/*
* Copyright (C) 2017 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 <dirent.h>
#include <fcntl.h>
#include <poll.h>
#include <pthread.h>
#include <stddef.h>
#include <sys/ucontext.h>
#include <syscall.h>
#include <unistd.h>
#include <atomic>
#include <memory>
#include <android-base/file.h>
#include <android-base/unique_fd.h>
#include <async_safe/log.h>
#include <backtrace/BacktraceMap.h>
#include <unwindstack/Memory.h>
#include <unwindstack/Regs.h>
#include "debuggerd/handler.h"
#include "tombstoned/tombstoned.h"
#include "util.h"
#include "libdebuggerd/backtrace.h"
#include "libdebuggerd/tombstone.h"
using android::base::unique_fd;
using unwindstack::Regs;
extern "C" void __linker_enable_fallback_allocator();
extern "C" void __linker_disable_fallback_allocator();
// This is incredibly sketchy to do inside of a signal handler, especially when libbacktrace
// uses the C++ standard library throughout, but this code runs in the linker, so we'll be using
// the linker's malloc instead of the libc one. Switch it out for a replacement, just in case.
//
// This isn't the default method of dumping because it can fail in cases such as address space
// exhaustion.
static void debuggerd_fallback_trace(int output_fd, ucontext_t* ucontext) {
__linker_enable_fallback_allocator();
{
std::unique_ptr<Regs> regs;
ThreadInfo thread;
thread.pid = getpid();
thread.tid = gettid();
thread.thread_name = get_thread_name(gettid());
thread.registers.reset(Regs::CreateFromUcontext(Regs::CurrentArch(), ucontext));
// TODO: Create this once and store it in a global?
std::unique_ptr<BacktraceMap> map(BacktraceMap::Create(getpid()));
dump_backtrace_thread(output_fd, map.get(), thread);
}
__linker_disable_fallback_allocator();
}
static void debuggerd_fallback_tombstone(int output_fd, ucontext_t* ucontext, siginfo_t* siginfo,
void* abort_message) {
__linker_enable_fallback_allocator();
engrave_tombstone_ucontext(output_fd, reinterpret_cast<uintptr_t>(abort_message), siginfo,
ucontext);
__linker_disable_fallback_allocator();
}
static void iterate_siblings(bool (*callback)(pid_t, int), int output_fd) {
pid_t current_tid = gettid();
char buf[BUFSIZ];
snprintf(buf, sizeof(buf), "/proc/%d/task", current_tid);
DIR* dir = opendir(buf);
if (!dir) {
async_safe_format_log(ANDROID_LOG_ERROR, "libc", "failed to open %s: %s", buf, strerror(errno));
return;
}
struct dirent* ent;
while ((ent = readdir(dir))) {
char* end;
long tid = strtol(ent->d_name, &end, 10);
if (end == ent->d_name || *end != '\0') {
continue;
}
if (tid != current_tid) {
callback(tid, output_fd);
}
}
closedir(dir);
}
static bool forward_output(int src_fd, int dst_fd) {
// Make sure the thread actually got the signal.
struct pollfd pfd = {
.fd = src_fd, .events = POLLIN,
};
// Wait for up to a second for output to start flowing.
if (poll(&pfd, 1, 1000) != 1) {
return false;
}
while (true) {
char buf[512];
ssize_t rc = TEMP_FAILURE_RETRY(read(src_fd, buf, sizeof(buf)));
if (rc == 0) {
return true;
} else if (rc < 0) {
return false;
}
if (!android::base::WriteFully(dst_fd, buf, rc)) {
// We failed to write to tombstoned, but there's not much we can do.
// Keep reading from src_fd to keep things going.
continue;
}
}
}
static void trace_handler(siginfo_t* info, ucontext_t* ucontext) {
static std::atomic<int> trace_output_fd(-1);
if (info->si_value.sival_int == ~0) {
// Asked to dump by the original signal recipient.
debuggerd_fallback_trace(trace_output_fd, ucontext);
int tmp = trace_output_fd.load();
trace_output_fd.store(-1);
close(tmp);
return;
}
// Only allow one thread to perform a trace at a time.
static pthread_mutex_t trace_mutex = PTHREAD_MUTEX_INITIALIZER;
int ret = pthread_mutex_trylock(&trace_mutex);
if (ret != 0) {
async_safe_format_log(ANDROID_LOG_INFO, "libc", "pthread_mutex_try_lock failed: %s",
strerror(ret));
return;
}
// Fetch output fd from tombstoned.
unique_fd tombstone_socket, output_fd;
if (!tombstoned_connect(getpid(), &tombstone_socket, &output_fd, kDebuggerdNativeBacktrace)) {
goto exit;
}
dump_backtrace_header(output_fd.get());
// Dump our own stack.
debuggerd_fallback_trace(output_fd.get(), ucontext);
// Send a signal to all of our siblings, asking them to dump their stack.
iterate_siblings(
[](pid_t tid, int output_fd) {
// Use a pipe, to be able to detect situations where the thread gracefully exits before
// receiving our signal.
unique_fd pipe_read, pipe_write;
if (!Pipe(&pipe_read, &pipe_write)) {
async_safe_format_log(ANDROID_LOG_ERROR, "libc", "failed to create pipe: %s",
strerror(errno));
return false;
}
trace_output_fd.store(pipe_write.get());
siginfo_t siginfo = {};
siginfo.si_code = SI_QUEUE;
siginfo.si_value.sival_int = ~0;
siginfo.si_pid = getpid();
siginfo.si_uid = getuid();
if (syscall(__NR_rt_tgsigqueueinfo, getpid(), tid, DEBUGGER_SIGNAL, &siginfo) != 0) {
async_safe_format_log(ANDROID_LOG_ERROR, "libc", "failed to send trace signal to %d: %s",
tid, strerror(errno));
return false;
}
bool success = forward_output(pipe_read.get(), output_fd);
if (success) {
// The signaled thread has closed trace_output_fd already.
(void)pipe_write.release();
} else {
trace_output_fd.store(-1);
}
return true;
},
output_fd.get());
dump_backtrace_footer(output_fd.get());
tombstoned_notify_completion(tombstone_socket.get());
exit:
pthread_mutex_unlock(&trace_mutex);
}
static void crash_handler(siginfo_t* info, ucontext_t* ucontext, void* abort_message) {
// Only allow one thread to handle a crash at a time (this can happen multiple times without
// exit, since tombstones can be requested without a real crash happening.)
static pthread_mutex_t crash_mutex = PTHREAD_MUTEX_INITIALIZER;
int ret = pthread_mutex_lock(&crash_mutex);
if (ret != 0) {
async_safe_format_log(ANDROID_LOG_INFO, "libc", "pthread_mutex_lock failed: %s", strerror(ret));
return;
}
unique_fd tombstone_socket, output_fd;
bool tombstoned_connected =
tombstoned_connect(getpid(), &tombstone_socket, &output_fd, kDebuggerdTombstone);
debuggerd_fallback_tombstone(output_fd.get(), ucontext, info, abort_message);
if (tombstoned_connected) {
tombstoned_notify_completion(tombstone_socket.get());
}
pthread_mutex_unlock(&crash_mutex);
}
extern "C" void debuggerd_fallback_handler(siginfo_t* info, ucontext_t* ucontext,
void* abort_message) {
if (info->si_signo == DEBUGGER_SIGNAL && info->si_value.sival_int != 0) {
return trace_handler(info, ucontext);
} else {
return crash_handler(info, ucontext, abort_message);
}
}
