diff options
Diffstat (limited to 'libgo/go/syscall/exec_linux.go')
| -rw-r--r-- | libgo/go/syscall/exec_linux.go | 251 |
1 files changed, 251 insertions, 0 deletions
diff --git a/libgo/go/syscall/exec_linux.go b/libgo/go/syscall/exec_linux.go new file mode 100644 index 00000000000..98dbeb27750 --- /dev/null +++ b/libgo/go/syscall/exec_linux.go @@ -0,0 +1,251 @@ +// 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 linux + +package syscall + +import ( + "unsafe" +) + +//sysnb raw_prctl(option int, arg2 int, arg3 int, arg4 int, arg5 int) (ret int, err Errno) +//prctl(option int, arg2 _C_long, arg3 _C_long, arg4 _C_long, arg5 _C_long) int + +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 + Pdeathsig int // Signal that the process will get when its parent dies (Linux only) +} + +// 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. + + // Parent death signal + if sys.Pdeathsig != 0 { + _, err1 = raw_prctl(PR_SET_PDEATHSIG, sys.Pdeathsig, 0, 0, 0) + if err1 != 0 { + goto childerror + } + + // Signal self if parent is already dead. This might cause a + // duplicate signal in rare cases, but it won't matter when + // using SIGKILL. + ppid := Getppid() + if ppid == 1 { + pid = Getpid() + err2 := Kill(pid, sys.Pdeathsig) + if err2 != nil { + err1 = err2.(Errno) + goto childerror + } + } + } + + // 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 { + _, err2 := Dup2(pipe, nextfd) + if err2 != nil { + err1 = err2.(Errno) + 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) { + _, err2 := Dup2(fd[i], nextfd) + if err2 != nil { + err1 = err2.(Errno) + 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. + _, err2 := Dup2(fd[i], i); + if err2 != nil { + err1 = err2.(Errno) + 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") +} |