addr_space_t addr_space, uint64_t ip,
-                                    unw_proc_info_t* proc_info, int need_unwind_info) {
-  backtrace_map_t map;
-  FillInMap(ip, &map);
-  if (!BacktraceMap::IsValid(map)) {
-    error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;
-    return false;
-  }
-  const std::string& filename = map.name;
-  DebugFrameInfo* debug_frame = GetDebugFrameInFile(filename);
-  if (debug_frame == nullptr) {
-    error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;
-    return false;
-  }
-  // Each FindProcInfo() is a new attempt to unwind, so reset the reason.
-  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;
-
-  eh_frame_hdr_space_.Clear();
-  eh_frame_space_.Clear();
-  arm_exidx_space_.Clear();
-  arm_extab_space_.Clear();
-
-  // vaddr in the elf file.
-  uint64_t ip_vaddr = ip - map.start + debug_frame->min_vaddr;
-
-  // The unwind info can come from .ARM.exidx or .eh_frame, or .debug_frame/.gnu_debugdata.
-  // First check .eh_frame/.debug_frame, then check .ARM.exidx. Because .eh_frame/.debug_frame has
-  // function range for each entry, by matching ip address with the function range, we know exactly
-  // whether the ip address hits an entry. But .ARM.exidx doesn't have function range for each
-  // entry, it thinks that an ip address hits an entry when (entry.addr <= ip < next_entry.addr).
-  // To prevent ip addresses hit in .eh_frame/.debug_frame being regarded as addresses hit in
-  // .ARM.exidx, we need to check .eh_frame/.debug_frame first.
-
-  // Check .debug_frame/.gnu_debugdata before .eh_frame, because .debug_frame can unwind from
-  // instructions setting up or destroying stack frames, while .eh_frame can't.
-  if (!is_debug_frame_used_ && (debug_frame->has_debug_frame || debug_frame->has_gnu_debugdata)) {
-    is_debug_frame_used_ = true;
-    unw_dyn_info_t di;
-    unw_word_t segbase = map.start - debug_frame->min_vaddr;
-    // TODO: http://b/32916571
-    // TODO: Do it ourselves is more efficient than calling libunwind functions.
-    int found = dwarf_find_debug_frame(0, &di, ip, segbase, filename.c_str(), map.start, map.end);
-    if (found == 1) {
-      int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
-      if (ret == 0) {
-        return true;
-      }
-    }
-  }
-  if (debug_frame->has_eh_frame) {
-    if (ip_vaddr >= debug_frame->eh_frame.min_func_vaddr &&
-        ip_vaddr < debug_frame->text_end_vaddr) {
-      // Prepare eh_frame_hdr space and eh_frame space.
-      eh_frame_hdr_space_.start = ip - ip_vaddr + debug_frame->eh_frame.hdr_vaddr;
-      eh_frame_hdr_space_.end =
-          eh_frame_hdr_space_.start + debug_frame->eh_frame.hdr_data.size();
-      eh_frame_hdr_space_.data = debug_frame->eh_frame.hdr_data.data();
-      eh_frame_space_.start = ip - ip_vaddr + debug_frame->eh_frame.vaddr;
-      eh_frame_space_.end = eh_frame_space_.start + debug_frame->eh_frame.data.size();
-      eh_frame_space_.data = debug_frame->eh_frame.data.data();
-
-      unw_dyn_info di;
-      memset(&di, '\0', sizeof(di));
-      di.start_ip = map.start;
-      di.end_ip = map.end;
-      di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
-      di.u.rti.name_ptr = 0;
-      di.u.rti.segbase = eh_frame_hdr_space_.start;
-      di.u.rti.table_data =
-          eh_frame_hdr_space_.start + debug_frame->eh_frame.fde_table_offset;
-      di.u.rti.table_len = (eh_frame_hdr_space_.end - di.u.rti.table_data) / sizeof(unw_word_t);
-      // TODO: Do it ourselves is more efficient than calling this function.
-      int ret = dwarf_search_unwind_table(addr_space, ip, &di, proc_info, need_unwind_info, this);
-      if (ret == 0) {
-        return true;
-      }
-    }
-  }
-
-  if (debug_frame->has_arm_exidx) {
-    auto& func_vaddrs = debug_frame->arm_exidx.func_vaddr_array;
-    if (ip_vaddr >= func_vaddrs[0] && ip_vaddr < debug_frame->text_end_vaddr) {
-      // Use binary search to find the correct function.
-      auto it = std::upper_bound(func_vaddrs.begin(), func_vaddrs.end(),
-                                 static_cast<uint32_t>(ip_vaddr));
-      if (it != func_vaddrs.begin()) {
-        --it;
-        // Found the exidx entry.
-        size_t index = it - func_vaddrs.begin();
-        proc_info->start_ip = *it;
-        proc_info->format = UNW_INFO_FORMAT_ARM_EXIDX;
-        proc_info->unwind_info = reinterpret_cast<void*>(
-            static_cast<uint64_t>(index * sizeof(ArmIdxEntry) + debug_frame->arm_exidx.exidx_vaddr +
-                                  debug_frame->min_vaddr));
-        eh_frame_hdr_space_.Clear();
-        eh_frame_space_.Clear();
-        // Prepare arm_exidx space and arm_extab space.
-        arm_exidx_space_.start = debug_frame->min_vaddr + debug_frame->arm_exidx.exidx_vaddr;
-        arm_exidx_space_.end = arm_exidx_space_.start +
-            debug_frame->arm_exidx.exidx_data.size() * sizeof(ArmIdxEntry);
-        arm_exidx_space_.data = reinterpret_cast<const uint8_t*>(
-            debug_frame->arm_exidx.exidx_data.data());
-
-        arm_extab_space_.start = debug_frame->min_vaddr + debug_frame->arm_exidx.extab_vaddr;
-        arm_extab_space_.end = arm_extab_space_.start +
-            debug_frame->arm_exidx.extab_data.size();
-        arm_extab_space_.data = debug_frame->arm_exidx.extab_data.data();
-        return true;
-      }
-    }
-  }
-  error_.error_code = BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED;
-  return false;
-}
-
-bool BacktraceOffline::ReadReg(size_t reg, uint64_t* value) {
-  bool result = true;
-#if defined(__arm__)
-  switch (reg) {
-    case UNW_ARM_R0:
-      *value = context_->uc_mcontext.arm_r0;
-      break;
-    case UNW_ARM_R1:
-      *value = context_->uc_mcontext.arm_r1;
-      break;
-    case UNW_ARM_R2:
-      *value = context_->uc_mcontext.arm_r2;
-      break;
-    case UNW_ARM_R3:
-      *value = context_->uc_mcontext.arm_r3;
-      break;
-    case UNW_ARM_R4:
-      *value = context_->uc_mcontext.arm_r4;
-      break;
-    case UNW_ARM_R5:
-      *value = context_->uc_mcontext.arm_r5;
-      break;
-    case UNW_ARM_R6:
-      *value = context_->uc_mcontext.arm_r6;
-      break;
-    case UNW_ARM_R7:
-      *value = context_->uc_mcontext.arm_r7;
-      break;
-    case UNW_ARM_R8:
-      *value = context_->uc_mcontext.arm_r8;
-      break;
-    case UNW_ARM_R9:
-      *value = context_->uc_mcontext.arm_r9;
-      break;
-    case UNW_ARM_R10:
-      *value = context_->uc_mcontext.arm_r10;
-      break;
-    case UNW_ARM_R11:
-      *value = context_->uc_mcontext.arm_fp;
-      break;
-    case UNW_ARM_R12:
-      *value = context_->uc_mcontext.arm_ip;
-      break;
-    case UNW_ARM_R13:
-      *value = context_->uc_mcontext.arm_sp;
-      break;
-    case UNW_ARM_R14:
-      *value = context_->uc_mcontext.arm_lr;
-      break;
-    case UNW_ARM_R15:
-      *value = context_->uc_mcontext.arm_pc;
-      break;
-    default:
-      result = false;
-  }
-#elif defined(__aarch64__)
-  if (reg <= UNW_AARCH64_PC) {
-    *value = context_->uc_mcontext.regs[reg];
-  } else {
-    result = false;
-  }
-#elif defined(__x86_64__)
-  switch (reg) {
-    case UNW_X86_64_R8:
-      *value = context_->uc_mcontext.gregs[REG_R8];
-      break;
-    case UNW_X86_64_R9:
-      *value = context_->uc_mcontext.gregs[REG_R9];
-      break;
-    case UNW_X86_64_R10:
-      *value = context_->uc_mcontext.gregs[REG_R10];
-      break;
-    case UNW_X86_64_R11:
-      *value = context_->uc_mcontext.gregs[REG_R11];
-      break;
-    case UNW_X86_64_R12:
-      *value = context_->uc_mcontext.gregs[REG_R12];
-      break;
-    case UNW_X86_64_R13:
-      *value = context_->uc_mcontext.gregs[REG_R13];
-      break;
-    case UNW_X86_64_R14:
-      *value = context_->uc_mcontext.gregs[REG_R14];
-      break;
-    case UNW_X86_64_R15:
-      *value = context_->uc_mcontext.gregs[REG_R15];
-      break;
-    case UNW_X86_64_RDI:
-      *value = context_->uc_mcontext.gregs[REG_RDI];
-      break;
-    case UNW_X86_64_RSI:
-      *value = context_->uc_mcontext.gregs[REG_RSI];
-      break;
-    case UNW_X86_64_RBP:
-      *value = context_->uc_mcontext.gregs[REG_RBP];
-      break;
-    case UNW_X86_64_RBX:
-      *value = context_->uc_mcontext.gregs[REG_RBX];
-      break;
-    case UNW_X86_64_RDX:
-      *value = context_->uc_mcontext.gregs[REG_RDX];
-      break;
-    case UNW_X86_64_RAX:
-      *value = context_->uc_mcontext.gregs[REG_RAX];
-      break;
-    case UNW_X86_64_RCX:
-      *value = context_->uc_mcontext.gregs[REG_RCX];
-      break;
-    case UNW_X86_64_RSP:
-      *value = context_->uc_mcontext.gregs[REG_RSP];
-      break;
-    case UNW_X86_64_RIP:
-      *value = context_->uc_mcontext.gregs[REG_RIP];
-      break;
-    default:
-      result = false;
-  }
-#elif defined(__i386__)
-  switch (reg) {
-    case UNW_X86_GS:
-      *value = context_->uc_mcontext.gregs[REG_GS];
-      break;
-    case UNW_X86_FS:
-      *value = context_->uc_mcontext.gregs[REG_FS];
-      break;
-    case UNW_X86_ES:
-      *value = context_->uc_mcontext.gregs[REG_ES];
-      break;
-    case UNW_X86_DS:
-      *value = context_->uc_mcontext.gregs[REG_DS];
-      break;
-    case UNW_X86_EAX:
-      *value = context_->uc_mcontext.gregs[REG_EAX];
-      break;
-    case UNW_X86_EBX:
-      *value = context_->uc_mcontext.gregs[REG_EBX];
-      break;
-    case UNW_X86_ECX:
-      *value = context_->uc_mcontext.gregs[REG_ECX];
-      break;
-    case UNW_X86_EDX:
-      *value = context_->uc_mcontext.gregs[REG_EDX];
-      break;
-    case UNW_X86_ESI:
-      *value = context_->uc_mcontext.gregs[REG_ESI];
-      break;
-    case UNW_X86_EDI:
-      *value = context_->uc_mcontext.gregs[REG_EDI];
-      break;
-    case UNW_X86_EBP:
-      *value = context_->uc_mcontext.gregs[REG_EBP];
-      break;
-    case UNW_X86_EIP:
-      *value = context_->uc_mcontext.gregs[REG_EIP];
-      break;
-    case UNW_X86_ESP:
-      *value = context_->uc_mcontext.gregs[REG_ESP];
-      break;
-    case UNW_X86_TRAPNO:
-      *value = context_->uc_mcontext.gregs[REG_TRAPNO];
-      break;
-    case UNW_X86_CS:
-      *value = context_->uc_mcontext.gregs[REG_CS];
-      break;
-    case UNW_X86_EFLAGS:
-      *value = context_->uc_mcontext.gregs[REG_EFL];
-      break;
-    case UNW_X86_SS:
-      *value = context_->uc_mcontext.gregs[REG_SS];
-      break;
-    default:
-      result = false;
-  }
-#else
-  UNUSED(reg);
-  UNUSED(value);
-  result = false;
-#endif
-  if (!result) {
-    error_.error_code = BACKTRACE_UNWIND_ERROR_ACCESS_REG_FAILED;
-    error_.error_info.regno = reg;
-  }
-  return result;
-}
-
-std::string BacktraceOffline::GetFunctionNameRaw(uint64_t, uint64_t* offset) {
-  // We don't have enough information to support this. And it is expensive.
-  *offset = 0;
-  return "";
-}
-
-static std::mutex g_lock;
-static std::unordered_map<std::string, std::unique_ptr<DebugFrameInfo>>* g_debug_frames = nullptr;
-
-static DebugFrameInfo* ReadDebugFrameFromFile(const std::string& filename);
-
-DebugFrameInfo* BacktraceOffline::GetDebugFrameInFile(const std::string& filename) {
-  if (cache_file_) {
-    std::lock_guard<std::mutex> lock(g_lock);
-    if (g_debug_frames != nullptr) {
-      auto it = g_debug_frames->find(filename);
-      if (it != g_debug_frames->end()) {
-        return it->second.get();
-      }
-    }
-  }
-  DebugFrameInfo* debug_frame = ReadDebugFrameFromFile(filename);
-  if (cache_file_) {
-    std::lock_guard<std::mutex> lock(g_lock);
-    if (g_debug_frames == nullptr) {
-      g_debug_frames = new std::unordered_map<std::string, std::unique_ptr<DebugFrameInfo>>;
-    }
-    auto pair = g_debug_frames->emplace(filename, std::unique_ptr<DebugFrameInfo>(debug_frame));
-    if (!pair.second) {
-      debug_frame = pair.first->second.get();
-    }
-  }
-  return debug_frame;
-}
-
-static bool OmitEncodedValue(uint8_t encode, const uint8_t*& p, bool is_elf64) {
-  if (encode == DW_EH_PE_omit) {
-    return 0;
-  }
-  uint8_t format = encode & 0x0f;
-  switch (format) {
-    case DW_EH_PE_ptr:
-      p += is_elf64 ? 8 : 4;
-      break;
-    case DW_EH_PE_uleb128:
-    case DW_EH_PE_sleb128:
-      while ((*p & 0x80) != 0) {
-        ++p;
-      }
-      ++p;
-      break;
-    case DW_EH_PE_udata2:
-    case DW_EH_PE_sdata2:
-      p += 2;
-      break;
-    case DW_EH_PE_udata4:
-    case DW_EH_PE_sdata4:
-      p += 4;
-      break;
-    case DW_EH_PE_udata8:
-    case DW_EH_PE_sdata8:
-      p += 8;
-      break;
-    default:
-      return false;
-  }
-  return true;
-}
-
-static bool GetFdeTableOffsetInEhFrameHdr(const std::vector<uint8_t>& data,
-                                          uint64_t* table_offset_in_eh_frame_hdr, bool is_elf64) {
-  const uint8_t* p = data.data();
-  const uint8_t* end = p + data.size();
-  if (p + 4 > end) {
-    return false;
-  }
-  uint8_t version = *p++;
-  if (version != 1) {
-    return false;
-  }
-  uint8_t eh_frame_ptr_encode = *p++;
-  uint8_t fde_count_encode = *p++;
-  uint8_t fde_table_encode = *p++;
-
-  if (fde_table_encode != (DW_EH_PE_datarel | DW_EH_PE_sdata4)) {
-    return false;
-  }
-
-  if (!OmitEncodedValue(eh_frame_ptr_encode, p, is_elf64) ||
-      !OmitEncodedValue(fde_count_encode, p, is_elf64)) {
-    return false;
-  }
-  if (p >= end) {
-    return false;
-  }
-  *table_offset_in_eh_frame_hdr = p - data.data();
-  return true;
-}
-
-static uint64_t ReadFromBuffer(const uint8_t*& p, size_t size) {
-  uint64_t result = 0;
-  int shift = 0;
-  while (size-- > 0) {
-    uint64_t tmp = *p++;
-    result |= tmp << shift;
-    shift += 8;
-  }
-  return result;
-}
-
-static uint64_t ReadSignValueFromBuffer(const uint8_t*& p, size_t size) {
-  uint64_t result = 0;
-  int shift = 0;
-  for (size_t i = 0; i < size; ++i) {
-    uint64_t tmp = *p++;
-    result |= tmp << shift;
-    shift += 8;
-  }
-  if (*(p - 1) & 0x80) {
-    result |= (-1ULL) << (size * 8);
-  }
-  return result;
-}
-
-static const char* ReadStrFromBuffer(const uint8_t*& p) {
-  const char* result = reinterpret_cast<const char*>(p);
-  p += strlen(result) + 1;
-  return result;
-}
-
-static int64_t ReadLEB128FromBuffer(const uint8_t*& p) {
-  int64_t result = 0;
-  int64_t tmp;
-  int shift = 0;
-  while (*p & 0x80) {
-    tmp = *p & 0x7f;
-    result |= tmp << shift;
-    shift += 7;
-    p++;
-  }
-  tmp = *p;
-  result |= tmp << shift;
-  if (*p & 0x40) {
-    result |= -((tmp & 0x40) << shift);
-  }
-  p++;
-  return result;
-}
-
-static uint64_t ReadULEB128FromBuffer(const uint8_t*& p) {
-  uint64_t result = 0;
-  uint64_t tmp;
-  int shift = 0;
-  while (*p & 0x80) {
-    tmp = *p & 0x7f;
-    result |= tmp << shift;
-    shift += 7;
-    p++;
-  }
-  tmp = *p;
-  result |= tmp << shift;
-  p++;
-  return result;
-}
-
-static uint64_t ReadEhEncoding(const uint8_t*& p, uint8_t encoding, bool is_elf64,
-                               uint64_t section_vaddr, const uint8_t* section_begin) {
-  const uint8_t* init_addr = p;
-  uint64_t result = 0;
-  switch (encoding & 0x0f) {
-    case DW_EH_PE_absptr:
-      result = ReadFromBuffer(p, is_elf64 ? 8 : 4);
-      break;
-    case DW_EH_PE_omit:
-      result = 0;
-      break;
-    case DW_EH_PE_uleb128:
-      result = ReadULEB128FromBuffer(p);
-      break;
-    case DW_EH_PE_udata2:
-      result = ReadFromBuffer(p, 2);
-      break;
-    case DW_EH_PE_udata4:
-      result = ReadFromBuffer(p, 4);
-      break;
-    case DW_EH_PE_udata8:
-      result = ReadFromBuffer(p, 8);
-      break;
-    case DW_EH_PE_sleb128:
-      result = ReadLEB128FromBuffer(p);
-      break;
-    case DW_EH_PE_sdata2:
-      result = ReadSignValueFromBuffer(p, 2);
-      break;
-    case DW_EH_PE_sdata4:
-      result = ReadSignValueFromBuffer(p, 4);
-      break;
-    case DW_EH_PE_sdata8:
