src/libstd/sys/unix/process.rs

   1 // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use prelude::v1::*;
  12 use os::unix::prelude::*;
  13
  14 use collections::HashMap;
  15 use env;
  16 use ffi::{OsString, OsStr, CString, CStr};
  17 use fmt;
  18 use io::{self, Error, ErrorKind};
  19 use libc::{self, pid_t, c_void, c_int, gid_t, uid_t};
  20 use ptr;
  21 use sys::pipe::AnonPipe;
  22 use sys::{self, c, cvt, cvt_r};
  23 use sys::fs::{File, OpenOptions};
  24
  25 ////////////////////////////////////////////////////////////////////////////////
  26 // Command
  27 ////////////////////////////////////////////////////////////////////////////////
  28
  29 #[derive(Clone)]
  30 pub struct Command {
  31     pub program: CString,
  32     pub args: Vec<CString>,
  33     pub env: Option<HashMap<OsString, OsString>>,
  34     pub cwd: Option<CString>,
  35     pub uid: Option<uid_t>,
  36     pub gid: Option<gid_t>,
  37     pub detach: bool, // not currently exposed in std::process
  38 }
  39
  40 impl Command {
  41     pub fn new(program: &OsStr) -> Command {
  42         Command {
  43             program: program.to_cstring().unwrap(),
  44             args: Vec::new(),
  45             env: None,
  46             cwd: None,
  47             uid: None,
  48             gid: None,
  49             detach: false,
  50         }
  51     }
  52
  53     pub fn arg(&mut self, arg: &OsStr) {
  54         self.args.push(arg.to_cstring().unwrap())
  55     }
  56     pub fn args<'a, I: Iterator<Item = &'a OsStr>>(&mut self, args: I) {
  57         self.args.extend(args.map(|s| s.to_cstring().unwrap()))
  58     }
  59     fn init_env_map(&mut self) {
  60         if self.env.is_none() {
  61             self.env = Some(env::vars_os().collect());
  62         }
  63     }
  64     pub fn env(&mut self, key: &OsStr, val: &OsStr) {
  65         self.init_env_map();
  66         self.env.as_mut().unwrap().insert(key.to_os_string(), val.to_os_string());
  67     }
  68     pub fn env_remove(&mut self, key: &OsStr) {
  69         self.init_env_map();
  70         self.env.as_mut().unwrap().remove(&key.to_os_string());
  71     }
  72     pub fn env_clear(&mut self) {
  73         self.env = Some(HashMap::new())
  74     }
  75     pub fn cwd(&mut self, dir: &OsStr) {
  76         self.cwd = Some(dir.to_cstring().unwrap())
  77     }
  78 }
  79
  80 ////////////////////////////////////////////////////////////////////////////////
  81 // Processes
  82 ////////////////////////////////////////////////////////////////////////////////
  83
  84 /// Unix exit statuses
  85 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
  86 pub enum ExitStatus {
  87     /// Normal termination with an exit code.
  88     Code(i32),
  89
  90     /// Termination by signal, with the signal number.
  91     ///
  92     /// Never generated on Windows.
  93     Signal(i32),
  94 }
  95
  96 impl ExitStatus {
  97     pub fn success(&self) -> bool {
  98         *self == ExitStatus::Code(0)
  99     }
 100     pub fn code(&self) -> Option<i32> {
 101         match *self {
 102             ExitStatus::Code(c) => Some(c),
 103             _ => None
 104         }
 105     }
 106 }
 107
 108 impl fmt::Display for ExitStatus {
 109     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 110         match *self {
 111             ExitStatus::Code(code) =>  write!(f, "exit code: {}", code),
 112             ExitStatus::Signal(code) =>  write!(f, "signal: {}", code),
 113         }
 114     }
 115 }
 116
 117 /// The unique id of the process (this should never be negative).
