b37477c03e
This commit implements the `exec` function proposed in [RFC 1359][rfc] which is a function on the `CommandExt` trait to execute all parts of a `Command::spawn` without the `fork` on Unix. More details on the function itself can be found in the comments in the commit. [rfc]: https://github.com/rust-lang/rfcs/pull/1359 cc #31398
697 lines
24 KiB
Rust
697 lines
24 KiB
Rust
// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use prelude::v1::*;
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use os::unix::prelude::*;
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use collections::hash_map::{HashMap, Entry};
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use env;
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use ffi::{OsString, OsStr, CString, CStr};
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use fmt;
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use io::{self, Error, ErrorKind};
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use libc::{self, pid_t, c_int, gid_t, uid_t, c_char};
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use mem;
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use ptr;
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use sys::fd::FileDesc;
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use sys::fs::{File, OpenOptions};
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use sys::pipe::{self, AnonPipe};
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use sys::{self, cvt, cvt_r};
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////////////////////////////////////////////////////////////////////////////////
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// Command
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////////////////////////////////////////////////////////////////////////////////
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pub struct Command {
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// Currently we try hard to ensure that the call to `.exec()` doesn't
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// actually allocate any memory. While many platforms try to ensure that
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// memory allocation works after a fork in a multithreaded process, it's
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// been observed to be buggy and somewhat unreliable, so we do our best to
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// just not do it at all!
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//
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// Along those lines, the `argv` and `envp` raw pointers here are exactly
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// what's gonna get passed to `execvp`. The `argv` array starts with the
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// `program` and ends with a NULL, and the `envp` pointer, if present, is
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// also null-terminated.
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//
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// Right now we don't support removing arguments, so there's no much fancy
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// support there, but we support adding and removing environment variables,
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// so a side table is used to track where in the `envp` array each key is
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// located. Whenever we add a key we update it in place if it's already
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// present, and whenever we remove a key we update the locations of all
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// other keys.
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program: CString,
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args: Vec<CString>,
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env: Option<HashMap<OsString, (usize, CString)>>,
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argv: Vec<*const c_char>,
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envp: Option<Vec<*const c_char>>,
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cwd: Option<CString>,
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uid: Option<uid_t>,
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gid: Option<gid_t>,
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session_leader: bool,
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saw_nul: bool,
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closures: Vec<Box<FnMut() -> io::Result<()> + Send + Sync>>,
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stdin: Option<Stdio>,
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stdout: Option<Stdio>,
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stderr: Option<Stdio>,
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}
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// passed back to std::process with the pipes connected to the child, if any
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// were requested
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pub struct StdioPipes {
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pub stdin: Option<AnonPipe>,
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pub stdout: Option<AnonPipe>,
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pub stderr: Option<AnonPipe>,
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}
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// passed to do_exec() with configuration of what the child stdio should look
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// like
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struct ChildPipes {
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stdin: ChildStdio,
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stdout: ChildStdio,
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stderr: ChildStdio,
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}
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enum ChildStdio {
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Inherit,
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Explicit(c_int),
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Owned(FileDesc),
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}
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pub enum Stdio {
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Inherit,
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Null,
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MakePipe,
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Fd(FileDesc),
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}
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impl Command {
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pub fn new(program: &OsStr) -> Command {
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let mut saw_nul = false;
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let program = os2c(program, &mut saw_nul);
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Command {
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argv: vec![program.as_ptr(), 0 as *const _],
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program: program,
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args: Vec::new(),
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env: None,
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envp: None,
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cwd: None,
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uid: None,
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gid: None,
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session_leader: false,
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saw_nul: saw_nul,
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closures: Vec::new(),
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stdin: None,
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stdout: None,
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stderr: None,
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}
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}
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pub fn arg(&mut self, arg: &OsStr) {
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// Overwrite the trailing NULL pointer in `argv` and then add a new null
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// pointer.
