Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 611 insertions, 0 deletions

diff --git a/src/syscall/exec_plan9.go b/src/syscall/exec_plan9.go
new file mode 100644
index 0000000..8762237
--- /dev/null
+++ b/src/syscall/exec_plan9.go
@@ -0,0 +1,611 @@
+// Copyright 2009 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.
+
+// Fork, exec, wait, etc.
+
+package syscall
+
+import (
+	"internal/itoa"
+	"runtime"
+	"sync"
+	"unsafe"
+)
+
+// ForkLock is not used on plan9.
+var ForkLock sync.RWMutex
+
+// gstringb reads a non-empty string from b, prefixed with a 16-bit length in little-endian order.
+// It returns the string as a byte slice, or nil if b is too short to contain the length or
+// the full string.
+//
+//go:nosplit
+func gstringb(b []byte) []byte {
+	if len(b) < 2 {
+		return nil
+	}
+	n, b := gbit16(b)
+	if int(n) > len(b) {
+		return nil
+	}
+	return b[:n]
+}
+
+// Offset of the name field in a 9P directory entry - see UnmarshalDir() in dir_plan9.go
+const nameOffset = 39
+
+// gdirname returns the first filename from a buffer of directory entries,
+// and a slice containing the remaining directory entries.
+// If the buffer doesn't start with a valid directory entry, the returned name is nil.
+//
+//go:nosplit
+func gdirname(buf []byte) (name []byte, rest []byte) {
+	if len(buf) < 2 {
+		return
+	}
+	size, buf := gbit16(buf)
+	if size < STATFIXLEN || int(size) > len(buf) {
+		return
+	}
+	name = gstringb(buf[nameOffset:size])
+	rest = buf[size:]
+	return
+}
+
+// StringSlicePtr converts a slice of strings to a slice of pointers
+// to NUL-terminated byte arrays. If any string contains a NUL byte
+// this function panics instead of returning an error.
+//
+// Deprecated: Use SlicePtrFromStrings instead.
+func StringSlicePtr(ss []string) []*byte {
+	bb := make([]*byte, len(ss)+1)
+	for i := 0; i < len(ss); i++ {
+		bb[i] = StringBytePtr(ss[i])
+	}
+	bb[len(ss)] = nil
+	return bb
+}
+
+// SlicePtrFromStrings converts a slice of strings to a slice of
+// pointers to NUL-terminated byte arrays. If any string contains
+// a NUL byte, it returns (nil, EINVAL).
+func SlicePtrFromStrings(ss []string) ([]*byte, error) {
+	var err error
+	bb := make([]*byte, len(ss)+1)
+	for i := 0; i < len(ss); i++ {
+		bb[i], err = BytePtrFromString(ss[i])
+		if err != nil {
+			return nil, err
+		}
+	}
+	bb[len(ss)] = nil
+	return bb, nil
+}
+
+// readdirnames returns the names of files inside the directory represented by dirfd.
+func readdirnames(dirfd int) (names []string, err error) {
+	names = make([]string, 0, 100)
+	var buf [STATMAX]byte
+
+	for {
+		n, e := Read(dirfd, buf[:])
+		if e != nil {
+			return nil, e
+		}
+		if n == 0 {
+			break
+		}
+		for b := buf[:n]; len(b) > 0; {
+			var s []byte
+			s, b = gdirname(b)
+			if s == nil {
+				return nil, ErrBadStat
+			}
+			names = append(names, string(s))
+		}
+	}
+	return
+}
+
+// name of the directory containing names and control files for all open file descriptors
+var dupdev, _ = BytePtrFromString("#d")
+
+// forkAndExecInChild forks the process, calling dup onto 0..len(fd)
+// and finally invoking exec(argv0, argvv, envv) in the child.
+// If a dup or exec fails, it writes the error string to pipe.
+// (The pipe write end 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.
+//
+//go:norace
+func forkAndExecInChild(argv0 *byte, argv []*byte, envv []envItem, dir *byte, attr *ProcAttr, pipe int, rflag int) (pid int, err error) {
+	// Declare all variables at top in case any
+	// declarations require heap allocation (e.g., errbuf).
+	var (
+		r1       uintptr
+		nextfd   int
+		i        int
+		clearenv int
+		envfd    int
+		errbuf   [ERRMAX]byte
+		statbuf  [STATMAX]byte
+		dupdevfd int
+		n        int
+		b        []byte
+	)
+
+	// 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++
+
+	if envv != nil {
+		clearenv = RFCENVG
+	}
+
+	// About to call fork.
