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Diffstat (limited to 'src/libutil/processes.cc')
| -rw-r--r-- | src/libutil/processes.cc | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/src/libutil/processes.cc b/src/libutil/processes.cc new file mode 100644 index 000000000..8d1b119b0 --- /dev/null +++ b/src/libutil/processes.cc @@ -0,0 +1,404 @@ +#include "environment-variables.hh" +#include "finally.hh" +#include "logging.hh" +#include "processes.hh" +#include "serialise.hh" +#include "signals.hh" + +#include <cerrno> +#include <cstdlib> +#include <cstring> +#include <future> +#include <iostream> +#include <thread> + +#include <grp.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <unistd.h> + +#ifdef __APPLE__ +# include <sys/syscall.h> +#endif + +#ifdef __linux__ +# include <sys/prctl.h> +# include <sys/mman.h> +#endif + + +namespace nix { + +Pid::Pid() +{ +} + + +Pid::Pid(pid_t pid) + : pid(pid) +{ +} + + +Pid::~Pid() noexcept(false) +{ + if (pid != -1) kill(); +} + + +void Pid::operator =(pid_t pid) +{ + if (this->pid != -1 && this->pid != pid) kill(); + this->pid = pid; + killSignal = SIGKILL; // reset signal to default +} + + +Pid::operator pid_t() +{ + return pid; +} + + +int Pid::kill() +{ + assert(pid != -1); + + debug("killing process %1%", pid); + + /* Send the requested signal to the child. If it has its own + process group, send the signal to every process in the child + process group (which hopefully includes *all* its children). */ + if (::kill(separatePG ? -pid : pid, killSignal) != 0) { + /* 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 || ::kill(pid, 0) != 0) +#endif + 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(); + } +} + + +void Pid::setSeparatePG(bool separatePG) +{ + this->separatePG = separatePG; +} + + +void Pid::setKillSignal(int signal) +{ + this->killSignal = signal; +} + + +pid_t Pid::release() +{ + pid_t p = pid; + pid = -1; + return p; +} + + +void killUser(uid_t uid) +{ + debug("killing all processes running under uid '%1%'", uid); + + assert(uid != 0); /* just to be safe... */ + + /* The system call kill(-1, sig) sends the signal `sig' to all + users to which the current process can send signals. So we + fork a process, switch to uid, and send a mass kill. */ + + Pid pid = startProcess([&]() { + + if (setuid(uid) == -1) + throw SysError("setting uid"); + + while (true) { +#ifdef __APPLE__ + /* OSX's kill syscall takes a third parameter that, among + other things, determines if kill(-1, signo) affects the + calling process. In the OSX libc, it's set to true, + which means "follow POSIX", which we don't want here + */ + if (syscall(SYS_kill, -1, SIGKILL, false) == 0) break; +#else + if (kill(-1, SIGKILL) == 0) break; +#endif + if (errno == ESRCH || errno == EPERM) break; /* no more processes */ + if (errno != EINTR) + throw SysError("cannot kill processes for uid '%1%'", uid); + } + + _exit(0); + }); + + int status = pid.wait(); + if (status != 0) + throw Error("cannot kill processes for uid '%1%': %2%", uid, statusToString(status)); + + /* !!! We should really do some check to make sure that there are + no processes left running under `uid', but there is no portable + way to do so (I think). The most reliable way may be `ps -eo + uid | grep -q $uid'. */ +} + + +////////////////////////////////////////////////////////////////////// + + +static pid_t doFork(std::function<void()> fun) +{ + pid_t pid = fork(); + if (pid != 0) return pid; + fun(); + abort(); +} + +#if __linux__ +static int childEntry(void * arg) +{ + auto main = (std::function<void()> *) arg; + (*main)(); + return 1; +} +#endif + + +pid_t startProcess(std::function<void()> fun, const ProcessOptions & options) +{ + std::function<void()> wrapper = [&]() { + logger = makeSimpleLogger(); + try { +#if __linux__ + if (options.dieWithParent && prctl(PR_SET_PDEATHSIG, SIGKILL) == -1) + throw SysError("setting death signal"); +#endif + fun(); + } catch (std::exception & e) { + try { + std::cerr << options.errorPrefix << e.what() << "\n"; + } catch (...) { } + } catch (...) { } + if (options.runExitHandlers) + exit(1); + else + _exit(1); + }; + + pid_t pid = -1; + + if (options.cloneFlags) { + #ifdef __linux__ + // Not supported, since then we don't know when to free the stack. + assert(!