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#include "async-io.hh"
#include "c-calls.hh"
#include "file-descriptor.hh"
#include "lix/libutil/current-process.hh"
#include "lix/libutil/environment-variables.hh"
#include "lix/libutil/finally.hh"
#include "lix/libutil/logging.hh"
#include "lix/libutil/processes.hh"
#include "lix/libutil/strings.hh"
#include "lix/libutil/serialise.hh"
#include "lix/libutil/signals.hh"
#include "manually-drop.hh"
#include "sync.hh"
#include <cerrno>
#include <csignal>
#include <cstdlib>
#include <cstring>
#include <fcntl.h>
#include <iostream>
#include <grp.h>
#include <string>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utility>
// both apple and linux must use raw syscalls for some things that are not exposed otherwise
#include <sys/syscall.h>
#ifdef __linux__
# include <linux/capability.h>
# include <sys/prctl.h>
# include <sys/mman.h>
#endif
namespace nix {
Pid::Pid()
{
}
Pid::Pid(Pid && other) : pid(other.pid)
{
other.pid = -1;
}
Pid & Pid::operator=(Pid && other)
{
Pid tmp(std::move(other));
std::swap(pid, tmp.pid);
return *this;
}
Pid::~Pid() noexcept(false)
{
if (pid != -1) kill();
}
int Pid::kill()
{
assert(pid != -1);
debug("killing process %1%", pid);
/* Send the requested signal to the child. */
if (::kill(pid, SIGKILL) != 0) {
logError(SysError("killing process %d", pid).info());
}
return wait();
}
int Pid::wait()
{
assert(pid != -1);
while (1) {
int status;
int res = waitpid(pid, &status, 0);
if (res == pid) {
pid = -1;
return status;
}
if (errno != EINTR)
throw SysError("cannot get exit status of PID %d", pid);
checkInterrupt();
}
}
pid_t Pid::release()
{
pid_t p = pid;
pid = -1;
return p;
}
int ProcessGroup::kill()
{
assert(leader);
debug("killing process group %1%", leader.get());
// send a kill signal to the leader *only* first. the leader we know may not have
// actually set its pgid yet, in which case the following kill for the group will
// fail. if this happens we still want to clean up the whole (hopefully singular)
// group, thus we start small. we will always attempt to kill the group too; only
// when we've waited on the pid we know can it be reused as a pgid. we are not in
// danger of killing any other processes we don't want to be killing as a result.
const auto leaderKillResult = ::kill(leader.get(), SIGKILL);
(void) leaderKillResult;
/* Send the requested signal to every process in the child
process group (which hopefully includes *all* its children). */
if (::kill(-leader.get(), SIGKILL) != 0 && errno != ESRCH) {
/* On BSDs, killing a process group will return EPERM if all
processes in the group are zombies (or something like
that). So try to detect and ignore that situation. */
#if __FreeBSD__ || __APPLE__
if (errno != EPERM || leaderKillResult != 0)
#endif
logError(SysError("killing process group %d", leader.get()).info());
}
return wait();
}
ProcessGroup::~ProcessGroup() noexcept(false)
{
if (leader) {
kill();
}
}
void killUser(uid_t uid)
{
debug("killing all processes running under uid '%1%'", uid);
assert(uid != 0); /* just to be safe... */
runHelper("kill-user", {.args = {std::to_string(uid)}}).waitAndCheck();
}
//////////////////////////////////////////////////////////////////////
kj::Promise<Result<std::string>>
runProgram(Path program, bool searchPath, const Strings args, bool isInteractive)
try {
// allow only one interactive program per unit time so they don't mess with each other.
//
// see https://git.lix.systems/lix-project/lix/issues/702 for why this is ManuallyDrop.
static ManuallyDrop<Sync<int, AsyncMutex>> interactiveMutex{std::in_place, 0};
std::optional<Sync<int, AsyncMutex>::Lock> interactiveLock;
KJ_DEFER({
if (interactiveLock) {
logger->resume();
}
});
if (isInteractive) {
interactiveLock = co_await interactiveMutex->lock();
logger->pause();
}
auto res = TRY_AWAIT(runProgram(RunOptions{
.program = program,
.searchPath = searchPath,
.args = args,
}));
if (!statusOk(res.first)) {
throw ExecError(res.first, "program '%1%' %2%", program, statusToString(res.first));
}
co_return res.second;
} catch (...) {
co_return result::current_exception();
}
// Output = error code + "standard out" output stream
kj::Promise<Result<std::pair<int, std::string>>> runProgram(RunOptions options)
try {
options.captureStdout = true;
int status = 0;
std::string childStdout;
try {
auto proc = runProgram2(options);
Finally const _wait([&] { proc.waitAndCheck(); });
childStdout = TRY_AWAIT(proc.getStdout()->drain());
} catch (ExecError & e) {
status = e.status;
}
co_return {status, std::move(childStdout)};
} catch (...) {
co_return result::current_exception();
}
RunningProgram::RunningProgram(PathView program, Pid pid, AutoCloseFD childStdout)
: program(program)
, pid(std::move(pid))
, childStdout(childStdout ? std::make_unique<AsyncFdIoStream>(std::move(childStdout)) : nullptr)
{
}
RunningProgram::~RunningProgram()
{
if (pid) {
// we will not kill a subprocess because we *can't* kill a subprocess
// reliably without placing it in its own process group, and then too
// we could not be sure to terminate the entire subprocess hierarchy.
