internal/syscall/unix: implement Eaccess on darwin

Like on other Unix-like platforms, use faccessat(AT_FDCWD, path, mode,
AT_EACCESS).

Change-Id: I6e04b4244f8e90bd3b35b1b8a9ca38fe845b34ae
Reviewed-on: https://go-review.googlesource.com/c/go/+/579976
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/internal/syscall/unix/asm_darwin.s

diff --git a/src/internal/syscall/unix/asm_darwin.s b/src/internal/syscall/unix/asm_darwin.s
index 0b8efb1..99f2876 100644
--- a/src/internal/syscall/unix/asm_darwin.s
+++ b/src/internal/syscall/unix/asm_darwin.s
@@ -22,3 +22,4 @@
 TEXT ·libc_getgrnam_r_trampoline(SB),NOSPLIT,$0-0; JMP libc_getgrnam_r(SB)
 TEXT ·libc_getgrgid_r_trampoline(SB),NOSPLIT,$0-0; JMP libc_getgrgid_r(SB)
 TEXT ·libc_sysconf_trampoline(SB),NOSPLIT,$0-0; JMP libc_sysconf(SB)
+TEXT ·libc_faccessat_trampoline(SB),NOSPLIT,$0-0; JMP libc_faccessat(SB)

src/internal/syscall/unix/at_sysnum_darwin.go

diff --git a/src/internal/syscall/unix/at_sysnum_darwin.go b/src/internal/syscall/unix/at_sysnum_darwin.go
index 208ff34..77b0af8 100644
--- a/src/internal/syscall/unix/at_sysnum_darwin.go
+++ b/src/internal/syscall/unix/at_sysnum_darwin.go
@@ -4,7 +4,11 @@
 
 package unix
 
-const AT_REMOVEDIR = 0x80
-const AT_SYMLINK_NOFOLLOW = 0x0020
+const (
+	AT_EACCESS          = 0x10
+	AT_FDCWD            = -0x2
+	AT_REMOVEDIR        = 0x80
+	AT_SYMLINK_NOFOLLOW = 0x0020
 
-const UTIME_OMIT = -0x2
+	UTIME_OMIT = -0x2
+)

src/internal/syscall/unix/eaccess_darwin.go

diff --git a/src/internal/syscall/unix/eaccess_darwin.go b/src/internal/syscall/unix/eaccess_darwin.go
new file mode 100644
index 0000000..0fa8d17
--- /dev/null
+++ b/src/internal/syscall/unix/eaccess_darwin.go
@@ -0,0 +1,31 @@
+// Copyright 2024 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 (
+	"internal/abi"
+	"syscall"
+	"unsafe"
+)
+
+func libc_faccessat_trampoline()
+
+//go:cgo_import_dynamic libc_faccessat faccessat "/usr/lib/libSystem.B.dylib"
+
+func faccessat(dirfd int, path string, mode uint32, flags int) error {
+	p, err := syscall.BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+	_, _, errno := syscall_syscall6(abi.FuncPCABI0(libc_faccessat_trampoline), uintptr(dirfd), uintptr(unsafe.Pointer(p)), uintptr(mode), uintptr(flags), 0, 0)
+	if errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+func Eaccess(path string, mode uint32) error {
+	return faccessat(AT_FDCWD, path, mode, AT_EACCESS)
+}

src/internal/syscall/unix/eaccess_other.go

diff --git a/src/internal/syscall/unix/eaccess_other.go b/src/internal/syscall/unix/eaccess_other.go
index 1a633ae..3da3a64 100644
--- a/src/internal/syscall/unix/eaccess_other.go
+++ b/src/internal/syscall/unix/eaccess_other.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.
 
-//go:build unix && !dragonfly && !freebsd && !linux && !openbsd && !netbsd
+//go:build unix && !darwin && !dragonfly && !freebsd && !linux && !openbsd && !netbsd
 
 package unix