diff options
Diffstat (limited to 'src/syscall/exec_bsd.go')
-rw-r--r-- | src/syscall/exec_bsd.go | 247 |
1 files changed, 247 insertions, 0 deletions
diff --git a/src/syscall/exec_bsd.go b/src/syscall/exec_bsd.go new file mode 100644 index 000000000..ff78f197f --- /dev/null +++ b/src/syscall/exec_bsd.go @@ -0,0 +1,247 @@ +// 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 dragonfly freebsd netbsd openbsd + +package syscall + +import ( + "runtime" + "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 +} + +// Implemented in runtime package. +func runtime_BeforeFork() +func runtime_AfterFork() + +// 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. +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, r2 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++ + + darwin := runtime.GOOS == "darwin" + + // About to call fork. + // No more allocation or calls of non-assembly functions. + runtime_BeforeFork() + r1, r2, err1 = RawSyscall(SYS_FORK, 0, 0, 0) + if err1 != 0 { + runtime_AfterFork() + return 0, err1 + } + + // On Darwin: + // r1 = child pid in both parent and child. + // r2 = 0 in parent, 1 in child. + // Convert to normal Unix r1 = 0 in child. + if darwin && r2 == 1 { + r1 = 0 + } + + 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 = RawSyscall(SYS_PTRACE, uintptr(PTRACE_TRACEME), 0, 0) + if err1 != 0 { + goto childerror + } + } + + // Session ID + if sys.Setsid { + _, _, err1 = RawSyscall(SYS_SETSID, 0, 0, 0) + if err1 != 0 { + goto childerror + } + } + + // Set process group + if sys.Setpgid { + _, _, err1 = RawSyscall(SYS_SETPGID, 0, 0, 0) + if err1 != 0 { + goto childerror + } + } + + // Chroot + if chroot != nil { + _, _, err1 = RawSyscall(SYS_CHROOT, 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])) + } + _, _, err1 = RawSyscall(SYS_SETGROUPS, ngroups, groups, 0) + if err1 != 0 { + goto childerror + } + _, _, err1 = RawSyscall(SYS_SETGID, uintptr(cred.Gid), 0, 0) + if err1 != 0 { + goto childerror + } + _, _, err1 = RawSyscall(SYS_SETUID, uintptr(cred.Uid), 0, 0) + if err1 != 0 { + goto childerror + } + } + + // Chdir + if dir != nil { + _, _, err1 = RawSyscall(SYS_CHDIR, 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 { + _, _, err1 = RawSyscall(SYS_DUP2, uintptr(pipe), uintptr(nextfd), 0) + if err1 != 0 { + goto childerror + } + RawSyscall(SYS_FCNTL, uintptr(nextfd), F_SETFD, FD_CLOEXEC) + pipe = nextfd + nextfd++ + } + for i = 0; i < len(fd); i++ { + if fd[i] >= 0 && fd[i] < int(i) { + _, _, err1 = RawSyscall(SYS_DUP2, uintptr(fd[i]), uintptr(nextfd), 0) + if err1 != 0 { + goto childerror + } + RawSyscall(SYS_FCNTL, uintptr(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 { + RawSyscall(SYS_CLOSE, 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(SYS_FCNTL, 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(SYS_DUP2, 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(SYS_CLOSE, uintptr(i), 0, 0) + } + + // Detach fd 0 from tty + if sys.Noctty { + _, _, err1 = RawSyscall(SYS_IOCTL, 0, uintptr(TIOCNOTTY), 0) + if err1 != 0 { + goto childerror + } + } + + // Make fd 0 the tty + if sys.Setctty { + _, _, err1 = RawSyscall(SYS_IOCTL, 0, uintptr(TIOCSCTTY), 0) + if err1 != 0 { + goto childerror + } + } + + // Time to exec. + _, _, err1 = RawSyscall(SYS_EXECVE, + uintptr(unsafe.Pointer(argv0)), + uintptr(unsafe.Pointer(&argv[0])), + uintptr(unsafe.Pointer(&envv[0]))) + +childerror: + // send error code on pipe + RawSyscall(SYS_WRITE, uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1)) + for { + RawSyscall(SYS_EXIT, 253, 0, 0) + } +} + +// Try to open a pipe with O_CLOEXEC set on both file descriptors. +func forkExecPipe(p []int) error { + err := Pipe(p) + if err != nil { + return err + } + _, err = fcntl(p[0], F_SETFD, FD_CLOEXEC) + if err != nil { + return err + } + _, err = fcntl(p[1], F_SETFD, FD_CLOEXEC) + return err +} |