+	// No more allocation or calls of non-assembly functions.
+	r1, _, _ = RawSyscall(SYS_RFORK, uintptr(RFPROC|RFFDG|RFREND|clearenv|rflag), 0, 0)
+
+	if r1 != 0 {
+		if int32(r1) == -1 {
+			return 0, NewError(errstr())
+		}
+		// parent; return PID
+		return int(r1), nil
+	}
+
+	// Fork succeeded, now in child.
+
+	// Close fds we don't need.
+	r1, _, _ = RawSyscall(SYS_OPEN, uintptr(unsafe.Pointer(dupdev)), uintptr(O_RDONLY), 0)
+	dupdevfd = int(r1)
+	if dupdevfd == -1 {
+		goto childerror
+	}
+dirloop:
+	for {
+		r1, _, _ = RawSyscall6(SYS_PREAD, uintptr(dupdevfd), uintptr(unsafe.Pointer(&statbuf[0])), uintptr(len(statbuf)), ^uintptr(0), ^uintptr(0), 0)
+		n = int(r1)
+		switch n {
+		case -1:
+			goto childerror
+		case 0:
+			break dirloop
+		}
+		for b = statbuf[:n]; len(b) > 0; {
+			var s []byte
+			s, b = gdirname(b)
+			if s == nil {
+				copy(errbuf[:], ErrBadStat.Error())
+				goto childerror1
+			}
+			if s[len(s)-1] == 'l' {
+				// control file for descriptor <N> is named <N>ctl
+				continue
+			}
+			closeFdExcept(int(atoi(s)), pipe, dupdevfd, fd)
+		}
+	}
+	RawSyscall(SYS_CLOSE, uintptr(dupdevfd), 0, 0)
+
+	// Write new environment variables.
+	if envv != nil {
+		for i = 0; i < len(envv); i++ {
+			r1, _, _ = RawSyscall(SYS_CREATE, uintptr(unsafe.Pointer(envv[i].name)), uintptr(O_WRONLY), uintptr(0666))
+
+			if int32(r1) == -1 {
+				goto childerror
+			}
+
+			envfd = int(r1)
+
+			r1, _, _ = RawSyscall6(SYS_PWRITE, uintptr(envfd), uintptr(unsafe.Pointer(envv[i].value)), uintptr(envv[i].nvalue),
+				^uintptr(0), ^uintptr(0), 0)
+
+			if int32(r1) == -1 || int(r1) != envv[i].nvalue {
+				goto childerror
+			}
+
+			r1, _, _ = RawSyscall(SYS_CLOSE, uintptr(envfd), 0, 0)
+
+			if int32(r1) == -1 {
+				goto childerror
+			}
+		}
+	}
+
+	// Chdir
+	if dir != nil {
+		r1, _, _ = RawSyscall(SYS_CHDIR, uintptr(unsafe.Pointer(dir)), 0, 0)
+		if int32(r1) == -1 {
+			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 {
+		r1, _, _ = RawSyscall(SYS_DUP, uintptr(pipe), uintptr(nextfd), 0)
+		if int32(r1) == -1 {
+			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++
+			}
+			r1, _, _ = RawSyscall(SYS_DUP, uintptr(fd[i]), uintptr(nextfd), 0)
+			if int32(r1) == -1 {
+				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(SYS_CLOSE, uintptr(i), 0, 0)
+			continue
+		}
+		if fd[i] == i {
+			continue
+		}
+		r1, _, _ = RawSyscall(SYS_DUP, uintptr(fd[i]), uintptr(i), 0)
+		if int32(r1) == -1 {
+			goto childerror
+		}
+	}
+
+	// Pass 3: close fd[i] if it was moved in the previous pass.
+	for i = 0; i < len(fd); i++ {
+		if fd[i] >= len(fd) {
+			RawSyscall(SYS_CLOSE, uintptr(fd[i]), 0, 0)
+		}
+	}
+
+	// Time to exec.