 118 pub struct Process {
 119     pid: pid_t
 120 }
 121
 122 pub enum Stdio {
 123     Inherit,
 124     Piped(AnonPipe),
 125     None,
 126 }
 127
 128 const CLOEXEC_MSG_FOOTER: &'static [u8] = b"NOEX";
 129
 130 impl Process {
 131     pub unsafe fn kill(&self) -> io::Result<()> {
 132         try!(cvt(libc::funcs::posix88::signal::kill(self.pid, libc::SIGKILL)));
 133         Ok(())
 134     }
 135
 136     pub fn spawn(cfg: &Command,
 137                  in_fd: Stdio,
 138                  out_fd: Stdio,
 139                  err_fd: Stdio) -> io::Result<Process> {
 140         let dirp = cfg.cwd.as_ref().map(|c| c.as_ptr()).unwrap_or(ptr::null());
 141
 142         let (envp, _a, _b) = make_envp(cfg.env.as_ref());
 143         let (argv, _a) = make_argv(&cfg.program, &cfg.args);
 144         let (input, output) = try!(sys::pipe::anon_pipe());
 145
 146         let pid = unsafe {
 147             match libc::fork() {
 148                 0 => {
 149                     drop(input);
 150                     Process::child_after_fork(cfg, output, argv, envp, dirp,
 151                                               in_fd, out_fd, err_fd)
 152                 }
 153                 n if n < 0 => return Err(Error::last_os_error()),
 154                 n => n,
 155             }
 156         };
 157
 158         let p = Process{ pid: pid };
 159         drop(output);
 160         let mut bytes = [0; 8];
 161
 162         // loop to handle EINTR
 163         loop {
 164             match input.read(&mut bytes) {
 165                 Ok(0) => return Ok(p),
 166                 Ok(8) => {
 167                     assert!(combine(CLOEXEC_MSG_FOOTER) == combine(&bytes[4.. 8]),
 168                             "Validation on the CLOEXEC pipe failed: {:?}", bytes);
 169                     let errno = combine(&bytes[0.. 4]);
 170                     assert!(p.wait().is_ok(),
 171                             "wait() should either return Ok or panic");
 172                     return Err(Error::from_raw_os_error(errno))
 173                 }
 174                 Err(ref e) if e.kind() == ErrorKind::Interrupted => {}
 175                 Err(e) => {
 176                     assert!(p.wait().is_ok(),
 177                             "wait() should either return Ok or panic");
 178                     panic!("the CLOEXEC pipe failed: {:?}", e)
 179                 },
 180                 Ok(..) => { // pipe I/O up to PIPE_BUF bytes should be atomic
 181                     assert!(p.wait().is_ok(),
 182                             "wait() should either return Ok or panic");
 183                     panic!("short read on the CLOEXEC pipe")
 184                 }
 185             }
 186         }
 187
 188         fn combine(arr: &[u8]) -> i32 {
 189             let a = arr[0] as u32;
 190             let b = arr[1] as u32;
 191             let c = arr[2] as u32;
 192             let d = arr[3] as u32;
 193
 194             ((a << 24) | (b << 16) | (c << 8) | (d << 0)) as i32
 195         }
 196     }
 197
 198     // And at this point we've reached a special time in the life of the
 199     // child. The child must now be considered hamstrung and unable to
 200     // do anything other than syscalls really. Consider the following
 201     // scenario:
 202     //
 203     //      1. Thread A of process 1 grabs the malloc() mutex
 204     //      2. Thread B of process 1 forks(), creating thread C
 205     //      3. Thread C of process 2 then attempts to malloc()
 206     //      4. The memory of process 2 is the same as the memory of
 207     //         process 1, so the mutex is locked.
 208     //
 209     // This situation looks a lot like deadlock, right? It turns out
 210     // that this is what pthread_atfork() takes care of, which is
 211     // presumably implemented across platforms. The first thing that
 212     // threads to *before* forking is to do things like grab the malloc
 213     // mutex, and then after the fork they unlock it.
 214     //
 215     // Despite this information, libnative's spawn has been witnessed to
 216     // deadlock on both OSX and FreeBSD. I'm not entirely sure why, but
 217     // all collected backtraces point at malloc/free traffic in the
 218     // child spawned process.
 219     //
 220     // For this reason, the block of code below should contain 0
 221     // invocations of either malloc of free (or their related friends).
