diff options
Diffstat (limited to 'library/std/src/sys/unix/process/process_unix.rs')
| -rw-r--r-- | library/std/src/sys/unix/process/process_unix.rs | 494 |
1 files changed, 494 insertions, 0 deletions
diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs new file mode 100644 index 00000000000..0f349dfa302 --- /dev/null +++ b/library/std/src/sys/unix/process/process_unix.rs @@ -0,0 +1,494 @@ +use crate::convert::TryInto; +use crate::fmt; +use crate::io::{self, Error, ErrorKind}; +use crate::ptr; +use crate::sys; +use crate::sys::cvt; +use crate::sys::process::process_common::*; + +use libc::{c_int, gid_t, pid_t, uid_t}; + +//////////////////////////////////////////////////////////////////////////////// +// Command +//////////////////////////////////////////////////////////////////////////////// + +impl Command { + pub fn spawn( + &mut self, + default: Stdio, + needs_stdin: bool, + ) -> io::Result<(Process, StdioPipes)> { + const CLOEXEC_MSG_FOOTER: [u8; 4] = *b"NOEX"; + + let envp = self.capture_env(); + + if self.saw_nul() { + return Err(io::Error::new(ErrorKind::InvalidInput, "nul byte found in provided data")); + } + + let (ours, theirs) = self.setup_io(default, needs_stdin)?; + + if let Some(ret) = self.posix_spawn(&theirs, envp.as_ref())? { + return Ok((ret, ours)); + } + + let (input, output) = sys::pipe::anon_pipe()?; + + // Whatever happens after the fork is almost for sure going to touch or + // look at the environment in one way or another (PATH in `execvp` or + // accessing the `environ` pointer ourselves). Make sure no other thread + // is accessing the environment when we do the fork itself. + // + // Note that as soon as we're done with the fork there's no need to hold + // a lock any more because the parent won't do anything and the child is + // in its own process. + let result = unsafe { + let _env_lock = sys::os::env_lock(); + cvt(libc::fork())? + }; + + let pid = unsafe { + match result { + 0 => { + drop(input); + let Err(err) = self.do_exec(theirs, envp.as_ref()); + let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32; + let errno = errno.to_be_bytes(); + let bytes = [ + errno[0], + errno[1], + errno[2], + errno[3], + CLOEXEC_MSG_FOOTER[0], + CLOEXEC_MSG_FOOTER[1], + CLOEXEC_MSG_FOOTER[2], + CLOEXEC_MSG_FOOTER[3], + ]; + // pipe I/O up to PIPE_BUF bytes should be atomic, and then + // we want to be sure we *don't* run at_exit destructors as + // we're being torn down regardless + assert!(output.write(&bytes).is_ok()); + libc::_exit(1) + } + n => n, + } + }; + + let mut p = Process { pid, status: None }; + drop(output); + let mut bytes = [0; 8]; + + // loop to handle EINTR + loop { + match input.read(&mut bytes) { + Ok(0) => return Ok((p, ours)), + Ok(8) => { + let (errno, footer) = bytes.split_at(4); + assert_eq!( + CLOEXEC_MSG_FOOTER, footer, + "Validation on the CLOEXEC pipe failed: {:?}", + bytes + ); + let errno = i32::from_be_bytes(errno.try_into().unwrap()); + assert!(p.wait().is_ok(), "wait() should either return Ok or panic"); + return Err(Error::from_raw_os_error(errno)); + } + Err(ref e) if e.kind() == ErrorKind::Interrupted => {} + Err(e) => { + assert!(p.wait().is_ok(), "wait() should either return Ok or panic"); + panic!("the CLOEXEC pipe failed: {:?}", e) + } + Ok(..) => { + // pipe I/O up to PIPE_BUF bytes should be atomic + assert!(p.wait().is_ok(), "wait() should either return Ok or panic"); + panic!