diff --git a/.clang-format b/.clang-format
index b8c6428..7630d16 100644
--- a/.clang-format
+++ b/.clang-format
@@ -12,3 +12,4 @@
 PenaltyExcessCharacter: 32
 
 Cpp11BracedListStyle: false
+IncludeBlocks: Preserve
\ No newline at end of file
diff --git a/libc/Android.bp b/libc/Android.bp
index 53a26a6..c5ea4c5 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -142,19 +142,21 @@
 }
 
 // ========================================================
-// libc_stack_protector.a - stack protector code
+// libc_bootstrap.a - -fno-stack-protector and -ffreestanding
 // ========================================================
 //
-// Code that implements the stack protector (or that runs
-// before TLS has been set up) needs to be compiled with
-// -fno-stack-protector, since it accesses the stack canary
-// TLS slot.
+// Code that implements the stack protector (or that runs before TLS has been set up) needs to be
+// compiled with -fno-stack-protector, since it accesses the stack canary TLS slot. In the linker,
+// some of this code runs before ifunc resolvers have made string.h functions work, so compile with
+// -ffreestanding.
 
 cc_library_static {
 
     srcs: [
         "bionic/__libc_init_main_thread.cpp",
         "bionic/__stack_chk_fail.cpp",
+        "bionic/bionic_call_ifunc_resolver.cpp",
+        "bionic/getauxval.cpp",
     ],
     arch: {
         arm64: {
@@ -172,20 +174,25 @@
     },
 
     defaults: ["libc_defaults"],
-    cflags: ["-fno-stack-protector"],
-    name: "libc_stack_protector",
+    cflags: ["-fno-stack-protector", "-ffreestanding"],
+    name: "libc_bootstrap",
 }
 
-// libc_init_static.cpp also needs to be built without stack protector,
-// because it's responsible for setting up TLS for static executables.
-// This isn't the case for dynamic executables because the dynamic linker
-// has already set up the main thread's TLS.
+// libc_init_static.cpp and libc_init_dynamic.cpp need to be built without stack protector.
+// libc_init_static.cpp sets up TLS for static executables, and libc_init_dynamic.cpp initializes
+// the stack protector global variable.
 
 cc_library_static {
     name: "libc_init_static",
     defaults: ["libc_defaults"],
     srcs: ["bionic/libc_init_static.cpp"],
-    cflags: ["-fno-stack-protector"],
+    cflags: [
+        "-fno-stack-protector",
+
+        // Compile libc_init_static.cpp with -ffreestanding, because some of its code is called
+        // from the linker before ifunc resolvers have made string.h functions available.
+        "-ffreestanding",
+    ],
 }
 
 cc_library_static {
@@ -784,12 +791,6 @@
 cc_library_static {
     defaults: ["libc_defaults"],
     srcs: [
-        // The data that backs getauxval is initialized in the libc init
-        // functions which are invoked by the linker. If this file is included
-        // in libc_ndk.a, only one of the copies of the global data will be
-        // initialized, resulting in nullptr dereferences.
-        "bionic/getauxval.cpp",
-
         // These require getauxval, which isn't available on older platforms.
         "bionic/sysconf.cpp",
         "bionic/vdso.cpp",
@@ -1084,7 +1085,6 @@
         "bionic/atof.cpp",
         "bionic/bionic_allocator.cpp",
         "bionic/bionic_arc4random.cpp",
-        "bionic/bionic_call_ifunc_resolver.cpp",
         "bionic/bionic_futex.cpp",
         "bionic/bionic_netlink.cpp",
         "bionic/bionic_systrace.cpp",
@@ -1427,6 +1427,7 @@
 
     whole_static_libs: [
         "libc_bionic_ndk",
+        "libc_bootstrap",
         "libc_fortify",
         "libc_freebsd",
         "libc_freebsd_large_stack",
@@ -1434,7 +1435,6 @@
         "libc_netbsd",
         "libc_openbsd_large_stack",
         "libc_openbsd_ndk",
-        "libc_stack_protector",
         "libc_syscalls",
         "libc_tzcode",
         "libm",
@@ -1458,6 +1458,7 @@
     whole_static_libs: [
         "libc_bionic",
         "libc_bionic_ndk",
+        "libc_bootstrap",
         "libc_dns",
         "libc_fortify",
         "libc_freebsd",
@@ -1467,7 +1468,6 @@
         "libc_openbsd",
         "libc_openbsd_large_stack",
         "libc_openbsd_ndk",
-        "libc_stack_protector",
         "libc_syscalls",
         "libc_tzcode",
         "libstdc++",
@@ -1495,11 +1495,11 @@
 }
 
 // ========================================================
-// libc_common_static.a For static binaries.
+// libc_static_dispatch.a
 // ========================================================
 cc_library_static {
     defaults: ["libc_defaults"],
-    name: "libc_common_static",
+    name: "libc_static_dispatch",
 
     arch: {
         x86: {
@@ -1512,18 +1512,14 @@
             srcs: ["arch-arm64/static_function_dispatch.S"],
         },
     },
-
-    whole_static_libs: [
-        "libc_common",
-    ],
 }
 
 // ========================================================
-// libc_common_shared.a For shared libraries.
+// libc_dynamic_dispatch.a
 // ========================================================
 cc_library_static {
     defaults: ["libc_defaults"],
-    name: "libc_common_shared",
+    name: "libc_dynamic_dispatch",
 
     cflags: [
         "-ffreestanding",
@@ -1541,9 +1537,31 @@
             srcs: ["arch-arm64/dynamic_function_dispatch.cpp"],
         },
     },
+}
+
+// ========================================================
+// libc_common_static.a For static binaries.
+// ========================================================
+cc_library_static {
+    defaults: ["libc_defaults"],
+    name: "libc_common_static",
 
     whole_static_libs: [
         "libc_common",
+        "libc_static_dispatch",
+    ],
+}
+
+// ========================================================
+// libc_common_shared.a For shared libraries.
+// ========================================================
+cc_library_static {
+    defaults: ["libc_defaults"],
+    name: "libc_common_shared",
+
+    whole_static_libs: [
+        "libc_common",
+        "libc_dynamic_dispatch",
     ],
 }
 
@@ -1567,19 +1585,16 @@
 // libc_nomalloc.a
 // ========================================================
 //
-// This is a version of the static C library that does not
-// include malloc. It's useful in situations when the user wants
-// to provide their own malloc implementation, or wants to
-// explicitly disallow the use of malloc, such as in the
-// dynamic linker.
+// This is a version of the static C library used by the dynamic linker that exclude malloc. It also
+// excludes functions selected using ifunc's (e.g. for string.h). Link in either
+// libc_static_dispatch or libc_dynamic_dispatch to provide those functions.
 
 cc_library_static {
     name: "libc_nomalloc",
     defaults: ["libc_defaults"],
-    cflags: ["-DLIBC_STATIC"],
 
     whole_static_libs: [
-        "libc_common_static",
+        "libc_common",
         "libc_init_static",
         "libc_unwind_static",
     ],
diff --git a/libc/bionic/__libc_init_main_thread.cpp b/libc/bionic/__libc_init_main_thread.cpp
index 6e1b0de..94cf1f8 100644
--- a/libc/bionic/__libc_init_main_thread.cpp
+++ b/libc/bionic/__libc_init_main_thread.cpp
@@ -57,7 +57,9 @@
 //
 // This is in a file by itself because it needs to be built with
 // -fno-stack-protector because it's responsible for setting up the main
-// thread's TLS (which stack protector relies on).
+// thread's TLS (which stack protector relies on). It's also built with
+// -ffreestanding because the early init function runs in the linker before
+// ifunc resolvers have run.
 
