internal/poll, internal/syscall/unix, net: enable writev on illumos

Illumos supports iovec read/write. Add the writev wrapper to
internal/syscall/unix and use it to implement internal/poll.writev for
net.(*netFD).writeBuffers.

Change-Id: Ie256c2f96aba8e61fb21991788789a049425f792
Reviewed-on: https://go-review.googlesource.com/c/go/+/254638
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Tobias Klauser <tobias.klauser@gmail.com>

src/internal/poll/fd_writev_illumos.go

@@ -0,0 +1,16 @@
+// Copyright 2020 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 illumos
+
+package poll
+
+import (
+	"internal/syscall/unix"
+	"syscall"
+)
+
+func writev(fd int, iovecs []syscall.Iovec) (uintptr, error) {
+	return unix.Writev(fd, iovecs)
+}

src/internal/poll/iovec_illumos.go

@@ -0,0 +1,16 @@
+// Copyright 2020 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 illumos
+
+package poll
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func newIovecWithBase(base *byte) syscall.Iovec {
+	return syscall.Iovec{Base: (*int8)(unsafe.Pointer(base))}
+}

src/internal/poll/iovec_unix.go

@@ -0,0 +1,13 @@
+// Copyright 2020 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 linux netbsd openbsd
+
+package poll
+
+import "syscall"
+
+func newIovecWithBase(base *byte) syscall.Iovec {
+	return syscall.Iovec{Base: base}
+}

src/internal/poll/writev.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd illumos linux netbsd openbsd
 
 package poll
 
@@ -38,7 +38,7 @@ func (fd *FD) Writev(v *[][]byte) (int64, error) {
 			if len(chunk) == 0 {
 				continue
 			}
-			iovecs = append(iovecs, syscall.Iovec{Base: &chunk[0]})
+			iovecs = append(iovecs, newIovecWithBase(&chunk[0]))
 			if fd.IsStream && len(chunk) > 1<<30 {
 				iovecs[len(iovecs)-1].SetLen(1 << 30)
 				break // continue chunk on next writev

src/internal/syscall/unix/writev_illumos.go

@@ -0,0 +1,30 @@
+// Copyright 2020 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 illumos
+
+package unix
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+//go:cgo_import_dynamic libc_writev writev "libc.so"
+
+//go:linkname procwritev libc_writev
+
+var procwritev uintptr
+
+func Writev(fd int, iovs []syscall.Iovec) (uintptr, error) {
+	var p *syscall.Iovec
+	if len(iovs) > 0 {
+		p = &iovs[0]
+	}
+	n, _, errno := syscall6(uintptr(unsafe.Pointer(&procwritev)), 3, uintptr(fd), uintptr(unsafe.Pointer(p)), uintptr(len(iovs)), 0, 0, 0)
+	if errno != 0 {
+		return 0, errno
+	}
+	return n, nil
+}

src/net/writev_test.go

@@ -154,7 +154,7 @@ func testBuffer_writeTo(t *testing.T, chunks int, useCopy bool) {
 
 		var wantSum int
 		switch runtime.GOOS {
-		case "android", "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd":
+		case "android", "darwin", "dragonfly", "freebsd", "illumos", "linux", "netbsd", "openbsd":
 			var wantMinCalls int
 			wantSum = want.Len()
 			v := chunks

src/net/writev_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd illumos linux netbsd openbsd
 
 package net