-      result = ReadSignValueFromBuffer(p, 8);
-      break;
-  }
-  switch (encoding & 0xf0) {
-    case DW_EH_PE_pcrel:
-      result += init_addr - section_begin + section_vaddr;
-      break;
-    case DW_EH_PE_datarel:
-      result += section_vaddr;
-      break;
-  }
-  return result;
-}
-
-static bool BuildEhFrameHdr(DebugFrameInfo* info, bool is_elf64) {
-  // For each fde entry, collect its (func_vaddr, fde_vaddr) pair.
-  std::vector<std::pair<uint64_t, uint64_t>> index_table;
-  // Map form cie_offset to fde encoding.
-  std::unordered_map<size_t, uint8_t> cie_map;
-  const uint8_t* eh_frame_begin = info->eh_frame.data.data();
-  const uint8_t* eh_frame_end = eh_frame_begin + info->eh_frame.data.size();
-  const uint8_t* p = eh_frame_begin;
-  uint64_t eh_frame_vaddr = info->eh_frame.vaddr;
-  while (p < eh_frame_end) {
-    const uint8_t* unit_begin = p;
-    uint64_t unit_len = ReadFromBuffer(p, 4);
-    size_t secbytes = 4;
-    if (unit_len == 0xffffffff) {
-      unit_len = ReadFromBuffer(p, 8);
-      secbytes = 8;
-    }
-    const uint8_t* unit_end = p + unit_len;
-    uint64_t cie_id = ReadFromBuffer(p, secbytes);
-    if (cie_id == 0) {
-      // This is a CIE.
-      // Read version
-      uint8_t version = *p++;
-      // Read augmentation
-      const char* augmentation = ReadStrFromBuffer(p);
-      if (version >= 4) {
-        // Read address size and segment size
-        p += 2;
-      }
-      // Read code alignment factor
-      ReadULEB128FromBuffer(p);
-      // Read data alignment factor
-      ReadLEB128FromBuffer(p);
-      // Read return address register
-      if (version == 1) {
-        p++;
-      } else {
-        ReadULEB128FromBuffer(p);
-      }
-      uint8_t fde_pointer_encoding = 0;
-      if (augmentation[0] == 'z') {
-        // Read augmentation length.
-        ReadULEB128FromBuffer(p);
-        for (int i = 1; augmentation[i] != '\0'; ++i) {
-          char c = augmentation[i];
-          if (c == 'R') {
-            fde_pointer_encoding = *p++;
-          } else if (c == 'P') {
-            // Read personality handler
-            uint8_t encoding = *p++;
-            OmitEncodedValue(encoding, p, is_elf64);
-          } else if (c == 'L') {
-            // Read lsda encoding
-            p++;
-          }
-        }
-      }
-      cie_map[unit_begin - eh_frame_begin] = fde_pointer_encoding;
-    } else {
-      // This is an FDE.
-      size_t cie_offset = p - secbytes - eh_frame_begin - cie_id;
-      auto it = cie_map.find(cie_offset);
-      if (it != cie_map.end()) {
-        uint8_t fde_pointer_encoding = it->second;
-        uint64_t initial_location =
-            ReadEhEncoding(p, fde_pointer_encoding, is_elf64, eh_frame_vaddr, eh_frame_begin);
-        uint64_t fde_vaddr = unit_begin - eh_frame_begin + eh_frame_vaddr;
-        index_table.push_back(std::make_pair(initial_location, fde_vaddr));
-      }
-    }
-    p = unit_end;
-  }
-  if (index_table.empty()) {
-    return false;
-  }
-  std::sort(index_table.begin(), index_table.end());
-  info->eh_frame.hdr_vaddr = 0;
-  info->eh_frame.hdr_data.resize(index_table.size() * 8);
-  uint32_t* ptr = reinterpret_cast<uint32_t*>(info->eh_frame.hdr_data.data());
-  for (auto& pair : index_table) {
-    *ptr++ = static_cast<uint32_t>(pair.first - info->eh_frame.hdr_vaddr);
-    *ptr++ = static_cast<uint32_t>(pair.second - info->eh_frame.hdr_vaddr);
-  }
-  info->eh_frame.fde_table_offset = 0;
-  info->eh_frame.min_func_vaddr = index_table[0].first;
-  return true;
-}
-
-template <class ELFT>
-DebugFrameInfo* ReadDebugFrameFromELFFile(const llvm::object::ELFFile<ELFT>* elf) {
-  DebugFrameInfo* result = new DebugFrameInfo;
-  result->eh_frame.hdr_vaddr = 0;
-  result->text_end_vaddr = std::numeric_limits<uint64_t>::max();
-
-  bool is_elf64 = (elf->getHeader()->getFileClass() == llvm::ELF::ELFCLASS64);
-  bool has_eh_frame_hdr = false;
-  bool has_eh_frame = false;
-
-  for (auto it = elf->section_begin(); it != elf->section_end(); ++it) {
-    llvm::ErrorOr<llvm::StringRef> name = elf->getSectionName(&*it);
-    if (name) {
-      std::string s = name.get();
-      if (s == ".debug_frame") {
-        result->has_debug_frame = true;
-      } else if (s == ".gnu_debugdata") {
-        result->has_gnu_debugdata = true;
-      } else if (s == ".eh_frame_hdr") {
-        result->eh_frame.hdr_vaddr = it->sh_addr;
-        llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
-        if (data) {
-          result->eh_frame.hdr_data.insert(result->eh_frame.hdr_data.end(),
-              data->data(), data->data() + data->size());
-
-          uint64_t fde_table_offset;
-          if (GetFdeTableOffsetInEhFrameHdr(result->eh_frame.hdr_data, &fde_table_offset, is_elf64)) {
-            result->eh_frame.fde_table_offset = fde_table_offset;
-            // Make sure we have at least one entry in fde_table.
-            if (fde_table_offset + 2 * sizeof(int32_t) <= data->size()) {
-              intptr_t eh_frame_hdr_vaddr = it->sh_addr;
-              int32_t sdata;
-              uint8_t* p = result->eh_frame.hdr_data.data() + fde_table_offset;
-              memcpy(&sdata, p, sizeof(sdata));
-              result->eh_frame.min_func_vaddr = eh_frame_hdr_vaddr + sdata;
-              has_eh_frame_hdr = true;
-            }
-          }
-        }
-      } else if (s == ".eh_frame") {
-        result->eh_frame.vaddr = it->sh_addr;
-        llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
-        if (data) {
-          result->eh_frame.data.insert(result->eh_frame.data.end(),
-                                                data->data(), data->data() + data->size());
-          has_eh_frame = true;
-        }
-      } else if (s == ".ARM.exidx") {
-        result->arm_exidx.exidx_vaddr = it->sh_addr;
-        llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
-        if (data) {
-          size_t entry_count = data->size() / sizeof(ArmIdxEntry);
-          result->arm_exidx.exidx_data.resize(entry_count);
-          memcpy(result->arm_exidx.exidx_data.data(), data->data(),
-                 entry_count * sizeof(ArmIdxEntry));
-          if (entry_count > 0u) {
-            // Change IdxEntry.func_offset into vaddr.
-            result->arm_exidx.func_vaddr_array.reserve(entry_count);
-            uint32_t vaddr = it->sh_addr;
-            for (auto& entry : result->arm_exidx.exidx_data) {
-              uint32_t func_offset = entry.func_offset + vaddr;
-              // Clear bit 31 for the prel31 offset.
-              // Arm sets bit 0 to mark it as thumb code, remove the flag.
-              result->arm_exidx.func_vaddr_array.push_back(
-                  func_offset & 0x7ffffffe);
-              vaddr += 8;
-            }
-            result->has_arm_exidx = true;
-          }
-        }
-      } else if (s == ".ARM.extab") {
-        result->arm_exidx.extab_vaddr = it->sh_addr;
-        llvm::ErrorOr<llvm::ArrayRef<uint8_t>> data = elf->getSectionContents(&*it);
-        if (data) {
-          result->arm_exidx.extab_data.insert(result->arm_exidx.extab_data.end(),
-                                              data->data(), data->data() + data->size());
-        }
-      } else if (s == ".text") {
-        result->text_end_vaddr = it->sh_addr + it->sh_size;
-      }
-    }
-  }
-
-  if (has_eh_frame) {
-    if (!has_eh_frame_hdr) {
-      // Some libraries (like /vendor/lib64/egl/eglSubDriverAndroid.so) contain empty
-      // .eh_frame_hdr.
-      if (BuildEhFrameHdr(result, is_elf64)) {
-        has_eh_frame_hdr = true;
-      }
-    }
-    if (has_eh_frame_hdr) {
-      result->has_eh_frame = true;
-    }
-  }
-  if (has_eh_frame_hdr && has_eh_frame) {
-    result->has_eh_frame = true;
-  }
-
-  result->min_vaddr = std::numeric_limits<uint64_t>::max();
-  for (auto it = elf->program_header_begin(); it != elf->program_header_end(); ++it) {
-    if ((it->p_type == llvm::ELF::PT_LOAD) && (it->p_flags & llvm::ELF::PF_X)) {
-      if (it->p_vaddr < result->min_vaddr) {
-        result->min_vaddr = it->p_vaddr;
-      }
-    }
-  }
-  if (!result->has_eh_frame && !result->has_arm_exidx && !result->has_debug_frame &&
-      !result->has_gnu_debugdata) {
-    delete result;
-    return nullptr;
-  }
-  return result;
-}
-
-static bool IsValidElfPath(const std::string& filename) {
-  static const char elf_magic[] = {0x7f, 'E', 'L', 'F'};
-
-  struct stat st;
-  if (stat(filename.c_str(), &st) != 0 || !S_ISREG(st.st_mode)) {
-    return false;
-  }
-  FILE* fp = fopen(filename.c_str(), "reb");
-  if (fp == nullptr) {
-    return false;
-  }
-  char buf[4];
-  if (fread(buf, 4, 1, fp) != 1) {
-    fclose(fp);
-    return false;
-  }
-  fclose(fp);
-  return memcmp(buf, elf_magic, 4) == 0;
-}
-
-static bool IsValidApkPath(const std::string& apk_path) {
-  static const char zip_preamble[] = {0x50, 0x4b, 0x03, 0x04};
-  struct stat st;
-  if (stat(apk_path.c_str(), &st) != 0 || !S_ISREG(st.st_mode)) {
-    return false;
-  }
-  FILE* fp = fopen(apk_path.c_str(), "reb");
-  if (fp == nullptr) {
-    return false;
-  }
-  char buf[4];
-  if (fread(buf, 4, 1, fp) != 1) {
-    fclose(fp);
-    return false;
-  }
-  fclose(fp);
-  return memcmp(buf, zip_preamble, 4) == 0;
-}
-
-class ScopedZiparchiveHandle {
- public:
-  explicit ScopedZiparchiveHandle(ZipArchiveHandle handle) : handle_(handle) {
-  }
-
-  ~ScopedZiparchiveHandle() {
-    CloseArchive(handle_);
-  }
-
- private:
-  ZipArchiveHandle handle_;
-};
-
-llvm::object::OwningBinary<llvm::object::Binary> OpenEmbeddedElfFile(const std::string& filename) {
-  llvm::object::OwningBinary<llvm::object::Binary> nothing;
-  size_t pos = filename.find("!/");
-  if (pos == std::string::npos) {
-    return nothing;
-  }
-  std::string apk_file = filename.substr(0, pos);
-  std::string elf_file = filename.substr(pos + 2);
-  if (!IsValidApkPath(apk_file)) {
-    BACK_LOGW("%s is not a valid apk file", apk_file.c_str());
-    return nothing;
-  }
-  ZipArchiveHandle handle;
-  int32_t ret_code = OpenArchive(apk_file.c_str(), &handle);
-  if (ret_code != 0) {
-    CloseArchive(handle);
-    BACK_LOGW("failed to open archive %s: %s", apk_file.c_str(), ErrorCodeString(ret_code));
-    return nothing;
-  }
-  ScopedZiparchiveHandle scoped_handle(handle);
-  ZipEntry zentry;
-  ret_code = FindEntry(handle, ZipString(elf_file.c_str()), &zentry);
-  if (ret_code != 0) {
-    BACK_LOGW("failed to find %s in %s: %s", elf_file.c_str(), apk_file.c_str(),
-              ErrorCodeString(ret_code));
-    return nothing;
-  }
-  if (zentry.method != kCompressStored || zentry.compressed_length != zentry.uncompressed_length) {
-    BACK_LOGW("%s is compressed in %s, which doesn't support running directly", elf_file.c_str(),
-              apk_file.c_str());
-    return nothing;
-  }
-  auto buffer_or_err = llvm::MemoryBuffer::getOpenFileSlice(GetFileDescriptor(handle), apk_file,
-                                                            zentry.uncompressed_length,
-                                                            zentry.offset);
-  if (!buffer_or_err) {
-    BACK_LOGW("failed to read %s in %s: %s", elf_file.c_str(), apk_file.c_str(),
-              buffer_or_err.getError().message().c_str());
-    return nothing;
-  }
-  auto binary_or_err = llvm::object::createBinary(buffer_or_err.get()->getMemBufferRef());
-  if (!binary_or_err) {
-    BACK_LOGW("failed to create binary for %s in %s: %s", elf_file.c_str(), apk_file.c_str(),
-              llvm::toString(binary_or_err.takeError()).c_str());
-    return nothing;
-  }
-  return llvm::object::OwningBinary<llvm::object::Binary>(std::move(binary_or_err.get()),
-                                                          std::move(buffer_or_err.get()));
-}
-
-static DebugFrameInfo* ReadDebugFrameFromFile(const std::string& filename) {
-  llvm::object::OwningBinary<llvm::object::Binary> owning_binary;
-  if (filename.find("!/") != std::string::npos) {
-    owning_binary = OpenEmbeddedElfFile(filename);
-  } else {
-    if (!IsValidElfPath(filename)) {
-      return nullptr;
-    }
-    auto binary_or_err = llvm::object::createBinary(llvm::StringRef(filename));
-    if (!binary_or_err) {
-      return nullptr;
-    }
-    owning_binary = std::move(binary_or_err.get());
-  }
-  llvm::object::Binary* binary = owning_binary.getBinary();
-  auto obj = llvm::dyn_cast<llvm::object::ObjectFile>(binary);
-  if (obj == nullptr) {
-    return nullptr;
-  }
-  if (auto elf = llvm::dyn_cast<llvm::object::ELF32LEObjectFile>(obj)) {
-    return ReadDebugFrameFromELFFile(elf->getELFFile());
-  }
-  if (auto elf = llvm::dyn_cast<llvm::object::ELF64LEObjectFile>(obj)) {
-    return ReadDebugFrameFromELFFile(elf->getELFFile());
-  }
-  return nullptr;
-}
-
-Backtrace* Backtrace::CreateOffline(pid_t pid, pid_t tid, BacktraceMap* map,
-                                    const backtrace_stackinfo_t& stack, bool cache_file) {
-  return new BacktraceOffline(pid, tid, map, stack, cache_file);
-}
diff --git a/libbacktrace/BacktraceOffline.h b/libbacktrace/BacktraceOffline.h
deleted file mode 100644
index e028cd8..0000000
--- a/libbacktrace/BacktraceOffline.h
+++ /dev/null
@@ -1,90 +0,0 @@
-/*
- * Copyright (C) 2015 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#ifndef _LIBBACKTRACE_UNWIND_OFFLINE_H
-#define _LIBBACKTRACE_UNWIND_OFFLINE_H
-
-#include <libunwind.h>
-#include <stdint.h>
-#include <sys/types.h>
-#include <ucontext.h>
-
-#include <unordered_map>
-#include <unordered_set>
-
-#include <backtrace/Backtrace.h>
-
-struct Space {
-  uint64_t start;
-  uint64_t end;
-  const uint8_t* data;
-
-  Space() { Clear(); }
-
-  void Clear();
-  size_t Read(uint64_t addr, uint8_t* buffer, size_t size);
-};
-
-struct DebugFrameInfo;
-
-class BacktraceOffline : public Backtrace {
- public:
-  BacktraceOffline(pid_t pid, pid_t tid, BacktraceMap* map, const backtrace_stackinfo_t& stack,
-                   bool cache_file)
-      : Backtrace(pid, tid, map),
-        cache_file_(cache_file),
-        context_(nullptr),
-        is_debug_frame_used_(false) {
-    stack_space_.start = stack.start;
-    stack_space_.end = stack.end;
-    stack_space_.data = stack.data;
-  }
-
-  virtual ~BacktraceOffline() = default;
-
-  bool Unwind(size_t num_ignore_frames, ucontext_t* context) override;
-
-  bool ReadWord(uint64_t ptr, word_t* out_value) override;
-
-  size_t Read(uint64_t addr, uint8_t* buffer, size_t bytes) override;
-
-  bool FindProcInfo(unw_addr_space_t addr_space, uint64_t ip, unw_proc_info_t* proc_info,
-                    int need_unwind_info);
-
-  bool ReadReg(size_t reg_index, uint64_t* value);
-
- protected:
-  std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset) override;
-  DebugFrameInfo* GetDebugFrameInFile(const std::string& filename);
-
-  bool cache_file_;
-  ucontext_t* context_;
-  Space eh_frame_hdr_space_;
-  Space eh_frame_space_;
-  Space arm_extab_space_;
-  Space arm_exidx_space_;
-  Space stack_space_;
-
-  // is_debug_frame_used_ is to make sure we can try both .debug_frame and .ARM.exidx in
-  // FindProcInfo() on ARM. One example is EsxContext::Clear() in
-  // vendor/lib/egl/libGLESv2_adreno.so. EsxContext::Clear() appears in both .debug_frame and
-  // .ARM.exidx. However, libunwind fails to execute debug_frame instruction
-  // "DW_CFA_offset_extended: r265 at cfa-48". So we need to try .ARM.exidx to unwind that
-  // function.
-  bool is_debug_frame_used_;
-};
-
-#endif  // _LIBBACKTRACE_BACKTRACE_OFFLINE_H
diff --git a/libbacktrace/UnwindStack.cpp b/libbacktrace/UnwindStack.cpp
index c5d498c..158467e 100644
--- a/libbacktrace/UnwindStack.cpp
+++ b/libbacktrace/UnwindStack.cpp
@@ -18,7 +18,6 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
-#include <ucontext.h>
 