 // Do enough setup to:
 //  - Let the dynamic linker invoke system calls (and access errno)
@@ -65,7 +67,8 @@
 //  - Allow the stack protector to work (with a zero cookie)
 // Avoid doing much more because, when this code is called within the dynamic
 // linker, the linker binary hasn't been relocated yet, so certain kinds of code
-// are hazardous, such as accessing non-hidden global variables.
+// are hazardous, such as accessing non-hidden global variables or calling
+// string.h functions.
 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
 extern "C" void __libc_init_main_thread_early(const KernelArgumentBlock& args,
                                               bionic_tcb* temp_tcb) {
@@ -80,6 +83,23 @@
   main_thread.set_cached_pid(main_thread.tid);
 }
 
+// This code is used both by each new pthread and the code that initializes the main thread.
+void __init_tcb(bionic_tcb* tcb, pthread_internal_t* thread) {
+#ifdef TLS_SLOT_SELF
+  // On x86, slot 0 must point to itself so code can read the thread pointer by
+  // loading %fs:0 or %gs:0.
+  tcb->tls_slot(TLS_SLOT_SELF) = &tcb->tls_slot(TLS_SLOT_SELF);
+#endif
+  tcb->tls_slot(TLS_SLOT_THREAD_ID) = thread;
+}
+
+void __init_tcb_dtv(bionic_tcb* tcb) {
+  // Initialize the DTV slot to a statically-allocated empty DTV. The first
+  // access to a dynamic TLS variable allocates a new DTV.
+  static const TlsDtv zero_dtv = {};
+  __set_tcb_dtv(tcb, const_cast<TlsDtv*>(&zero_dtv));
+}
+
 // Finish initializing the main thread.
 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
 extern "C" void __libc_init_main_thread_late() {
diff --git a/libc/bionic/bionic_call_ifunc_resolver.cpp b/libc/bionic/bionic_call_ifunc_resolver.cpp
index 8522835..437de78 100644
--- a/libc/bionic/bionic_call_ifunc_resolver.cpp
+++ b/libc/bionic/bionic_call_ifunc_resolver.cpp
@@ -30,14 +30,32 @@
 #include <sys/auxv.h>
 #include <sys/ifunc.h>
 
+#include "private/bionic_auxv.h"
+
+// This code is called in the linker before it has been relocated, so minimize calls into other
+// parts of Bionic. In particular, we won't ever have two ifunc resolvers called concurrently, so
+// initializing the ifunc resolver argument doesn't need to be thread-safe.
+
 ElfW(Addr) __bionic_call_ifunc_resolver(ElfW(Addr) resolver_addr) {
 #if defined(__aarch64__)
   typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, __ifunc_arg_t*);
-  static __ifunc_arg_t arg = { sizeof(__ifunc_arg_t), getauxval(AT_HWCAP), getauxval(AT_HWCAP2) };
+  static __ifunc_arg_t arg;
+  static bool initialized = false;
+  if (!initialized) {
+    initialized = true;
+    arg._size = sizeof(__ifunc_arg_t);
+    arg._hwcap = getauxval(AT_HWCAP);
+    arg._hwcap2 = getauxval(AT_HWCAP2);
+  }
   return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(arg._hwcap | _IFUNC_ARG_HWCAP, &arg);
 #elif defined(__arm__)
   typedef ElfW(Addr) (*ifunc_resolver_t)(unsigned long);
-  static unsigned long hwcap = getauxval(AT_HWCAP);
+  static unsigned long hwcap;
+  static bool initialized = false;
+  if (!initialized) {
+    initialized = true;
+    hwcap = getauxval(AT_HWCAP);
+  }
   return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap);
 #else
   typedef ElfW(Addr) (*ifunc_resolver_t)(void);
diff --git a/libc/bionic/getauxval.cpp b/libc/bionic/getauxval.cpp
index c8f867b..f865f97 100644
--- a/libc/bionic/getauxval.cpp
+++ b/libc/bionic/getauxval.cpp
@@ -36,7 +36,6 @@
 
 // This function needs to be safe to call before TLS is set up, so it can't
 // access errno or the stack protector.
-__attribute__((no_stack_protector))
 __LIBC_HIDDEN__ unsigned long __bionic_getauxval(unsigned long type, bool& exists) {
   for (ElfW(auxv_t)* v = __libc_shared_globals()->auxv; v->a_type != AT_NULL; ++v) {
     if (v->a_type == type) {
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index 0b74023..28c0b0c 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -231,6 +231,9 @@
   g_target_sdk_version = target;
 }
 
+// This function is called in the dynamic linker before ifunc resolvers have run, so this file is
+// compiled with -ffreestanding to avoid implicit string.h function calls. (It shouldn't strictly
+// be necessary, though.)
 __LIBC_HIDDEN__ libc_shared_globals* __libc_shared_globals() {
   static libc_shared_globals globals;
   return &globals;
diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 1dc1066..03af2d9 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -54,31 +54,12 @@
 void __init_user_desc(struct user_desc*, bool, void*);
 #endif
 
-// This code is used both by each new pthread and the code that initializes the main thread.
-__attribute__((no_stack_protector))
-void __init_tcb(bionic_tcb* tcb, pthread_internal_t* thread) {
-#ifdef TLS_SLOT_SELF
-  // On x86, slot 0 must point to itself so code can read the thread pointer by
-  // loading %fs:0 or %gs:0.
-  tcb->tls_slot(TLS_SLOT_SELF) = &tcb->tls_slot(TLS_SLOT_SELF);
-#endif
-  tcb->tls_slot(TLS_SLOT_THREAD_ID) = thread;
-}
-
 __attribute__((no_stack_protector))
 void __init_tcb_stack_guard(bionic_tcb* tcb) {
   // GCC looks in the TLS for the stack guard on x86, so copy it there from our global.
   tcb->tls_slot(TLS_SLOT_STACK_GUARD) = reinterpret_cast<void*>(__stack_chk_guard);
 }
 
-__attribute__((no_stack_protector))
-void __init_tcb_dtv(bionic_tcb* tcb) {
-  // Initialize the DTV slot to a statically-allocated empty DTV. The first
-  // access to a dynamic TLS variable allocates a new DTV.
-  static const TlsDtv zero_dtv = {};
-  __set_tcb_dtv(tcb, const_cast<TlsDtv*>(&zero_dtv));
-}
-
 void __init_bionic_tls_ptrs(bionic_tcb* tcb, bionic_tls* tls) {
   tcb->thread()->bionic_tls = tls;
   tcb->tls_slot(TLS_SLOT_BIONIC_TLS) = tls;
diff --git a/libc/dns/net/getaddrinfo.c b/libc/dns/net/getaddrinfo.c
index 4e1aa61..d0c11d2 100644
--- a/libc/dns/net/getaddrinfo.c
+++ b/libc/dns/net/getaddrinfo.c
@@ -470,7 +470,7 @@
 			break;
 		}
 
-		struct addrinfo* ai = calloc(1, sizeof(struct addrinfo) + sizeof(struct sockaddr_storage));
+		ai = calloc(1, sizeof(struct addrinfo) + sizeof(struct sockaddr_storage));
 		if (ai == NULL) {
 			break;
 		}
diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 1c5d64c..c45c91f 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -26,9 +26,14 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _FCNTL_H
+#pragma once
 #define _FCNTL_H
 