+	r1, _, _ = RawSyscall(SYS_EXEC,
+		uintptr(unsafe.Pointer(argv0)),
+		uintptr(unsafe.Pointer(&argv[0])), 0)
+
+childerror:
+	// send error string on pipe
+	RawSyscall(SYS_ERRSTR, uintptr(unsafe.Pointer(&errbuf[0])), uintptr(len(errbuf)), 0)
+childerror1:
+	errbuf[len(errbuf)-1] = 0
+	i = 0
+	for i < len(errbuf) && errbuf[i] != 0 {
+		i++
+	}
+
+	RawSyscall6(SYS_PWRITE, uintptr(pipe), uintptr(unsafe.Pointer(&errbuf[0])), uintptr(i),
+		^uintptr(0), ^uintptr(0), 0)
+
+	for {
+		RawSyscall(SYS_EXITS, 0, 0, 0)
+	}
+}
+
+// close the numbered file descriptor, unless it is fd1, fd2, or a member of fds.
+//
+//go:nosplit
+func closeFdExcept(n int, fd1 int, fd2 int, fds []int) {
+	if n == fd1 || n == fd2 {
+		return
+	}
+	for _, fd := range fds {
+		if n == fd {
+			return
+		}
+	}
+	RawSyscall(SYS_CLOSE, uintptr(n), 0, 0)
+}
+
+func cexecPipe(p []int) error {
+	e := Pipe(p)
+	if e != nil {
+		return e
+	}
+
+	fd, e := Open("#d/"+itoa.Itoa(p[1]), O_RDWR|O_CLOEXEC)
+	if e != nil {
+		Close(p[0])
+		Close(p[1])
+		return e
+	}
+
+	Close(p[1])
+	p[1] = fd
+	return nil
+}
+
+type envItem struct {
+	name   *byte
+	value  *byte
+	nvalue int
+}
+
+type ProcAttr struct {
+	Dir   string    // Current working directory.
+	Env   []string  // Environment.
+	Files []uintptr // File descriptors.
+	Sys   *SysProcAttr
+}
+
+type SysProcAttr struct {
+	Rfork int // additional flags to pass to rfork
+}
+
+var zeroProcAttr ProcAttr
+var zeroSysProcAttr SysProcAttr
+
+func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
+	var (
+		p      [2]int
+		n      int
+		errbuf [ERRMAX]byte
+		wmsg   Waitmsg
+	)
+
+	if attr == nil {
+		attr = &zeroProcAttr
+	}
+	sys := attr.Sys
+	if sys == nil {
+		sys = &zeroSysProcAttr
+	}
+
+	p[0] = -1
+	p[1] = -1
+
+	// Convert args to C form.
+	argv0p, err := BytePtrFromString(argv0)
+	if err != nil {
+		return 0, err
+	}
+	argvp, err := SlicePtrFromStrings(argv)
+	if err != nil {
+		return 0, err
+	}
+
+	destDir := attr.Dir
+	if destDir == "" {
+		wdmu.Lock()
+		destDir = wdStr
+		wdmu.Unlock()
+	}
+	var dir *byte
+	if destDir != "" {
+		dir, err = BytePtrFromString(destDir)
+		if err != nil {
+			return 0, err
+		}
+	}
+	var envvParsed []envItem
+	if attr.Env != nil {
+		envvParsed = make([]envItem, 0, len(attr.Env))
+		for _, v := range attr.Env {
+			i := 0
+			for i < len(v) && v[i] != '=' {
+				i++
+			}
+
+			envname, err := BytePtrFromString("/env/" + v[:i])
+			if err != nil {
+				return 0, err
+			}
+			envvalue := make([]byte, len(v)-i)
+			copy(envvalue, v[i+1:])
+			envvParsed = append(envvParsed, envItem{envname, &envvalue[0], len(v) - i})
+		}
+	}
+
+	// Allocate child status pipe close on exec.
+	e := cexecPipe(p[:])
+
+	if e != nil {
+		return 0, e
+	}
+
+	// Kick off child.
+	pid, err = forkAndExecInChild(argv0p, argvp, envvParsed, dir, attr, p[1], sys.Rfork)
+
+	if err != nil {
+		if p[0] >= 0 {
+			Close(p[0])
+			Close(p[1])
+		}
+		return 0, err
+	}
+
+	// Read child error status from pipe.
+	Close(p[1])
+	n, err = Read(p[0], errbuf[:])
+	Close(p[0])
+
+	if err != nil || n != 0 {
+		if n > 0 {
+			err = NewError(string(errbuf[:n]))
+		} else if err == nil {
+			err = NewError("failed to read exec status")
+		}
+
+		// Child failed; wait for it to exit, to make sure
+		// the zombies don't accumulate.