 #include <memory>
 #include <set>
@@ -103,7 +102,7 @@
 
 bool Backtrace::Unwind(unwindstack::Regs* regs, BacktraceMap* back_map,
                        std::vector<backtrace_frame_data_t>* frames, size_t num_ignore_frames,
-                       std::vector<std::string>* skip_names) {
+                       std::vector<std::string>* skip_names, BacktraceUnwindError* error) {
   UnwindStackMap* stack_map = reinterpret_cast<UnwindStackMap*>(back_map);
   auto process_memory = stack_map->process_memory();
   unwindstack::Unwinder unwinder(MAX_BACKTRACE_FRAMES + num_ignore_frames, stack_map->stack_maps(),
@@ -112,6 +111,38 @@
     unwinder.SetJitDebug(stack_map->GetJitDebug(), regs->Arch());
   }
   unwinder.Unwind(skip_names, &stack_map->GetSuffixesToIgnore());
+  if (error != nullptr) {
+    switch (unwinder.LastErrorCode()) {
+      case unwindstack::ERROR_NONE:
+        error->error_code = BACKTRACE_UNWIND_NO_ERROR;
+        break;
+
+      case unwindstack::ERROR_MEMORY_INVALID:
+        error->error_code = BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED;
+        error->error_info.addr = unwinder.LastErrorAddress();
+        break;
+
+      case unwindstack::ERROR_UNWIND_INFO:
+        error->error_code = BACKTRACE_UNWIND_ERROR_UNWIND_INFO;
+        break;
+
+      case unwindstack::ERROR_UNSUPPORTED:
+        error->error_code = BACKTRACE_UNWIND_ERROR_UNSUPPORTED_OPERATION;
+        break;
+
+      case unwindstack::ERROR_INVALID_MAP:
+        error->error_code = BACKTRACE_UNWIND_ERROR_MAP_MISSING;
+        break;
+
+      case unwindstack::ERROR_MAX_FRAMES_EXCEEDED:
+        error->error_code = BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT;
+        break;
+
+      case unwindstack::ERROR_REPEATED_FRAME:
+        error->error_code = BACKTRACE_UNWIND_ERROR_REPEATED_FRAME;
+        break;
+    }
+  }
 
   if (num_ignore_frames >= unwinder.NumFrames()) {
     frames->resize(0);
@@ -178,7 +209,7 @@
   return GetMap()->GetFunctionName(pc, offset);
 }
 