+/**
+ * @file fcntl.h
+ * @brief File control operations.
+ */
+
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #include <linux/fadvise.h>
@@ -48,47 +53,180 @@
 
 #ifdef __LP64__
 /* LP64 kernels don't have F_*64 defines because their flock is 64-bit. */
+/** Flag for flock(). */
 #define F_GETLK64  F_GETLK
+/** Flag for flock(). */
 #define F_SETLK64  F_SETLK
+/** Flag for flock(). */
 #define F_SETLKW64 F_SETLKW
 #endif
 
+/** Flag for open(). */
 #define O_ASYNC FASYNC
+/** Flag for open(). */
 #define O_RSYNC O_SYNC
 
 #if __ANDROID_API__ >= __ANDROID_API_L__
+/** Flag for splice(). */
 #define SPLICE_F_MOVE 1
+/** Flag for splice(). */
 #define SPLICE_F_NONBLOCK 2
+/** Flag for splice(). */
 #define SPLICE_F_MORE 4
+/** Flag for splice(). */
 #define SPLICE_F_GIFT 8
 #endif
 
 #if __ANDROID_API__ >= __ANDROID_API_O__
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WAIT_BEFORE 1
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WRITE 2
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WAIT_AFTER 4
 #endif
 
+/**
+ * [creat(2)](http://man7.org/linux/man-pages/man2/creat.2.html)
+ * creates a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int creat(const char* __path, mode_t __mode);
+/** See creat(). */
 int creat64(const char* __path, mode_t __mode) __INTRODUCED_IN(21);
+
+/**
+ * [openat(2)](http://man7.org/linux/man-pages/man2/openat.2.html)
+ * opens (and possibly creates) a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int openat(int __dir_fd, const char* __path, int __flags, ...);
+/** See openat(). */
 int openat64(int __dir_fd, const char* __path, int __flags, ...) __INTRODUCED_IN(21);
+
+/**
+ * [open(2)](http://man7.org/linux/man-pages/man2/open.2.html)
+ * opens (and possibly creates) a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int open(const char* __path, int __flags, ...);
+/** See open(). */
 int open64(const char* __path, int __flags, ...) __INTRODUCED_IN(21);
+
+/**
+ * [splice(2)](http://man7.org/linux/man-pages/man2/splice.2.html)
+ * splices data to/from a pipe.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes spliced on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t splice(int __in_fd, off64_t* __in_offset, int __out_fd, off64_t* __out_offset, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
+
+/**
+ * [tee(2)](http://man7.org/linux/man-pages/man2/tee.2.html)
+ * duplicates data from one pipe to another.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes duplicated on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t tee(int __in_fd, int __out_fd, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
+
+/**
+ * [vmsplice(2)](http://man7.org/linux/man-pages/man2/vmsplice.2.html)
+ * splices data to/from a pipe.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes spliced on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t vmsplice(int __fd, const struct iovec* __iov, size_t __count, unsigned int __flags) __INTRODUCED_IN(21);
 
+/**
+ * [fallocate(2)](http://man7.org/linux/man-pages/man2/fallocate.2.html)
+ * is a Linux-specific extension of posix_fallocate().
+ *
+ * Valid flags are `FALLOC_FL_KEEP_SIZE`, `FALLOC_FL_PUNCH_HOLE`,
+ * `FALLOC_FL_NO_HIDE_STALE`, `FALLOC_FL_COLLAPSE_RANGE`,
+ * `FALLOC_FL_ZERO_RANGE`, `FALLOC_FL_INSERT_RANGE`, and
+ * `FALLOC_FL_UNSHARE_RANGE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 int fallocate(int __fd, int __mode, off_t __offset, off_t __length) __RENAME_IF_FILE_OFFSET64(fallocate64) __INTRODUCED_IN(21);
+/** See fallocate(). */
 int fallocate64(int __fd, int __mode, off64_t __offset, off64_t __length) __INTRODUCED_IN(21);
+
+/**
+ * [posix_fadvise(2)](http://man7.org/linux/man-pages/man2/posix_fadvise.2.html)
+ * declares an expected access pattern for file data.
+ *
+ * Valid flags are `POSIX_FADV_NORMAL`, `POSIX_FADV_RANDOM`,
+ * `POSIX_FADV_SEQUENTIAL`, `POSIX_FADV_WILLNEED`, `POSIX_FADV_DONTNEED`,
+ * and `POSIX_FADV_NOREUSE`.
+ *
+ * Returns 0 on success and returns an error number on failure.
+ *
+ * Available since API level 21.
+ */
 int posix_fadvise(int __fd, off_t __offset, off_t __length, int __advice) __RENAME_IF_FILE_OFFSET64(posix_fadvise64) __INTRODUCED_IN(21);
+/** See posix_fadvise(). */
 int posix_fadvise64(int __fd, off64_t __offset, off64_t __length, int __advice) __INTRODUCED_IN(21);
+
+/**
+ * [posix_fallocate(2)](http://man7.org/linux/man-pages/man2/posix_fallocate.2.html)
+ * allocates file space.
+ *
+ * Returns 0 on success and returns an error number on failure.
+ *
+ * Available since API level 21.
+ */
 int posix_fallocate(int __fd, off_t __offset, off_t __length) __RENAME_IF_FILE_OFFSET64(posix_fallocate64) __INTRODUCED_IN(21);
+/** See posix_fallocate(). */
 int posix_fallocate64(int __fd, off64_t __offset, off64_t __length) __INTRODUCED_IN(21);
 
 #if defined(__USE_GNU)
-ssize_t readahead(int __fd, off64_t __offset, size_t __length) __INTRODUCED_IN(16);
+
+/**
+ * [readahead(2)](http://man7.org/linux/man-pages/man2/readahead.2.html)
+ * initiates readahead for the given file.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+ssize_t readahead(int __fd, off64_t __offset, size_t __length);
+
+/**
+ * [sync_file_range(2)](http://man7.org/linux/man-pages/man2/sync_file_range.2.html)
+ * syncs part of a file with disk.
+ *
+ * Valid flags are `SYNC_FILE_RANGE_WAIT_BEFORE`, `SYNC_FILE_RANGE_WRITE`, and
+ * `SYNC_FILE_RANGE_WAIT_AFTER`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
 int sync_file_range(int __fd, off64_t __offset, off64_t __length, unsigned int __flags) __INTRODUCED_IN(26);
+
 #endif
 
 #if defined(__BIONIC_INCLUDE_FORTIFY_HEADERS)
@@ -96,5 +234,3 @@
 #endif
 
 __END_DECLS
-
-#endif
diff --git a/libc/include/search.h b/libc/include/search.h
index 97fdeda..7a75404 100644
--- a/libc/include/search.h
+++ b/libc/include/search.h
@@ -6,30 +6,56 @@
  * $FreeBSD: release/9.0.0/include/search.h 105250 2002-10-16 14:29:23Z robert $
  */
 
-#ifndef _SEARCH_H_
-#define _SEARCH_H_
+#pragma once
+
+/**
+ * @file search.h
+ * @brief Queues, hash tables, trees, and linear array searches.
+ */
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
+/** See hsearch()/hsearch_r(). */
 typedef enum {
   FIND,
   ENTER
 } ACTION;
 