+		for wmsg.Pid != pid {
+			Await(&wmsg)
+		}
+		return 0, err
+	}
+
+	// Read got EOF, so pipe closed on exec, so exec succeeded.
+	return pid, nil
+}
+
+type waitErr struct {
+	Waitmsg
+	err error
+}
+
+var procs struct {
+	sync.Mutex
+	waits map[int]chan *waitErr
+}
+
+// startProcess starts a new goroutine, tied to the OS
+// thread, which runs the process and subsequently waits
+// for it to finish, communicating the process stats back
+// to any goroutines that may have been waiting on it.
+//
+// Such a dedicated goroutine is needed because on
+// Plan 9, only the parent thread can wait for a child,
+// whereas goroutines tend to jump OS threads (e.g.,
+// between starting a process and running Wait(), the
+// goroutine may have been rescheduled).
+func startProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
+	type forkRet struct {
+		pid int
+		err error
+	}
+
+	forkc := make(chan forkRet, 1)
+	go func() {
+		runtime.LockOSThread()
+		var ret forkRet
+
+		ret.pid, ret.err = forkExec(argv0, argv, attr)
+		// If fork fails there is nothing to wait for.
+		if ret.err != nil || ret.pid == 0 {
+			forkc <- ret
+			return
+		}
+
+		waitc := make(chan *waitErr, 1)
+
+		// Mark that the process is running.
+		procs.Lock()
+		if procs.waits == nil {
+			procs.waits = make(map[int]chan *waitErr)
+		}
+		procs.waits[ret.pid] = waitc
+		procs.Unlock()
+
+		forkc <- ret
+
+		var w waitErr
+		for w.err == nil && w.Pid != ret.pid {
+			w.err = Await(&w.Waitmsg)
+		}
+		waitc <- &w
+		close(waitc)
+	}()
+	ret := <-forkc
+	return ret.pid, ret.err
+}
+
+// Combination of fork and exec, careful to be thread safe.
+func ForkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
+	return startProcess(argv0, argv, attr)
+}
+
+// StartProcess wraps ForkExec for package os.
+func StartProcess(argv0 string, argv []string, attr *ProcAttr) (pid int, handle uintptr, err error) {
+	pid, err = startProcess(argv0, argv, attr)
+	return pid, 0, err
+}
+
+// Ordinary exec.
+func Exec(argv0 string, argv []string, envv []string) (err error) {
+	if envv != nil {
+		r1, _, _ := RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
+		if int32(r1) == -1 {
+			return NewError(errstr())
+		}
+
+		for _, v := range envv {
+			i := 0
+			for i < len(v) && v[i] != '=' {
+				i++
+			}
+
+			fd, e := Create("/env/"+v[:i], O_WRONLY, 0666)
+			if e != nil {
+				return e
+			}
+
+			_, e = Write(fd, []byte(v[i+1:]))
+			if e != nil {
+				Close(fd)
+				return e
+			}
+			Close(fd)
+		}
+	}
+
+	argv0p, err := BytePtrFromString(argv0)
+	if err != nil {
+		return err
+	}
+	argvp, err := SlicePtrFromStrings(argv)
+	if err != nil {
+		return err
+	}
+	_, _, e1 := Syscall(SYS_EXEC,
+		uintptr(unsafe.Pointer(argv0p)),
+		uintptr(unsafe.Pointer(&argvp[0])),
+		0)
+
+	return e1
+}
+
+// WaitProcess waits until the pid of a
+// running process is found in the queue of
+// wait messages. It is used in conjunction
+// with ForkExec/StartProcess to wait for a
+// running process to exit.
+func WaitProcess(pid int, w *Waitmsg) (err error) {
+	procs.Lock()
+	ch := procs.waits[pid]
+	procs.Unlock()
+
+	var wmsg *waitErr
+	if ch != nil {
+		wmsg = <-ch
+		procs.Lock()
+		if procs.waits[pid] == ch {
+			delete(procs.waits, pid)
+		}
+		procs.Unlock()
+	}
+	if wmsg == nil {
+		// ch was missing or ch is closed
+		return NewError("process not found")
+	}
+	if wmsg.err != nil {
+		return wmsg.err
+	}
+	if w != nil {
+		*w = wmsg.Waitmsg
+	}
+	return nil
+}