(options.cloneFlags & CLONE_VM)); + + size_t stackSize = 1 * 1024 * 1024; + auto stack = (char *) mmap(0, stackSize, + PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0); + if (stack == MAP_FAILED) throw SysError("allocating stack"); + + Finally freeStack([&]() { munmap(stack, stackSize); }); + + pid = clone(childEntry, stack + stackSize, options.cloneFlags | SIGCHLD, &wrapper); + #else + throw Error("clone flags are only supported on Linux"); + #endif + } else + pid = doFork(wrapper); + + if (pid == -1) throw SysError("unable to fork"); + + return pid; +} + +std::string runProgram(Path program, bool searchPath, const Strings & args, + const std::optional<std::string> & input, bool isInteractive) +{ + auto res = runProgram(RunOptions {.program = program, .searchPath = searchPath, .args = args, .input = input, .isInteractive = isInteractive}); + + if (!statusOk(res.first)) + throw ExecError(res.first, "program '%1%' %2%", program, statusToString(res.first)); + + return res.second; +} + +// Output = error code + "standard out" output stream +std::pair<int, std::string> runProgram(RunOptions && options) +{ + StringSink sink; + options.standardOut = &sink; + + int status = 0; + + try { + runProgram2(options); + } catch (ExecError & e) { + status = e.status; + } + + return {status, std::move(sink.s)}; +} + +void runProgram2(const RunOptions & options) +{ + checkInterrupt(); + + assert(!(options.standardIn && options.input)); + + std::unique_ptr<Source> source_; + Source * source = options.standardIn; + + if (options.input) { + source_ = std::make_unique<StringSource>(*options.input); + source = source_.get(); + } + + /* Create a pipe. */ + Pipe out, in; + if (options.standardOut) out.create(); + if (source) in.create(); + + ProcessOptions processOptions; + + std::optional<Finally<std::function<void()>>> resumeLoggerDefer; + if (options.isInteractive) { + logger->pause(); + resumeLoggerDefer.emplace( + []() { + logger->resume(); + } + ); + } + + /* Fork. */ + Pid pid = startProcess([&]() { + if (options.environment) + replaceEnv(*options.environment); + if (options.standardOut && dup2(out.writeSide.get(), STDOUT_FILENO) == -1) + throw SysError("dupping stdout"); + if (options.mergeStderrToStdout) + if (dup2(STDOUT_FILENO, STDERR_FILENO) == -1) + throw SysError("cannot dup stdout into stderr"); + if (source && dup2(in.readSide.get(), STDIN_FILENO) == -1) + throw SysError("dupping stdin"); + + if (options.chdir && chdir((*options.chdir).c_str()) == -1) + throw SysError("chdir failed"); + if (options.gid && setgid(*options.gid) == -1) + throw SysError("setgid failed"); + /* Drop all other groups if we're setgid. */ + if (options.gid && setgroups(0, 0) == -1) + throw SysError("setgroups failed"); + if (options.uid && setuid(*options.uid) == -1) + throw SysError("setuid failed"); + + Strings args_(options.args); + args_.push_front(options.program); + + restoreProcessContext(); + + if (options.searchPath) + execvp(options.program.c_str(), stringsToCharPtrs(args_).data()); + // This allows you to refer to a program with a pathname relative + // to the PATH variable. + else + execv(options.program.c_str(), stringsToCharPtrs(args_).data()); + + throw SysError("executing '%1%'", options.program); + }, processOptions); + + out.writeSide.close(); + + std::thread writerThread; + + std::promise<void> promise; + + Finally doJoin([&]() { + if (writerThread.joinable()) + writerThread.join(); + }); + + + if (source) { + in.readSide.close(); + writerThread = std::thread([&]() { + try { + std::vector<char> buf(8 * 1024); + while (true) { + size_t n; + try { + n = source->read(buf.data(), buf.size()); + } catch (EndOfFile &) { + break; + } + writeFull(in.writeSide.get(), {buf.data(), n}); + } + promise.set_value(); + } catch (...) { + promise.set_exception(std::current_exception()); + } + in.writeSide.close(); + }); + } + + if (options.standardOut) + drainFD(out.readSide.get(), *options.standardOut); + + /* Wait for the child to finish. */ + int status = pid.wait(); + + /* Wait for the writer thread to finish. */ + if (source) promise.get_future().get(); + + if (status) + throw ExecError(status, "program '%1%' %2%", options.program, statusToString(status)); +} + +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; +} + +} |