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// Copyright (c) 2011, Google Inc.
// 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.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// 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.
// crash_generator.cc: Implement google_breakpad::CrashGenerator.
// See crash_generator.h for details.
#include "common/linux/tests/crash_generator.h"
#include <pthread.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>
#include <string>
#if defined(__ANDROID__)
#include "common/android/testing/pthread_fixes.h"
#endif
#include "common/linux/eintr_wrapper.h"
#include "common/tests/auto_tempdir.h"
#include "common/tests/file_utils.h"
#include "common/using_std_string.h"
namespace {
struct ThreadData {
pthread_t thread;
pthread_barrier_t* barrier;
pid_t* thread_id_ptr;
};
const char* const kProcFilesToCopy[] = {
"auxv", "cmdline", "environ", "maps", "status"
};
const size_t kNumProcFilesToCopy =
sizeof(kProcFilesToCopy) / sizeof(kProcFilesToCopy[0]);
int gettid() {
// Glibc does not provide a wrapper for this.
return syscall(__NR_gettid);
}
int tkill(pid_t tid, int sig) {
// Glibc does not provide a wrapper for this.
return syscall(__NR_tkill, tid, sig);
}
// Core file size limit set to 1 MB, which is big enough for test purposes.
const rlim_t kCoreSizeLimit = 1024 * 1024;
void *thread_function(void *data) {
ThreadData* thread_data = reinterpret_cast<ThreadData*>(data);
volatile pid_t thread_id = gettid();
*(thread_data->thread_id_ptr) = thread_id;
int result = pthread_barrier_wait(thread_data->barrier);
if (result != 0 && result != PTHREAD_BARRIER_SERIAL_THREAD) {
perror("Failed to wait for sync barrier");
exit(1);
}
while (true) {
sched_yield();
}
}
} // namespace
namespace google_breakpad {
CrashGenerator::CrashGenerator()
: shared_memory_(NULL),
shared_memory_size_(0) {
}
CrashGenerator::~CrashGenerator() {
UnmapSharedMemory();
}
bool CrashGenerator::HasDefaultCorePattern() const {
char buffer[8];
ssize_t buffer_size = sizeof(buffer);
return ReadFile("/proc/sys/kernel/core_pattern", buffer, &buffer_size) &&
buffer_size == 5 && memcmp(buffer, "core", 4) == 0;
}
string CrashGenerator::GetCoreFilePath() const {
return temp_dir_.path() + "/core";
}
string CrashGenerator::GetDirectoryOfProcFilesCopy() const {
return temp_dir_.path() + "/proc";
}
pid_t CrashGenerator::GetThreadId(unsigned index) const {
return reinterpret_cast<pid_t*>(shared_memory_)[index];
}
pid_t* CrashGenerator::GetThreadIdPointer(unsigned index) {
return reinterpret_cast<pid_t*>(shared_memory_) + index;
}
bool CrashGenerator::MapSharedMemory(size_t memory_size) {
if (!UnmapSharedMemory())
return false;
void* mapped_memory = mmap(0, memory_size, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
if (mapped_memory == MAP_FAILED) {
perror("CrashGenerator: Failed to map shared memory");
return false;
}
memset(mapped_memory, 0, memory_size);
shared_memory_ = mapped_memory;
shared_memory_size_ = memory_size;
return true;
}
bool CrashGenerator::UnmapSharedMemory() {
if (!shared_memory_)
return true;
if (munmap(shared_memory_, shared_memory_size_) == 0) {
shared_memory_ = NULL;
shared_memory_size_ = 0;
return true;
}
perror("CrashGenerator: Failed to unmap shared memory");
return false;
}
bool CrashGenerator::SetCoreFileSizeLimit(rlim_t limit) const {
struct rlimit limits = { limit, limit };
if (setrlimit(RLIMIT_CORE, &limits) == -1) {
perror("CrashGenerator: Failed to set core file size limit");
return false;
}
return true;
}
bool CrashGenerator::CreateChildCrash(
unsigned num_threads, unsigned crash_thread, int crash_signal,
pid_t* child_pid) {
if (num_threads == 0 || crash_thread >= num_threads) {
fprintf(stderr, "CrashGenerator: Invalid thread counts; num_threads=%u"
" crash_thread=%u\n", num_threads, crash_thread);
return false;
}
if (!MapSharedMemory(num_threads * sizeof(pid_t))) {
perror("CrashGenerator: Unable to map shared memory");
return false;
}
pid_t pid = fork();
if (pid == 0) {
// Custom signal handlers, which may have been installed by a test launcher,
// are undesirable in this child.
