blob: a62b3e920e6985c0023126a43f7713444c049c3f [file] [log] [blame]
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build hurd
package syscall
import (
"runtime"
"unsafe"
)
type SysProcAttr struct {
Chroot string // Chroot.
Credential *Credential // Credential.
Ptrace bool // Enable tracing.
Setsid bool // Create session.
// Setpgid sets the process group ID of the child to Pgid,
// or, if Pgid == 0, to the new child's process ID.
Setpgid bool
// Setctty sets the controlling terminal of the child to
// file descriptor Ctty. Ctty must be a descriptor number
// in the child process: an index into ProcAttr.Files.
// This is only meaningful if Setsid is true.
Setctty bool
Noctty bool // Detach fd 0 from controlling terminal
Ctty int // Controlling TTY fd
// Foreground places the child process group in the foreground.
// This implies Setpgid. The Ctty field must be set to
// the descriptor of the controlling TTY.
// Unlike Setctty, in this case Ctty must be a descriptor
// number in the parent process.
Foreground bool
Pgid int // Child's process group ID if Setpgid.
}
// Implemented in runtime package.
func runtime_BeforeFork()
func runtime_AfterFork()
func runtime_AfterForkInChild()
// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
// If a dup or exec fails, write the errno error to pipe.
// (Pipe is close-on-exec so if exec succeeds, it will be closed.)
// In the child, this function must not acquire any locks, because
// they might have been locked at the time of the fork. This means
// no rescheduling, no malloc calls, and no new stack segments.
// For the same reason compiler does not race instrument it.
// The calls to RawSyscall are okay because they are assembly
// functions that do not grow the stack.
//
//go:norace
func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
// Declare all variables at top in case any
// declarations require heap allocation (e.g., err1).
var (
r1 Pid_t
err1 Errno
nextfd int
i int
)
// guard against side effects of shuffling fds below.
// Make sure that nextfd is beyond any currently open files so
// that we can't run the risk of overwriting any of them.
fd := make([]int, len(attr.Files))
nextfd = len(attr.Files)
for i, ufd := range attr.Files {
if nextfd < int(ufd) {
nextfd = int(ufd)
}
fd[i] = int(ufd)
}
nextfd++
// About to call fork.
// No more allocation or calls of non-assembly functions.
runtime_BeforeFork()
r1, err1 = raw_fork()
if err1 != 0 {
runtime_AfterFork()
return 0, err1
}
if r1 != 0 {
// parent; return PID
runtime_AfterFork()
return int(r1), 0
}
// Fork succeeded, now in child.
// Enable tracing if requested.
if sys.Ptrace {
err1 = raw_ptrace(_PTRACE_TRACEME, 0, 0, 0)
if err1 != 0 {
goto childerror
}
}
// Session ID
if sys.Setsid {
err1 = raw_setsid()
if err1 != 0 {
goto childerror
}
}
// Set process group
if sys.Setpgid || sys.Foreground {
// Place child in process group.
err1 = raw_setpgid(0, sys.Pgid)
if err1 != 0 {
goto childerror
}
}
if sys.Foreground {
pgrp := Pid_t(sys.Pgid)
if pgrp == 0 {
pgrp = raw_getpid()
}
// Place process group in foreground.
_, err1 = raw_ioctl_ptr(sys.Ctty, TIOCSPGRP, unsafe.Pointer(&pgrp))
if err1 != 0 {
goto childerror
}
}
// Restore the signal mask. We do this after TIOCSPGRP to avoid
// having the kernel send a SIGTTOU signal to the process group.
runtime_AfterForkInChild()
// Chroot
if chroot != nil {
err1 = raw_chroot(chroot)
if err1 != 0 {
goto childerror
}
}
// User and groups
if cred := sys.Credential; cred != nil {
ngroups := len(cred.Groups)
var groups unsafe.Pointer
if ngroups > 0 {
groups = unsafe.Pointer(&cred.Groups[0])
}
if !cred.NoSetGroups {
err1 = raw_setgroups(ngroups, groups)
if err1 != 0 {
goto childerror
}
}
err2 := Setgid(int(cred.Gid))
if err2 != nil {
err1 = err2.(Errno)
goto childerror
}
err2 = Setuid(int(cred.Uid))
if err2 != nil {
err1 = err2.(Errno)
goto childerror
}
}
// Chdir
if dir != nil {
err1 = raw_chdir(dir)
if err1 != 0 {
goto childerror
}
}
// Pass 1: look for fd[i] < i and move those up above len(fd)
// so that pass 2 won't stomp on an fd it needs later.
if pipe < nextfd {
switch runtime.GOOS {
case "netbsd":
err1 = raw_dup3(pipe, nextfd, O_CLOEXEC)
if err1 != 0 {
goto childerror
}
default:
err1 = raw_dup2(pipe, nextfd)
if err1 != 0 {
goto childerror
}
raw_fcntl(nextfd, F_SETFD, FD_CLOEXEC)
}
pipe = nextfd
nextfd++
}
for i = 0; i < len(fd); i++ {
if fd[i] >= 0 && fd[i] < int(i) {
if nextfd == pipe { // don't stomp on pipe
nextfd++
}
switch runtime.GOOS {
case "netbsd":
err1 = raw_dup3(fd[i], nextfd, O_CLOEXEC)
if err1 != 0 {
goto childerror
}
default:
err1 = raw_dup2(fd[i], nextfd)
if err1 != 0 {
goto childerror
}
raw_fcntl(nextfd, F_SETFD, FD_CLOEXEC)
}
fd[i] = nextfd
nextfd++
}
}
// Pass 2: dup fd[i] down onto i.
for i = 0; i < len(fd); i++ {
if fd[i] == -1 {
raw_close(i)
continue
}
if fd[i] == int(i) {
// dup2(i, i) won't clear close-on-exec flag on Linux,
// probably not elsewhere either.
_, err1 = raw_fcntl(fd[i], F_SETFD, 0)
if err1 != 0 {
goto childerror
}
continue
}
// The new fd is created NOT close-on-exec,
// which is exactly what we want.
err1 = raw_dup2(fd[i], i)
if err1 != 0 {
goto childerror
}
}
// By convention, we don't close-on-exec the fds we are
// started with, so if len(fd) < 3, close 0, 1, 2 as needed.
// Programs that know they inherit fds >= 3 will need
// to set them close-on-exec.
for i = len(fd); i < 3; i++ {
raw_close(i)
}
// Detach fd 0 from tty
if sys.Noctty {
_, err1 = raw_ioctl(0, TIOCNOTTY, 0)
if err1 != 0 {
goto childerror
}
}
// Set the controlling TTY to Ctty
if sys.Setctty {
if TIOCSCTTY == 0 {
err1 = ENOSYS
goto childerror
}
_, err1 = raw_ioctl(sys.Ctty, TIOCSCTTY, 0)
if err1 != 0 {
goto childerror
}
}
// Time to exec.
err1 = raw_execve(argv0, &argv[0], &envv[0])
childerror:
// send error code on pipe
raw_write(pipe, (*byte)(unsafe.Pointer(&err1)), int(unsafe.Sizeof(err1)))
for {
raw_exit(253)
}
}