-bool UnwindStackCurrent::UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) {
+bool UnwindStackCurrent::UnwindFromContext(size_t num_ignore_frames, void* ucontext) {
   std::unique_ptr<unwindstack::Regs> regs;
   if (ucontext == nullptr) {
     regs.reset(unwindstack::Regs::CreateFromLocal());
@@ -189,9 +220,8 @@
     regs.reset(unwindstack::Regs::CreateFromUcontext(unwindstack::Regs::CurrentArch(), ucontext));
   }
 
-  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;
   std::vector<std::string> skip_names{"libunwindstack.so", "libbacktrace.so"};
-  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, &skip_names);
+  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, &skip_names, &error_);
 }
 
 UnwindStackPtrace::UnwindStackPtrace(pid_t pid, pid_t tid, BacktraceMap* map)
@@ -201,7 +231,7 @@
   return GetMap()->GetFunctionName(pc, offset);
 }
 
-bool UnwindStackPtrace::Unwind(size_t num_ignore_frames, ucontext_t* context) {
+bool UnwindStackPtrace::Unwind(size_t num_ignore_frames, void* context) {
   std::unique_ptr<unwindstack::Regs> regs;
   if (context == nullptr) {
     regs.reset(unwindstack::Regs::RemoteGet(Tid()));
@@ -209,10 +239,77 @@
     regs.reset(unwindstack::Regs::CreateFromUcontext(unwindstack::Regs::CurrentArch(), context));
   }
 
-  error_.error_code = BACKTRACE_UNWIND_NO_ERROR;
-  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, nullptr);
+  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, nullptr, &error_);
 }
 
 size_t UnwindStackPtrace::Read(uint64_t addr, uint8_t* buffer, size_t bytes) {
   return memory_.Read(addr, buffer, bytes);
 }
+
+UnwindStackOffline::UnwindStackOffline(ArchEnum arch, pid_t pid, pid_t tid, BacktraceMap* map,
+                                       bool map_shared)
+    : Backtrace(pid, tid, map), arch_(arch) {
+  map_shared_ = map_shared;
+}
+
+bool UnwindStackOffline::Unwind(size_t num_ignore_frames, void* ucontext) {
+  if (ucontext == nullptr) {
+    return false;
+  }
+
+  unwindstack::ArchEnum arch;
+  switch (arch_) {
+    case ARCH_ARM:
+      arch = unwindstack::ARCH_ARM;
+      break;
+    case ARCH_ARM64:
+      arch = unwindstack::ARCH_ARM64;
+      break;
+    case ARCH_X86:
+      arch = unwindstack::ARCH_X86;
+      break;
+    case ARCH_X86_64:
+      arch = unwindstack::ARCH_X86_64;
+      break;
+    default:
+      return false;
+  }
+
+  std::unique_ptr<unwindstack::Regs> regs(unwindstack::Regs::CreateFromUcontext(arch, ucontext));
+
+  return Backtrace::Unwind(regs.get(), GetMap(), &frames_, num_ignore_frames, nullptr, &error_);
+}
+
+std::string UnwindStackOffline::GetFunctionNameRaw(uint64_t, uint64_t*) {
+  return "";
+}
+
+size_t UnwindStackOffline::Read(uint64_t, uint8_t*, size_t) {
+  return 0;
+}
+
+bool UnwindStackOffline::ReadWord(uint64_t, word_t*) {
+  return false;
+}
+
+Backtrace* Backtrace::CreateOffline(ArchEnum arch, pid_t pid, pid_t tid,
+                                    const std::vector<backtrace_map_t>& maps,
+                                    const backtrace_stackinfo_t& stack) {
+  BacktraceMap* map = BacktraceMap::CreateOffline(pid, maps, stack);
+  if (map == nullptr) {
+    return nullptr;
+  }
+
+  return new UnwindStackOffline(arch, pid, tid, map, false);
+}
+
+Backtrace* Backtrace::CreateOffline(ArchEnum arch, pid_t pid, pid_t tid, BacktraceMap* map) {
+  if (map == nullptr) {
+    return nullptr;
+  }
+  return new UnwindStackOffline(arch, pid, tid, map, true);
+}
+
+void Backtrace::SetGlobalElfCache(bool enable) {
+  unwindstack::Elf::SetCachingEnabled(enable);
+}
diff --git a/libbacktrace/UnwindStack.h b/libbacktrace/UnwindStack.h
index 498ad4e..33c4282 100644
--- a/libbacktrace/UnwindStack.h
+++ b/libbacktrace/UnwindStack.h
@@ -34,7 +34,7 @@
 
   std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset) override;
 
-  bool UnwindFromContext(size_t num_ignore_frames, ucontext_t* ucontext) override;
+  bool UnwindFromContext(size_t num_ignore_frames, void* ucontext) override;
 };
 
 class UnwindStackPtrace : public BacktracePtrace {
@@ -42,9 +42,9 @@
   UnwindStackPtrace(pid_t pid, pid_t tid, BacktraceMap* map);
   virtual ~UnwindStackPtrace() = default;
 
-  bool Unwind(size_t num_ignore_frames, ucontext_t* context) override;
+  bool Unwind(size_t num_ignore_frames, void* context) override;
 
-  std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset);
+  std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset) override;
 
   size_t Read(uint64_t addr, uint8_t* buffer, size_t bytes) override;
 
@@ -52,4 +52,20 @@
   unwindstack::MemoryRemote memory_;
 };
 
+class UnwindStackOffline : public Backtrace {
+ public:
+  UnwindStackOffline(ArchEnum arch, pid_t pid, pid_t tid, BacktraceMap* map, bool map_shared);
+
+  bool Unwind(size_t num_ignore_frames, void* context) override;
+
+  std::string GetFunctionNameRaw(uint64_t pc, uint64_t* offset);
+
+  size_t Read(uint64_t addr, uint8_t* buffer, size_t bytes) override;
+
+  bool ReadWord(uint64_t ptr, word_t* out_value) override;
+
+ private:
+  ArchEnum arch_;
+};
+
 #endif  // _LIBBACKTRACE_UNWIND_STACK_H
diff --git a/libbacktrace/UnwindStackMap.cpp b/libbacktrace/UnwindStackMap.cpp
index 11ff84a..97f8d78 100644
--- a/libbacktrace/UnwindStackMap.cpp
+++ b/libbacktrace/UnwindStackMap.cpp
@@ -147,6 +147,43 @@
 }
 #endif
 
+UnwindStackOfflineMap::UnwindStackOfflineMap(pid_t pid) : UnwindStackMap(pid) {}
+
+bool UnwindStackOfflineMap::Build() {
+  return false;
+}
+
+bool UnwindStackOfflineMap::Build(const std::vector<backtrace_map_t>& backtrace_maps,
+                                  const backtrace_stackinfo_t& stack) {
+  if (stack.start >= stack.end) {
+    return false;
+  }
+
+  for (const backtrace_map_t& map : backtrace_maps) {
+    maps_.push_back(map);
+  }
+
+  std::sort(maps_.begin(), maps_.end(),
+            [](const backtrace_map_t& a, const backtrace_map_t& b) { return a.start < b.start; });
+
+  unwindstack::Maps* maps = new unwindstack::Maps;
+  stack_maps_.reset(maps);
+  for (const backtrace_map_t& map : maps_) {
+    maps->Add(map.start, map.end, map.offset, map.flags, map.name, map.load_bias);
+  }
+
+  // Create the process memory from the stack data.
+  uint64_t size = stack.end - stack.start;
+  unwindstack::MemoryBuffer* memory = new unwindstack::MemoryBuffer;
+  memory->Resize(size);
+  memcpy(memory->GetPtr(0), stack.data, size);
+  std::shared_ptr<unwindstack::Memory> shared_memory(memory);
+
+  process_memory_.reset(new unwindstack::MemoryRange(shared_memory, 0, size, stack.start));
+
+  return true;
+}
+
 //-------------------------------------------------------------------------
 // BacktraceMap create function.
 //-------------------------------------------------------------------------
@@ -167,3 +204,16 @@
   }
   return map;
 }
+
+//-------------------------------------------------------------------------
+// BacktraceMap create offline function.
+//-------------------------------------------------------------------------
+BacktraceMap* BacktraceMap::CreateOffline(pid_t pid, const std::vector<backtrace_map_t>& maps,
+                                          const backtrace_stackinfo_t& stack) {
+  UnwindStackOfflineMap* map = new UnwindStackOfflineMap(pid);
+  if (!map->Build(maps, stack)) {
+    delete map;
+    return nullptr;
+  }
+  return map;
+}
diff --git a/libbacktrace/UnwindStackMap.h b/libbacktrace/UnwindStackMap.h
index a815aae..be5c59e 100644
--- a/libbacktrace/UnwindStackMap.h
+++ b/libbacktrace/UnwindStackMap.h
@@ -23,7 +23,9 @@
 #include <memory>
 #include <mutex>
 #include <unordered_map>
+#include <vector>
 
+#include <backtrace/Backtrace.h>
 #include <backtrace/BacktraceMap.h>
 #include <unwindstack/JitDebug.h>
 #include <unwindstack/Maps.h>
@@ -63,4 +65,14 @@
 #endif
 };
 
+class UnwindStackOfflineMap : public UnwindStackMap {
+ public:
+  UnwindStackOfflineMap(pid_t pid);
+  ~UnwindStackOfflineMap() = default;
+
+  bool Build() override;
+
+  bool Build(const std::vector<backtrace_map_t>& maps, const backtrace_stackinfo_t& stack);
+};
+
 #endif  // _LIBBACKTRACE_UNWINDSTACK_MAP_H
diff --git a/libbacktrace/backtrace_offline_test.cpp b/libbacktrace/backtrace_offline_test.cpp
index e2a7441..9877f29 100644
--- a/libbacktrace/backtrace_offline_test.cpp
+++ b/libbacktrace/backtrace_offline_test.cpp
@@ -15,9 +15,9 @@
  */
 
 #include <inttypes.h>
-#include <libunwind.h>
 #include <pthread.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include <functional>
@@ -44,33 +44,7 @@
 int test_level_three(int, int, int, int, void (*)(void*), void*);
 int test_level_four(int, int, int, int, void (*)(void*), void*);
 int test_recursive_call(int, void (*)(void*), void*);
-void test_get_context_and_wait(unw_context_t* unw_context, volatile int* exit_flag);
-}
-
-static ucontext_t GetUContextFromUnwContext(const unw_context_t& unw_context) {
-  ucontext_t ucontext;
-  memset(&ucontext, 0, sizeof(ucontext));
-#if defined(__arm__)
-  ucontext.uc_mcontext.arm_r0 = unw_context.regs[0];
-  ucontext.uc_mcontext.arm_r1 = unw_context.regs[1];
-  ucontext.uc_mcontext.arm_r2 = unw_context.regs[2];
-  ucontext.uc_mcontext.arm_r3 = unw_context.regs[3];
-  ucontext.uc_mcontext.arm_r4 = unw_context.regs[4];
-  ucontext.uc_mcontext.arm_r5 = unw_context.regs[5];
-  ucontext.uc_mcontext.arm_r6 = unw_context.regs[6];
-  ucontext.uc_mcontext.arm_r7 = unw_context.regs[7];
-  ucontext.uc_mcontext.arm_r8 = unw_context.regs[8];
-  ucontext.uc_mcontext.arm_r9 = unw_context.regs[9];
-  ucontext.uc_mcontext.arm_r10 = unw_context.regs[10];
-  ucontext.uc_mcontext.arm_fp = unw_context.regs[11];
-  ucontext.uc_mcontext.arm_ip = unw_context.regs[12];
-  ucontext.uc_mcontext.arm_sp = unw_context.regs[13];
-  ucontext.uc_mcontext.arm_lr = unw_context.regs[14];
-  ucontext.uc_mcontext.arm_pc = unw_context.regs[15];
-#else
-  ucontext.uc_mcontext = unw_context.uc_mcontext;
-#endif
-  return ucontext;
+void test_get_context_and_wait(void* context, volatile int* exit_flag);
 }
 
 struct FunctionSymbol {
@@ -108,18 +82,17 @@
   return s;
 }
 
-static void HexStringToRawData(const char* s, void* data, size_t size) {
-  uint8_t* p = static_cast<uint8_t*>(data);
+static void HexStringToRawData(const char* s, std::vector<uint8_t>* data, size_t size) {
   for (size_t i = 0; i < size; ++i) {
     int value;
     sscanf(s, "%02x", &value);
-    *p++ = static_cast<uint8_t>(value);
+    data->push_back(value);
     s += 2;
   }
 }
 
 struct OfflineThreadArg {
-  unw_context_t unw_context;
+  std::vector<uint8_t> ucontext;
   pid_t tid;
   volatile int exit_flag;
 };
@@ -127,12 +100,12 @@
 static void* OfflineThreadFunc(void* arg) {
   OfflineThreadArg* fn_arg = reinterpret_cast<OfflineThreadArg*>(arg);
   fn_arg->tid = gettid();
-  test_get_context_and_wait(&fn_arg->unw_context, &fn_arg->exit_flag);
+  test_get_context_and_wait(&fn_arg->ucontext, &fn_arg->exit_flag);
   return nullptr;
 }
 
