implement futimens on Darwin and Linux (#1210)

Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

internal/platform/utimes_darwin.go

@@ -0,0 +1,34 @@
+package platform
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func futimens(fd uintptr, atimeNsec, mtimeNsec int64) error {
+	tv := []syscall.Timespec{
+		syscall.NsecToTimespec(atimeNsec),
+		syscall.NsecToTimespec(mtimeNsec),
+	}
+
+	// Warning: futimens only exists since High Sierra (10.13).
+	_, _, e1 := syscall_syscall6(libc_futimens_trampoline_addr, fd, uintptr(unsafe.Pointer(&tv[0])), 0, 0, 0, 0)
+	if e1 != 0 {
+		return e1
+	}
+	return nil
+}
+
+// libc_futimens_trampoline_addr is the address of the libc_futimens_trampoline symbol, defined in utimes_darwin.s
+// we use this value to invoke the syscall through syscall_syscall6 imported below
+var libc_futimens_trampoline_addr uintptr
+
+// Imports the futimens symbol from libc as libc_futimens
+//go:cgo_import_dynamic libc_futimens futimens "/usr/lib/libSystem.B.dylib"
+
+// syscall_syscall6 is a private symbol that we link below. We need to use this instead of syscall.Syscall6
+// because the public syscall.Syscall6 won't work when fn is an address
+func syscall_syscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err syscall.Errno)
+
+// Import syscall.syscall6 as syscall_syscall6.
+//go:linkname syscall_syscall6 syscall.syscall6

internal/platform/utimes_darwin.s

@@ -0,0 +1,8 @@
+// lifted from golang.org/x/sys unix
+#include "textflag.h"
+
+TEXT libc_futimens_trampoline<>(SB), NOSPLIT, $0-0
+	JMP libc_futimens(SB)
+
+GLOBL ·libc_futimens_trampoline_addr(SB), RODATA, $8
+DATA ·libc_futimens_trampoline_addr(SB)/8, $libc_futimens_trampoline<>(SB)

internal/platform/utimes_linux.go

@@ -0,0 +1,18 @@
+package platform
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func futimens(fd uintptr, atimeNsec, mtimeNsec int64) error {
+	times := []syscall.Timespec{
+		syscall.NsecToTimespec(atimeNsec),
+		syscall.NsecToTimespec(mtimeNsec),
+	}
+	_, _, err := syscall.Syscall6(syscall.SYS_UTIMENSAT, fd, uintptr(0), uintptr(unsafe.Pointer(&times[0])), uintptr(0), 0, 0)
+	if err != 0 {
+		return err
+	}
+	return nil
+}

internal/platform/utimes_test.go

@@ -73,7 +73,7 @@ func TestUtimesNano(t *testing.T) {
 }
 
 func TestUtimesNanoFile(t *testing.T) {
-	if !(runtime.GOOS == "windows" && IsGo120) {
+	if !IsGo120 {
 		t.Skip("TODO: implement futimens on darwin, freebsd, linux w/o CGO")
 	}
 

internal/platform/utimes_unsupported.go

@@ -1,4 +1,4 @@
-//go:build !windows
+//go:build !windows && !linux && !darwin
 
 package platform