if (signal(crash_signal, SIG_DFL) == SIG_ERR) {
perror("CrashGenerator: signal");
exit(1);
}
if (chdir(temp_dir_.path().c_str()) == -1) {
perror("CrashGenerator: Failed to change directory");
exit(1);
}
if (SetCoreFileSizeLimit(kCoreSizeLimit)) {
CreateThreadsInChildProcess(num_threads);
string proc_dir = GetDirectoryOfProcFilesCopy();
if (mkdir(proc_dir.c_str(), 0755) == -1) {
perror("CrashGenerator: Failed to create proc directory");
exit(1);
}
if (!CopyProcFiles(getpid(), proc_dir.c_str())) {
fprintf(stderr, "CrashGenerator: Failed to copy proc files\n");
exit(1);
}
// On Android the signal sometimes doesn't seem to get sent even though
// tkill returns '0'. Retry a couple of times if the signal doesn't get
// through on the first go:
#if defined(__ANDROID__)
const int kRetries = 60;
const unsigned int kSleepTimeInSeconds = 1;
#else
const int kRetries = 1;
const unsigned int kSleepTimeInSeconds = 600;
#endif
for (int i = 0; i < kRetries; i++) {
if (tkill(*GetThreadIdPointer(crash_thread), crash_signal) == -1) {
perror("CrashGenerator: Failed to kill thread by signal");
} else {
// At this point, we've queued the signal for delivery, but there's no
// guarantee when it'll be delivered. We don't want the main thread to
// race and exit before the thread we signaled is processed. So sleep
// long enough that we won't flake even under fairly high load.
// TODO: See if we can't be a bit more deterministic. There doesn't
// seem to be an API to check on signal delivery status, so we can't
// really poll and wait for the kernel to declare the signal has been
// delivered. If it has, and things worked, we'd be killed, so the
// sleep length doesn't really matter.
sleep(kSleepTimeInSeconds);
}
}
} else {
perror("CrashGenerator: Failed to set core limit");
}
exit(1);
} else if (pid == -1) {
perror("CrashGenerator: Failed to create child process");
return false;
}
int status;
if (HANDLE_EINTR(waitpid(pid, &status, 0)) == -1) {
perror("CrashGenerator: Failed to wait for child process");
return false;
}
if (!WIFSIGNALED(status) || WTERMSIG(status) != crash_signal) {
fprintf(stderr, "CrashGenerator: Child process not killed by the expected signal\n"
" exit status=0x%x pid=%u signaled=%s sig=%d expected=%d\n",
status, pid, WIFSIGNALED(status) ? "true" : "false",
WTERMSIG(status), crash_signal);
return false;
}
if (child_pid)
*child_pid = pid;
return true;
}
bool CrashGenerator::CopyProcFiles(pid_t pid, const char* path) const {
char from_path[PATH_MAX], to_path[PATH_MAX];
for (size_t i = 0; i < kNumProcFilesToCopy; ++i) {
int num_chars = snprintf(from_path, PATH_MAX, "/proc/%d/%s",
pid, kProcFilesToCopy[i]);
if (num_chars < 0 || num_chars >= PATH_MAX)
return false;
num_chars = snprintf(to_path, PATH_MAX, "%s/%s",
path, kProcFilesToCopy[i]);
if (num_chars < 0 || num_chars >= PATH_MAX)
return false;
if (!CopyFile(from_path, to_path))
return false;
}
return true;
}
void CrashGenerator::CreateThreadsInChildProcess(unsigned num_threads) {
*GetThreadIdPointer(0) = getpid();
if (num_threads <= 1)
return;
// This method does not clean up any pthread resource, as the process
// is expected to be killed anyway.
ThreadData* thread_data = new ThreadData[num_threads];
// Create detached threads so that we do not worry about pthread_join()
// later being called or not.
pthread_attr_t thread_attributes;
if (pthread_attr_init(&thread_attributes) != 0 ||
pthread_attr_setdetachstate(&thread_attributes,
PTHREAD_CREATE_DETACHED) != 0) {
fprintf(stderr, "CrashGenerator: Failed to initialize thread attribute\n");
exit(1);
}
pthread_barrier_t thread_barrier;
if (pthread_barrier_init(&thread_barrier, NULL, num_threads) != 0) {
fprintf(stderr, "CrashGenerator: Failed to initialize thread barrier\n");
exit(1);
}
for (unsigned i = 1; i < num_threads; ++i) {
thread_data[i].barrier = &thread_barrier;
thread_data[i].thread_id_ptr = GetThreadIdPointer(i);
if (pthread_create(&thread_data[i].thread, &thread_attributes,
thread_function, &thread_data[i]) != 0) {
fprintf(stderr, "CrashGenerator: Failed to create thread %d\n", i);
exit(1);
}
}
int result = pthread_barrier_wait(&thread_barrier);
if (result != 0 && result != PTHREAD_BARRIER_SERIAL_THREAD) {
fprintf(stderr, "CrashGenerator: Failed to wait for thread barrier\n");
exit(1);
}
pthread_barrier_destroy(&thread_barrier);
pthread_attr_destroy(&thread_attributes);
delete[] thread_data;
}
} // namespace google_breakpad