-std::string GetTestPath(std::string path) {
-  return android::base::GetExecutableDirectory() + "/testdata/" + ABI_STRING + '/' + path;
+std::string GetTestPath(const std::string& arch, const std::string& path) {
+  return android::base::GetExecutableDirectory() + "/testdata/" + arch + '/' + path;
 }
 
 // This test is disable because it is for generating test data.
@@ -149,7 +122,7 @@
   OfflineThreadArg arg;
   arg.exit_flag = 0;
   ASSERT_EQ(0, pthread_create(&thread, &attr, OfflineThreadFunc, &arg));
-  // Wait for the offline thread to generate the stack and unw_context information.
+  // Wait for the offline thread to generate the stack and context information.
   sleep(1);
   // Copy the stack information.
   std::vector<uint8_t> stack_data(reinterpret_cast<uint8_t*>(stack),
@@ -179,9 +152,9 @@
                                     entry->start, entry->end, entry->offset, entry->load_bias,
                                     entry->flags, entry->name.c_str());
   }
-  // 3. Dump registers
-  testdata += android::base::StringPrintf("registers: %zu ", sizeof(arg.unw_context));
-  testdata += RawDataToHexString(&arg.unw_context, sizeof(arg.unw_context));
+  // 3. Dump ucontext
+  testdata += android::base::StringPrintf("ucontext: %zu ", arg.ucontext.size());
+  testdata += RawDataToHexString(arg.ucontext.data(), arg.ucontext.size());
   testdata.push_back('\n');
 
   // 4. Dump stack
@@ -218,7 +191,7 @@
   int pid;
   int tid;
   std::vector<backtrace_map_t> maps;
-  unw_context_t unw_context;
+  std::vector<uint8_t> ucontext;
   backtrace_stackinfo_t stack_info;
   std::vector<uint8_t> stack;
   std::vector<FunctionSymbol> symbols;
@@ -231,7 +204,6 @@
   }
   // Parse offline_testdata.
   std::vector<std::string> lines = android::base::Split(s, "\n");
-  memset(&testdata->unw_context, 0, sizeof(testdata->unw_context));
   for (const auto& line : lines) {
     if (android::base::StartsWith(line, "pid:")) {
       sscanf(line.c_str(), "pid: %d tid: %d", &testdata->pid, &testdata->tid);
@@ -244,50 +216,12 @@
              " flags: %d name: %n",
              &map.start, &map.end, &map.offset, &map.load_bias, &map.flags, &pos);
       map.name = android::base::Trim(line.substr(pos));
-    } else if (android::base::StartsWith(line, "registers:")) {
+    } else if (android::base::StartsWith(line, "ucontext:")) {
       size_t size;
       int pos;
-      sscanf(line.c_str(), "registers: %zu %n", &size, &pos);
-      if (sizeof(testdata->unw_context) != size) {
-        return false;
-      }
-      HexStringToRawData(&line[pos], &testdata->unw_context, size);
-    } else if (android::base::StartsWith(line, "regs:")) {
-      std::vector<std::string> strs = android::base::Split(line.substr(6), " ");
-      if (strs.size() % 2 != 0) {
-        return false;
-      }
-      std::vector<std::pair<std::string, uint64_t>> items;
-      for (size_t i = 0; i + 1 < strs.size(); i += 2) {
-        if (!android::base::EndsWith(strs[i], ":")) {
-          return false;
-        }
-        uint64_t value = std::stoul(strs[i + 1], nullptr, 16);
-        items.push_back(std::make_pair(strs[i].substr(0, strs[i].size() - 1), value));
-      }
-#if defined(__arm__)
-      for (auto& item : items) {
-        if (item.first == "sp") {
-          testdata->unw_context.regs[13] = item.second;
-        } else if (item.first == "pc") {
-          testdata->unw_context.regs[15] = item.second;
-        } else {
-          return false;
-        }
-      }
-#elif defined(__aarch64__)
-      for (auto& item : items) {
-        if (item.first == "pc") {
-          testdata->unw_context.uc_mcontext.pc = item.second;
-        } else if (item.first == "sp") {
-          testdata->unw_context.uc_mcontext.sp = item.second;
-        } else if (item.first == "x29") {
-          testdata->unw_context.uc_mcontext.regs[UNW_AARCH64_X29] = item.second;
-        } else {
-          return false;
-        }
-      }
-#endif
+      testdata->ucontext.clear();
+      sscanf(line.c_str(), "ucontext: %zu %n", &size, &pos);
+      HexStringToRawData(&line[pos], &testdata->ucontext, size);
     } else if (android::base::StartsWith(line, "stack:")) {
       size_t size;
       int pos;
@@ -295,8 +229,8 @@
              "stack: start: %" SCNx64 " end: %" SCNx64 " size: %zu %n",
              &testdata->stack_info.start, &testdata->stack_info.end, &size, &pos);
       CHECK_EQ(testdata->stack_info.end - testdata->stack_info.start, size);
-      testdata->stack.resize(size);
-      HexStringToRawData(&line[pos], &testdata->stack[0], size);
+      testdata->stack.clear();
+      HexStringToRawData(&line[pos], &testdata->stack, size);
       testdata->stack_info.data = testdata->stack.data();
     } else if (android::base::StartsWith(line, "function:")) {
       testdata->symbols.resize(testdata->symbols.size() + 1);
@@ -310,17 +244,11 @@
   return true;
 }
 
-static void BacktraceOfflineTest(const char* arch, const std::string& testlib_name) {
-  // TODO: For now, we can only run this on the same arch as the library arch.
-  if (std::string(ABI_STRING) != arch) {
-    GTEST_LOG_(INFO) << "Ignoring arch " << arch << " for lib " << testlib_name;
-    return;
-  }
-
-  const std::string testlib_path(GetTestPath(testlib_name));
-  const std::string offline_testdata_path(GetTestPath("offline_testdata"));
+static void BacktraceOfflineTest(std::string arch_str, const std::string& testlib_name) {
+  const std::string testlib_path(GetTestPath(arch_str, testlib_name));
+  const std::string offline_testdata_path(GetTestPath(arch_str, "offline_testdata"));
   OfflineTestData testdata;
-  ASSERT_TRUE(ReadOfflineTestData(offline_testdata_path, &testdata));
+  ASSERT_TRUE(ReadOfflineTestData(offline_testdata_path, &testdata)) << "Failed " << arch_str;
 
   // Fix path of libbacktrace_testlib.so.
   for (auto& map : testdata.maps) {
@@ -329,16 +257,24 @@
     }
   }
 
-  // Do offline backtrace.
-  std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(testdata.pid, testdata.maps));
-  ASSERT_TRUE(map != nullptr);
+  Backtrace::ArchEnum arch;
+  if (arch_str == "arm") {
+    arch = Backtrace::ARCH_ARM;
+  } else if (arch_str == "arm64") {
+    arch = Backtrace::ARCH_ARM64;
+  } else if (arch_str == "x86") {
+    arch = Backtrace::ARCH_X86;
+  } else if (arch_str == "x86_64") {
+    arch = Backtrace::ARCH_X86_64;
+  } else {
+    abort();
+  }
 
-  std::unique_ptr<Backtrace> backtrace(
-      Backtrace::CreateOffline(testdata.pid, testdata.tid, map.get(), testdata.stack_info));
-  ASSERT_TRUE(backtrace != nullptr);
+  std::unique_ptr<Backtrace> backtrace(Backtrace::CreateOffline(
+      arch, testdata.pid, testdata.tid, testdata.maps, testdata.stack_info));
+  ASSERT_TRUE(backtrace != nullptr) << "Failed " << arch_str;
 
-  ucontext_t ucontext = GetUContextFromUnwContext(testdata.unw_context);
-  ASSERT_TRUE(backtrace->Unwind(0, &ucontext));
+  ASSERT_TRUE(backtrace->Unwind(0, testdata.ucontext.data())) << "Failed " << arch_str;
 
   // Collect pc values of the call stack frames.
   std::vector<uint64_t> pc_values;
@@ -354,14 +290,17 @@
     }
   }
 
-  ASSERT_GE(test_one_index, 3u);
-  ASSERT_EQ("test_level_one", FunctionNameForAddress(pc_values[test_one_index], testdata.symbols));
-  ASSERT_EQ("test_level_two", FunctionNameForAddress(pc_values[test_one_index - 1],
-                                                     testdata.symbols));
-  ASSERT_EQ("test_level_three", FunctionNameForAddress(pc_values[test_one_index - 2],
-                                                       testdata.symbols));
-  ASSERT_EQ("test_level_four", FunctionNameForAddress(pc_values[test_one_index - 3],
-                                                      testdata.symbols));
+  ASSERT_GE(test_one_index, 3u) << "Failed " << arch_str;
+  ASSERT_EQ("test_level_one", FunctionNameForAddress(pc_values[test_one_index], testdata.symbols))
+      << "Failed " << arch_str;
+  ASSERT_EQ("test_level_two", FunctionNameForAddress(pc_values[test_one_index - 1], testdata.symbols))
+      << "Failed " << arch_str;
+  ASSERT_EQ("test_level_three",
+            FunctionNameForAddress(pc_values[test_one_index - 2], testdata.symbols))
+      << "Failed " << arch_str;
+  ASSERT_EQ("test_level_four",
+            FunctionNameForAddress(pc_values[test_one_index - 3], testdata.symbols))
+      << "Failed " << arch_str;
 }
 
 // For now, these tests can only run on the given architectures.
@@ -384,18 +323,13 @@
   BacktraceOfflineTest("arm", "libbacktrace_test_arm_exidx.so");
 }
 
-static void LibUnwindingTest(const std::string& arch, const std::string& testdata_name,
+static void LibUnwindingTest(const std::string& arch_str, const std::string& testdata_name,
                              const std::string& testlib_name) {
-  if (std::string(ABI_STRING) != arch) {
-    GTEST_LOG_(INFO) << "Skipping test since offline for arm on " << ABI_STRING
-                     << " isn't supported.";
-    return;
-  }
-  const std::string testlib_path(GetTestPath(testlib_name));
+  const std::string testlib_path(GetTestPath(arch_str, testlib_name));
   struct stat st;
   ASSERT_EQ(0, stat(testlib_path.c_str(), &st)) << "can't find testlib " << testlib_path;
 
-  const std::string offline_testdata_path(GetTestPath(testdata_name));
+  const std::string offline_testdata_path(GetTestPath(arch_str, testdata_name));
   OfflineTestData testdata;
   ASSERT_TRUE(ReadOfflineTestData(offline_testdata_path, &testdata));
 
@@ -406,26 +340,35 @@
     }
   }
 
-  // Do offline backtrace.
-  std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(testdata.pid, testdata.maps));
-  ASSERT_TRUE(map != nullptr);
+  Backtrace::ArchEnum arch;
+  if (arch_str == "arm") {
+    arch = Backtrace::ARCH_ARM;
+  } else if (arch_str == "arm64") {
+    arch = Backtrace::ARCH_ARM64;
+  } else if (arch_str == "x86") {
+    arch = Backtrace::ARCH_X86;
+  } else if (arch_str == "x86_64") {
+    arch = Backtrace::ARCH_X86_64;
+  } else {
+    ASSERT_TRUE(false) << "Unsupported arch " << arch_str;
+    abort();
+  }
 
-  std::unique_ptr<Backtrace> backtrace(
-      Backtrace::CreateOffline(testdata.pid, testdata.tid, map.get(), testdata.stack_info));
+  // Do offline backtrace.
+  std::unique_ptr<Backtrace> backtrace(Backtrace::CreateOffline(
+      arch, testdata.pid, testdata.tid, testdata.maps, testdata.stack_info));
   ASSERT_TRUE(backtrace != nullptr);
 
-  ucontext_t ucontext = GetUContextFromUnwContext(testdata.unw_context);
-  ASSERT_TRUE(backtrace->Unwind(0, &ucontext));
+  ASSERT_TRUE(backtrace->Unwind(0, testdata.ucontext.data()));
 
