1 files changed, 288 insertions, 0 deletions
diff --git a/src/syscall/exec_libc2.go b/src/syscall/exec_libc2.go
new file mode 100644
index 0000000..88d3b60
--- /dev/null
+++ b/src/syscall/exec_libc2.go
@@ -0,0 +1,288 @@
+// 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
+	)
+
+	rlim, rlimOK := origRlimitNofile.Load().(Rlimit)
+
+	// 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] < 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] == 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
+		}
+	}
+
+	// Restore original rlimit.
+	if rlimOK && rlim.Cur != 0 {
+		rawSyscall(abi.FuncPCABI0(libc_setrlimit_trampoline), uintptr(RLIMIT_NOFILE), uintptr(unsafe.Pointer(&rlim)), 0)
+	}
+
+	// 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)
+	}
+}