blob: b47cd2ad2de800fd0682be2c79393e89c36bf835 [file] [log] [blame]
/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <linux/futex.h>
#include <pthread.h>
#include <signal.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <ucontext.h>
#include <cutils/atomic.h>
#include "BacktraceLog.h"
#include "BacktraceThread.h"
#include "thread_utils.h"
static inline int futex(volatile int* uaddr, int op, int val, const struct timespec* ts, volatile int* uaddr2, int val3) {
return syscall(__NR_futex, uaddr, op, val, ts, uaddr2, val3);
}
//-------------------------------------------------------------------------
// ThreadEntry implementation.
//-------------------------------------------------------------------------
ThreadEntry* ThreadEntry::list_ = NULL;
pthread_mutex_t ThreadEntry::list_mutex_ = PTHREAD_MUTEX_INITIALIZER;
// Assumes that ThreadEntry::list_mutex_ has already been locked before
// creating a ThreadEntry object.
ThreadEntry::ThreadEntry(pid_t pid, pid_t tid)
: pid_(pid), tid_(tid), futex_(0), ref_count_(1), mutex_(PTHREAD_MUTEX_INITIALIZER), next_(ThreadEntry::list_), prev_(NULL) {
// Add ourselves to the list.
if (ThreadEntry::list_) {
ThreadEntry::list_->prev_ = this;
}
ThreadEntry::list_ = this;
}
ThreadEntry* ThreadEntry::Get(pid_t pid, pid_t tid, bool create) {
pthread_mutex_lock(&ThreadEntry::list_mutex_);
ThreadEntry* entry = list_;
while (entry != NULL) {
if (entry->Match(pid, tid)) {
break;
}
entry = entry->next_;
}
if (!entry) {
if (create) {
entry = new ThreadEntry(pid, tid);
}
} else {
entry->ref_count_++;
}
pthread_mutex_unlock(&ThreadEntry::list_mutex_);
return entry;
}
void ThreadEntry::Remove(ThreadEntry* entry) {
pthread_mutex_unlock(&entry->mutex_);
pthread_mutex_lock(&ThreadEntry::list_mutex_);
if (--entry->ref_count_ == 0) {
delete entry;
}
pthread_mutex_unlock(&ThreadEntry::list_mutex_);
}
// Assumes that ThreadEntry::list_mutex_ has already been locked before
// deleting a ThreadEntry object.
ThreadEntry::~ThreadEntry() {
if (list_ == this) {
list_ = next_;
} else {
if (next_) {
next_->prev_ = prev_;
}
prev_->next_ = next_;
}
next_ = NULL;
prev_ = NULL;
}
void ThreadEntry::Wait(int value) {
timespec ts;
ts.tv_sec = 10;
ts.tv_nsec = 0;
errno = 0;
futex(&futex_, FUTEX_WAIT, value, &ts, NULL, 0);
if (errno != 0 && errno != EWOULDBLOCK) {
BACK_LOGW("futex wait failed, futex = %d: %s", futex_, strerror(errno));
}
}
void ThreadEntry::Wake() {
futex_++;
futex(&futex_, FUTEX_WAKE, INT_MAX, NULL, NULL, 0);
}
void ThreadEntry::CopyUcontextFromSigcontext(void* sigcontext) {
ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(sigcontext);
// The only thing the unwinder cares about is the mcontext data.
memcpy(&ucontext_.uc_mcontext, &ucontext->uc_mcontext, sizeof(ucontext->uc_mcontext));
}
//-------------------------------------------------------------------------
// BacktraceThread functions.
//-------------------------------------------------------------------------
static pthread_mutex_t g_sigaction_mutex = PTHREAD_MUTEX_INITIALIZER;
static void SignalHandler(int, siginfo_t*, void* sigcontext) {
ThreadEntry* entry = ThreadEntry::Get(getpid(), gettid(), false);
if (!entry) {
BACK_LOGW("Unable to find pid %d tid %d information", getpid(), gettid());
return;
}
entry->CopyUcontextFromSigcontext(sigcontext);
// Indicate the ucontext is now valid.
entry->Wake();
// Pause the thread until the unwind is complete. This avoids having
// the thread run ahead causing problems.
entry->Wait(1);
ThreadEntry::Remove(entry);
}
BacktraceThread::BacktraceThread(BacktraceImpl* impl, pid_t tid, BacktraceMap* map)
: BacktraceCurrent(impl, map) {
tid_ = tid;
}
BacktraceThread::~BacktraceThread() {
}
bool BacktraceThread::Unwind(size_t num_ignore_frames, ucontext_t* ucontext) {
if (ucontext) {
// Unwind using an already existing ucontext.
return impl_->Unwind(num_ignore_frames, ucontext);
}
// Prevent multiple threads trying to set the trigger action on different
// threads at the same time.
if (pthread_mutex_lock(&g_sigaction_mutex) < 0) {
BACK_LOGW("sigaction failed: %s", strerror(errno));
return false;
}
ThreadEntry* entry = ThreadEntry::Get(Pid(), Tid());
entry->Lock();
struct sigaction act, oldact;
memset(&act, 0, sizeof(act));
act.sa_sigaction = SignalHandler;
act.sa_flags = SA_RESTART | SA_SIGINFO | SA_ONSTACK;
sigemptyset(&act.sa_mask);
if (sigaction(THREAD_SIGNAL, &act, &oldact) != 0) {
BACK_LOGW("sigaction failed %s", strerror(errno));
entry->Unlock();
ThreadEntry::Remove(entry);
pthread_mutex_unlock(&g_sigaction_mutex);
return false;
}
if (tgkill(Pid(), Tid(), THREAD_SIGNAL) != 0) {
BACK_LOGW("tgkill %d failed: %s", Tid(), strerror(errno));
sigaction(THREAD_SIGNAL, &oldact, NULL);
entry->Unlock();
ThreadEntry::Remove(entry);
pthread_mutex_unlock(&g_sigaction_mutex);
return false;
}
// Wait for the thread to get the ucontext.
entry->Wait(0);
// After the thread has received the signal, allow other unwinders to
// continue.
sigaction(THREAD_SIGNAL, &oldact, NULL);
pthread_mutex_unlock(&g_sigaction_mutex);
bool unwind_done = impl_->Unwind(num_ignore_frames, entry->GetUcontext());
// Tell the signal handler to exit and release the entry.
entry->Wake();
return unwind_done;
}