   ASSERT_EQ(testdata.symbols.size(), backtrace->NumFrames());
   for (size_t i = 0; i < backtrace->NumFrames(); ++i) {
-    uint64_t vaddr_in_file =
-        backtrace->GetFrame(i)->pc - testdata.maps[0].start + testdata.maps[0].load_bias;
-    std::string name = FunctionNameForAddress(vaddr_in_file, testdata.symbols);
+    std::string name = FunctionNameForAddress(backtrace->GetFrame(i)->rel_pc, testdata.symbols);
     ASSERT_EQ(name, testdata.symbols[i].name);
   }
   ASSERT_TRUE(backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_ACCESS_MEM_FAILED ||
-              backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_MAP_MISSING);
+              backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_MAP_MISSING ||
+              backtrace->GetError().error_code == BACKTRACE_UNWIND_ERROR_REPEATED_FRAME);
 }
 
 // This test tests the situation that ranges of functions covered by .eh_frame and .ARM.exidx
diff --git a/libbacktrace/backtrace_test.cpp b/libbacktrace/backtrace_test.cpp
index 10152f7..aab6db9 100644
--- a/libbacktrace/backtrace_test.cpp
+++ b/libbacktrace/backtrace_test.cpp
@@ -31,6 +31,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <time.h>
+#include <ucontext.h>
 #include <unistd.h>
 
 #include <algorithm>
@@ -143,6 +144,17 @@
   ASSERT_EQ(waitpid(pid, nullptr, 0), pid);
 }
 
+#if !defined(__ANDROID__) || defined(__arm__)
+// On host and arm target we aren't guaranteed that we will terminate cleanly.
+#define VERIFY_NO_ERROR(error_code)                               \
+  ASSERT_TRUE(error_code == BACKTRACE_UNWIND_NO_ERROR ||          \
+              error_code == BACKTRACE_UNWIND_ERROR_UNWIND_INFO || \
+              error_code == BACKTRACE_UNWIND_ERROR_MAP_MISSING)   \
+      << "Unknown error code " << std::to_string(error_code);
+#else
+#define VERIFY_NO_ERROR(error_code) ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, error_code);
+#endif
+
 static bool ReadyLevelBacktrace(Backtrace* backtrace) {
   // See if test_level_four is in the backtrace.
   bool found = false;
@@ -189,7 +201,7 @@
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
   VerifyLevelDump(backtrace.get());
 }
@@ -211,7 +223,7 @@
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  ASSERT_EQ(BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT, backtrace->GetError().error_code);
 
   VerifyMaxDump(backtrace.get());
 }
@@ -241,7 +253,7 @@
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), getpid()));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
   ASSERT_TRUE(backtrace->NumFrames() != 0);
   for (const auto& frame : *backtrace ) {
@@ -292,19 +304,19 @@
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(all.get() != nullptr);
   ASSERT_TRUE(all->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, all->GetError().error_code);
+  VERIFY_NO_ERROR(all->GetError().error_code);
 
   std::unique_ptr<Backtrace> ign1(
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(ign1.get() != nullptr);
   ASSERT_TRUE(ign1->Unwind(1));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError().error_code);
+  VERIFY_NO_ERROR(ign1->GetError().error_code);
 
   std::unique_ptr<Backtrace> ign2(
       Backtrace::Create(BACKTRACE_CURRENT_PROCESS, BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(ign2.get() != nullptr);
   ASSERT_TRUE(ign2->Unwind(2));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError().error_code);
+  VERIFY_NO_ERROR(ign2->GetError().error_code);
 
   VerifyIgnoreFrames(all.get(), ign1.get(), ign2.get(), "VerifyLevelIgnoreFrames");
 }
@@ -340,7 +352,6 @@
       std::unique_ptr<Backtrace> backtrace(create_func(pid, tid, map.get()));
       ASSERT_TRUE(backtrace.get() != nullptr);
       ASSERT_TRUE(backtrace->Unwind(0));
-      ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
       if (ReadyFunc(backtrace.get())) {
         VerifyFunc(backtrace.get(), create_func, map_create_func);
         verified = true;
@@ -389,12 +400,12 @@
   std::unique_ptr<Backtrace> ign1(create_func(bt_all->Pid(), BACKTRACE_CURRENT_THREAD, map.get()));
   ASSERT_TRUE(ign1.get() != nullptr);
   ASSERT_TRUE(ign1->Unwind(1));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError().error_code);
+  VERIFY_NO_ERROR(ign1->GetError().error_code);
 
   std::unique_ptr<Backtrace> ign2(create_func(bt_all->Pid(), BACKTRACE_CURRENT_THREAD, map.get()));
   ASSERT_TRUE(ign2.get() != nullptr);
   ASSERT_TRUE(ign2->Unwind(2));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError().error_code);
+  VERIFY_NO_ERROR(ign2->GetError().error_code);
 
   VerifyIgnoreFrames(bt_all, ign1.get(), ign2.get(), nullptr);
 }
@@ -480,7 +491,7 @@
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), gettid()));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
   VerifyLevelDump(backtrace.get());
 }
@@ -493,7 +504,7 @@
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), gettid()));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  ASSERT_EQ(BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT, backtrace->GetError().error_code);
 
   VerifyMaxDump(backtrace.get());
 }
@@ -535,7 +546,7 @@
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), thread_data.tid));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
   VerifyLevelDump(backtrace.get());
 
@@ -575,17 +586,17 @@
   std::unique_ptr<Backtrace> all(Backtrace::Create(getpid(), thread_data.tid));
   ASSERT_TRUE(all.get() != nullptr);
   ASSERT_TRUE(all->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, all->GetError().error_code);
+  VERIFY_NO_ERROR(all->GetError().error_code);
 
   std::unique_ptr<Backtrace> ign1(Backtrace::Create(getpid(), thread_data.tid));
   ASSERT_TRUE(ign1.get() != nullptr);
   ASSERT_TRUE(ign1->Unwind(1));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign1->GetError().error_code);
+  VERIFY_NO_ERROR(ign1->GetError().error_code);
 
   std::unique_ptr<Backtrace> ign2(Backtrace::Create(getpid(), thread_data.tid));
   ASSERT_TRUE(ign2.get() != nullptr);
   ASSERT_TRUE(ign2->Unwind(2));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, ign2->GetError().error_code);
+  VERIFY_NO_ERROR(ign2->GetError().error_code);
 
   VerifyIgnoreFrames(all.get(), ign1.get(), ign2.get(), nullptr);
 
@@ -616,7 +627,7 @@
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(getpid(), thread_data.tid));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  ASSERT_EQ(BACKTRACE_UNWIND_ERROR_EXCEED_MAX_FRAMES_LIMIT, backtrace->GetError().error_code);
 
   VerifyMaxDump(backtrace.get());
 
@@ -713,21 +724,21 @@
   Backtrace* back1 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map1);
   ASSERT_TRUE(back1 != nullptr);
   EXPECT_TRUE(back1->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back1->GetError().error_code);
+  VERIFY_NO_ERROR(back1->GetError().error_code);
   delete back1;
   delete map1;
 
   Backtrace* back2 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map2);
   ASSERT_TRUE(back2 != nullptr);
   EXPECT_TRUE(back2->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back2->GetError().error_code);
+  VERIFY_NO_ERROR(back2->GetError().error_code);
   delete back2;
   delete map2;
 
   Backtrace* back3 = Backtrace::Create(getpid(), BACKTRACE_CURRENT_THREAD, map3);
   ASSERT_TRUE(back3 != nullptr);
   EXPECT_TRUE(back3->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, back3->GetError().error_code);
+  VERIFY_NO_ERROR(back3->GetError().error_code);
   delete back3;
   delete map3;
 }
@@ -991,7 +1002,7 @@
   uint8_t* expected = new uint8_t[pagesize];
   InitMemory(expected, pagesize);
 
-  uint8_t* data = new uint8_t[2*pagesize];
+  uint8_t* data = new uint8_t[2 * pagesize];
   // Verify that we can only read one page worth of data.
   size_t bytes_read = backtrace->Read(read_addr, data, 2 * pagesize);
   ASSERT_EQ(pagesize, bytes_read);
@@ -1042,8 +1053,10 @@
   ASSERT_TRUE(WaitForNonZero(&thread_data.state, 10));
 }
 
+// The code requires these variables are the same size.
 volatile uint64_t g_ready = 0;
 volatile uint64_t g_addr = 0;
+static_assert(sizeof(g_ready) == sizeof(g_addr), "g_ready/g_addr must be same size");
 
 static void ForkedReadTest() {
   // Create two map pages.
@@ -1091,13 +1104,13 @@
 
       uint64_t read_addr;
       size_t bytes_read = backtrace->Read(reinterpret_cast<uint64_t>(&g_ready),
-                                          reinterpret_cast<uint8_t*>(&read_addr), sizeof(uint64_t));
-      ASSERT_EQ(sizeof(uint64_t), bytes_read);
+                                          reinterpret_cast<uint8_t*>(&read_addr), sizeof(g_ready));
+      ASSERT_EQ(sizeof(g_ready), bytes_read);
       if (read_addr) {
         // The forked process is ready to be read.
         bytes_read = backtrace->Read(reinterpret_cast<uint64_t>(&g_addr),
-                                     reinterpret_cast<uint8_t*>(&read_addr), sizeof(uint64_t));
-        ASSERT_EQ(sizeof(uint64_t), bytes_read);
+                                     reinterpret_cast<uint8_t*>(&read_addr), sizeof(g_addr));
+        ASSERT_EQ(sizeof(g_addr), bytes_read);
 
         RunReadTest(backtrace.get(), read_addr);
 
@@ -1176,7 +1189,7 @@
   int fd = open(tmp_so_name, O_RDONLY);
   ASSERT_TRUE(fd != -1);
 
-  void* map = mmap(NULL, map_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
+  void* map = mmap(nullptr, map_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
   ASSERT_TRUE(map != MAP_FAILED);
   close(fd);
   ASSERT_TRUE(unlink(tmp_so_name) != -1);
@@ -1225,7 +1238,7 @@
       exit(0);
     }
 
-    void* map = mmap(NULL, map_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
+    void* map = mmap(nullptr, map_size, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0);
     if (map == MAP_FAILED) {
       fprintf(stderr, "Failed to map in memory: %s\n", strerror(errno));
       unlink(tmp_so_name);
@@ -1258,11 +1271,11 @@
     ASSERT_TRUE(backtrace.get() != nullptr);
 
     uint64_t read_addr;
-    ASSERT_EQ(sizeof(uint64_t),
+    ASSERT_EQ(sizeof(g_ready),
               backtrace->Read(reinterpret_cast<uint64_t>(&g_ready),
-                              reinterpret_cast<uint8_t*>(&read_addr), sizeof(uint64_t)));
+                              reinterpret_cast<uint8_t*>(&read_addr), sizeof(g_ready)));
     if (read_addr) {
-      ASSERT_EQ(sizeof(uint64_t),
+      ASSERT_EQ(sizeof(g_addr),
                 backtrace->Read(reinterpret_cast<uint64_t>(&g_addr),
                                 reinterpret_cast<uint8_t*>(&read_addr), sizeof(uint64_t)));
 
@@ -1328,15 +1341,16 @@
 }
 
 static void VerifyUnreadableElfBacktrace(void* func) {
-  uint64_t test_func = reinterpret_cast<uint64_t>(func);
   std::unique_ptr<Backtrace> backtrace(Backtrace::Create(BACKTRACE_CURRENT_PROCESS,
                                                          BACKTRACE_CURRENT_THREAD));
   ASSERT_TRUE(backtrace.get() != nullptr);
   ASSERT_TRUE(backtrace->Unwind(0));
-  ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+  VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
   size_t frame_num;
-  ASSERT_TRUE(FindFuncFrameInBacktrace(backtrace.get(), test_func, &frame_num));
+  uint64_t test_func = reinterpret_cast<uint64_t>(func);
+  ASSERT_TRUE(FindFuncFrameInBacktrace(backtrace.get(), test_func, &frame_num))
+      << DumpFrames(backtrace.get());
 
   VerifyUnreadableElfFrame(backtrace.get(), test_func, frame_num);
 }
@@ -1390,7 +1404,7 @@
     std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, BACKTRACE_CURRENT_THREAD));
     ASSERT_TRUE(backtrace.get() != nullptr);
     ASSERT_TRUE(backtrace->Unwind(0));
-    ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+    VERIFY_NO_ERROR(backtrace->GetError().error_code);
 
     size_t frame_num;
     if (FindFuncFrameInBacktrace(backtrace.get(), reinterpret_cast<uint64_t>(test_func),
@@ -1786,7 +1800,7 @@
     Backtrace* backtrace = Backtrace::Create(pid, tid, map.get());
     ASSERT_TRUE(backtrace != nullptr);
     ASSERT_TRUE(backtrace->Unwind(0));
-    ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+    VERIFY_NO_ERROR(backtrace->GetError().error_code);
     delete backtrace;
   }
   size_t stable_pss = GetPssBytes();
@@ -1797,7 +1811,7 @@
     Backtrace* backtrace = Backtrace::Create(pid, tid, map.get());
     ASSERT_TRUE(backtrace != nullptr);
     ASSERT_TRUE(backtrace->Unwind(0));
-    ASSERT_EQ(BACKTRACE_UNWIND_NO_ERROR, backtrace->GetError().error_code);
+    VERIFY_NO_ERROR(backtrace->GetError().error_code);
     delete backtrace;
   }
   size_t new_pss = GetPssBytes();
diff --git a/libbacktrace/backtrace_testlib.cpp b/libbacktrace/backtrace_testlib.cpp
index 3081d64..fec7d98 100644
--- a/libbacktrace/backtrace_testlib.cpp
+++ b/libbacktrace/backtrace_testlib.cpp
@@ -14,9 +14,15 @@
  * limitations under the License.
  */
 