 222     //
 223     // As an example of not having malloc/free traffic, we don't close
 224     // this file descriptor by dropping the FileDesc (which contains an
 225     // allocation). Instead we just close it manually. This will never
 226     // have the drop glue anyway because this code never returns (the
 227     // child will either exec() or invoke libc::exit)
 228     unsafe fn child_after_fork(cfg: &Command,
 229                                mut output: AnonPipe,
 230                                argv: *const *const libc::c_char,
 231                                envp: *const libc::c_void,
 232                                dirp: *const libc::c_char,
 233                                in_fd: Stdio,
 234                                out_fd: Stdio,
 235                                err_fd: Stdio) -> ! {
 236         fn fail(output: &mut AnonPipe) -> ! {
 237             let errno = sys::os::errno() as u32;
 238             let bytes = [
 239                 (errno >> 24) as u8,
 240                 (errno >> 16) as u8,
 241                 (errno >>  8) as u8,
 242                 (errno >>  0) as u8,
 243                 CLOEXEC_MSG_FOOTER[0], CLOEXEC_MSG_FOOTER[1],
 244                 CLOEXEC_MSG_FOOTER[2], CLOEXEC_MSG_FOOTER[3]
 245             ];
 246             // pipe I/O up to PIPE_BUF bytes should be atomic, and then we want
 247             // to be sure we *don't* run at_exit destructors as we're being torn
 248             // down regardless
 249             assert!(output.write(&bytes).is_ok());
 250             unsafe { libc::_exit(1) }
 251         }
 252
 253         let setup = |src: Stdio, dst: c_int| {
 254             let fd = match src {
 255                 Stdio::Inherit => return true,
 256                 Stdio::Piped(pipe) => pipe.into_fd(),
 257
 258                 // If a stdio file descriptor is set to be ignored, we open up
 259                 // /dev/null into that file descriptor. Otherwise, the first
 260                 // file descriptor opened up in the child would be numbered as
 261                 // one of the stdio file descriptors, which is likely to wreak
 262                 // havoc.
 263                 Stdio::None => {
 264                     let mut opts = OpenOptions::new();
 265                     opts.read(dst == libc::STDIN_FILENO);
 266                     opts.write(dst != libc::STDIN_FILENO);
 267                     let devnull = CStr::from_ptr(b"/dev/null\0".as_ptr()
 268                                                     as *const _);
 269                     if let Ok(f) = File::open_c(devnull, &opts) {
 270                         f.into_fd()
 271                     } else {
 272                         return false
 273                     }
 274                 }
 275             };
 276             cvt_r(|| libc::dup2(fd.raw(), dst)).is_ok()
 277         };
 278
 279         if !setup(in_fd, libc::STDIN_FILENO) { fail(&mut output) }
 280         if !setup(out_fd, libc::STDOUT_FILENO) { fail(&mut output) }
 281         if !setup(err_fd, libc::STDERR_FILENO) { fail(&mut output) }
 282
 283         if let Some(u) = cfg.gid {
 284             if libc::setgid(u as libc::gid_t) != 0 {
 285                 fail(&mut output);
 286             }
 287         }
 288         if let Some(u) = cfg.uid {
 289             // When dropping privileges from root, the `setgroups` call
 290             // will remove any extraneous groups. If we don't call this,
 291             // then even though our uid has dropped, we may still have
 292             // groups that enable us to do super-user things. This will
 293             // fail if we aren't root, so don't bother checking the
 294             // return value, this is just done as an optimistic
 295             // privilege dropping function.
 296             let _ = c::setgroups(0, ptr::null());
 297
 298             if libc::setuid(u as libc::uid_t) != 0 {
 299                 fail(&mut output);
 300             }
 301         }
 302         if cfg.detach {
 303             // Don't check the error of setsid because it fails if we're the
 304             // process leader already. We just forked so it shouldn't return
 305             // error, but ignore it anyway.
