golang exec_libc2 代码
文件路径：/src/syscall/exec_libc2.go
/ 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.
/go:build darwin || (openbsd && !mips64)
package syscall
import (
"internal/abi"
"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 uintptr
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 = rawSyscall(abi.FuncPCABI0(libc_fork_trampoline), 0, 0, 0)
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 {
if err := ptrace(PTRACE_TRACEME, 0, 0, 0); err != nil {
err1 = err.(Errno)
goto childerror
}
}
/ Session ID
if sys.Setsid {
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setsid_trampoline), 0, 0, 0)
if err1 != 0 {
goto childerror
}
}
/ Set process group
if sys.Setpgid || sys.Foreground {
/ Place child in process group.
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setpgid_trampoline), 0, uintptr(sys.Pgid), 0)
if err1 != 0 {
goto childerror
}
}
if sys.Foreground {
/ This should really be pid_t, however _C_int (aka int32) is
/ generally equivalent.
pgrp := _C_int(sys.Pgid)
if pgrp == 0 {
r1, _, err1 = rawSyscall(abi.FuncPCABI0(libc_getpid_trampoline), 0, 0, 0)
if err1 != 0 {
goto childerror
}
pgrp = _C_int(r1)
}
/ Place process group in foreground.
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_ioctl_trampoline), uintptr(sys.Ctty), uintptr(TIOCSPGRP), uintptr(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 = rawSyscall(abi.FuncPCABI0(libc_chroot_trampoline), uintptr(unsafe.Pointer(chroot)), 0, 0)
if err1 != 0 {
goto childerror
}
}
/ User and groups
if cred := sys.Credential; cred != nil {
ngroups := uintptr(len(cred.Groups))
groups := uintptr(0)
if ngroups > 0 {
groups = uintptr(unsafe.Pointer(&cred.Groups[0]))
}
if !cred.NoSetGroups {
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setgroups_trampoline), ngroups, groups, 0)
if err1 != 0 {
goto childerror
}
}
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setgid_trampoline), uintptr(cred.Gid), 0, 0)
if err1 != 0 {
goto childerror
}
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setuid_trampoline), uintptr(cred.Uid), 0, 0)
if err1 != 0 {
goto childerror
}
}
/ Chdir
if dir != nil {
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_chdir_trampoline), uintptr(unsafe.Pointer(dir)), 0, 0)
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 {
if runtime.GOOS == "openbsd" {
_, _, err1 = rawSyscall(dupTrampoline, uintptr(pipe), uintptr(nextfd), O_CLOEXEC)
} else {
_, _, err1 = rawSyscall(dupTrampoline, uintptr(pipe), uintptr(nextfd), 0)
if err1 != 0 {
goto childerror
}
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_fcntl_trampoline), uintptr(nextfd), F_SETFD, FD_CLOEXEC)
}
if err1 != 0 {
goto childerror
}
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++
}
if runtime.GOOS == "openbsd" {
_, _, err1 = rawSyscall(dupTrampoline, uintptr(fd[i]), uintptr(nextfd), O_CLOEXEC)
} else {
_, _, err1 = rawSyscall(dupTrampoline, uintptr(fd[i]), uintptr(nextfd), 0)
if err1 != 0 {
goto childerror
}
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_fcntl_trampoline), uintptr(nextfd), F_SETFD, FD_CLOEXEC)
}
if err1 != 0 {
goto childerror
}
fd[i] = nextfd
nextfd++
}
}
/ Pass 2: dup fd[i] down onto i.
for i = 0; i < len(fd); i++ {
if fd[i] == -1 {
rawSyscall(abi.FuncPCABI0(libc_close_trampoline), uintptr(i), 0, 0)
continue
}
if fd[i] == int(i) {
/ dup2(i, i) won't clear close-on-exec flag on Linux,
/ probably not elsewhere either.
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_fcntl_trampoline), uintptr(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 = rawSyscall(abi.FuncPCABI0(libc_dup2_trampoline), uintptr(fd[i]), uintptr(i), 0)
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++ {
rawSyscall(abi.FuncPCABI0(libc_close_trampoline), uintptr(i), 0, 0)
}
/ Detach fd 0 from tty
if sys.Noctty {
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_ioctl_trampoline), 0, uintptr(TIOCNOTTY), 0)
if err1 != 0 {
goto childerror
}
}
/ Set the controlling TTY to Ctty
if sys.Setctty {
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_ioctl_trampoline), uintptr(sys.Ctty), uintptr(TIOCSCTTY), 0)
if err1 != 0 {
goto childerror
}
}
/ Time to exec.
_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_execve_trampoline),
uintptr(unsafe.Pointer(argv0)),
uintptr(unsafe.Pointer(&argv[0])),
uintptr(unsafe.Pointer(&envv[0])))
childerror:
/ send error code on pipe
rawSyscall(abi.FuncPCABI0(libc_write_trampoline), uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1))
for {
rawSyscall(abi.FuncPCABI0(libc_exit_trampoline), 253, 0, 0)
}
}