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/*
* Copyright (C) 2011 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 "exec_utils.h"
#include <poll.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "base/macros.h"
#ifdef __BIONIC__
#include <sys/pidfd.h>
#endif
#include <cstdint>
#include <string>
#include <vector>
#include "android-base/scopeguard.h"
#include "android-base/stringprintf.h"
#include "android-base/strings.h"
#include "runtime.h"
namespace art {
namespace {
using ::android::base::StringPrintf;
std::string ToCommandLine(const std::vector<std::string>& args) {
return android::base::Join(args, ' ');
}
// Fork and execute a command specified in a subprocess.
// If there is a runtime (Runtime::Current != nullptr) then the subprocess is created with the
// same environment that existed when the runtime was started.
// Returns the process id of the child process on success, -1 otherwise.
pid_t ExecWithoutWait(const std::vector<std::string>& arg_vector, std::string* error_msg) {
// Convert the args to char pointers.
const char* program = arg_vector[0].c_str();
std::vector<char*> args;
for (const auto& arg : arg_vector) {
args.push_back(const_cast<char*>(arg.c_str()));
}
args.push_back(nullptr);
// fork and exec
pid_t pid = fork();
if (pid == 0) {
// no allocation allowed between fork and exec
// change process groups, so we don't get reaped by ProcessManager
setpgid(0, 0);
// (b/30160149): protect subprocesses from modifications to LD_LIBRARY_PATH, etc.
// Use the snapshot of the environment from the time the runtime was created.
char** envp = (Runtime::Current() == nullptr) ? nullptr : Runtime::Current()->GetEnvSnapshot();
if (envp == nullptr) {
execv(program, &args[0]);
} else {
execve(program, &args[0], envp);
}
// This should be regarded as a crash rather than a normal return.
PLOG(FATAL) << "Failed to execute (" << ToCommandLine(arg_vector) << ")";
UNREACHABLE();
} else if (pid == -1) {
*error_msg = StringPrintf("Failed to execute (%s) because fork failed: %s",
ToCommandLine(arg_vector).c_str(),
strerror(errno));
return -1;
} else {
return pid;
}
}
int WaitChild(pid_t pid, const std::vector<std::string>& arg_vector, std::string* error_msg) {
int status = -1;
pid_t got_pid = TEMP_FAILURE_RETRY(waitpid(pid, &status, 0));
if (got_pid != pid) {
*error_msg =
StringPrintf("Failed to execute (%s) because waitpid failed: wanted %d, got %d: %s",
ToCommandLine(arg_vector).c_str(),
pid,
got_pid,
strerror(errno));
return -1;
}
if (!WIFEXITED(status)) {
*error_msg =
StringPrintf("Failed to execute (%s) because the child process is terminated by signal %d",
ToCommandLine(arg_vector).c_str(),
WTERMSIG(status));
return -1;
}
return WEXITSTATUS(status);
}
int WaitChildWithTimeout(pid_t pid,
const std::vector<std::string>& arg_vector,
int timeout_sec,
bool* timed_out,
std::string* error_msg) {
auto cleanup = android::base::make_scope_guard([&]() {
kill(pid, SIGKILL);
std::string ignored_error_msg;
WaitChild(pid, arg_vector, &ignored_error_msg);
});
#ifdef __BIONIC__
int pidfd = pidfd_open(pid, /*flags=*/0);
#else
// There is no glibc wrapper for pidfd_open.
constexpr int SYS_pidfd_open = 434;
int pidfd = syscall(SYS_pidfd_open, pid, /*flags=*/0);
#endif
if (pidfd < 0) {
*error_msg = StringPrintf("pidfd_open failed for pid %d: %s", pid, strerror(errno));
return -1;
}
struct pollfd pfd;
pfd.fd = pidfd;
pfd.events = POLLIN;
int poll_ret = TEMP_FAILURE_RETRY(poll(&pfd, /*nfds=*/1, timeout_sec * 1000));
close(pidfd);
if (poll_ret < 0) {
*error_msg = StringPrintf("poll failed for pid %d: %s", pid, strerror(errno));
return -1;
}
if (poll_ret == 0) {
*timed_out = true;
*error_msg = StringPrintf("Child process %d timed out after %ds. Killing it", pid, timeout_sec);
return -1;
}
cleanup.Disable();
return WaitChild(pid, arg_vector, error_msg);
}
} // namespace
int ExecAndReturnCode(const std::vector<std::string>& arg_vector, std::string* error_msg) {
// Start subprocess.
pid_t pid = ExecWithoutWait(arg_vector, error_msg);
if (pid == -1) {
return -1;
}
// Wait for subprocess to finish.
return WaitChild(pid, arg_vector, error_msg);
}
int ExecAndReturnCode(const std::vector<std::string>& arg_vector,
int timeout_sec,
bool* timed_out,
std::string* error_msg) {
*timed_out = false;
// Start subprocess.
pid_t pid = ExecWithoutWait(arg_vector, error_msg);
if (pid == -1) {
return -1;
}
// Wait for subprocess to finish.
return WaitChildWithTimeout(pid, arg_vector, timeout_sec, timed_out, error_msg);
}
bool Exec(const std::vector<std::string>& arg_vector, std::string* error_msg) {
int status = ExecAndReturnCode(arg_vector, error_msg);
if (status < 0) {
// Internal error. The error message is already set.
return false;
}
if (status > 0) {
*error_msg =
StringPrintf("Failed to execute (%s) because the child process returns non-zero exit code",
ToCommandLine(arg_vector).c_str());
return false;
}
return true;
}
} // namespace art
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