+/** See hsearch()/hsearch_r(). */
 typedef struct entry {
+  /** The string key. */
   char* key;
+  /** The associated data. */
   void* data;
 } ENTRY;
 
+/**
+ * Constants given to the twalk() visitor.
+ * Note that the constant names are misleading.
+ */
 typedef enum {
+  /**
+   * If this is the first visit to a non-leaf node.
+   * Use this for *preorder* traversal.
+   */
   preorder,
+  /**
+   * If this is the second visit to a non-leaf node.
+   * Use this for *inorder* traversal.
+   */
   postorder,
+  /**
+   * If this is the third visit to a non-leaf node.
+   * Use this for *postorder* traversal.
+   */
   endorder,
+  /** If this is the first and only visit to a leaf node. */
   leaf
 } VISIT;
 
 #if defined(__USE_BSD) || defined(__USE_GNU)
+/** The hash table type for hcreate_r()/hdestroy_r()/hsearch_r(). */
 struct hsearch_data {
   struct __hsearch* __hsearch;
 };
@@ -37,30 +63,157 @@
 
 __BEGIN_DECLS
 
+/**
+ * [insque(3)](http://man7.org/linux/man-pages/man3/insque.3.html) inserts
+ * an item in a queue (an intrusive doubly-linked list).
+ *
+ * Available since API level 21.
+ */
 void insque(void* __element, void* __previous) __INTRODUCED_IN(21);
+
+/**
+ * [remque(3)](http://man7.org/linux/man-pages/man3/remque.3.html) removes
+ * an item from a queue (an intrusive doubly-linked list).
+ *
+ * Available since API level 21.
+ */
 void remque(void* __element) __INTRODUCED_IN(21);
 
-int hcreate(size_t) __INTRODUCED_IN(28);
+/**
+ * [hcreate(3)](http://man7.org/linux/man-pages/man3/hcreate.3.html)
+ * initializes the global hash table, with space for at least `__n` elements.
+ *
+ * See hcreate_r() if you need more than one hash table.
+ *
+ * Returns *non-zero* on success and returns 0 and sets `errno` on failure.
+ *
+ * Available since API level 28.
+ */
+int hcreate(size_t __n) __INTRODUCED_IN(28);
+
+/**
+ * [hdestroy(3)](http://man7.org/linux/man-pages/man3/hdestroy.3.html) destroys
+ * the global hash table.
+ *
+ * See hdestroy_r() if you need more than one hash table.
+ *
+ * Available since API level 28.
+ */
 void hdestroy(void) __INTRODUCED_IN(28);
-ENTRY* hsearch(ENTRY, ACTION) __INTRODUCED_IN(28);
+
+/**
+ * [hsearch(3)](http://man7.org/linux/man-pages/man3/hsearch.3.html) finds or
+ * inserts `__entry` in the global hash table, based on `__action`.
+ *
+ * See hsearch_r() if you need more than one hash table.
+ *
+ * Returns a pointer to the entry on success, and returns NULL and sets
+ * `errno` on failure.
+ *
+ * Available since API level 28.
+ */
+ENTRY* hsearch(ENTRY __entry, ACTION __action) __INTRODUCED_IN(28);
 
 #if defined(__USE_BSD) || defined(__USE_GNU)
-int hcreate_r(size_t, struct hsearch_data*) __INTRODUCED_IN(28);
-void hdestroy_r(struct hsearch_data*) __INTRODUCED_IN(28);
-int hsearch_r(ENTRY, ACTION, ENTRY**, struct hsearch_data*) __INTRODUCED_IN(28);
+
+/**
+ * [hcreate_r(3)](http://man7.org/linux/man-pages/man3/hcreate_r.3.html)
+ * initializes a hash table `__table` with space for at least `__n` elements.
+ *
+ * Returns *non-zero* on success and returns 0 and sets `errno` on failure.
+ *
+ * Available since API level 28.
+ */
+int hcreate_r(size_t __n, struct hsearch_data* __table) __INTRODUCED_IN(28);
+
+/**
+ * [hdestroy_r(3)](http://man7.org/linux/man-pages/man3/hdestroy_r.3.html) destroys
+ * the hash table `__table`.
+ *
+ * Available since API level 28.
+ */
+void hdestroy_r(struct hsearch_data* __table) __INTRODUCED_IN(28);
+
+/**
+ * [hsearch_r(3)](http://man7.org/linux/man-pages/man3/hsearch_r.3.html) finds or
+ * inserts `__entry` in the hash table `__table`, based on `__action`.
+ *
+ * Returns *non-zero* on success and returns 0 and sets `errno` on failure.
+ * A pointer to the entry is returned in `*__result`.
+ *
+ * Available since API level 28.
+ */
+int hsearch_r(ENTRY __entry, ACTION __action, ENTRY** __result, struct hsearch_data* __table) __INTRODUCED_IN(28);
+
 #endif
 
-void* lfind(const void* __key, const void* __base, size_t* __count, size_t __size, int (*__comparator)(const void*, const void*))
-  __INTRODUCED_IN(21);
-void* lsearch(const void* __key, void* __base, size_t* __count, size_t __size, int (*__comparator)(const void*, const void*))
-  __INTRODUCED_IN(21);
+/**
+ * [lfind(3)](http://man7.org/linux/man-pages/man3/lfind.3.html) brute-force
+ * searches the unsorted array `__array` (of `__count` items each of size `__size`)
+ * for `__key`, using `__comparator`.
+ *
+ * See bsearch() if you have a sorted array.
+ *
+ * Returns a pointer to the matching element on success, or NULL on failure.
+ *
+ * Available since API level 21.
+ */
+void* lfind(const void* __key, const void* __array, size_t* __count, size_t __size, int (*__comparator)(const void*, const void*)) __INTRODUCED_IN(21);
 
-void* tdelete(const void* __key, void** __root_ptr, int (*__comparator)(const void*, const void*)) __INTRODUCED_IN(16);
-void tdestroy(void* __root, void (*__free_fn)(void*)) __INTRODUCED_IN(16);
-void* tfind(const void* __key, void* const* __root_ptr, int (*__comparator)(const void*, const void*)) __INTRODUCED_IN(16);
-void* tsearch(const void* __key, void** __root_ptr, int (*__comparator)(const void*, const void*)) __INTRODUCED_IN(16);
-void twalk(const void* __root, void (*__visitor)(const void*, VISIT, int)) __INTRODUCED_IN(21);
+/**
+ * [lsearch(3)](http://man7.org/linux/man-pages/man3/lsearch.3.html) brute-force
+ * searches the unsorted array `__array` (of `__count` items each of size `__size`)
+ * for `__key`, using `__comparator`.
+ *
+ * Unlike lfind(), on failure lsearch() will *insert* `__key` at the end of
+ * `__array` and increment `*__count`.
+ *
+ * Returns a pointer to the matching element on success, or to the newly-added
+ * element on failure.
+ *
+ * Available since API level 21.
+ */
+void* lsearch(const void* __key, void* __array, size_t* __count, size_t __size, int (*__comparator)(const void*, const void*)) __INTRODUCED_IN(21);
+
+/**
+ * [tdelete(3)](http://man7.org/linux/man-pages/man3/tdelete.3.html) searches
+ * for and removes an element in the tree `*__root_ptr`. The search is performed
+ * using `__comparator`.
+ *
+ * Returns a pointer to the parent of the deleted node, or NULL on failure.
+ */
+void* tdelete(const void* __key, void** __root_ptr, int (*__comparator)(const void*, const void*));
+
+/**
+ * [tdestroy(3)](http://man7.org/linux/man-pages/man3/tdestroy.3.html) destroys
+ * the hash table `__root` using `__free_fn` on each node.
+ */
+void tdestroy(void* __root, void (*__free_fn)(void*));
+
+/**
+ * [tfind(3)](http://man7.org/linux/man-pages/man3/tfind.3.html) searches
+ * for an element in the tree `*__root_ptr`. The search is performed using
+ * `__comparator`.
+ *
+ * Returns a pointer to the matching node, or NULL on failure.
+ */
+void* tfind(const void* __key, void* const* __root_ptr, int (*__comparator)(const void*, const void*));
+
+/**
+ * [tsearch(3)](http://man7.org/linux/man-pages/man3/tsearch.3.html) searches
+ * for an element in the tree `*__root_ptr`. The search is performed using
+ * `__comparator`.
+ *
+ * Unlike tfind(), on failure tsearch() will *insert* `__key` into the tree.
+ *
+ * Returns a pointer to the matching node, or to the newly-added node.
+ */
+void* tsearch(const void* __key, void** __root_ptr, int (*__comparator)(const void*, const void*));
+
+/**
+ * [twalk(3)](http://man7.org/linux/man-pages/man3/twalk.3.html) calls
+ * `__visitor` on every node in the tree.
+ */
+void twalk(const void* __root, void (*__visitor)(const void*, VISIT, int));
 