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let arg = os2c(arg, &mut self.saw_nul);
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self.argv[self.args.len() + 1] = arg.as_ptr();
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self.argv.push(0 as *const _);
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// Also make sure we keep track of the owned value to schedule a
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// destructor for this memory.
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self.args.push(arg);
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}
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fn init_env_map(&mut self) -> (&mut HashMap<OsString, (usize, CString)>,
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&mut Vec<*const c_char>) {
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if self.env.is_none() {
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let mut map = HashMap::new();
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let mut envp = Vec::new();
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for (k, v) in env::vars_os() {
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let s = pair_to_key(&k, &v, &mut self.saw_nul);
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envp.push(s.as_ptr());
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map.insert(k, (envp.len() - 1, s));
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}
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envp.push(0 as *const _);
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self.env = Some(map);
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self.envp = Some(envp);
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}
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(self.env.as_mut().unwrap(), self.envp.as_mut().unwrap())
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}
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pub fn env(&mut self, key: &OsStr, val: &OsStr) {
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let new_key = pair_to_key(key, val, &mut self.saw_nul);
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let (map, envp) = self.init_env_map();
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// If `key` is already present then we we just update `envp` in place
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// (and store the owned value), but if it's not there we override the
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// trailing NULL pointer, add a new NULL pointer, and store where we
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// were located.
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match map.entry(key.to_owned()) {
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Entry::Occupied(mut e) => {
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let (i, ref mut s) = *e.get_mut();
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envp[i] = new_key.as_ptr();
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*s = new_key;
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}
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Entry::Vacant(e) => {
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let len = envp.len();
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envp[len - 1] = new_key.as_ptr();
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envp.push(0 as *const _);
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e.insert((len - 1, new_key));
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}
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}
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}
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pub fn env_remove(&mut self, key: &OsStr) {
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let (map, envp) = self.init_env_map();
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// If we actually ended up removing a key, then we need to update the
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// position of all keys that come after us in `envp` because they're all
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// one element sooner now.
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if let Some((i, _)) = map.remove(key) {
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envp.remove(i);
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for (_, &mut (ref mut j, _)) in map.iter_mut() {
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if *j >= i {
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*j -= 1;
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}
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}
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}
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}
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pub fn env_clear(&mut self) {
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self.env = Some(HashMap::new());
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self.envp = Some(vec![0 as *const _]);
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}
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pub fn cwd(&mut self, dir: &OsStr) {
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self.cwd = Some(os2c(dir, &mut self.saw_nul));
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}
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pub fn uid(&mut self, id: uid_t) {
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self.uid = Some(id);
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}
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pub fn gid(&mut self, id: gid_t) {
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self.gid = Some(id);
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}
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pub fn session_leader(&mut self, session_leader: bool) {
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self.session_leader = session_leader;
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}
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pub fn before_exec(&mut self,
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f: Box<FnMut() -> io::Result<()> + Send + Sync>) {
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self.closures.push(f);
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}
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pub fn stdin(&mut self, stdin: Stdio) {
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self.stdin = Some(stdin);
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}
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pub fn stdout(&mut self, stdout: Stdio) {
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self.stdout = Some(stdout);
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}
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pub fn stderr(&mut self, stderr: Stdio) {
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self.stderr = Some(stderr);
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}
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pub fn spawn(&mut self, default: Stdio)
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-> io::Result<(Process, StdioPipes)> {
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if self.saw_nul {
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return Err(io::Error::new(ErrorKind::InvalidInput,
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"nul byte found in provided data"));
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}
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let (ours, theirs) = try!(self.setup_io(default));
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let (input, output) = try!(sys::pipe::anon_pipe());
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let pid = unsafe {
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match try!(cvt(libc::fork())) {
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0 => {
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drop(input);
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let err = self.do_exec(theirs);
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let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
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let bytes = [
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(errno >> 24) as u8,
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(errno >> 16) as u8,
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(errno >> 8) as u8,
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(errno >> 0) as u8,
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CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
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CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
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];
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// pipe I/O up to PIPE_BUF bytes should be atomic, and then
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// we want to be sure we *don't* run at_exit destructors as
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// we're being torn down regardless
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assert!(output.write(&bytes).is_ok());
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libc::_exit(1)
