// 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 aix || solaris // This file handles forkAndExecInChild function for OS using libc syscall like AIX or Solaris. package syscall import ( "runtime" "unsafe" ) type SysProcAttr struct { Chroot string // Chroot. Credential *Credential // Credential. 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() func chdir(path uintptr) (err Errno) func chroot1(path uintptr) (err Errno) func closeFD(fd uintptr) (err Errno) func dup2child(old uintptr, new uintptr) (val uintptr, err Errno) func execve(path uintptr, argv uintptr, envp uintptr) (err Errno) func exit(code uintptr) func fcntl1(fd uintptr, cmd uintptr, arg uintptr) (val uintptr, err Errno) func forkx(flags uintptr) (pid uintptr, err Errno) func getpid() (pid uintptr, err Errno) func ioctl(fd uintptr, req uintptr, arg uintptr) (err Errno) func setgid(gid uintptr) (err Errno) func setgroups1(ngid uintptr, gid uintptr) (err Errno) func setrlimit1(which uintptr, lim unsafe.Pointer) (err Errno) func setsid() (pid uintptr, err Errno) func setuid(uid uintptr) (err Errno) func setpgid(pid uintptr, pgid uintptr) (err Errno) func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err Errno) // syscall defines this global on our behalf to avoid a build dependency on other platforms func init() { execveLibc = execve } // 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. // // We call hand-crafted syscalls, implemented in // ../runtime/syscall_solaris.go, rather than generated libc wrappers // because we need to avoid lazy-loading the functions (might malloc, // split the stack, or acquire mutexes). We can't call RawSyscall // because it's not safe even for BSD-subsystem calls. // //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 pgrp _Pid_t cred *Credential ngroups, groups uintptr ) rlim := origRlimitNofile.Load() // 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 = forkx(0x1) // FORK_NOSIGCHLD 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. // Session ID if sys.Setsid { _, err1 = setsid() if err1 != 0 { goto childerror } } // Set process group if sys.Setpgid || sys.Foreground { // Place child in process group. err1 = setpgid(0, uintptr(sys.Pgid)) if err1 != 0 { goto childerror } } if sys.Foreground { pgrp = _Pid_t(sys.Pgid) if pgrp == 0 { r1, err1 = getpid() if err1 != 0 { goto childerror } pgrp = _Pid_t(r1) } // Place process group in foreground. err1 = ioctl(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 = chroot1(uintptr(unsafe.Pointer(chroot))) 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 = setgroups1(ngroups, groups) if err1 != 0 { goto childerror } } err1 = setgid(uintptr(cred.Gid)) if err1 != 0 { goto childerror } err1 = setuid(uintptr(cred.Uid)) if err1 != 0 { goto childerror } } // Chdir if dir != nil { err1 = chdir(uintptr(unsafe.Pointer(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. if pipe < nextfd { switch runtime.GOOS { case "illumos", "solaris": _, err1 = fcntl1(uintptr(pipe), _F_DUP2FD_CLOEXEC, uintptr(nextfd)) default: _, err1 = dup2child(uintptr(pipe), uintptr(nextfd)) if err1 != 0 { goto childerror } _, err1 = fcntl1(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] < i { if nextfd == pipe { // don't stomp on pipe nextfd++ } switch runtime.GOOS { case "illumos", "solaris": _, err1 = fcntl1(uintptr(fd[i]), _F_DUP2FD_CLOEXEC, uintptr(nextfd)) default: _, err1 = dup2child(uintptr(fd[i]), uintptr(nextfd)) if err1 != 0 { goto childerror } _, err1 = fcntl1(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 { closeFD(uintptr(i)) continue } if fd[i] == i { // dup2(i, i) won't clear close-on-exec flag on Linux, // probably not elsewhere either. _, err1 = fcntl1(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 = dup2child(uintptr(fd[i]), uintptr(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++ { closeFD(uintptr(i)) } // Detach fd 0 from tty if sys.Noctty { err1 = ioctl(0, uintptr(TIOCNOTTY), 0) if err1 != 0 { goto childerror } } // Set the controlling TTY to Ctty if sys.Setctty { // On AIX, TIOCSCTTY is undefined if TIOCSCTTY == 0 { err1 = ENOSYS goto childerror } err1 = ioctl(uintptr(sys.Ctty), uintptr(TIOCSCTTY), 0) if err1 != 0 { goto childerror } } // Restore original rlimit. if rlim != nil { setrlimit1(RLIMIT_NOFILE, unsafe.Pointer(rlim)) } // Time to exec. err1 = execve( uintptr(unsafe.Pointer(argv0)), uintptr(unsafe.Pointer(&argv[0])), uintptr(unsafe.Pointer(&envv[0]))) childerror: // send error code on pipe write1(uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1)) for { exit(253) } } func ioctlPtr(fd, req uintptr, arg unsafe.Pointer) (err Errno) { return ioctl(fd, req, uintptr(arg)) }