-#include <libunwind.h>
 #include <signal.h>
 #include <stdio.h>
+#include <unistd.h>
+
+#include <memory>
+#include <vector>
+
+#include <unwindstack/Regs.h>
+#include <unwindstack/RegsGetLocal.h>
 
 #include "backtrace_testlib.h"
 
@@ -66,21 +72,70 @@
 }
 
 typedef struct {
-  unw_context_t* unw_context;
+  std::vector<uint8_t>* ucontext;
   volatile int* exit_flag;
 } GetContextArg;
 
 static void GetContextAndExit(void* data) {
-  GetContextArg* arg = (GetContextArg*)data;
-  unw_getcontext(arg->unw_context);
+  GetContextArg* arg = reinterpret_cast<GetContextArg*>(data);
+
+  std::unique_ptr<unwindstack::Regs> regs(unwindstack::Regs::CreateFromLocal());
+  unwindstack::RegsGetLocal(regs.get());
+
+  ucontext_t ucontext;
+  memset(&ucontext, 0, sizeof(ucontext));
+#if defined(__arm__)
+  memcpy(&ucontext.uc_mcontext, regs->RawData(), sizeof(uint32_t) * 16);
+#elif defined(__aarch64__)
+  memcpy(&ucontext.uc_mcontext, regs->RawData(), sizeof(uint64_t) * 33);
+#elif defined(__i386__)
+  uint32_t* reg_data = reinterpret_cast<uint32_t*>(regs->RawData());
+  ucontext.uc_mcontext.gregs[0] = reg_data[15];
+  ucontext.uc_mcontext.gregs[1] = reg_data[14];
+  ucontext.uc_mcontext.gregs[2] = reg_data[13];
+  ucontext.uc_mcontext.gregs[3] = reg_data[12];
+  ucontext.uc_mcontext.gregs[4] = reg_data[7];
+  ucontext.uc_mcontext.gregs[5] = reg_data[6];
+  ucontext.uc_mcontext.gregs[6] = reg_data[5];
+  ucontext.uc_mcontext.gregs[7] = reg_data[4];
+  ucontext.uc_mcontext.gregs[8] = reg_data[3];
+  ucontext.uc_mcontext.gregs[9] = reg_data[2];
+  ucontext.uc_mcontext.gregs[10] = reg_data[1];
+  ucontext.uc_mcontext.gregs[11] = reg_data[0];
+  ucontext.uc_mcontext.gregs[14] = reg_data[8];
+  ucontext.uc_mcontext.gregs[15] = reg_data[10];
+#elif defined(__x86_64__)
+  uint64_t* reg_data = reinterpret_cast<uint64_t*>(regs->RawData());
+  ucontext.uc_mcontext.gregs[0] = reg_data[8];
+  ucontext.uc_mcontext.gregs[1] = reg_data[9];
+  ucontext.uc_mcontext.gregs[2] = reg_data[10];
+  ucontext.uc_mcontext.gregs[3] = reg_data[11];
+  ucontext.uc_mcontext.gregs[4] = reg_data[12];
+  ucontext.uc_mcontext.gregs[5] = reg_data[13];
+  ucontext.uc_mcontext.gregs[6] = reg_data[14];
+  ucontext.uc_mcontext.gregs[7] = reg_data[15];
+  ucontext.uc_mcontext.gregs[8] = reg_data[5];
+  ucontext.uc_mcontext.gregs[9] = reg_data[4];
+  ucontext.uc_mcontext.gregs[10] = reg_data[6];
+  ucontext.uc_mcontext.gregs[11] = reg_data[3];
+  ucontext.uc_mcontext.gregs[12] = reg_data[1];
+  ucontext.uc_mcontext.gregs[13] = reg_data[0];
+  ucontext.uc_mcontext.gregs[14] = reg_data[2];
+  ucontext.uc_mcontext.gregs[15] = reg_data[7];
+  ucontext.uc_mcontext.gregs[16] = reg_data[16];
+#endif
+
+  arg->ucontext->resize(sizeof(ucontext));
+  memcpy(arg->ucontext->data(), &ucontext, sizeof(ucontext));
+
   // Don't touch the stack anymore.
   while (*arg->exit_flag == 0) {
   }
 }
 
-void test_get_context_and_wait(unw_context_t* unw_context, volatile int* exit_flag) {
+void test_get_context_and_wait(void* ucontext, volatile int* exit_flag) {
   GetContextArg arg;
-  arg.unw_context = unw_context;
+  arg.ucontext = reinterpret_cast<std::vector<uint8_t>*>(ucontext);
   arg.exit_flag = exit_flag;
   test_level_one(1, 2, 3, 4, GetContextAndExit, &arg);
 }
diff --git a/libbacktrace/backtrace_testlib.h b/libbacktrace/backtrace_testlib.h
index 16fedc4..9b55e56 100644
--- a/libbacktrace/backtrace_testlib.h
+++ b/libbacktrace/backtrace_testlib.h
@@ -19,8 +19,6 @@
 
 #include <sys/cdefs.h>
 
-#include <libunwind.h>
-
 __BEGIN_DECLS
 
 void test_loop_forever();
@@ -31,7 +29,7 @@
 int test_level_two(int, int, int, int, void (*)(void*), void*);
 int test_level_one(int, int, int, int, void (*)(void*), void*);
 int test_recursive_call(int, void (*)(void*), void*);
-void test_get_context_and_wait(unw_context_t*, volatile int*);
+void test_get_context_and_wait(void*, volatile int*);
 
 __END_DECLS
 
diff --git a/libbacktrace/include/backtrace/Backtrace.h b/libbacktrace/include/backtrace/Backtrace.h
index 18e9f61..7a37015 100644
--- a/libbacktrace/include/backtrace/Backtrace.h
+++ b/libbacktrace/include/backtrace/Backtrace.h
@@ -60,6 +60,10 @@
   BACKTRACE_UNWIND_ERROR_FIND_PROC_INFO_FAILED,
   // Failed to execute dwarf instructions in debug sections.
   BACKTRACE_UNWIND_ERROR_EXECUTE_DWARF_INSTRUCTION_FAILED,
+  // Unwind information is incorrect.
+  BACKTRACE_UNWIND_ERROR_UNWIND_INFO,
+  // Unwind information stopped due to sp/pc repeating.
+  BACKTRACE_UNWIND_ERROR_REPEATED_FRAME,
 };
 
 struct BacktraceUnwindError {
@@ -87,14 +91,6 @@
                          // NULL.
 };
 
-#if defined(__APPLE__)
-struct __darwin_ucontext;
-typedef __darwin_ucontext ucontext_t;
-#else
-struct ucontext;
-typedef ucontext ucontext_t;
-#endif
-
 struct backtrace_stackinfo_t {
   uint64_t start;
   uint64_t end;
@@ -106,7 +102,16 @@
 }
 
 class Backtrace {
-public:
+ public:
+  enum ArchEnum : uint8_t {
+    ARCH_ARM,
+    ARCH_ARM64,
+    ARCH_X86,
+    ARCH_X86_64,
+  };
+
+  static void SetGlobalElfCache(bool enable);
+
   // Create the correct Backtrace object based on what is to be unwound.
   // If pid < 0 or equals the current pid, then the Backtrace object
   // corresponds to the current process.
@@ -120,6 +125,16 @@
   static Backtrace* Create(pid_t pid, pid_t tid, BacktraceMap* map = NULL);
 
   // Create an offline Backtrace object that can be used to do an unwind without a process
+  // that is still running. By default, information is only cached in the map
+  // file. If the calling code creates the map, data can be cached between
+  // unwinds. If not, all cached data will be destroyed when the Backtrace
+  // object is destroyed.
+  static Backtrace* CreateOffline(ArchEnum arch, pid_t pid, pid_t tid,
+                                  const std::vector<backtrace_map_t>& maps,
+                                  const backtrace_stackinfo_t& stack);
+  static Backtrace* CreateOffline(ArchEnum arch, pid_t pid, pid_t tid, BacktraceMap* map);
+
+  // Create an offline Backtrace object that can be used to do an unwind without a process
   // that is still running. If cache_file is set to true, then elf information will be cached
   // for this call. The cached information survives until the calling process ends. This means
   // that subsequent calls to create offline Backtrace objects will continue to use the same
@@ -130,11 +145,11 @@
   virtual ~Backtrace();
 
   // Get the current stack trace and store in the backtrace_ structure.
-  virtual bool Unwind(size_t num_ignore_frames, ucontext_t* context = NULL) = 0;
+  virtual bool Unwind(size_t num_ignore_frames, void* context = NULL) = 0;
 
   static bool Unwind(unwindstack::Regs* regs, BacktraceMap* back_map,
                      std::vector<backtrace_frame_data_t>* frames, size_t num_ignore_frames,
-                     std::vector<std::string>* skip_names);
+                     std::vector<std::string>* skip_names, BacktraceUnwindError* error = nullptr);
 
   // Get the function name and offset into the function given the pc.
   // If the string is empty, then no valid function name was found,
@@ -184,7 +199,7 @@
 
   std::string GetErrorString(BacktraceUnwindError error);
 
-protected:
+ protected:
   Backtrace(pid_t pid, pid_t tid, BacktraceMap* map);
 
   // The name returned is not demangled, GetFunctionName() takes care of
diff --git a/libbacktrace/include/backtrace/BacktraceMap.h b/libbacktrace/include/backtrace/BacktraceMap.h
index 4d020e6..e19c413 100644
--- a/libbacktrace/include/backtrace/BacktraceMap.h
+++ b/libbacktrace/include/backtrace/BacktraceMap.h
@@ -34,6 +34,9 @@
 #include <string>
 #include <vector>
 
+// Forward declaration.
+struct backtrace_stackinfo_t;
+
 // Special flag to indicate a map is in /dev/. However, a map in
 // /dev/ashmem/... does not set this flag.
 static constexpr int PROT_DEVICE_MAP = 0x8000;
@@ -58,7 +61,8 @@
   // is unsupported.
   static BacktraceMap* Create(pid_t pid, bool uncached = false);
 
-  static BacktraceMap* Create(pid_t pid, const std::vector<backtrace_map_t>& maps);
+  static BacktraceMap* CreateOffline(pid_t pid, const std::vector<backtrace_map_t>& maps,
+                                     const backtrace_stackinfo_t& stack);
 
   virtual ~BacktraceMap();
 