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}
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n => n,
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}
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};
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let mut p = Process { pid: pid, status: None };
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drop(output);
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let mut bytes = [0; 8];
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// loop to handle EINTR
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loop {
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match input.read(&mut bytes) {
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Ok(0) => return Ok((p, ours)),
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Ok(8) => {
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assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
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"Validation on the CLOEXEC pipe failed: {:?}", bytes);
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let errno = combine(&bytes[0.. 4]);
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assert!(p.wait().is_ok(),
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"wait() should either return Ok or panic");
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return Err(Error::from_raw_os_error(errno))
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}
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Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
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Err(e) => {
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assert!(p.wait().is_ok(),
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"wait() should either return Ok or panic");
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panic!("the CLOEXEC pipe failed: {:?}", e)
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},
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Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
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assert!(p.wait().is_ok(),
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"wait() should either return Ok or panic");
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panic!("short read on the CLOEXEC pipe")
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}
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}
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}
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fn combine(arr: &[u8]) -> i32 {
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let a = arr[0] as u32;
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let b = arr[1] as u32;
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let c = arr[2] as u32;
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let d = arr[3] as u32;
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((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
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}
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}
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pub fn exec(&mut self, default: Stdio) -> io::Error {
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if self.saw_nul {
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return io::Error::new(ErrorKind::InvalidInput,
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"nul byte found in provided data")
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}
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match self.setup_io(default) {
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Ok((_, theirs)) => unsafe { self.do_exec(theirs) },
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Err(e) => e,
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}
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}
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// And at this point we've reached a special time in the life of the
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// child. The child must now be considered hamstrung and unable to
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// do anything other than syscalls really. Consider the following
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// scenario:
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//
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// 1. Thread A of process 1 grabs the malloc() mutex
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// 2. Thread B of process 1 forks(), creating thread C
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// 3. Thread C of process 2 then attempts to malloc()
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// 4. The memory of process 2 is the same as the memory of
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// process 1, so the mutex is locked.
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//
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// This situation looks a lot like deadlock, right? It turns out
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// that this is what pthread_atfork() takes care of, which is
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// presumably implemented across platforms. The first thing that
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// threads to *before* forking is to do things like grab the malloc
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// mutex, and then after the fork they unlock it.
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//
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// Despite this information, libnative's spawn has been witnessed to
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// deadlock on both OSX and FreeBSD. I'm not entirely sure why, but
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// all collected backtraces point at malloc/free traffic in the
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// child spawned process.
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//
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// For this reason, the block of code below should contain 0
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// invocations of either malloc of free (or their related friends).
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//
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// As an example of not having malloc/free traffic, we don't close
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// this file descriptor by dropping the FileDesc (which contains an
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// allocation). Instead we just close it manually. This will never
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// have the drop glue anyway because this code never returns (the
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// child will either exec() or invoke libc::exit)
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unsafe fn do_exec(&mut self, stdio: ChildPipes) -> io::Error {
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macro_rules! try {
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($e:expr) => (match $e {
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Ok(e) => e,
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Err(e) => return e,
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})
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}
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if let Some(fd) = stdio.stdin.fd() {
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try!(cvt_r(|| libc::dup2(fd, libc::STDIN_FILENO)));
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}
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if let Some(fd) = stdio.stdout.fd() {
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try!(cvt_r(|| libc::dup2(fd, libc::STDOUT_FILENO)));
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}
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if let Some(fd) = stdio.stderr.fd() {
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try!(cvt_r(|| libc::dup2(fd, libc::STDERR_FILENO)));
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}
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if let Some(u) = self.gid {
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try!(cvt(libc::setgid(u as gid_t)));
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}
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if let Some(u) = self.uid {
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// When dropping privileges from root, the `setgroups` call
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// will remove any extraneous groups. If we don't call this,
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// then even though our uid has dropped, we may still have
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// groups that enable us to do super-user things. This will
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// fail if we aren't root, so don't bother checking the
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// return value, this is just done as an optimistic
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// privilege dropping function.