("short read on the CLOEXEC pipe") + } + } + } + } + + pub fn exec(&mut self, default: Stdio) -> io::Error { + let envp = self.capture_env(); + + if self.saw_nul() { + return io::Error::new(ErrorKind::InvalidInput, "nul byte found in provided data"); + } + + match self.setup_io(default, true) { + Ok((_, theirs)) => { + unsafe { + // Similar to when forking, we want to ensure that access to + // the environment is synchronized, so make sure to grab the + // environment lock before we try to exec. + let _lock = sys::os::env_lock(); + + let Err(e) = self.do_exec(theirs, envp.as_ref()); + e + } + } + Err(e) => e, + } + } + + // And at this point we've reached a special time in the life of the + // child. The child must now be considered hamstrung and unable to + // do anything other than syscalls really. Consider the following + // scenario: + // + // 1. Thread A of process 1 grabs the malloc() mutex + // 2. Thread B of process 1 forks(), creating thread C + // 3. Thread C of process 2 then attempts to malloc() + // 4. The memory of process 2 is the same as the memory of + // process 1, so the mutex is locked. + // + // This situation looks a lot like deadlock, right? It turns out + // that this is what pthread_atfork() takes care of, which is + // presumably implemented across platforms. The first thing that + // threads to *before* forking is to do things like grab the malloc + // mutex, and then after the fork they unlock it. + // + // Despite this information, libnative's spawn has been witnessed to + // deadlock on both macOS and FreeBSD. I'm not entirely sure why, but + // all collected backtraces point at malloc/free traffic in the + // child spawned process. + // + // For this reason, the block of code below should contain 0 + // invocations of either malloc of free (or their related friends). + // + // As an example of not having malloc/free traffic, we don't close + // this file descriptor by dropping the FileDesc (which contains an + // allocation). Instead we just close it manually. This will never + // have the drop glue anyway because this code never returns (the + // child will either exec() or invoke libc::exit) + unsafe fn do_exec( + &mut self, + stdio: ChildPipes, + maybe_envp: Option<&CStringArray>, + ) -> Result<!, io::Error> { + use crate::sys::{self, cvt_r}; + + if let Some(fd) = stdio.stdin.fd() { + cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO))?; + } + if let Some(fd) = stdio.stdout.fd() { + cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO))?; + } + if let Some(fd) = stdio.stderr.fd() { + cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO))?; + } + + #[cfg(not(target_os = "l4re"))] + { + if let Some(u) = self.get_gid() { + cvt(libc::setgid(u as gid_t))?; + } + if let Some(u) = self.get_uid() { + // When dropping privileges from root, the `setgroups` call + // will remove any extraneous groups. If we don't call this, + // then even though our uid has dropped, we may still have + // groups that enable us to do super-user things. This will + // fail if we aren't root, so don't bother checking the + // return value, this is just done as an optimistic + // privilege dropping function. + //FIXME: Redox kernel does not support setgroups yet + #[cfg(not(target_os = "redox"))] + let _ = libc::setgroups(0, ptr::null()); + cvt(libc::setuid(u as uid_t))?; + } + } + if let Some(ref cwd) = *self.get_cwd() { + cvt(libc::chdir(cwd.as_ptr()))?; + } + + // emscripten has no signal support. + #[cfg(not(target_os = "emscripten"))] + { + use crate::mem::MaybeUninit; + // Reset signal handling so the child process starts in a + // standardized state. libstd ignores SIGPIPE, and signal-handling + // libraries often set a mask. Child processes inherit ignored + // signals and the signal mask from their parent, but most + // UNIX programs do not reset these things on their own, so we + // need to clean things up now to avoid confusing the program + // we're about to run. + let mut set = MaybeUninit::<libc::sigset_t>::uninit(); + cvt(sigemptyset(set.as_mut_ptr()))?; + cvt(libc::pthread_sigmask(libc::SIG_SETMASK, set.as_ptr(), ptr::null_mut()))?; + let ret = sys::signal(libc::SIGPIPE, libc::SIG_DFL); + if ret == libc::SIG_ERR { + return Err(io::Error::last_os_error()); + } + } + + for callback in self.get_closures().iter_mut() { + callback()?; + } + + // Although we're performing an exec here we may also return with an + // error from this function (without actually exec'ing) in which case we + // want to be sure to restore the global environment back to what it + // once was, ensuring that our temporary override, when free'd, doesn't + // corrupt our process's environment. + let mut _reset = None; + if let Some(envp) = maybe_envp { + struct Reset(*const *const libc::c_char); + + impl Drop for Reset { + fn drop(&mut self) { + unsafe { + *sys::os::environ() = self.0; + } + } + } + + _reset = Some(Reset(*sys::os::environ())); + *sys::os::environ() = envp.as_ptr(); + } + + libc::execvp(self.get_program().as_ptr(), self.get_argv().as_ptr()); + Err(io::Error::last_os_error()) + } + + #[cfg(not(any( + target_os = "macos", + target_os = "freebsd", + all(target_os = "linux", target_env = "gnu") + )))] + fn posix_spawn( + &mut self, + _: &ChildPipes, + _: Option<&CStringArray>, + ) -> io::Result<Option<Process>> { + Ok(None) + } + + // Only support platforms for which posix_spawn() can return ENOENT + // directly. + #[cfg(any( + target_os = "macos", + target_os = "freebsd", + all(target_os = "linux", target_env = "gnu") + ))] + fn posix_spawn( + &mut self, + stdio: &ChildPipes, + envp: Option<&CStringArray>, + ) -> io::Result<Option<Process>> { + use crate::mem::MaybeUninit; + use crate::sys; + + if self.get_gid().is_some() + || self.get_uid().is_some() + || self.env_saw_path() + || !self.get_closures().is_empty() + { + return Ok(None); + } + + // Only glibc 2.24+ posix_spawn() supports returning ENOENT directly. + #[cfg(all(target_os = "linux", target_env = "gnu"))] + { + if let Some(version) = sys::os::glibc_version() { + if version < (2, 24) { + return Ok(None); + } + } else { + return Ok(None); + } + } + + // Solaris and glibc 2.29+ can set a new working directory, and maybe + // others will gain this non-POSIX function too. We'll check for this + // weak symbol as soon as it's needed, so we can return early otherwise + // to do a manual chdir before exec. + weak! { + fn posix_spawn_file_actions_addchdir_np( + *mut libc::posix_spawn_file_actions_t, + *const libc::c_char + ) -> libc::c_int + } + let addchdir = match self.get_cwd() { + Some(cwd) => match posix_spawn_file_actions_addchdir_np.get() { + Some(f) => Some((f, cwd)), + None => return Ok(None), + }, + None => None, + }; + + let mut p = Process { pid: 0, status: None }; + + struct PosixSpawnFileActions(MaybeUninit<libc::posix_spawn_file_actions_t>); + + impl Drop for PosixSpawnFileActions { + fn drop(&mut self) { + unsafe { + libc::posix_spawn_file_actions_destroy(self.0.as_mut_ptr()); + } + } + } + + struct PosixSpawnattr(MaybeUninit<libc::posix_spawnattr_t>); + + impl Drop for PosixSpawnattr { + fn drop(&mut self) { + unsafe { + libc::posix_spawnattr_destroy(self.0.as_mut_ptr()); + } + } + } + + unsafe { + let mut file_actions = PosixSpawnFileActions(MaybeUninit::uninit()); + let mut attrs = PosixSpawnattr(MaybeUninit::uninit()); + + libc::posix_spawnattr_init(attrs.0.as_mut_ptr()); + libc::posix_spawn_file_actions_init(file_actions.0.as_mut_ptr()); + + if let Some(fd) = stdio.stdin.fd() { + cvt(libc::posix_spawn_file_actions_adddup2( + file_actions.0.as_mut_ptr(), + fd, + libc::STDIN_FILENO, + ))?; + } + if let Some(fd) = stdio.stdout.fd() { + cvt(libc::posix_spawn_file_actions_adddup2( + file_actions.0.as_mut_ptr(), + fd, + libc::STDOUT_FILENO, + ))?; + } + if let