 __END_DECLS
-
-#endif
diff --git a/libc/include/sys/xattr.h b/libc/include/sys/xattr.h
index d15b3fc..dc58026 100644
--- a/libc/include/sys/xattr.h
+++ b/libc/include/sys/xattr.h
@@ -26,8 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_XATTR_H_
-#define _SYS_XATTR_H_
+#pragma once
+
+/**
+ * @file sys/xattr.h
+ * @brief Extended attribute functions.
+ */
 
 #include <linux/xattr.h>
 #include <sys/cdefs.h>
@@ -35,25 +39,120 @@
 
 __BEGIN_DECLS
 
-int fsetxattr(int __fd, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
-int setxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
-int lsetxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
+/**
+ * [fsetxattr(2)](http://man7.org/linux/man-pages/man2/fsetxattr.2.html)
+ * sets an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int fsetxattr(int __fd, const char* __name, const void* __value, size_t __size, int __flags);
 
-ssize_t fgetxattr(int __fd, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
-ssize_t getxattr(const char* __path, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
-ssize_t lgetxattr(const char* __path, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
+/**
+ * [setxattr(2)](http://man7.org/linux/man-pages/man2/setxattr.2.html)
+ * sets an extended attribute on the file referred to by the given path.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int setxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags);
 
-ssize_t listxattr(const char* __path, char* __list, size_t __size) __INTRODUCED_IN(16);
-ssize_t llistxattr(const char* __path, char* __list, size_t __size) __INTRODUCED_IN(16);
-ssize_t flistxattr(int __fd, char* __list, size_t __size) __INTRODUCED_IN(16);
+/**
+ * [lsetxattr(2)](http://man7.org/linux/man-pages/man2/lsetxattr.2.html)
+ * sets an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int lsetxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags);
 
-int removexattr(const char* __path, const char* __name) __INTRODUCED_IN(16);
-int lremovexattr(const char* __path, const char* __name) __INTRODUCED_IN(16);
-int fremovexattr(int __fd, const char* __name) __INTRODUCED_IN(16);
+/**
+ * [fgetxattr(2)](http://man7.org/linux/man-pages/man2/fgetxattr.2.html)
+ * gets an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t fgetxattr(int __fd, const char* __name, void* __value, size_t __size);
+
+/**
+ * [getxattr(2)](http://man7.org/linux/man-pages/man2/getxattr.2.html)
+ * gets an extended attribute on the file referred to by the given path.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t getxattr(const char* __path, const char* __name, void* __value, size_t __size);
+
+/**
+ * [lgetxattr(2)](http://man7.org/linux/man-pages/man2/lgetxattr.2.html)
+ * gets an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t lgetxattr(const char* __path, const char* __name, void* __value, size_t __size);
+
+/**
+ * [flistxattr(2)](http://man7.org/linux/man-pages/man2/flistxattr.2.html)
+ * lists the extended attributes on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t flistxattr(int __fd, char* __list, size_t __size);
+
+/**
+ * [listxattr(2)](http://man7.org/linux/man-pages/man2/listxattr.2.html)
+ * lists the extended attributes on the file referred to by the given path.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t listxattr(const char* __path, char* __list, size_t __size);
+
+/**
+ * [llistxattr(2)](http://man7.org/linux/man-pages/man2/llistxattr.2.html)
+ * lists the extended attributes on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t llistxattr(const char* __path, char* __list, size_t __size);
+
+/**
+ * [fremovexattr(2)](http://man7.org/linux/man-pages/man2/fremovexattr.2.html)
+ * removes an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int fremovexattr(int __fd, const char* __name);
+
+/**
+ * [lremovexattr(2)](http://man7.org/linux/man-pages/man2/lremovexattr.2.html)
+ * removes an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int lremovexattr(const char* __path, const char* __name);
+
+/**
+ * [removexattr(2)](http://man7.org/linux/man-pages/man2/removexattr.2.html)
+ * removes an extended attribute on the file referred to by the given path.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int removexattr(const char* __path, const char* __name);
 
 __END_DECLS
-
-#endif
diff --git a/libc/private/ScopedFd.h b/libc/private/ScopedFd.h
index 9b1cd9d..1cec916 100644
--- a/libc/private/ScopedFd.h
+++ b/libc/private/ScopedFd.h
@@ -46,7 +46,7 @@
   }
 
   void reset(int fd = -1) {
-    if (fd != -1) {
+    if (fd_ != -1) {
       ErrnoRestorer e;
       close(fd_);
     }
diff --git a/linker/Android.bp b/linker/Android.bp
index bb9d26d..1800bdb 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -1,22 +1,6 @@
-cc_library_static {
-    name: "liblinker_malloc",
-    defaults: ["linux_bionic_supported"],
-    recovery_available: true,
-    native_bridge_supported: true,
-
-    srcs: [
-        "linker_memory.cpp",
-    ],
-    cflags: [
-        "-Wall",
-        "-Werror",
-    ],
-
-    // We need to access Bionic private headers in the linker.
-    include_dirs: ["bionic/libc"],
-
-    static_libs: ["libasync_safe", "libbase"],
-}
+// ========================================================
+// linker_wrapper - Linux Bionic (on the host)
+// ========================================================
 
 // This is used for bionic on (host) Linux to bootstrap our linker embedded into
 // a binary.
@@ -66,6 +50,103 @@
     include_dirs: ["bionic/libc"],
 }
 