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let _ = libc::setgroups(0, ptr::null());
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try!(cvt(libc::setuid(u as uid_t)));
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}
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if self.session_leader {
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// Don't check the error of setsid because it fails if we're the
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// process leader already. We just forked so it shouldn't return
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// error, but ignore it anyway.
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let _ = libc::setsid();
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}
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if let Some(ref cwd) = self.cwd {
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try!(cvt(libc::chdir(cwd.as_ptr())));
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}
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if let Some(ref envp) = self.envp {
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*sys::os::environ() = envp.as_ptr();
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}
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// NaCl has no signal support.
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if cfg!(not(target_os = "nacl")) {
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// Reset signal handling so the child process starts in a
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// standardized state. libstd ignores SIGPIPE, and signal-handling
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// libraries often set a mask. Child processes inherit ignored
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// signals and the signal mask from their parent, but most
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// UNIX programs do not reset these things on their own, so we
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// need to clean things up now to avoid confusing the program
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// we're about to run.
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let mut set: libc::sigset_t = mem::uninitialized();
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try!(cvt(libc::sigemptyset(&mut set)));
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try!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set,
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ptr::null_mut())));
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let ret = libc::signal(libc::SIGPIPE, libc::SIG_DFL);
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if ret == libc::SIG_ERR {
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return io::Error::last_os_error()
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}
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}
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for callback in self.closures.iter_mut() {
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try!(callback());
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}
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libc::execvp(self.argv[0], self.argv.as_ptr());
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io::Error::last_os_error()
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}
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fn setup_io(&self, default: Stdio) -> io::Result<(StdioPipes, ChildPipes)> {
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let stdin = self.stdin.as_ref().unwrap_or(&default);
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let stdout = self.stdout.as_ref().unwrap_or(&default);
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let stderr = self.stderr.as_ref().unwrap_or(&default);
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let (their_stdin, our_stdin) = try!(stdin.to_child_stdio(true));
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let (their_stdout, our_stdout) = try!(stdout.to_child_stdio(false));
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let (their_stderr, our_stderr) = try!(stderr.to_child_stdio(false));
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let ours = StdioPipes {
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stdin: our_stdin,
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stdout: our_stdout,
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stderr: our_stderr,
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};
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let theirs = ChildPipes {
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stdin: their_stdin,
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stdout: their_stdout,
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stderr: their_stderr,
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};
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Ok((ours, theirs))
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}
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}
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fn os2c(s: &OsStr, saw_nul: &mut bool) -> CString {
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CString::new(s.as_bytes()).unwrap_or_else(|_e| {
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*saw_nul = true;
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CString::new("<string-with-nul>").unwrap()
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})
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}
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impl Stdio {
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fn to_child_stdio(&self, readable: bool)
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-> io::Result<(ChildStdio, Option<AnonPipe>)> {
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match *self {
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Stdio::Inherit => Ok((ChildStdio::Inherit, None)),
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// Make sure that the source descriptors are not an stdio
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// descriptor, otherwise the order which we set the child's
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// descriptors may blow away a descriptor which we are hoping to
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// save. For example, suppose we want the child's stderr to be the
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// parent's stdout, and the child's stdout to be the parent's
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// stderr. No matter which we dup first, the second will get
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// overwritten prematurely.