 306             let _ = libc::setsid();
 307         }
 308         if !dirp.is_null() && libc::chdir(dirp) == -1 {
 309             fail(&mut output);
 310         }
 311         if !envp.is_null() {
 312             *sys::os::environ() = envp as *const _;
 313         }
 314         let _ = libc::execvp(*argv, argv as *mut _);
 315         fail(&mut output)
 316     }
 317
 318     pub fn wait(&self) -> io::Result<ExitStatus> {
 319         let mut status = 0 as c_int;
 320         try!(cvt_r(|| unsafe { c::waitpid(self.pid, &mut status, 0) }));
 321         Ok(translate_status(status))
 322     }
 323
 324     pub fn try_wait(&self) -> Option<ExitStatus> {
 325         let mut status = 0 as c_int;
 326         match cvt_r(|| unsafe {
 327             c::waitpid(self.pid, &mut status, c::WNOHANG)
 328         }) {
 329             Ok(0) => None,
 330             Ok(n) if n == self.pid => Some(translate_status(status)),
 331             Ok(n) => panic!("unknown pid: {}", n),
 332             Err(e) => panic!("unknown waitpid error: {}", e),
 333         }
 334     }
 335 }
 336
 337 fn make_argv(prog: &CString, args: &[CString])
 338              -> (*const *const libc::c_char, Vec<*const libc::c_char>)
 339 {
 340     let mut ptrs: Vec<*const libc::c_char> = Vec::with_capacity(args.len()+1);
 341
 342     // Convert the CStrings into an array of pointers. Note: the
 343     // lifetime of the various CStrings involved is guaranteed to be
 344     // larger than the lifetime of our invocation of cb, but this is
 345     // technically unsafe as the callback could leak these pointers
 346     // out of our scope.
 347     ptrs.push(prog.as_ptr());
 348     ptrs.extend(args.iter().map(|tmp| tmp.as_ptr()));
 349
 350     // Add a terminating null pointer (required by libc).
 351     ptrs.push(ptr::null());
 352
 353     (ptrs.as_ptr(), ptrs)
 354 }
 355
 356 fn make_envp(env: Option<&HashMap<OsString, OsString>>)
 357              -> (*const c_void, Vec<Vec<u8>>, Vec<*const libc::c_char>)
 358 {
 359     // On posixy systems we can pass a char** for envp, which is a
 360     // null-terminated array of "k=v\0" strings. Since we must create
 361     // these strings locally, yet expose a raw pointer to them, we
 362     // create a temporary vector to own the CStrings that outlives the
 363     // call to cb.
 364     if let Some(env) = env {
 365         let mut tmps = Vec::with_capacity(env.len());
 366
 367         for pair in env {
 368             let mut kv = Vec::new();
 369             kv.push_all(pair.0.as_bytes());
 370             kv.push('=' as u8);
 371             kv.push_all(pair.1.as_bytes());
 372             kv.push(0); // terminating null
 373             tmps.push(kv);
 374         }
 375
 376         let mut ptrs: Vec<*const libc::c_char> =
 377             tmps.iter()
 378                 .map(|tmp| tmp.as_ptr() as *const libc::c_char)
 379                 .collect();
 380         ptrs.push(ptr::null());
 381
 382         (ptrs.as_ptr() as *const _, tmps, ptrs)
 383     } else {
 384         (0 as *const _, Vec::new(), Vec::new())
 385     }
 386 }
 387
 388 fn translate_status(status: c_int) -> ExitStatus {
 389     #![allow(non_snake_case)]
 390     #[cfg(any(target_os = "linux", target_os = "android"))]
 391     mod imp {
 392         pub fn WIFEXITED(status: i32) -> bool { (status & 0xff) == 0 }
 393         pub fn WEXITSTATUS(status: i32) -> i32 { (status >> 8) & 0xff }
 394         pub fn WTERMSIG(status: i32) -> i32 { status & 0x7f }
 395     }
 396
 397     #[cfg(any(target_os = "macos",
 398               target_os = "ios",
 399               target_os = "freebsd",
 400               target_os = "dragonfly",
 401               target_os = "bitrig",
 402               target_os = "openbsd"))]
 403     mod imp {
 404         pub fn WIFEXITED(status: i32) -> bool { (status & 0x7f) == 0 }
 405         pub fn WEXITSTATUS(status: i32) -> i32 { status >> 8 }
 406         pub fn WTERMSIG(status: i32) -> i32 { status & 0o177 }
 407     }
 408
 409     if imp::WIFEXITED(status) {
 410         ExitStatus::Code(imp::WEXITSTATUS(status))
 411     } else {
 412         ExitStatus::Signal(imp::WTERMSIG(status))
 413     }
 414 }