diff --git a/libbacktrace/testdata/arm/offline_testdata b/libbacktrace/testdata/arm/offline_testdata
index 6acea29..d5b8f47 100644
--- a/libbacktrace/testdata/arm/offline_testdata
+++ b/libbacktrace/testdata/arm/offline_testdata
@@ -93,7 +93,7 @@
 map: start: e8813000 end: e8815000 offset: 0 load_bias: 0 flags: 3 name: 
 map: start: ff886000 end: ff8a9000 offset: 0 load_bias: 0 flags: 3 name: [stack]
 map: start: ffff0000 end: ffff1000 offset: 0 load_bias: 0 flags: 5 name: [vectors]
-registers: 64 34868affdc8871e8150000001c0000001c000000150000000e00000007000000e08771e834868aff2354d2aa24f9ffffdc8871e88c8771e875b86ee778ba6ee7
+ucontext: 104 000000000000000000000000000000000000000000000000000000000000000034868affdc8871e8150000001c0000001c000000150000000e00000007000000e08771e834868aff2354d2aa24f9ffffdc8871e88c8771e875b86ee778ba6ee70000000000000000
 stack: start: e8715000 end: e8719000 size: 16384 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 function: start: 0 end: e76eb835 name: unknown_start
 function: start: e76eb835 end: e76eb88d name: test_level_four
diff --git a/libbacktrace/testdata/arm/offline_testdata_for_libGLESv2_adreno b/libbacktrace/testdata/arm/offline_testdata_for_libGLESv2_adreno
index 1f96834..d7c186e 100644
--- a/libbacktrace/testdata/arm/offline_testdata_for_libGLESv2_adreno
+++ b/libbacktrace/testdata/arm/offline_testdata_for_libGLESv2_adreno
@@ -1,6 +1,6 @@
 pid: 7288 tid: 31656
-regs: pc: cc416235 sp: cc17f000
+ucontext: 104 00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000f017cc00000000356241cc0000000000000000
 map: start: cc361000 end: cc758000 offset: 0 load_bias: 9000 flags: 5 name: /vendor/lib/egl/libGLESv2_adreno.so
-stack: start: cc17f254 end: cc17f258 size: 4 b36141cc
+stack: start: cc17f234 end: cc17f258 size: 36 0000000000000000000000000000000000000000000000000000000000000000b36141cc
 function: start: be1f0 end: be304 name: EsxContext::Clear(unsigned int, unsigned int, unsigned int, EsxClearValues*)
 function: start: be058 end: be1f0 name: EsxContext::ClearBuffersForDebug()
diff --git a/libbacktrace/testdata/arm/offline_testdata_for_libandroid_runtime b/libbacktrace/testdata/arm/offline_testdata_for_libandroid_runtime
index a12bc3c..54f3525 100644
--- a/libbacktrace/testdata/arm/offline_testdata_for_libandroid_runtime
+++ b/libbacktrace/testdata/arm/offline_testdata_for_libandroid_runtime
@@ -1,6 +1,6 @@
 pid: 7288 tid: 31656
-regs: pc: f1f6dc49 sp: d8fe6930
+ucontext: 104 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000003069fed80000000049dcf6f10000000000000000
 map: start: f1f10000 end: f2049000 offset: 0 load_bias: 10000 flags: 5 name: /system/lib/libandroid_runtime.so
-stack: start: d8fe6954 end: d8fe6958 size: 4 e7dcf6f1
+stack: start: d8fe6948 end: d8fe6958 size: 16 000000000000000000000000e7dcf6f1
 function: start: 6dbf9 end: 6dce5 name: android::AndroidRuntime::javaThreadShell
 function: start: 6dce5 end: 6dd79 name: android::AndroidRuntime::javaCreateThreadEtc
diff --git a/libbacktrace/testdata/arm/offline_testdata_for_libart b/libbacktrace/testdata/arm/offline_testdata_for_libart
index db9bf8d..c1369ff 100644
--- a/libbacktrace/testdata/arm/offline_testdata_for_libart
+++ b/libbacktrace/testdata/arm/offline_testdata_for_libart
@@ -1,5 +1,5 @@
 pid: 32232 tid: 32233
-registers: 64 000000000000000000000000000000006473602451b3e2e700000000d82fd1ff5600000000908eec00000000d42dd1ff00000000c02dd1ff617171e9617171e9
+ucontext: 104 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006473602451b3e2e700000000d82fd1ff5600000000908eec00000000d42dd1ff00000000c02dd1ff617171e9617171e90000000000000000
 map: start: e9380000 end: e9766000 offset: 0 load_bias: b000 flags: 5 name: /system/lib/libart.so
 stack: start: ffd12dc0 end: ffd1306c size: 684 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
 function: start: 3a2121 end: 3a217a name: art_quick_invoke_stub_internal
diff --git a/libbacktrace/testdata/arm64/offline_testdata b/libbacktrace/testdata/arm64/offline_testdata
index 75a2f12..cee9f72 100644
--- a/libbacktrace/testdata/arm64/offline_testdata
+++ b/libbacktrace/testdata/arm64/offline_testdata
@@ -95,7 +95,7 @@
 map: start: 70160e4000 end: 70160e5000 offset: 0 load_bias: 0 flags: 1 name: 
 map: start: 70160e5000 end: 70160e8000 offset: 0 load_bias: 0 flags: 3 name: 
 map: start: 7fd8baf000 end: 7fd8be6000 offset: 0 load_bias: 0 flags: 3 name: [stack]
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 function: start: 0 end: 7015cf5760 name: unknown_start
 function: start: 7015cf5760 end: 7015cf57cc name: test_level_four
diff --git a/libbacktrace/testdata/arm64/offline_testdata_for_eglSubDriverAndroid b/libbacktrace/testdata/arm64/offline_testdata_for_eglSubDriverAndroid
index dfad172..673e30e 100644
--- a/libbacktrace/testdata/arm64/offline_testdata_for_eglSubDriverAndroid
+++ b/libbacktrace/testdata/arm64/offline_testdata_for_eglSubDriverAndroid
@@ -1,6 +1,6 @@
 pid: 12276 tid: 12303
-regs: pc: 7b8c027f64 sp: 7b8c157010 x29: 7b8c157040
 map: start: 7b8c01e000 end: 7b8c030000 offset: 0 load_bias: 0 flags: 5 name: /vendor/lib64/egl/eglSubDriverAndroid.so
-stack: start: 7b8c157048 end: 7b8c157050 size: 8 547e028c7b000000
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+stack: start: 7b8c157020 end: 7b8c157050 size: 48 00000000000000000000000000000000000000000000000000000000000000000000000000000000547e028c7b000000
 function: start: 9ed8 end: a1b0 name: EglAndroidWindowSurface::Initialize(EglAndroidConfig*, int const*)
 function: start: 9dcc end: 9ed8 name: EglAndroidWindowSurface::Create(ANativeWindow*, EglAndroidConfig*, EglAndroidWindowSurface**, int const*)
diff --git a/libbacktrace/testdata/arm64/offline_testdata_for_libskia b/libbacktrace/testdata/arm64/offline_testdata_for_libskia
index 1027c55..da820c0 100644
--- a/libbacktrace/testdata/arm64/offline_testdata_for_libskia
+++ b/libbacktrace/testdata/arm64/offline_testdata_for_libskia
@@ -1,6 +1,6 @@
 pid: 32232 tid: 32233
-regs: pc: 7c25189a0c sp: 7b8c154b50 x29: 7b8c154bb0
 map: start: 7c24c80000 end: 7c25413000 offset: 0 load_bias: 5f000 flags: 5 name: /system/lib64/libskia.so
-stack: start: 7b8c154bb8 end: 7b8c154bc0 size: 8 ec43f2247c000000
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+stack: start: 7b8c154b80 end: 7b8c154bc0 size: 64 0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000ec43f2247c000000
 function: start: 568970 end: 568c08 name: SkScalerContext_FreeType::generateImage(SkGlyph const&)
 function: start: 30330c end: 3044b0 name: SkScalerContext::getImage(SkGlyph const&)
diff --git a/libbacktrace/testdata/x86/offline_testdata b/libbacktrace/testdata/x86/offline_testdata
index e8b7a99..920b338 100644
--- a/libbacktrace/testdata/x86/offline_testdata
+++ b/libbacktrace/testdata/x86/offline_testdata
@@ -70,7 +70,7 @@
 map: start: f77d5000 end: f77d6000 offset: 0 load_bias: 0 flags: 3 name: 
 map: start: f7ec6000 end: f7ee7000 offset: 0 load_bias: 0 flags: 3 name: [heap]
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 function: start: 0 end: f748c740 name: unknown_start
 function: start: f748c740 end: f748c7c0 name: test_level_four
diff --git a/libbacktrace/testdata/x86_64/offline_testdata b/libbacktrace/testdata/x86_64/offline_testdata
index f8d0dc0..c6bb241 100644
--- a/libbacktrace/testdata/x86_64/offline_testdata
+++ b/libbacktrace/testdata/x86_64/offline_testdata
@@ -81,7 +81,7 @@
 map: start: 7ffcf47ed000 end: 7ffcf480f000 offset: 0 load_bias: 0 flags: 3 name: [stack]
 map: start: 7ffcf48d5000 end: 7ffcf48d7000 offset: 0 load_bias: ffffffffff700000 flags: 5 name: [vdso]
 map: start: ffffffffff600000 end: ffffffffff601000 offset: 0 load_bias: 0 flags: 5 name: [vsyscall]
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 function: start: 0 end: 7fd5abcf7930 name: unknown_start
 function: start: 7fd5abcf7930 end: 7fd5abcf7990 name: test_level_four
diff --git a/libcutils/tests/AshmemTest.cpp b/libcutils/tests/AshmemTest.cpp
index a87e23e..b37d020 100644
--- a/libcutils/tests/AshmemTest.cpp
+++ b/libcutils/tests/AshmemTest.cpp
@@ -14,11 +14,18 @@
  * limitations under the License.
  */
 
+#include <errno.h>
+#include <linux/fs.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <android-base/macros.h>
 #include <android-base/unique_fd.h>
 #include <cutils/ashmem.h>
 #include <gtest/gtest.h>
-#include <linux/fs.h>
-#include <sys/mman.h>
 
 using android::base::unique_fd;
 
@@ -31,15 +38,21 @@
 }
 
 void TestMmap(const unique_fd& fd, size_t size, int prot, void** region, off_t off = 0) {
+    ASSERT_TRUE(fd >= 0);
+    ASSERT_TRUE(ashmem_valid(fd));
     *region = mmap(nullptr, size, prot, MAP_SHARED, fd, off);
     ASSERT_NE(MAP_FAILED, *region);
 }
 
 void TestProtDenied(const unique_fd &fd, size_t size, int prot) {
+    ASSERT_TRUE(fd >= 0);
+    ASSERT_TRUE(ashmem_valid(fd));
     EXPECT_EQ(MAP_FAILED, mmap(nullptr, size, prot, MAP_SHARED, fd, 0));
 }
 
 void TestProtIs(const unique_fd& fd, int prot) {
+    ASSERT_TRUE(fd >= 0);
+    ASSERT_TRUE(ashmem_valid(fd));
     EXPECT_EQ(prot, ioctl(fd, ASHMEM_GET_PROT_MASK));
 }
 
@@ -86,18 +99,23 @@
     ASSERT_EQ(0, memcmp(region1, &data, size));
     EXPECT_EQ(0, munmap(region1, size));
 
-    ASSERT_EXIT({
-        void *region2 = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-        if (region2 == MAP_FAILED) {
-            _exit(1);
-        }
-        if (memcmp(region2, &data, size) != 0) {
-            _exit(2);
-        }
-        memset(region2, 0, size);
-        munmap(region2, size);
-        _exit(0);
-    }, ::testing::ExitedWithCode(0),"");
+    ASSERT_EXIT(
+        {
+            if (!ashmem_valid(fd)) {
+                _exit(3);
+            }
+            void* region2 = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+            if (region2 == MAP_FAILED) {
+                _exit(1);
+            }
+            if (memcmp(region2, &data, size) != 0) {
+                _exit(2);
+            }
+            memset(region2, 0, size);
+            munmap(region2, size);
+            _exit(0);
+        },
+        ::testing::ExitedWithCode(0), "");
 
     memset(&data, 0, size);
     void *region2;
@@ -146,6 +164,7 @@
     };
     for (const auto& cfg : seeks) {
         errno = 0;
+        ASSERT_TRUE(ashmem_valid(fd));
         auto off = lseek(fd, cfg.offset, cfg.whence);
         ASSERT_EQ(cfg.ret, off) << "lseek(" << cfg.offset << ", " << cfg.whence << ") failed"
                                 << (errno ? ": " : "") << (errno ? strerror(errno) : "");
@@ -196,15 +215,19 @@
     constexpr size_t size = PAGE_SIZE;
 
     int protFlags[] = { PROT_READ, PROT_WRITE };
-    for (int i = 0; i < 2; i++) {
+    for (size_t i = 0; i < arraysize(protFlags); i++) {
         ASSERT_NO_FATAL_FAILURE(TestCreateRegion(size, fd, PROT_READ | PROT_WRITE));
-        ASSERT_EXIT({
-            if (ashmem_set_prot_region(fd, protFlags[i]) >= 0) {
-                _exit(0);
-            } else {
-                _exit(1);
-            }
-        }, ::testing::ExitedWithCode(0), "");
+        ASSERT_EXIT(
+            {
+                if (!ashmem_valid(fd)) {
+                    _exit(3);
+                } else if (ashmem_set_prot_region(fd, protFlags[i]) >= 0) {
+                    _exit(0);
+                } else {
+                    _exit(1);
+                }
+            },
+            ::testing::ExitedWithCode(0), "");
         ASSERT_NO_FATAL_FAILURE(TestProtDenied(fd, size, protFlags[1-i]));
     }
 }
@@ -227,6 +250,9 @@
 
     ASSERT_EXIT({
         for (int i = 0; i < nRegions; i++) {
+            if (!ashmem_valid(fd[i])) {
+                _exit(3);
+            }
             void *region = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd[i], 0);
             if (region == MAP_FAILED) {
                 _exit(1);
diff --git a/libcutils/trace-dev.cpp b/libcutils/trace-dev.cpp
index 4da8215..27255c2 100644
--- a/libcutils/trace-dev.cpp
+++ b/libcutils/trace-dev.cpp
@@ -25,6 +25,7 @@
 void atrace_set_tracing_enabled(bool enabled)
 {
     atomic_store_explicit(&atrace_is_enabled, enabled, memory_order_release);
+    atomic_store_explicit(&atrace_is_ready, false, memory_order_release);
     atrace_update_tags();
 }
 
@@ -34,18 +35,17 @@
     if (atrace_marker_fd == -1) {
         ALOGE("Error opening trace file: %s (%d)", strerror(errno), errno);
         atrace_enabled_tags = 0;
-        goto done;
+        return;
     }
-
     atrace_enabled_tags = atrace_get_property();
-
-done:
-    atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
 }
 
 void atrace_setup()
 {
-    pthread_once(&atrace_once_control, atrace_init_once);
+    if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
+        pthread_once(&atrace_once_control, atrace_init_once);
+    }
+    atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
 }
 
 void atrace_begin_body(const char* name)