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Stdio::Fd(ref fd) => {
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if fd.raw() >= 0 && fd.raw() <= libc::STDERR_FILENO {
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Ok((ChildStdio::Owned(try!(fd.duplicate())), None))
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} else {
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Ok((ChildStdio::Explicit(fd.raw()), None))
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}
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}
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Stdio::MakePipe => {
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let (reader, writer) = try!(pipe::anon_pipe());
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let (ours, theirs) = if readable {
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(writer, reader)
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} else {
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(reader, writer)
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};
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Ok((ChildStdio::Owned(theirs.into_fd()), Some(ours)))
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}
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Stdio::Null => {
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let mut opts = OpenOptions::new();
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opts.read(readable);
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opts.write(!readable);
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let path = unsafe {
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CStr::from_ptr("/dev/null\0".as_ptr() as *const _)
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};
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let fd = try!(File::open_c(&path, &opts));
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Ok((ChildStdio::Owned(fd.into_fd()), None))
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}
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}
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}
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|
}
|
|
|
|
impl ChildStdio {
|
|
fn fd(&self) -> Option<c_int> {
|
|
match *self {
|
|
ChildStdio::Inherit => None,
|
|
ChildStdio::Explicit(fd) => Some(fd),
|
|
ChildStdio::Owned(ref fd) => Some(fd.raw()),
|
|
}
|
|
}
|
|
}
|
|
|
|
fn pair_to_key(key: &OsStr, value: &OsStr, saw_nul: &mut bool) -> CString {
|
|
let (key, value) = (key.as_bytes(), value.as_bytes());
|
|
let mut v = Vec::with_capacity(key.len() + value.len() + 1);
|
|
v.extend(key);
|
|
v.push(b'=');
|
|
v.extend(value);
|
|
CString::new(v).unwrap_or_else(|_e| {
|
|
*saw_nul = true;
|
|
CString::new("foo=bar").unwrap()
|
|
})
|
|
}
|
|
|
|
impl fmt::Debug for Command {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
try!(write!(f, "{:?}", self.program));
|
|
for arg in &self.args {
|
|
try!(write!(f, " {:?}", arg));
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
// Processes
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
/// Unix exit statuses
|
|
#[derive(PartialEq, Eq, Clone, Copy, Debug)]
|
|
pub struct ExitStatus(c_int);
|
|
|
|
#[cfg(any(target_os = "linux", target_os = "android",
|
|
target_os = "nacl"))]
|
|
mod status_imp {
|
|
pub fn WIFEXITED(status: i32) -> bool { (status & 0xff) == 0 }
|
|
pub fn WEXITSTATUS(status: i32) -> i32 { (status >> 8) & 0xff }
|
|
pub fn WTERMSIG(status: i32) -> i32 { status & 0x7f }
|
|
}
|
|
|
|
#[cfg(any(target_os = "macos",
|
|
target_os = "ios",
|
|
target_os = "freebsd",
|
|
target_os = "dragonfly",
|
|
target_os = "bitrig",
|
|
target_os = "netbsd",
|
|
target_os = "openbsd"))]
|
|
mod status_imp {
|
|
pub fn WIFEXITED(status: i32) -> bool { (status & 0x7f) == 0 }
|
|
pub fn WEXITSTATUS(status: i32) -> i32 { status >> 8 }
|
|
pub fn WTERMSIG(status: i32) -> i32 { status & 0o177 }
|
|
}
|
|
|
|
impl ExitStatus {
|
|
fn exited(&self) -> bool {
|
|
status_imp::WIFEXITED(self.0)
|
|
}
|
|
|
|
pub fn success(&self) -> bool {
|
|
self.code() == Some(0)
|
|
}
|
|
|
|
pub fn code(&self) -> Option<i32> {
|
|
if self.exited() {
|
|
Some(status_imp::WEXITSTATUS(self.0))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
pub fn signal(&self) -> Option<i32> {
|
|
if !self.exited() {
|
|
Some(status_imp::WTERMSIG(self.0))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
}
|
|
|
|
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)
|
|
}
|
|
}
|
|
}
|
|
|
|
/// The unique id of the process (this should never be negative).
