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[/] [openrisc/] [tags/] [gnu-dev/] [fsf-gcc-snapshot-1-mar-12/] [or1k-gcc/] [libgo/] [go/] [syscall/] [exec_bsd.go] - Rev 747
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// Copyright 2011 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.
// +build darwin freebsd netbsd openbsd
package syscall
import (
"unsafe"
)
type SysProcAttr struct {
Chroot string // Chroot.
Credential *Credential // Credential.
Ptrace bool // Enable tracing.
Setsid bool // Create session.
Setpgid bool // Set process group ID to new pid (SYSV setpgrp)
Setctty bool // Set controlling terminal to fd 0
Noctty bool // Detach fd 0 from controlling terminal
}
// 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.
// The calls to RawSyscall are okay because they are assembly
// functions that do not grow the stack.
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.
fd := append([]int(nil), attr.Files...)
// About to call fork.
// No more allocation or calls of non-assembly functions.
r1, err1 = raw_fork()
if err1 != 0 {
return 0, err1
}
if r1 != 0 {
// parent; return PID
return int(r1), 0
}
// Fork succeeded, now in child.
// Enable tracing if requested.
if sys.Ptrace {
err1 = raw_ptrace(_PTRACE_TRACEME, 0, nil, nil)
if err1 != 0 {
goto childerror
}
}
// Session ID
if sys.Setsid {
err1 = raw_setsid()
if err1 != 0 {
goto childerror
}
}
// Set process group
if sys.Setpgid {
err1 = raw_setpgid(0, 0)
if err1 != 0 {
goto childerror
}
}
// 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)
if ngroups == 0 {
err2 := setgroups(0, nil)
if err2 == nil {
err1 = 0
} else {
err1 = err2.(Errno)
}
} else {
groups := make([]Gid_t, ngroups)
for i, v := range cred.Groups {
groups[i] = Gid_t(v)
}
err2 := setgroups(ngroups, &groups[0])
if err2 == nil {
err1 = 0
} else {
err1 = err2.(Errno)
}
}
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.
nextfd = int(len(fd))
if pipe < nextfd {
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) {
err1 = raw_dup2(fd[i], nextfd)
if err1 != 0 {
goto childerror
}
raw_fcntl(nextfd, F_SETFD, FD_CLOEXEC)
fd[i] = nextfd
nextfd++
if nextfd == pipe { // don't stomp on pipe
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
}
}
// Make fd 0 the tty
if sys.Setctty {
_, err1 = raw_ioctl(0, 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)
}
// Calling panic is not actually safe,
// but the for loop above won't break
// and this shuts up the compiler.
panic("unreached")
}
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