internal/poll, internal/syscall/unix, net: move and export fcntl syscall wrapper

This will allow to use the fcntl syscall in packages other than
internal/poll.

For #60181

Change-Id: I76703766a655f2343c61dad95faf81aad58e007f
Reviewed-on: https://go-review.googlesource.com/c/go/+/494916
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/internal/poll/fcntl_libc.go

@@ -1,14 +0,0 @@
-// Copyright 2019 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 || darwin || (openbsd && !mips64) || solaris
-
-package poll
-
-import _ "unsafe" // for go:linkname
-
-// Implemented in the syscall package.
-//
-//go:linkname fcntl syscall.fcntl
-func fcntl(fd int, cmd int, arg int) (int, error)

src/internal/poll/fcntl_syscall.go

@@ -1,20 +0,0 @@
-// Copyright 2019 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 dragonfly || freebsd || linux || netbsd || (openbsd && mips64)
-
-package poll
-
-import (
-	"internal/syscall/unix"
-	"syscall"
-)
-
-func fcntl(fd int, cmd int, arg int) (int, error) {
-	r, _, e := syscall.Syscall(unix.FcntlSyscall, uintptr(fd), uintptr(cmd), uintptr(arg))
-	if e != 0 {
-		return int(r), syscall.Errno(e)
-	}
-	return int(r), nil
-}

src/internal/poll/fcntl_wasm.go

@@ -1,14 +0,0 @@
-// Copyright 2019 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 (js && wasm) || wasip1
-
-package poll
-
-import "syscall"
-
-// fcntl not supported on js/wasm or wasip1/wasm.
-func fcntl(fd int, cmd int, arg int) (int, error) {
-	return 0, syscall.ENOSYS
-}

src/internal/poll/fd_fsync_darwin.go

@@ -4,7 +4,10 @@
 
 package poll
 
-import "syscall"
+import (
+	"internal/syscall/unix"
+	"syscall"
+)
 
 // Fsync invokes SYS_FCNTL with SYS_FULLFSYNC because
 // on OS X, SYS_FSYNC doesn't fully flush contents to disk.
@@ -15,7 +18,7 @@ func (fd *FD) Fsync() error {
 	}
 	defer fd.decref()
 	return ignoringEINTR(func() error {
-		_, err := fcntl(fd.Sysfd, syscall.F_FULLFSYNC, 0)
+		_, err := unix.Fcntl(fd.Sysfd, syscall.F_FULLFSYNC, 0)
 		return err
 	})
 }

src/internal/poll/fd_unix.go

@@ -653,18 +653,18 @@ var dupCloexecUnsupported atomic.Bool
 // DupCloseOnExec dups fd and marks it close-on-exec.
 func DupCloseOnExec(fd int) (int, string, error) {
 	if syscall.F_DUPFD_CLOEXEC != 0 && !dupCloexecUnsupported.Load() {
-		r0, e1 := fcntl(fd, syscall.F_DUPFD_CLOEXEC, 0)
+		r0, err := unix.Fcntl(fd, syscall.F_DUPFD_CLOEXEC, 0)
-		if e1 == nil {
+		if err == nil {
 			return r0, "", nil
 		}
-		switch e1.(syscall.Errno) {
+		switch err {
 		case syscall.EINVAL, syscall.ENOSYS:
 			// Old kernel, or js/wasm (which returns
 			// ENOSYS). Fall back to the portable way from
 			// now on.
 			dupCloexecUnsupported.Store(true)
 		default:
-			return -1, "fcntl", e1
+			return -1, "fcntl", err
 		}
 	}
 	return dupCloseOnExecOld(fd)

src/internal/poll/splice_linux.go

@@ -5,6 +5,7 @@
 package poll
 
 import (
+	"internal/syscall/unix"
 	"runtime"
 	"sync"
 	"syscall"
@@ -220,7 +221,7 @@ func newPipe() *splicePipe {
 	// Set the pipe buffer size to maxSpliceSize to optimize that.
 	// Ignore errors here, as a smaller buffer size will work,
 	// although it will require more system calls.
-	fcntl(fds[0], syscall.F_SETPIPE_SZ, maxSpliceSize)
+	unix.Fcntl(fds[0], syscall.F_SETPIPE_SZ, maxSpliceSize)
 
 	return &splicePipe{splicePipeFields: splicePipeFields{rfd: fds[0], wfd: fds[1]}}
 }

src/internal/syscall/unix/fcntl_linux_32bit.go

@@ -1,16 +0,0 @@
-// Copyright 2019 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.
-
-// On 32-bit Linux systems, use SYS_FCNTL64.
-// If you change the build tags here, see syscall/flock_linux_32bit.go.
-
-//go:build (linux && 386) || (linux && arm) || (linux && mips) || (linux && mipsle)
-
-package unix
-
-import "syscall"
-
-func init() {
-	FcntlSyscall = syscall.SYS_FCNTL64
-}