+// ========================================================
+// linker default configuration
+// ========================================================
+
+// Configuration for the linker binary and any of its static libraries.
+cc_defaults {
+    name: "linker_defaults",
+    arch: {
+        arm: {
+            cflags: ["-D__work_around_b_24465209__"],
+        },
+        x86: {
+            cflags: ["-D__work_around_b_24465209__"],
+        },
+    },
+
+    cflags: [
+        "-fno-stack-protector",
+        "-Wstrict-overflow=5",
+        "-fvisibility=hidden",
+        "-Wall",
+        "-Wextra",
+        "-Wunused",
+        "-Werror",
+    ],
+
+    // TODO: split out the asflags.
+    asflags: [
+        "-fno-stack-protector",
+        "-Wstrict-overflow=5",
+        "-fvisibility=hidden",
+        "-Wall",
+        "-Wextra",
+        "-Wunused",
+        "-Werror",
+    ],
+
+    product_variables: {
+        debuggable: {
+            cppflags: ["-DUSE_LD_CONFIG_FILE"],
+        },
+    },
+
+    cppflags: ["-Wold-style-cast"],
+
+    static_libs: [
+        "libziparchive",
+        "libbase",
+        "libz",
+
+        "libasync_safe",
+
+        "liblog",
+    ],
+
+    // We need to access Bionic private headers in the linker.
+    include_dirs: ["bionic/libc"],
+}
+
+// ========================================================
+// linker components
+// ========================================================
+
+// Enable a module on all targets the linker runs on (ordinary Android targets, Linux Bionic, and
+// native bridge implementations).
+cc_defaults {
+    name: "linker_all_targets",
+    defaults: ["linux_bionic_supported"],
+    recovery_available: true,
+    native_bridge_supported: true,
+}
+
+cc_library_static {
+    name: "liblinker_main",
+    defaults: ["linker_defaults", "linker_all_targets"],
+    srcs: ["linker_main.cpp"],
+
+    // Ensure that the compiler won't insert string function calls before ifuncs are resolved.
+    cflags: ["-ffreestanding"],
+}
+
+cc_library_static {
+    name: "liblinker_malloc",
+    defaults: ["linker_defaults", "linker_all_targets"],
+    srcs: ["linker_memory.cpp"],
+}
+
+cc_library_static {
+    name: "liblinker_debuggerd_stub",
+    defaults: ["linker_defaults", "linker_all_targets"],
+    srcs: ["linker_debuggerd_stub.cpp"],
+}
+
+// ========================================================
+// template for the linker binary
+// ========================================================
+
 filegroup {
     name: "linker_sources",
     srcs: [
@@ -79,7 +160,6 @@
         "linker_globals.cpp",
         "linker_libc_support.c",
         "linker_libcxx_support.cpp",
-        "linker_main.cpp",
         "linker_namespaces.cpp",
         "linker_logger.cpp",
         "linker_mapped_file_fragment.cpp",
@@ -137,30 +217,50 @@
     ],
 }
 
-filegroup {
-    name: "linker_version_script",
-    srcs: ["linker.generic.map"],
-}
-
-filegroup {
-    name: "linker_version_script_arm",
-    srcs: ["linker.arm.map"],
-}
-
 cc_defaults {
-    name: "linker_defaults",
+    name: "linker_version_script_overlay",
+    arch: {
+        arm:    { version_script: "linker.arm.map"      },
+        arm64:  { version_script: "linker.generic.map"  },
+        x86:    { version_script: "linker.generic.map"  },
+        x86_64: { version_script: "linker.generic.map"  },
+        mips:   { version_script: "linker.generic.map"  },
+        mips64: { version_script: "linker.generic.map"  },
+    },
+}
+
+// A template for the linker binary. May be inherited by native bridge implementations.
+cc_defaults {
+    name: "linker_bin_template",
+    defaults: ["linker_defaults"],
+
+    srcs: [":linker_sources"],
+
     arch: {
         arm: {
-            cflags: ["-D__work_around_b_24465209__"],
+            srcs: [":linker_sources_arm"],
+            static_libs: ["libunwind_llvm"],
+        },
+        arm64: {
+            srcs: [":linker_sources_arm64"],
         },
         x86: {
-            cflags: ["-D__work_around_b_24465209__"],
+            srcs: [":linker_sources_x86"],
+        },
+        x86_64: {
+            srcs: [":linker_sources_x86_64"],
+        },
+        mips: {
+            srcs: [":linker_sources_mips"],
+        },
+        mips64: {
+            srcs: [":linker_sources_mips64"],
         },
     },
 
-    // -shared is used to overwrite the -Bstatic and -static
-    // flags triggered by LOCAL_FORCE_STATIC_EXECUTABLE.
-    // This dynamic linker is actually a shared object linked with static libraries.
+    // -shared is used to overwrite the -Bstatic and -static flags triggered by enabling
+    // static_executable. This dynamic linker is actually a shared object linked with static
+    // libraries.
     ldflags: [
         "-shared",
         "-Wl,-Bsymbolic",
@@ -168,35 +268,6 @@
         "-Wl,-soname,ld-android.so",
     ],
 
-    cflags: [
-        "-fno-stack-protector",
-        "-Wstrict-overflow=5",
-        "-fvisibility=hidden",
-        "-Wall",
-        "-Wextra",
-        "-Wunused",
-        "-Werror",
-    ],
-
-    // TODO: split out the asflags.
-    asflags: [
-        "-fno-stack-protector",
-        "-Wstrict-overflow=5",
-        "-fvisibility=hidden",
-        "-Wall",
-        "-Wextra",
-        "-Wunused",
-        "-Werror",
-    ],
-
-    product_variables: {
-        debuggable: {
-            cppflags: ["-DUSE_LD_CONFIG_FILE"],
-        },
-    },
-
-    cppflags: ["-Wold-style-cast"],
-
     // we are going to link libc++_static manually because
     // when stl is not set to "none" build system adds libdl
     // to the list of static libraries which needs to be
@@ -222,58 +293,15 @@
     sanitize: {
         hwaddress: false,
     },
-}
-
-cc_binary {
-    defaults: ["linux_bionic_supported", "linker_defaults"],
-    srcs: [ ":linker_sources" ],
-
-    arch: {
-        arm: {
-            srcs: [ ":linker_sources_arm" ],
-            version_script: ":linker_version_script_arm",
-            static_libs: ["libunwind_llvm"],
-        },
-        arm64: {
-            srcs: [":linker_sources_arm64"],
-            version_script: ":linker_version_script",
-        },
-        x86: {
-            srcs: [":linker_sources_x86"],
-            version_script: ":linker_version_script",
-        },
-        x86_64: {
-            srcs: [":linker_sources_x86_64"],
-            version_script: ":linker_version_script",
-        },
-        mips: {
-            srcs: [":linker_sources_mips"],
-            version_script: ":linker_version_script",
-        },
-        mips64: {
-            srcs: [":linker_sources_mips64"],
-            version_script: ":linker_version_script",
-        },
-    },
-
-    // We need to access Bionic private headers in the linker.
-    include_dirs: ["bionic/libc"],
 
     static_libs: [
-        "libc_nomalloc",
-        "libm",
-        "libziparchive",
-        "libbase",
-        "libz",
-
-        "libasync_safe",
-
-        "liblog",
-        "libc++_static",
-
-        // Important: The liblinker_malloc should be the last library in the list
-        // to overwrite any other malloc implementations by other static libraries.
+        "liblinker_main",
         "liblinker_malloc",
+
+        "libc++_static",
+        "libc_nomalloc",
+        "libc_dynamic_dispatch",
+        "libm",
     ],
 
     // Ensure that if the linker needs __gnu_Unwind_Find_exidx, then the linker will have a
@@ -287,9 +315,25 @@
     // linker stops linking against libgcc.a's arm32 unwinder.
     whole_static_libs: ["libc_unwind_static"],
 
