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ThreadCapture.cpp
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ThreadCapture.cpp
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/*
* Copyright (C) 2016 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 "ThreadCapture.h"
#include <elf.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <map>
#include <memory>
#include <set>
#include <vector>
#include <android-base/unique_fd.h>
#include "Allocator.h"
#include "log.h"
// bionic interfaces used:
// atoi
// strlcat
// writev
// bionic interfaces reimplemented to avoid allocation:
// getdents64
// Convert a pid > 0 to a string. sprintf might allocate, so we can't use it.
// Returns a pointer somewhere in buf to a null terminated string, or NULL
// on error.
static char *pid_to_str(char *buf, size_t len, pid_t pid) {
if (pid <= 0) {
return nullptr;
}
char *ptr = buf + len - 1;
*ptr = 0;
while (pid > 0) {
ptr--;
if (ptr < buf) {
return nullptr;
}
*ptr = '0' + (pid % 10);
pid /= 10;
}
return ptr;
}
class ThreadCaptureImpl {
public:
ThreadCaptureImpl(pid_t pid, Allocator<ThreadCaptureImpl>& allocator);
~ThreadCaptureImpl() {}
bool ListThreads(TidList& tids);
bool CaptureThreads();
bool ReleaseThreads();
bool ReleaseThread(pid_t tid);
bool CapturedThreadInfo(ThreadInfoList& threads);
void InjectTestFunc(std::function<void(pid_t)>&& f) { inject_test_func_ = f; }
private:
int CaptureThread(pid_t tid);
bool ReleaseThread(pid_t tid, unsigned int signal);
int PtraceAttach(pid_t tid);
void PtraceDetach(pid_t tid, unsigned int signal);
bool PtraceThreadInfo(pid_t tid, ThreadInfo& thread_info);
allocator::map<pid_t, unsigned int> captured_threads_;
Allocator<ThreadCaptureImpl> allocator_;
pid_t pid_;
std::function<void(pid_t)> inject_test_func_;
};
ThreadCaptureImpl::ThreadCaptureImpl(pid_t pid, Allocator<ThreadCaptureImpl>& allocator) :
captured_threads_(allocator), allocator_(allocator), pid_(pid) {
}
bool ThreadCaptureImpl::ListThreads(TidList& tids) {
tids.clear();
char pid_buf[11];
char path[256] = "/proc/";
char* pid_str = pid_to_str(pid_buf, sizeof(pid_buf), pid_);
if (!pid_str) {
return false;
}
strlcat(path, pid_str, sizeof(path));
strlcat(path, "/task", sizeof(path));
android::base::unique_fd fd(open(path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
if (fd == -1) {
ALOGE("failed to open %s: %s", path, strerror(errno));
return false;
}
struct linux_dirent64 {
uint64_t d_ino;
int64_t d_off;
uint16_t d_reclen;
char d_type;
char d_name[];
} __attribute((packed));
char dirent_buf[4096];
ssize_t nread;
do {
nread = syscall(SYS_getdents64, fd.get(), dirent_buf, sizeof(dirent_buf));
if (nread < 0) {
ALOGE("failed to get directory entries from %s: %s", path, strerror(errno));
return false;
} else if (nread > 0) {
ssize_t off = 0;
while (off < nread) {
linux_dirent64* dirent = reinterpret_cast<linux_dirent64*>(dirent_buf + off);
off += dirent->d_reclen;
pid_t tid = atoi(dirent->d_name);
if (tid <= 0) {
continue;
}
tids.push_back(tid);
}
}
} while (nread != 0);
return true;
}
bool ThreadCaptureImpl::CaptureThreads() {
TidList tids{allocator_};
bool found_new_thread;
do {
if (!ListThreads(tids)) {
ReleaseThreads();
return false;
}
found_new_thread = false;
for (auto it = tids.begin(); it != tids.end(); it++) {
auto captured = captured_threads_.find(*it);
if (captured == captured_threads_.end()) {
if (CaptureThread(*it) < 0) {
ReleaseThreads();
return false;
}
found_new_thread = true;
}
}
} while (found_new_thread);
return true;
}
// Detatches from a thread, delivering signal if nonzero, logs on error
void ThreadCaptureImpl::PtraceDetach(pid_t tid, unsigned int signal) {
void* sig_ptr = reinterpret_cast<void*>(static_cast<uintptr_t>(signal));
if (ptrace(PTRACE_DETACH, tid, NULL, sig_ptr) < 0 && errno != ESRCH) {
ALOGE("failed to detach from thread %d of process %d: %s", tid, pid_,
strerror(errno));
}
}
// Attaches to and pauses thread.
