crash_dump: fork a copy of the target's address space.
Reduce the amount of time that a process remains paused by pausing its
threads, fetching their registers, and then performing unwinding on a
copy of its address space. This also works around a kernel change
that's in 4.9 that prevents ptrace from reading memory of processes
that we don't have immediate permissions to ptrace (even if we
previously ptraced them).
Bug: http://b/62112103
Bug: http://b/63989615
Test: treehugger
Change-Id: I7b9cc5dd8f54a354bc61f1bda0d2b7a8a55733c4
diff --git a/debuggerd/libdebuggerd/backtrace.cpp b/debuggerd/libdebuggerd/backtrace.cpp
index f616e1b..f0a01f4 100644
--- a/debuggerd/libdebuggerd/backtrace.cpp
+++ b/debuggerd/libdebuggerd/backtrace.cpp
@@ -30,12 +30,15 @@
#include <time.h>
#include <unistd.h>
+#include <map>
#include <memory>
#include <string>
+#include <android-base/unique_fd.h>
#include <backtrace/Backtrace.h>
#include <log/log.h>
+#include "libdebuggerd/types.h"
#include "libdebuggerd/utility.h"
static void dump_process_header(log_t* log, pid_t pid, const char* process_name) {
@@ -56,62 +59,46 @@
_LOG(log, logtype::BACKTRACE, "\n----- end %d -----\n", pid);
}
-static void log_thread_name(log_t* log, pid_t tid, const char* thread_name) {
- _LOG(log, logtype::BACKTRACE, "\n\"%s\" sysTid=%d\n", thread_name, tid);
-}
-
-static void dump_thread(log_t* log, BacktraceMap* map, pid_t pid, pid_t tid,
- const std::string& thread_name) {
- log_thread_name(log, tid, thread_name.c_str());
-
- std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, tid, map));
- if (backtrace->Unwind(0)) {
- dump_backtrace_to_log(backtrace.get(), log, " ");
- } else {
- ALOGE("Unwind failed: tid = %d: %s", tid,
- backtrace->GetErrorString(backtrace->GetError()).c_str());
- }
-}
-
-void dump_backtrace(int fd, BacktraceMap* map, pid_t pid, pid_t tid, const std::string& process_name,
- const std::map<pid_t, std::string>& threads, std::string* amfd_data) {
- log_t log;
- log.tfd = fd;
- log.amfd_data = amfd_data;
-
- dump_process_header(&log, pid, process_name.c_str());
- dump_thread(&log, map, pid, tid, threads.find(tid)->second.c_str());
-
- for (const auto& it : threads) {
- pid_t thread_tid = it.first;
- const std::string& thread_name = it.second;
- if (thread_tid != tid) {
- dump_thread(&log, map, pid, thread_tid, thread_name.c_str());
- }
- }
-
- dump_process_footer(&log, pid);
-}
-
-void dump_backtrace_ucontext(int output_fd, ucontext_t* ucontext) {
- pid_t pid = getpid();
- pid_t tid = gettid();
-
+void dump_backtrace_thread(int output_fd, BacktraceMap* map, const ThreadInfo& thread) {
log_t log;
log.tfd = output_fd;
log.amfd_data = nullptr;
- char thread_name[16];
- read_with_default("/proc/self/comm", thread_name, sizeof(thread_name), "<unknown>");
- log_thread_name(&log, tid, thread_name);
+ _LOG(&log, logtype::BACKTRACE, "\n\"%s\" sysTid=%d\n", thread.thread_name.c_str(), thread.tid);
- std::unique_ptr<Backtrace> backtrace(Backtrace::Create(pid, tid));
- if (backtrace->Unwind(0, ucontext)) {
- dump_backtrace_to_log(backtrace.get(), &log, " ");
- } else {
- ALOGE("Unwind failed: tid = %d: %s", tid,
- backtrace->GetErrorString(backtrace->GetError()).c_str());
+ std::vector<backtrace_frame_data_t> frames;
+ if (!Backtrace::Unwind(thread.registers.get(), map, &frames, 0, nullptr)) {
+ _LOG(&log, logtype::THREAD, "Unwind failed: tid = %d", thread.tid);
+ return;
}
+
+ for (auto& frame : frames) {
+ _LOG(&log, logtype::BACKTRACE, " %s\n", Backtrace::FormatFrameData(&frame).c_str());
+ }
+}
+
+void dump_backtrace(android::base::unique_fd output_fd, BacktraceMap* map,
+ const std::map<pid_t, ThreadInfo>& thread_info, pid_t target_thread) {
+ log_t log;
+ log.tfd = output_fd.get();
+ log.amfd_data = nullptr;
+
+ auto target = thread_info.find(target_thread);
+ if (target == thread_info.end()) {
+ ALOGE("failed to find target thread in thread info");
+ return;
+ }
+
+ dump_process_header(&log, target->second.pid, target->second.process_name.c_str());
+
+ dump_backtrace_thread(output_fd.get(), map, target->second);
+ for (const auto& [tid, info] : thread_info) {
+ if (tid != target_thread) {
+ dump_backtrace_thread(output_fd.get(), map, info);
+ }
+ }
+
+ dump_process_footer(&log, target->second.pid);
}
void dump_backtrace_header(int output_fd) {
@@ -131,9 +118,3 @@
dump_process_footer(&log, getpid());
}
-
-void dump_backtrace_to_log(Backtrace* backtrace, log_t* log, const char* prefix) {
- for (size_t i = 0; i < backtrace->NumFrames(); i++) {
- _LOG(log, logtype::BACKTRACE, "%s%s\n", prefix, backtrace->FormatFrameData(i).c_str());
- }
-}