src/internal/syscall/unix/fcntl_unix.go

@@ -0,0 +1,25 @@
+// Copyright 2023 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 unix
+
+package unix
+
+import (
+	"syscall"
+	_ "unsafe" // for go:linkname
+)
+
+// Implemented in the runtime package.
+//
+//go:linkname fcntl runtime.fcntl
+func fcntl(fd int32, cmd int32, arg int32) int32
+
+func Fcntl(fd int, cmd int, arg int) (int, error) {
+	val := fcntl(int32(fd), int32(cmd), int32(arg))
+	if val < 0 {
+		return 0, syscall.Errno(-val)
+	}
+	return int(val), nil
+}

src/internal/syscall/unix/fcntl_wasm.go

@@ -0,0 +1,11 @@
+// Copyright 2023 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.
+
+package unix
+
+import "syscall"
+
+func Fcntl(fd int, cmd int, arg int) (int, error) {
+	return 0, syscall.ENOSYS
+}

src/internal/syscall/unix/nonblocking.go

@@ -1,25 +0,0 @@
-// Copyright 2018 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 dragonfly || freebsd || linux || netbsd || (openbsd && mips64)
-
-package unix
-
-import "syscall"
-
-// FcntlSyscall is the number for the fcntl system call. This is
-// usually SYS_FCNTL, but can be overridden to SYS_FCNTL64.
-var FcntlSyscall uintptr = syscall.SYS_FCNTL
-
-func IsNonblock(fd int) (nonblocking bool, err error) {
-	flag, _, e1 := syscall.Syscall(FcntlSyscall, uintptr(fd), uintptr(syscall.F_GETFL), 0)
-	if e1 != 0 {
-		return false, e1
-	}
-	return flag&syscall.O_NONBLOCK != 0, nil
-}
-
-func HasNonblockFlag(flag int) bool {
-	return flag&syscall.O_NONBLOCK != 0
-}

src/internal/syscall/unix/nonblocking_unix.go

@@ -2,17 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build aix || darwin || (openbsd && !mips64) || solaris
+//go:build unix
 
 package unix
 
-import (
+import "syscall"
-	"syscall"
-	_ "unsafe" // for go:linkname
-)
 
 func IsNonblock(fd int) (nonblocking bool, err error) {
-	flag, e1 := fcntl(fd, syscall.F_GETFL, 0)
+	flag, e1 := Fcntl(fd, syscall.F_GETFL, 0)
 	if e1 != nil {
 		return false, e1
 	}
@@ -22,8 +19,3 @@ func IsNonblock(fd int) (nonblocking bool, err error) {
 func HasNonblockFlag(flag int) bool {
 	return flag&syscall.O_NONBLOCK != 0
 }
-
-// Implemented in the syscall package.
-//
-//go:linkname fcntl syscall.fcntl
-func fcntl(fd int, cmd int, arg int) (int, error)

src/net/fcntl_libc_test.go

@@ -1,14 +0,0 @@
-// Copyright 2021 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 || darwin || (openbsd && !mips64) || solaris
-
-package net
-
-import _ "unsafe" // for go:linkname
-
-// Implemented in the syscall package.
-//
-//go:linkname fcntl syscall.fcntl
-func fcntl(fd int, cmd int, arg int) (int, error)

src/net/fcntl_syscall_test.go

@@ -1,20 +0,0 @@
-// Copyright 2021 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 dragonfly || freebsd || linux || netbsd || (openbsd && mips64)
-
-package net
-
-import (
-	"internal/syscall/unix"
-	"syscall"
-)
-
-func fcntl(fd int, cmd int, arg int) (int, error) {
-	r, _, e := syscall.Syscall(unix.FcntlSyscall, uintptr(fd), uintptr(cmd), uintptr(arg))
-	if e != 0 {
-		return int(r), syscall.Errno(e)
-	}
-	return int(r), nil
-}

src/net/unixsock_readmsg_test.go

@@ -7,6 +7,7 @@
 package net
 
 import (
+	"internal/syscall/unix"
 	"os"
 	"syscall"
 	"testing"
@@ -94,7 +95,7 @@ func TestUnixConnReadMsgUnixSCMRightsCloseOnExec(t *testing.T) {
 		}
 	}()
 
-	flags, err := fcntl(gotFDs[0], syscall.F_GETFD, 0)
+	flags, err := unix.Fcntl(gotFDs[0], syscall.F_GETFD, 0)
 	if err != nil {
 		t.Fatalf("Can't get flags of fd:%#v, with err:%v", gotFDs[0], err)
 	}