mirror of https://go.googlesource.com/go
320 lines
8.2 KiB
Go
320 lines
8.2 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build aix || solaris
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// This file handles forkAndExecInChild function for OS using libc syscall like AIX or Solaris.
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package syscall
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import (
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"runtime"
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"unsafe"
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)
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type SysProcAttr struct {
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Chroot string // Chroot.
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Credential *Credential // Credential.
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Setsid bool // Create session.
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// Setpgid sets the process group ID of the child to Pgid,
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// or, if Pgid == 0, to the new child's process ID.
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Setpgid bool
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// Setctty sets the controlling terminal of the child to
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// file descriptor Ctty. Ctty must be a descriptor number
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// in the child process: an index into ProcAttr.Files.
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// This is only meaningful if Setsid is true.
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Setctty bool
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Noctty bool // Detach fd 0 from controlling terminal
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Ctty int // Controlling TTY fd
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// Foreground places the child process group in the foreground.
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// This implies Setpgid. The Ctty field must be set to
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// the descriptor of the controlling TTY.
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// Unlike Setctty, in this case Ctty must be a descriptor
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// number in the parent process.
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Foreground bool
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Pgid int // Child's process group ID if Setpgid.
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}
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// Implemented in runtime package.
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func runtime_BeforeFork()
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func runtime_AfterFork()
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func runtime_AfterForkInChild()
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func chdir(path uintptr) (err Errno)
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func chroot1(path uintptr) (err Errno)
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func closeFD(fd uintptr) (err Errno)
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func dup2child(old uintptr, new uintptr) (val uintptr, err Errno)
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func execve(path uintptr, argv uintptr, envp uintptr) (err Errno)
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func exit(code uintptr)
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func fcntl1(fd uintptr, cmd uintptr, arg uintptr) (val uintptr, err Errno)
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func forkx(flags uintptr) (pid uintptr, err Errno)
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func getpid() (pid uintptr, err Errno)
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func ioctl(fd uintptr, req uintptr, arg uintptr) (err Errno)
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func setgid(gid uintptr) (err Errno)
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func setgroups1(ngid uintptr, gid uintptr) (err Errno)
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func setrlimit1(which uintptr, lim unsafe.Pointer) (err Errno)
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func setsid() (pid uintptr, err Errno)
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func setuid(uid uintptr) (err Errno)
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func setpgid(pid uintptr, pgid uintptr) (err Errno)
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func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err Errno)
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// syscall defines this global on our behalf to avoid a build dependency on other platforms
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func init() {
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execveLibc = execve
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}
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// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
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// If a dup or exec fails, write the errno error to pipe.
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// (Pipe is close-on-exec so if exec succeeds, it will be closed.)
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// In the child, this function must not acquire any locks, because
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// they might have been locked at the time of the fork. This means
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// no rescheduling, no malloc calls, and no new stack segments.
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//
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// We call hand-crafted syscalls, implemented in
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// ../runtime/syscall_solaris.go, rather than generated libc wrappers
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// because we need to avoid lazy-loading the functions (might malloc,
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// split the stack, or acquire mutexes). We can't call RawSyscall
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// because it's not safe even for BSD-subsystem calls.
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//
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//go:norace
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func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
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// Declare all variables at top in case any
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// declarations require heap allocation (e.g., err1).
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var (
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r1 uintptr
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err1 Errno
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nextfd int
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i int
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pgrp _Pid_t
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cred *Credential
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ngroups, groups uintptr
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)
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rlim := origRlimitNofile.Load()
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// guard against side effects of shuffling fds below.
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// Make sure that nextfd is beyond any currently open files so
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// that we can't run the risk of overwriting any of them.
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fd := make([]int, len(attr.Files))
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nextfd = len(attr.Files)
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for i, ufd := range attr.Files {
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if nextfd < int(ufd) {
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nextfd = int(ufd)
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}
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fd[i] = int(ufd)
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}
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nextfd++
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// About to call fork.
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// No more allocation or calls of non-assembly functions.
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runtime_BeforeFork()
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r1, err1 = forkx(0x1) // FORK_NOSIGCHLD
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if err1 != 0 {
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runtime_AfterFork()
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return 0, err1
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}
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if r1 != 0 {
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// parent; return PID
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runtime_AfterFork()
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return int(r1), 0
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}
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// Fork succeeded, now in child.
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// Session ID
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if sys.Setsid {
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_, err1 = setsid()
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if err1 != 0 {
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goto childerror
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}
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}
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// Set process group
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if sys.Setpgid || sys.Foreground {
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// Place child in process group.
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err1 = setpgid(0, uintptr(sys.Pgid))
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if err1 != 0 {
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goto childerror
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}
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}
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if sys.Foreground {
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pgrp = _Pid_t(sys.Pgid)
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if pgrp == 0 {
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r1, err1 = getpid()
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if err1 != 0 {
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goto childerror
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}
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pgrp = _Pid_t(r1)
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}
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// Place process group in foreground.