+    system_shared_libs: [],
+
+    // Opt out of native_coverage when opting out of system_shared_libs
+    native_coverage: false,
+}
+
+// ========================================================
+// linker[_asan][64] binary
+// ========================================================
+
+cc_binary {
     name: "linker",
+    defaults: [
+        "linker_bin_template",
+        "linux_bionic_supported",
+        "linker_version_script_overlay",
+    ],
+
     symlinks: ["linker_asan"],
-    recovery_available: true,
     multilib: {
         lib32: {
             cflags: ["-DLIB_PATH=\"lib\""],
@@ -299,28 +343,38 @@
             suffix: "64",
         },
     },
-    system_shared_libs: [],
 
-    // Opt out of native_coverage when opting out of system_shared_libs
-    native_coverage: false,
+    compile_multilib: "both",
+    xom: false,
+
+    recovery_available: true,
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.runtime",
+    ],
 
     target: {
         android: {
+            srcs: [
+                "linker_debuggerd_android.cpp",
+            ],
             static_libs: [
                 "libc++demangle",
                 "libdebuggerd_handler_fallback",
             ],
         },
+        linux_bionic: {
+            static_libs: [
+                "liblinker_debuggerd_stub",
+            ],
+        }
     },
-    compile_multilib: "both",
-    xom: false,
-
-    apex_available: [
-        "//apex_available:platform",
-        "com.android.runtime",
-    ],
 }
 
+// ========================================================
+// assorted modules
+// ========================================================
+
 sh_binary {
     name: "ldd",
     src: "ldd",
@@ -347,25 +401,11 @@
 
     // for x86, exclude libgcc_eh.a for the same reasons as above
     arch: {
-        arm: {
-            version_script: "linker.arm.map",
-        },
-        arm64: {
-            version_script: "linker.generic.map",
-        },
         x86: {
             ldflags: ["-Wl,--exclude-libs=libgcc_eh.a"],
-            version_script: "linker.generic.map",
         },
         x86_64: {
             ldflags: ["-Wl,--exclude-libs=libgcc_eh.a"],
-            version_script: "linker.generic.map",
-        },
-        mips: {
-            version_script: "linker.generic.map",
-        },
-        mips64: {
-            version_script: "linker.generic.map",
         },
     },
 
@@ -379,7 +419,7 @@
     stl: "none",
 
     name: "ld-android",
-    defaults: ["linux_bionic_supported"],
+    defaults: ["linux_bionic_supported", "linker_version_script_overlay"],
     recovery_available: true,
     native_bridge_supported: true,
 
diff --git a/linker/linker.cpp b/linker/linker.cpp
index eedce70..1393eb5 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -3162,7 +3162,10 @@
         TRACE_TYPE(RELO, "RELO IRELATIVE %16p <- %16p\n",
                     reinterpret_cast<void*>(reloc),
                     reinterpret_cast<void*>(load_bias + addend));
-        {
+        // In the linker, ifuncs are called as soon as possible so that string functions work.
+        // We must not call them again. (e.g. On arm32, resolving an ifunc changes the meaning of
+        // the addend from a resolver function to the implementation.)
+        if (!is_linker()) {
 #if !defined(__LP64__)
           // When relocating dso with text_relocation .text segment is
           // not executable. We need to restore elf flags for this
diff --git a/linker/linker_debuggerd.h b/linker/linker_debuggerd.h
new file mode 100644
index 0000000..d701879
--- /dev/null
+++ b/linker/linker_debuggerd.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+void linker_debuggerd_init();
diff --git a/linker/linker_debuggerd_android.cpp b/linker/linker_debuggerd_android.cpp
new file mode 100644
index 0000000..b8c82f9
--- /dev/null
+++ b/linker/linker_debuggerd_android.cpp
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "linker_debuggerd.h"
+
+#include "debuggerd/handler.h"
+#include "private/bionic_globals.h"
+
+#include "linker_gdb_support.h"
+
+void linker_debuggerd_init() {
+  debuggerd_callbacks_t callbacks = {
+    .get_abort_message = []() {
+      return __libc_shared_globals()->abort_msg;
+    },
+    .post_dump = &notify_gdb_of_libraries,
+  };
+  debuggerd_init(&callbacks);
+}
diff --git a/linker/linker_debuggerd_stub.cpp b/linker/linker_debuggerd_stub.cpp
new file mode 100644
index 0000000..631e6e4
--- /dev/null
+++ b/linker/linker_debuggerd_stub.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "linker_debuggerd.h"
+
+void linker_debuggerd_init() {
+}
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index bea2e3c..8ba947f 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -32,6 +32,7 @@
 #include <sys/auxv.h>
 
 #include "linker_debug.h"
+#include "linker_debuggerd.h"
 #include "linker_cfi.h"
 #include "linker_gdb_support.h"
 #include "linker_globals.h"
@@ -39,6 +40,8 @@
 #include "linker_tls.h"
 #include "linker_utils.h"
 
+#include "private/bionic_auxv.h"
+#include "private/bionic_call_ifunc_resolver.h"
 #include "private/bionic_globals.h"
 #include "private/bionic_tls.h"
 #include "private/KernelArgumentBlock.h"
@@ -46,9 +49,6 @@
 #include "android-base/unique_fd.h"
 #include "android-base/strings.h"
 #include "android-base/stringprintf.h"
-#ifdef __ANDROID__
-#include "debuggerd/handler.h"
-#endif
 
 #include <async_safe/log.h>
 #include <bionic/libc_init_common.h>
@@ -311,15 +311,7 @@
   __system_properties_init(); // may use 'environ'
 
   // Register the debuggerd signal handler.
-#ifdef __ANDROID__
-  debuggerd_callbacks_t callbacks = {
-    .get_abort_message = []() {
-      return __libc_shared_globals()->abort_msg;
-    },
-    .post_dump = &notify_gdb_of_libraries,
-  };
-  debuggerd_init(&callbacks);
-#endif
+  linker_debuggerd_init();
 
   g_linker_logger.ResetState();
 
@@ -575,6 +567,39 @@
   }
 }
 
+// TODO: There is a similar ifunc resolver calling loop in libc_init_static.cpp, but that version
+// uses weak symbols, which don't work in the linker prior to its relocation. This version also
+// supports a load bias. When we stop supporting the gold linker in the NDK, then maybe we can use
+// non-weak definitions and merge the two loops.
+#if defined(USE_RELA)
+extern __LIBC_HIDDEN__ ElfW(Rela) __rela_iplt_start[], __rela_iplt_end[];
+
+static void call_ifunc_resolvers(ElfW(Addr) load_bias) {
+  for (ElfW(Rela) *r = __rela_iplt_start; r != __rela_iplt_end; ++r) {
+    ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset + load_bias);
+    ElfW(Addr) resolver = r->r_addend + load_bias;
+    *offset = __bionic_call_ifunc_resolver(resolver);
+  }
+}
+#else
+extern __LIBC_HIDDEN__ ElfW(Rel) __rel_iplt_start[], __rel_iplt_end[];
+
+static void call_ifunc_resolvers(ElfW(Addr) load_bias) {
+  for (ElfW(Rel) *r = __rel_iplt_start; r != __rel_iplt_end; ++r) {
+    ElfW(Addr)* offset = reinterpret_cast<ElfW(Addr)*>(r->r_offset + load_bias);
+    ElfW(Addr) resolver = *offset + load_bias;
+    *offset = __bionic_call_ifunc_resolver(resolver);
+  }
+}
+#endif
+
+// Usable before ifunc resolvers have been called. This function is compiled with -ffreestanding.
+static void linker_memclr(void* dst, size_t cnt) {
+  for (size_t i = 0; i < cnt; ++i) {
+    reinterpret_cast<char*>(dst)[i] = '\0';
+  }
+}
+
 // Detect an attempt to run the linker on itself. e.g.:
 //   /system/bin/linker64 /system/bin/linker64
 // Use priority-1 to run this constructor before other constructors.
@@ -608,7 +633,8 @@
 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
   // Initialize TLS early so system calls and errno work.
   KernelArgumentBlock args(raw_args);
-  bionic_tcb temp_tcb = {};
+  bionic_tcb temp_tcb __attribute__((uninitialized));
+  linker_memclr(&temp_tcb, sizeof(temp_tcb));
   __libc_init_main_thread_early(args, &temp_tcb);
 