assert(false && "destroying un-wait()ed running process");
std::terminate();
}
}
std::tuple<Pid, std::unique_ptr<AsyncFdIoStream>> RunningProgram::release()
{
return {std::move(pid), std::move(childStdout)};
}
int RunningProgram::kill()
{
return pid.kill();
}
int RunningProgram::wait()
{
return pid.wait();
}
int RunningHelper::killProcessGroup()
{
return ProcessGroup{std::move(pid)}.kill();
}
void RunningProgram::waitAndCheck()
{
if (std::uncaught_exceptions() == 0) {
int status = pid.wait();
if (status)
throw ExecError(status, "program '%1%' %2%", program, statusToString(status));
} else {
pid.kill();
debug("killed subprocess %1% during exception handling", program);
}
}
void RunningHelper::check()
{
char first;
try {
readFull(errPipe.get(), &first, 1);
} catch (EndOfFile &) {
return;
}
if (first == '\n') {
return;
}
auto rest = readFile(errPipe.get());
int status = kill();
throw ExecError(status, "helper %s failed: %s", name, first + rest);
}
void RunningHelper::waitAndCheck()
{
if (std::uncaught_exceptions() == 0) {
auto error = readFile(errPipe.get());
if (!error.empty()) {
int status = kill();
throw ExecError(status, "helper %s failed: %s", name, error);
}
RunningProgram::waitAndCheck();
} else {
RunningProgram::kill();
}
}
RunningProgram runProgram2(const RunOptions & options)
{
checkInterrupt();
/* Create a pipe. */
Pipe out;
if (options.captureStdout) out.create();
printMsg(
lvlChatty,
"running command%s%s: %s %s%s",
Uncolored(options.searchPath ? " from PATH" : ""),
Uncolored(options.argv0 ? " with explicit argv0" : ""),
shellEscape(options.program),
options.argv0 ? shellEscape(*options.argv0) + " " : "",
concatMapStringsSep(" ", options.args, shellEscape)
);
Pipe info;
info.create();
/* Fork. */
Pid pid{fork()};
if (!pid) {
throw SysError("fork failed");
} else if (pid.get() > 0) {
info.writeSide.close();
auto status = readFile(info.readSide.get());
if (!status.empty()) {
auto result = pid.kill();
throw ExecError(result, "failed to run %s: %s", options.program, status);
} else {
return RunningProgram{
options.program,
std::move(pid),
options.captureStdout ? std::move(out.readSide) : AutoCloseFD{}
};
}
} else {
// nothing in the child may access global state like loggers, otherwise the
// child may deadlock if we forked while a lock was held by another thread.
// we cannot use writeFull because it might throw, we want to exit instead.
auto writeStatus = [&](std::string_view data) {
while (!data.empty()) {
const auto sent = ::write(info.writeSide.get(), data.data(), data.size());
if (sent < 0) {
_exit(255);
}
data.remove_prefix(sent);
}
};
try {
info.readSide.close();
if (options.environment) {
replaceEnv(*options.environment);
}
if (options.captureStdout && dup2(out.writeSide.get(), STDOUT_FILENO) == -1) {
throw SysError("dupping stdout");
}
for (auto redirection : options.redirections) {
if (redirection.dup == redirection.from) {
if (int flags = fcntl(redirection.from, F_GETFD);
flags < 0 || fcntl(redirection.from, F_SETFD, flags & ~FD_CLOEXEC) < 0)
{
throw SysError("clearing O_CLOEXEC of fd %i", redirection.dup);
}
} else if (dup2(redirection.from, redirection.dup) == -1) {
throw SysError("dupping fd %i to %i", redirection.dup, redirection.from);
}
}
Strings args_(options.args);
args_.push_front(options.argv0.value_or(options.program));
if (!options.keepContext) {
restoreProcessContext();
}
if (options.searchPath) {
sys::execvp(options.program, args_);
// This allows you to refer to a program with a pathname relative
// to the PATH variable.
} else {
sys::execv(options.program, args_);
}
throw SysError("executing '%1%'", options.program);
} catch (std::exception & e) { // NOLINT(lix-foreign-exceptions)
writeStatus(e.what());
_exit(254);
} catch (...) {
writeStatus("unknown exception");
_exit(253);
}
}
}
RunningHelper runHelper(const char * name, RunOptions options)
{
Pipe errPipe;
errPipe.create();
options.program = fmt("%s/%s", LIX_LIBEXEC_DIR, name);
options.args.push_front(std::to_string(errPipe.writeSide.get()));
options.searchPath = false;
options.redirections.push_back({.dup = errPipe.writeSide.get(), .from = errPipe.writeSide.get()});
RunningHelper helper{name, runProgram2(options), std::move(errPipe.readSide)};
errPipe.writeSide.close();
helper.check();
return helper;
}
std::string statusToString(int status)
{
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
if (WIFEXITED(status))
return fmt("failed with exit code %1%", WEXITSTATUS(status));
else if (WIFSIGNALED(status)) {
int sig = WTERMSIG(status);
#if HAVE_STRSIGNAL
const char * description = strsignal(sig);
return fmt("failed due to signal %1% (%2%)", sig, description);
#else
return fmt("failed due to signal %1%", sig);
#endif
}
else
return "died abnormally";
} else return "succeeded";
}
bool statusOk(int status)
{
return WIFEXITED(status) && WEXITSTATUS(status) == 0;
}
}
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