|
|
pub struct Process {
|
|
pid: pid_t,
|
|
status: Option<ExitStatus>,
|
|
}
|
|
|
|
const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
|
|
|
|
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(|_| ())
|
|
}
|
|
}
|
|
|
|
pub fn wait(&mut self) -> io::Result<ExitStatus> {
|
|
if let Some(status) = self.status {
|
|
return Ok(status)
|
|
}
|
|
let mut status = 0 as c_int;
|
|
try!(cvt_r(|| unsafe { libc::waitpid(self.pid, &mut status, 0) }));
|
|
self.status = Some(ExitStatus(status));
|
|
Ok(ExitStatus(status))
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use super::*;
|
|
use prelude::v1::*;
|
|
|
|
use ffi::OsStr;
|
|
use mem;
|
|
use ptr;
|
|
use libc;
|
|
use sys::cvt;
|
|
|
|
macro_rules! t {
|
|
($e:expr) => {
|
|
match $e {
|
|
Ok(t) => t,
|
|
Err(e) => panic!("received error for `{}`: {}", stringify!($e), e),
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(not(target_os = "android"))]
|
|
extern {
|
|
#[cfg_attr(target_os = "netbsd", link_name = "__sigaddset14")]
|
|
fn sigaddset(set: *mut libc::sigset_t, signum: libc::c_int) -> libc::c_int;
|
|
}
|
|
|
|
#[cfg(target_os = "android")]
|
|
unsafe fn sigaddset(set: *mut libc::sigset_t, signum: libc::c_int) -> libc::c_int {
|
|
use slice;
|
|
|
|
let raw = slice::from_raw_parts_mut(set as *mut u8, mem::size_of::<libc::sigset_t>());
|
|
let bit = (signum - 1) as usize;
|
|
raw[bit / 8] |= 1 << (bit % 8);
|
|
return 0;
|
|
}
|
|
|
|
// See #14232 for more information, but it appears that signal delivery to a
|
|
// newly spawned process may just be raced in the OSX, so to prevent this
|
|
// test from being flaky we ignore it on OSX.
|
|
#[test]
|
|
#[cfg_attr(target_os = "macos", ignore)]
|
|
#[cfg_attr(target_os = "nacl", ignore)] // no signals on NaCl.
|
|
fn test_process_mask() {
|
|
unsafe {
|
|
// Test to make sure that a signal mask does not get inherited.
|
|
let mut cmd = Command::new(OsStr::new("cat"));
|
|
|
|
let mut set: libc::sigset_t = mem::uninitialized();
|
|
let mut old_set: libc::sigset_t = mem::uninitialized();
|
|
t!(cvt(libc::sigemptyset(&mut set)));
|
|
t!(cvt(sigaddset(&mut set, libc::SIGINT)));
|
|
t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set, &mut old_set)));
|
|
|
|
cmd.stdin(Stdio::MakePipe);
|
|
cmd.stdout(Stdio::MakePipe);
|
|
|
|
let (mut cat, mut pipes) = t!(cmd.spawn(Stdio::Null));
|
|
let stdin_write = pipes.stdin.take().unwrap();
|
|
let stdout_read = pipes.stdout.take().unwrap();
|
|
|
|
t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &old_set,
|
|
ptr::null_mut())));
|
|
|
|
t!(cvt(libc::kill(cat.id() as libc::pid_t, libc::SIGINT)));
|
|
// We need to wait until SIGINT is definitely delivered. The
|
|
// easiest way is to write something to cat, and try to read it
|
|
// back: if SIGINT is unmasked, it'll get delivered when cat is
|
|
// next scheduled.
|
|
let _ = stdin_write.write(b"Hello");
|
|
drop(stdin_write);
|
|
|
|
// Either EOF or failure (EPIPE) is okay.
|
|
let mut buf = [0; 5];
|
|
if let Ok(ret) = stdout_read.read(&mut buf) {
|
|
assert!(ret == 0);
|
|
}
|
|
|
|
t!(cat.wait());
|
|
}
|
|
}
|
|
}
|