Some(fd) = stdio.stderr.fd() { + cvt(libc::posix_spawn_file_actions_adddup2( + file_actions.0.as_mut_ptr(), + fd, + libc::STDERR_FILENO, + ))?; + } + if let Some((f, cwd)) = addchdir { + cvt(f(file_actions.0.as_mut_ptr(), cwd.as_ptr()))?; + } + + let mut set = MaybeUninit::<libc::sigset_t>::uninit(); + cvt(sigemptyset(set.as_mut_ptr()))?; + cvt(libc::posix_spawnattr_setsigmask(attrs.0.as_mut_ptr(), set.as_ptr()))?; + cvt(sigaddset(set.as_mut_ptr(), libc::SIGPIPE))?; + cvt(libc::posix_spawnattr_setsigdefault(attrs.0.as_mut_ptr(), set.as_ptr()))?; + + let flags = libc::POSIX_SPAWN_SETSIGDEF | libc::POSIX_SPAWN_SETSIGMASK; + cvt(libc::posix_spawnattr_setflags(attrs.0.as_mut_ptr(), flags as _))?; + + // Make sure we synchronize access to the global `environ` resource + let _env_lock = sys::os::env_lock(); + let envp = envp.map(|c| c.as_ptr()).unwrap_or_else(|| *sys::os::environ() as *const _); + let ret = libc::posix_spawnp( + &mut p.pid, + self.get_program().as_ptr(), + file_actions.0.as_ptr(), + attrs.0.as_ptr(), + self.get_argv().as_ptr() as *const _, + envp as *const _, + ); + if ret == 0 { Ok(Some(p)) } else { Err(io::Error::from_raw_os_error(ret)) } + } + } +} + +//////////////////////////////////////////////////////////////////////////////// +// Processes +//////////////////////////////////////////////////////////////////////////////// + +/// The unique ID of the process (this should never be negative). +pub struct Process { + pid: pid_t, + status: Option<ExitStatus>, +} + +impl Process { + pub fn id(&self) -> u32 { + self.pid as u32 + } + + pub fn kill(&mut self) -> io::Result<()> { + // If we've already waited on this process then the pid can be recycled + // and used for another process, and we probably shouldn't be killing + // random processes, so just return an error. + if self.status.is_some() { + Err(Error::new( + ErrorKind::InvalidInput, + "invalid argument: can't kill an exited process", + )) + } else { + cvt(unsafe { libc::kill(self.pid, libc::SIGKILL) }).map(drop) + } + } + + pub fn wait(&mut self) -> io::Result<ExitStatus> { + use crate::sys::cvt_r; + if let Some(status) = self.status { + return Ok(status); + } + let mut status = 0 as c_int; + cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) })?; + self.status = Some(ExitStatus::new(status)); + Ok(ExitStatus::new(status)) + } + + pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> { + if let Some(status) = self.status { + return Ok(Some(status)); + } + let mut status = 0 as c_int; + let pid = cvt(unsafe { libc::waitpid(self.pid, &mut status, libc::WNOHANG) })?; + if pid == 0 { + Ok(None) + } else { + self.status = Some(ExitStatus::new(status)); + Ok(Some(ExitStatus::new(status))) + } + } +} + +/// Unix exit statuses +#[derive(PartialEq, Eq, Clone, Copy, Debug)] +pub struct ExitStatus(c_int); + +impl ExitStatus { + pub fn new(status: c_int) -> ExitStatus { + ExitStatus(status) + } + + fn exited(&self) -> bool { + unsafe { libc::WIFEXITED(self.0) } + } + + pub fn success(&self) -> bool { + self.code() == Some(0) + } + + pub fn code(&self) -> Option<i32> { + if self.exited() { Some(unsafe { libc::WEXITSTATUS(self.0) }) } else { None } + } + + pub fn signal(&self) -> Option<i32> { + if !self.exited() { Some(unsafe { libc::WTERMSIG(self.0) }) } else { None } + } +} + +/// Converts a raw `c_int` to a type-safe `ExitStatus` by wrapping it without copying. +impl From<c_int> for ExitStatus { + fn from(a: c_int) -> ExitStatus { + ExitStatus(a) + } +} + +impl fmt::Display for ExitStatus { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + if let Some(code) = self.code() { + write!(f, "exit code: {}", code) + } else { + let signal = self.signal().unwrap(); + write!(f, "signal: {}", signal) + } + } +} |