   // When the linker is run by itself (rather than as an interpreter for
@@ -626,11 +652,15 @@
   ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
   ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
 
+  // string.h functions must not be used prior to calling the linker's ifunc resolvers.
+  const ElfW(Addr) load_bias = get_elf_exec_load_bias(elf_hdr);
+  call_ifunc_resolvers(load_bias);
+
   soinfo tmp_linker_so(nullptr, nullptr, nullptr, 0, 0);
 
   tmp_linker_so.base = linker_addr;
   tmp_linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
-  tmp_linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
+  tmp_linker_so.load_bias = load_bias;
   tmp_linker_so.dynamic = nullptr;
   tmp_linker_so.phdr = phdr;
   tmp_linker_so.phnum = elf_hdr->e_phnum;
diff --git a/tests/leak_test.cpp b/tests/leak_test.cpp
index 3cc1a0a..e0a3d57 100644
--- a/tests/leak_test.cpp
+++ b/tests/leak_test.cpp
@@ -127,22 +127,20 @@
 // http://b/36045112
 TEST(pthread_leak, detach) {
   LeakChecker lc;
-  constexpr int kThreadCount = 100;
 
-  // Devices with low power cores/low number of cores can not finish test in time hence decreasing
-  // threads count to 90.
-  // http://b/129924384.
-  int threads_count = (sysconf(_SC_NPROCESSORS_CONF) > 2) ? kThreadCount : (kThreadCount - 10);
+  // Ancient devices with only 2 cores need a lower limit.
+  // http://b/129924384 and https://issuetracker.google.com/142210680.
+  const int thread_count = (sysconf(_SC_NPROCESSORS_CONF) > 2) ? 100 : 50;
 
   for (size_t pass = 0; pass < 1; ++pass) {
-    struct thread_data { pthread_barrier_t* barrier; pid_t* tid; } threads[kThreadCount] = {};
+    struct thread_data { pthread_barrier_t* barrier; pid_t* tid; } threads[thread_count];
 
     pthread_barrier_t barrier;
-    ASSERT_EQ(pthread_barrier_init(&barrier, nullptr, threads_count + 1), 0);
+    ASSERT_EQ(pthread_barrier_init(&barrier, nullptr, thread_count + 1), 0);
 
     // Start child threads.
-    pid_t tids[kThreadCount];
-    for (int i = 0; i < threads_count; ++i) {
+    pid_t tids[thread_count];
+    for (int i = 0; i < thread_count; ++i) {
       threads[i] = {&barrier, &tids[i]};
       const auto thread_function = +[](void* ptr) -> void* {
         thread_data* data = static_cast<thread_data*>(ptr);
@@ -158,7 +156,7 @@
     pthread_barrier_wait(&barrier);
     ASSERT_EQ(pthread_barrier_destroy(&barrier), 0);
 
-    WaitUntilAllThreadsExited(tids, threads_count);
+    WaitUntilAllThreadsExited(tids, thread_count);
 
     // A native bridge implementation might need a warm up pass to reach a steady state.
     // http://b/37920774.
diff --git a/tests/system_properties_test2.cpp b/tests/system_properties_test2.cpp
index b9936dd..0953bde 100644
--- a/tests/system_properties_test2.cpp
+++ b/tests/system_properties_test2.cpp
@@ -14,8 +14,6 @@
  * limitations under the License.
  */
 
-#include <gtest/gtest.h>
-
 #include <errno.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -24,6 +22,10 @@
 #include <sstream>
 #include <string>
 
+#include <gtest/gtest.h>
+
+#include "utils.h"
+
 #if defined(__BIONIC__)
 #include <sys/system_properties.h>
 int64_t NanoTime() {
@@ -128,6 +130,29 @@
 #endif // __BIONIC__
 }
 
+TEST(properties, no_fd_leaks) {
+#if defined(__BIONIC__)
+  FdLeakChecker leak_checker;
+  std::stringstream ss;
+  ss << "debug.test." << getpid() << "." << NanoTime() << ".";
+  const std::string property_prefix = ss.str();
+  const std::string property_name = property_prefix + "property1";
+
+  for (size_t i = 0; i < 100; ++i) {
+    char propvalue[PROP_VALUE_MAX];
+    ASSERT_EQ(0, __system_property_set(property_name.c_str(), "value1"));
+    ASSERT_EQ(6, __system_property_get(property_name.c_str(), propvalue));
+    ASSERT_STREQ("value1", propvalue);
+
+    ASSERT_EQ(0, __system_property_set(property_name.c_str(), "value2"));
+    ASSERT_EQ(6, __system_property_get(property_name.c_str(), propvalue));
+    ASSERT_STREQ("value2", propvalue);
+  }
+#else   // __BIONIC__
+  GTEST_SKIP() << "bionic-only test";
+#endif  // __BIONIC__
+}
+
 TEST(properties, empty_value) {
 #if defined(__BIONIC__)
     char propvalue[PROP_VALUE_MAX];
@@ -136,13 +161,13 @@
     ss << "debug.test." << getpid() << "." << NanoTime() << "." << "property_empty";
     const std::string property_name = ss.str();
 
-    for (size_t i=0; i<1000; ++i) {
+    for (size_t i = 0; i < 1000; ++i) {
       ASSERT_EQ(0, __system_property_set(property_name.c_str(), ""));
       ASSERT_EQ(0, __system_property_get(property_name.c_str(), propvalue));
       ASSERT_STREQ("", propvalue);
     }
 
-#else // __BIONIC__
-    GTEST_SKIP() << "bionic-only test";
+#else  // __BIONIC__
+  GTEST_SKIP() << "bionic-only test";
 #endif // __BIONIC__
 }
diff --git a/tests/utils.h b/tests/utils.h
index 1f4cece..cfc68c9 100644
--- a/tests/utils.h
+++ b/tests/utils.h
@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <dirent.h>
 #include <dlfcn.h>
 #include <fcntl.h>
 #include <inttypes.h>
@@ -253,3 +254,29 @@
   std::string output_;
 };
 #endif
+
+class FdLeakChecker {
+ public:
+  FdLeakChecker() {
+  }
+
+  ~FdLeakChecker() {
+    size_t end_count = CountOpenFds();
+    EXPECT_EQ(start_count_, end_count);
+  }
+
+ private:
+  static size_t CountOpenFds() {
+    auto fd_dir = std::unique_ptr<DIR, decltype(&closedir)>{ opendir("/proc/self/fd"), closedir };
+    size_t count = 0;
+    dirent* de = nullptr;
+    while ((de = readdir(fd_dir.get())) != nullptr) {
+      if (de->d_type == DT_LNK) {
+        ++count;
+      }
+    }
+    return count;
+  }
+
+  size_t start_count_ = CountOpenFds();
+};