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/*
* Copyright (C) 2021 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 <fcntl.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <algorithm>
#include <array>
#include <atomic>
#include <csignal>
#include <cstddef>
#include <cstdio>
#include <cstring>
#include <memory>
#include <regex>
#include <string>
#include <unordered_set>
#include <vector>
#include <unwindstack/MapInfo.h>
#include <unwindstack/Maps.h>
#include <unwindstack/Regs.h>
#include <unwindstack/Unwinder.h>
#include <android-base/file.h>
#include <android-base/stringprintf.h>
#include <procinfo/process.h>
#include "ProcessTracer.h"
namespace unwindstack {
ProcessTracer::ProcessTracer(pid_t pid, bool is_tracing_threads)
: pid_(pid), is_tracing_threads_(is_tracing_threads) {
if (is_tracing_threads_) is_tracing_threads_ = InitProcessTids();
}
bool ProcessTracer::InitProcessTids() {
std::string error_msg;
if (!android::procinfo::GetProcessTids(pid_, &tids_, &error_msg)) {
fprintf(stderr,
"Failed to get process tids: %s. Reverting to tracing the "
"main thread only.\n",
error_msg.c_str());
return false;
}
if (tids_.erase(pid_) != 1) {
fprintf(stderr,
"Failed to erase the main thread from the thread id set. "
"Reverting to tracing the main thread only.\n");
return false;
}
return true;
}
ProcessTracer::~ProcessTracer() {
if (cur_attached_tid_ != kNoThreadAttached) Detach(cur_attached_tid_);
if (!is_running_) Resume();
}
bool ProcessTracer::Stop() {
if (kill(pid_, SIGSTOP) == kKillFailed) {
fprintf(stderr, "Failed to send stop signal to pid %d: %s\n", pid_, strerror(errno));
return false;
}
usleep(1000); // 1 ms. Without this sleep, any attempt to resume right away may fail.
is_running_ = false;
return true;
}
bool ProcessTracer::Resume() {
if (kill(pid_, SIGCONT) == kKillFailed) {
fprintf(stderr, "Failed to send continue signal to pid %d: %s\n", pid_, strerror(errno));
return false;
}
usleep(1000); // 1 ms. Without this sleep, any attempt to stop right away may fail.
is_running_ = true;
return true;
}
bool ProcessTracer::Detach(pid_t tid) {
if (tid != pid_ && tids_.find(tid) == tids_.end()) {
fprintf(stderr, "Tid %d does not belong to proc %d.\n", tid, pid_);
return false;
}
if (cur_attached_tid_ == kNoThreadAttached) {
fprintf(stderr, "Cannot detach because no thread is currently attached.\n");
return false;
}
if (is_running_ && !Stop()) return false;
if (ptrace(PTRACE_DETACH, tid, nullptr, nullptr) == kPtraceFailed) {
fprintf(stderr, "Failed to detach from tid %d: %s\n", tid, strerror(errno));
return false;
}
cur_attached_tid_ = kNoThreadAttached;
return true;
}
bool ProcessTracer::Attach(pid_t tid) {
if (tid != pid_ && tids_.find(tid) == tids_.end()) {
fprintf(stderr, "Tid %d does not belong to proc %d.\n", tid, pid_);
return false;
}
if (is_running_) Stop();
if (cur_attached_tid_ != kNoThreadAttached) {
fprintf(stderr, "Cannot attatch to tid %d. Already attached to tid %d.\n", tid,
cur_attached_tid_);
return false;
}
if (ptrace(PTRACE_ATTACH, tid, nullptr, nullptr) == kPtraceFailed) {
fprintf(stderr, "Failed to attached to tid %d: %s\n", tid, strerror(errno));
return false;
}
int status;
if (waitpid(tid, &status, 0) == kWaitpidFailed) {
fprintf(stderr, "Failed to stop tid %d: %s\n", tid, strerror(errno));
return false;
}
cur_attached_tid_ = tid;
return true;
}
bool ProcessTracer::StopInDesiredElf(const std::string& elf_name) {
signal(SIGINT, [](int) { keepWaitingForPcInElf = false; });
bool pc_in_desired_elf = true;
do {
if (!Attach(pid_)) return false;
pc_in_desired_elf = ProcIsInDesiredElf(pid_, elf_name);
if (!Detach(pid_)) return false;
if (!pc_in_desired_elf) {
for (pid_t tid : tids_) {
if (!Attach(tid)) return false;
pc_in_desired_elf = ProcIsInDesiredElf(tid, elf_name);
if (!Detach(tid)) return false;
if (pc_in_desired_elf) break;
}
}
// If the process is not in the desired ELF, resume it for a short time, then check again.
if (!pc_in_desired_elf) {
Resume();
usleep(1000); // 1 ms
Stop();
}
} while (!pc_in_desired_elf && keepWaitingForPcInElf);
if (!pc_in_desired_elf) {
fprintf(stderr, "\nExited while waiting for pid %d to enter %s.\n", pid_, elf_name.c_str());
return false;
}
return true;
}
bool ProcessTracer::UsesSharedLibrary(pid_t pid, const std::string& desired_elf_name) {
std::unique_ptr<Maps> maps = std::make_unique<RemoteMaps>(pid);
if (!maps->Parse()) {
fprintf(stderr, "Could not parse maps for pid %d.\n", pid);
return false;
}
for (const auto& map : *maps) {
if (android::base::Basename(map->name()).c_str() == desired_elf_name) return true;
}
return false;
}
bool ProcessTracer::ProcIsInDesiredElf(pid_t pid, const std::string& desired_elf_name) {
std::unique_ptr<Regs> regs(Regs::RemoteGet(pid));
if (regs == nullptr) {
fprintf(stderr, "Unable to get remote reg data.\n");
return false;
}
UnwinderFromPid unwinder(1024, pid);
unwinder.SetRegs(regs.get());
if (!unwinder.Init()) {
fprintf(stderr, "Unable to intitialize unwinder.\n");
return false;
}
Maps* maps = unwinder.GetMaps();
MapInfo* map_info = maps->Find(regs->pc());
if (map_info == nullptr) {
regs->fallback_pc();
map_info = maps->Find(regs->pc());
if (map_info == nullptr) {
return false;
}
}
const std::string& current_elf_name = android::base::Basename(map_info->name()).c_str();
bool in_desired_elf = current_elf_name == desired_elf_name;
if (in_desired_elf) printf("pid %d is in %s! Unwinding...\n\n", pid, desired_elf_name.c_str());
return in_desired_elf;
}
} // namespace unwindstack
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