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err1 = ioctl(uintptr(sys.Ctty), uintptr(TIOCSPGRP), uintptr(unsafe.Pointer(&pgrp)))
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if err1 != 0 {
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goto childerror
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}
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}
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// Restore the signal mask. We do this after TIOCSPGRP to avoid
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// having the kernel send a SIGTTOU signal to the process group.
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runtime_AfterForkInChild()
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// Chroot
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if chroot != nil {
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err1 = chroot1(uintptr(unsafe.Pointer(chroot)))
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if err1 != 0 {
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goto childerror
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}
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}
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// User and groups
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if cred = sys.Credential; cred != nil {
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ngroups = uintptr(len(cred.Groups))
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groups = uintptr(0)
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if ngroups > 0 {
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groups = uintptr(unsafe.Pointer(&cred.Groups[0]))
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}
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if !cred.NoSetGroups {
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err1 = setgroups1(ngroups, groups)
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if err1 != 0 {
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goto childerror
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}
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}
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err1 = setgid(uintptr(cred.Gid))
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if err1 != 0 {
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goto childerror
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}
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err1 = setuid(uintptr(cred.Uid))
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if err1 != 0 {
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goto childerror
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}
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}
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// Chdir
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if dir != nil {
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err1 = chdir(uintptr(unsafe.Pointer(dir)))
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if err1 != 0 {
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goto childerror
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}
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}
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// Pass 1: look for fd[i] < i and move those up above len(fd)
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// so that pass 2 won't stomp on an fd it needs later.
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if pipe < nextfd {
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switch runtime.GOOS {
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case "illumos", "solaris":
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_, err1 = fcntl1(uintptr(pipe), _F_DUP2FD_CLOEXEC, uintptr(nextfd))
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default:
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_, err1 = dup2child(uintptr(pipe), uintptr(nextfd))
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if err1 != 0 {
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goto childerror
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}
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_, err1 = fcntl1(uintptr(nextfd), F_SETFD, FD_CLOEXEC)
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}
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if err1 != 0 {
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goto childerror
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}
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pipe = nextfd
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nextfd++
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}
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for i = 0; i < len(fd); i++ {
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if fd[i] >= 0 && fd[i] < i {
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if nextfd == pipe { // don't stomp on pipe
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nextfd++
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}
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switch runtime.GOOS {
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case "illumos", "solaris":
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_, err1 = fcntl1(uintptr(fd[i]), _F_DUP2FD_CLOEXEC, uintptr(nextfd))
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default:
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_, err1 = dup2child(uintptr(fd[i]), uintptr(nextfd))
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if err1 != 0 {
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goto childerror
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}
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_, err1 = fcntl1(uintptr(nextfd), F_SETFD, FD_CLOEXEC)
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}
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if err1 != 0 {
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goto childerror
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}
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fd[i] = nextfd
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nextfd++
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}
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}
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// Pass 2: dup fd[i] down onto i.
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for i = 0; i < len(fd); i++ {
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if fd[i] == -1 {
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closeFD(uintptr(i))
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continue
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}
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if fd[i] == i {
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// dup2(i, i) won't clear close-on-exec flag on Linux,
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// probably not elsewhere either.
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_, err1 = fcntl1(uintptr(fd[i]), F_SETFD, 0)
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if err1 != 0 {
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goto childerror
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}
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continue
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}
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// The new fd is created NOT close-on-exec,
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// which is exactly what we want.
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_, err1 = dup2child(uintptr(fd[i]), uintptr(i))
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if err1 != 0 {
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goto childerror
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}
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}
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// By convention, we don't close-on-exec the fds we are
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// started with, so if len(fd) < 3, close 0, 1, 2 as needed.
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// Programs that know they inherit fds >= 3 will need
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// to set them close-on-exec.
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for i = len(fd); i < 3; i++ {
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closeFD(uintptr(i))
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}
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// Detach fd 0 from tty
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if sys.Noctty {
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err1 = ioctl(0, uintptr(TIOCNOTTY), 0)
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if err1 != 0 {
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goto childerror
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}
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}
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// Set the controlling TTY to Ctty
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if sys.Setctty {
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// On AIX, TIOCSCTTY is undefined
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if TIOCSCTTY == 0 {
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err1 = ENOSYS
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goto childerror
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}
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err1 = ioctl(uintptr(sys.Ctty), uintptr(TIOCSCTTY), 0)
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if err1 != 0 {
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goto childerror
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}
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}
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// Restore original rlimit.
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if rlim != nil {
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setrlimit1(RLIMIT_NOFILE, unsafe.Pointer(rlim))
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}
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// Time to exec.
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err1 = execve(
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uintptr(unsafe.Pointer(argv0)),
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uintptr(unsafe.Pointer(&argv[0])),
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uintptr(unsafe.Pointer(&envv[0])))
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childerror:
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// send error code on pipe
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write1(uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1))
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for {
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exit(253)
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}
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}
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func ioctlPtr(fd, req uintptr, arg unsafe.Pointer) (err Errno) {
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return ioctl(fd, req, uintptr(arg))
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}
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