os: add support for long path names on solaris RemoveAll

Follow CL 146020 and enable RemoveAll based on Unlinkat and Openat on
solaris.

Updates #27029

Change-Id: I0b0e92f4422fa960a13dcd3e9adb57cd23f09ed4
Reviewed-on: https://go-review.googlesource.com/c/145839
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/internal/syscall/unix/asm_solaris.s

+// 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.
+
+#include "textflag.h"
+
+// System calls for Solaris are implemented in runtime/syscall_solaris.go
+
+TEXT ·sysvicall6(SB),NOSPLIT,$0-88
+	JMP	syscall·sysvicall6(SB)

src/internal/syscall/unix/at_solaris.go

+// 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.
+
+package unix
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// Implemented in runtime/syscall_solaris.go.
+func sysvicall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
+
+//go:cgo_import_dynamic libc_fstatat fstatat "libc.so"
+//go:cgo_import_dynamic libc_openat openat "libc.so"
+//go:cgo_import_dynamic libc_unlinkat unlinkat "libc.so"
+
+//go:linkname procFstatat libc_fstatat
+//go:linkname procOpenat libc_openat
+//go:linkname procUnlinkat libc_unlinkat
+
+var (
+	procFstatat,
+	procOpenat,
+	procUnlinkat uintptr
+)
+
+const AT_REMOVEDIR = 0x1
+const AT_SYMLINK_NOFOLLOW = 0x1000
+
+func Unlinkat(dirfd int, path string, flags int) error {
+	var p *byte
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := sysvicall6(uintptr(unsafe.Pointer(&procUnlinkat)), 3, uintptr(dirfd), uintptr(unsafe.Pointer(p)), uintptr(flags), 0, 0, 0)
+	if errno != 0 {
+		return errno
+	}
+
+	return nil
+}
+
+func Openat(dirfd int, path string, flags int, perm uint32) (int, error) {
+	var p *byte
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return 0, err
+	}
+
+	fd, _, errno := sysvicall6(uintptr(unsafe.Pointer(&procOpenat)), 4, uintptr(dirfd), uintptr(unsafe.Pointer(p)), uintptr(flags), uintptr(perm), 0, 0)
+	if errno != 0 {
+		return 0, errno
+	}
+
+	return int(fd), nil
+}
+
+func Fstatat(dirfd int, path string, stat *syscall.Stat_t, flags int) error {
+	var p *byte
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	_, _, errno := sysvicall6(uintptr(unsafe.Pointer(&procFstatat)), 4, uintptr(dirfd), uintptr(unsafe.Pointer(p)), uintptr(unsafe.Pointer(stat)), uintptr(flags), 0, 0)
+	if errno != 0 {
+		return errno
+	}
+
+	return nil
+}

src/os/removeall_at.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 linux darwin openbsd netbsd dragonfly
+// +build linux darwin openbsd netbsd dragonfly solaris
 
 package os
 

src/os/removeall_noat.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 !linux,!darwin,!openbsd,!netbsd,!dragonfly
+// +build !linux,!darwin,!openbsd,!netbsd,!dragonfly,!solaris
 
 package os
 

src/os/removeall_test.go

@@ -153,7 +153,7 @@ func TestRemoveAllLarge(t *testing.T) {
 
 func TestRemoveAllLongPath(t *testing.T) {
 	switch runtime.GOOS {
-	case "linux", "darwin", "openbsd", "netbsd", "dragonfly":
+	case "linux", "darwin", "openbsd", "netbsd", "dragonfly", "solaris":
 		break
 	default:
 		t.Skip("skipping for not implemented platforms")
@@ -201,7 +201,7 @@ func TestRemoveAllLongPath(t *testing.T) {
 
 func TestRemoveAllDot(t *testing.T) {
 	switch runtime.GOOS {
-	case "linux", "darwin", "openbsd", "netbsd", "dragonfly":
+	case "linux", "darwin", "openbsd", "netbsd", "dragonfly", "solaris":
 		break
 	default:
 		t.Skip("skipping for not implemented platforms")