// Returns 1 on attach, 0 on tid not found, -1 and logs on error
int ThreadCaptureImpl::PtraceAttach(pid_t tid) {
int ret = ptrace(PTRACE_SEIZE, tid, NULL, NULL);
if (ret < 0) {
ALOGE("failed to attach to thread %d of process %d: %s", tid, pid_,
strerror(errno));
return -1;
}
if (inject_test_func_) {
inject_test_func_(tid);
}
if (ptrace(PTRACE_INTERRUPT, tid, 0, 0) < 0) {
if (errno == ESRCH) {
return 0;
} else {
ALOGE("failed to interrupt thread %d of process %d: %s", tid, pid_,
strerror(errno));
PtraceDetach(tid, 0);
return -1;
}
}
return 1;
}
bool ThreadCaptureImpl::PtraceThreadInfo(pid_t tid, ThreadInfo& thread_info) {
thread_info.tid = tid;
const unsigned int max_num_regs = 128; // larger than number of registers on any device
uintptr_t regs[max_num_regs];
struct iovec iovec;
iovec.iov_base = ®s;
iovec.iov_len = sizeof(regs);
if (ptrace(PTRACE_GETREGSET, tid, reinterpret_cast<void*>(NT_PRSTATUS), &iovec)) {
ALOGE("ptrace getregset for thread %d of process %d failed: %s",
tid, pid_, strerror(errno));
return false;
}
unsigned int num_regs = iovec.iov_len / sizeof(uintptr_t);
thread_info.regs.assign(®s[0], ®s[num_regs]);
const int sp =
#if defined(__x86_64__)
offsetof(struct pt_regs, rsp) / sizeof(uintptr_t)
#elif defined(__i386__)
offsetof(struct pt_regs, esp) / sizeof(uintptr_t)
#elif defined(__arm__)
offsetof(struct pt_regs, ARM_sp) / sizeof(uintptr_t)
#elif defined(__aarch64__)
offsetof(struct user_pt_regs, sp) / sizeof(uintptr_t)
#elif defined(__mips__) || defined(__mips64__)
offsetof(struct pt_regs, regs[29]) / sizeof(uintptr_t)
#else
#error Unrecognized architecture
#endif
;
// TODO(ccross): use /proc/tid/status or /proc/pid/maps to get start_stack
thread_info.stack = std::pair<uintptr_t, uintptr_t>(regs[sp], 0);
return true;
}
int ThreadCaptureImpl::CaptureThread(pid_t tid) {
int ret = PtraceAttach(tid);
if (ret <= 0) {
return ret;
}
int status = 0;
if (TEMP_FAILURE_RETRY(waitpid(tid, &status, __WALL)) < 0) {
ALOGE("failed to wait for pause of thread %d of process %d: %s", tid, pid_,
strerror(errno));
PtraceDetach(tid, 0);
return -1;
}
if (!WIFSTOPPED(status)) {
ALOGE("thread %d of process %d was not paused after waitpid, killed?",
tid, pid_);
return 0;
}
unsigned int resume_signal = 0;
unsigned int signal = WSTOPSIG(status);
if ((status >> 16) == PTRACE_EVENT_STOP) {
switch (signal) {
case SIGSTOP:
case SIGTSTP:
case SIGTTIN:
case SIGTTOU:
// group-stop signals
break;
case SIGTRAP:
// normal ptrace interrupt stop
break;
default:
ALOGE("unexpected signal %d with PTRACE_EVENT_STOP for thread %d of process %d",
signal, tid, pid_);
return -1;
}
} else {
// signal-delivery-stop
resume_signal = signal;
}
captured_threads_[tid] = resume_signal;
return 1;
}
bool ThreadCaptureImpl::ReleaseThread(pid_t tid) {
auto it = captured_threads_.find(tid);
if (it == captured_threads_.end()) {
return false;
}
return ReleaseThread(it->first, it->second);
}
bool ThreadCaptureImpl::ReleaseThread(pid_t tid, unsigned int signal) {
PtraceDetach(tid, signal);
return true;
}
bool ThreadCaptureImpl::ReleaseThreads() {
bool ret = true;
for (auto it = captured_threads_.begin(); it != captured_threads_.end(); ) {
if (ReleaseThread(it->first, it->second)) {
it = captured_threads_.erase(it);
} else {
it++;
ret = false;
}
}
return ret;
}
bool ThreadCaptureImpl::CapturedThreadInfo(ThreadInfoList& threads) {
threads.clear();
for (auto it = captured_threads_.begin(); it != captured_threads_.end(); it++) {
ThreadInfo t{0, allocator::vector<uintptr_t>(allocator_), std::pair<uintptr_t, uintptr_t>(0, 0)};
if (!PtraceThreadInfo(it->first, t)) {
return false;
}
threads.push_back(t);
}
return true;
}
ThreadCapture::ThreadCapture(pid_t pid, Allocator<ThreadCapture> allocator) {
Allocator<ThreadCaptureImpl> impl_allocator = allocator;
impl_ = impl_allocator.make_unique(pid, impl_allocator);
}
ThreadCapture::~ThreadCapture() {}
bool ThreadCapture::ListThreads(TidList& tids) {
return impl_->ListThreads(tids);
}
bool ThreadCapture::CaptureThreads() {
return impl_->CaptureThreads();
}
bool ThreadCapture::ReleaseThreads() {
return impl_->ReleaseThreads();
}
bool ThreadCapture::ReleaseThread(pid_t tid) {
return impl_->ReleaseThread(tid);
}
bool ThreadCapture::CapturedThreadInfo(ThreadInfoList& threads) {
return impl_->CapturedThreadInfo(threads);
}
void ThreadCapture::InjectTestFunc(std::function<void(pid_t)>&& f) {
impl_->InjectTestFunc(std::forward<std::function<void(pid_t)>>(f));
}