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Commit a16a4e10 authored by Christopher Ferris's avatar Christopher Ferris
Browse files

Fix problems in libbacktrace. 

- Add a wait for stop to backtrace_test. There is a possible race
  condition that is exposed when using libunwind.
- Fix a few calls to unwind function calls.

Bug: 8410085
Change-Id: I7487d687f6d4b7b05b8a96ad1c5f7183681e5c95
parent 61afb07b

libbacktrace/backtrace_test.c

+22 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <signal.h>

#include <sys/ptrace.h>

#include <sys/wait.h>

#include <errno.h>

#include <unistd.h>

#include <inttypes.h>
@@ -29,6 +30,8 @@ 


#define FINISH(pid) dump_frames(&backtrace); if (pid < 0) exit(1); else return false;



#define WAIT_INTERVAL_USECS   1000



// Prototypes for functions in the test library.

int test_level_one(int, int, int, int, bool (*)(pid_t));
@@ -52,6 +55,21 @@ void dump_frames(const backtrace_t* backtrace) { 
  }

}



void wait_for_stop(pid_t pid, size_t max_usecs_to_wait) {

  siginfo_t si;

  size_t usecs_waited = 0;



  while (ptrace(PTRACE_GETSIGINFO, pid, 0, &si) < 0 && (errno == EINTR || errno == ESRCH)) {

    if (usecs_waited >= max_usecs_to_wait) {

      printf("The process did not get to a stopping point in %zu usecs.\n",

             usecs_waited);

      break;

    }

    usleep(WAIT_INTERVAL_USECS);

    usecs_waited += WAIT_INTERVAL_USECS;

  }

}



bool check_frame(const backtrace_t* backtrace, size_t frame_num,

                 const char* expected_name) {

  if (backtrace->frames[frame_num].proc_name == NULL) {
@@ -153,6 +171,10 @@ void verify_proc_test(pid_t pid, bool (*verify_func)(pid_t)) { 
    kill(pid, SIGKILL);

    exit(1);

  }



  // Wait up to 1 second for the process to get to a point that we can trace it.

  wait_for_stop(pid, 1000000);



  bool pass = verify_func(pid);

  if (ptrace(PTRACE_DETACH, pid, 0, 0) != 0) {

    printf("Failed to detach from pid %d\n", pid);

libbacktrace/unwind_local.c

+10 −3
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ static bool local_get_frames(backtrace_t* backtrace) { 
  bool returnValue = true;

  backtrace->num_frames = 0;

  uintptr_t map_start;

  unw_word_t value;

  do {

    frame = &backtrace->frames[backtrace->num_frames];

    frame->stack_size = 0;
@@ -56,18 +57,21 @@ static bool local_get_frames(backtrace_t* backtrace) { 
    frame->proc_name = NULL;

    frame->proc_offset = 0;



    ret = unw_get_reg(&cursor, UNW_REG_IP, &frame->pc);

    ret = unw_get_reg(&cursor, UNW_REG_IP, &value);

    if (ret < 0) {

      ALOGW("get_frames: Failed to read IP %d\n", ret);

      returnValue = false;

      break;

    }

    ret = unw_get_reg(&cursor, UNW_REG_SP, &frame->sp);

    frame->pc = (uintptr_t)value;

    ret = unw_get_reg(&cursor, UNW_REG_SP, &value);

    if (ret < 0) {

      ALOGW("get_frames: Failed to read IP %d\n", ret);

      returnValue = false;

      break;

    }

    frame->sp = (uintptr_t)value;



    if (backtrace->num_frames) {

      backtrace_frame_data_t* prev = &backtrace->frames[backtrace->num_frames-1];

      prev->stack_size = frame->sp - prev->sp;
@@ -111,8 +115,11 @@ char* local_get_proc_name(const backtrace_t* backtrace, uintptr_t pc, 
  unw_context_t* context = (unw_context_t*)backtrace->private_data;

  char buf[512];



  *offset = 0;

  unw_word_t value;

  if (unw_get_proc_name_by_ip(unw_local_addr_space, pc, buf, sizeof(buf),

                              offset, context) >= 0 && buf[0] != '\0') {

                              &value, context) >= 0 && buf[0] != '\0') {

    *offset = (uintptr_t)value;

    char* symbol = demangle_symbol_name(buf);

    if (!symbol) {

      symbol = strdup(buf);

libbacktrace/unwind_remote.c

+10 −3
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ static bool remote_get_frames(backtrace_t* backtrace) { 
  bool returnValue = true;

  backtrace->num_frames = 0;

  uintptr_t map_start;

  unw_word_t value;

  do {

    frame = &backtrace->frames[backtrace->num_frames];

    frame->stack_size = 0;
@@ -54,18 +55,21 @@ static bool remote_get_frames(backtrace_t* backtrace) { 
    frame->proc_name = NULL;

    frame->proc_offset = 0;



    ret = unw_get_reg(&cursor, UNW_REG_IP, &frame->pc);

    ret = unw_get_reg(&cursor, UNW_REG_IP, &value);

    if (ret < 0) {

      ALOGW("remote_get_frames: Failed to read IP %d\n", ret);

      returnValue = false;

      break;

    }

    ret = unw_get_reg(&cursor, UNW_REG_SP, &frame->sp);

    frame->pc = (uintptr_t)value;

    ret = unw_get_reg(&cursor, UNW_REG_SP, &value);

    if (ret < 0) {

      ALOGW("remote_get_frames: Failed to read SP %d\n", ret);

      returnValue = false;

      break;

    }

    frame->sp = (uintptr_t)value;



    if (backtrace->num_frames) {

      backtrace_frame_data_t* prev = &backtrace->frames[backtrace->num_frames-1];

      prev->stack_size = frame->sp - prev->sp;
@@ -139,8 +143,11 @@ char* remote_get_proc_name(const backtrace_t* backtrace, uintptr_t pc, 
  backtrace_private_t* data = (backtrace_private_t*)backtrace->private_data;

  char buf[512];



  if (unw_get_proc_name_by_ip(data->addr_space, pc, buf, sizeof(buf), offset,

  *offset = 0;

  unw_word_t value;

  if (unw_get_proc_name_by_ip(data->addr_space, pc, buf, sizeof(buf), &value,

                              data->upt_info) >= 0 && buf[0] != '\0') {

    *offset = (uintptr_t)value;

    char* symbol = demangle_symbol_name(buf);

    if (!symbol) {

      symbol = strdup(buf);