internal/unix: add Errno wrapper for Windows

internal/sys/syscall.go

@@ -2,7 +2,6 @@ package sys
 
 import (
 	"runtime"
-	"syscall"
 	"unsafe"
 
 	"github.com/cilium/ebpf/internal/unix"
@@ -11,7 +10,7 @@ import (
 // ENOTSUPP is a Linux internal error code that has leaked into UAPI.
 //
 // It is not the same as ENOTSUP or EOPNOTSUPP.
-const ENOTSUPP = syscall.Errno(524)
+const ENOTSUPP = unix.Errno(524)
 
 // BPF wraps SYS_BPF.
 //
@@ -179,12 +178,12 @@ const (
 const BPF_TAG_SIZE = 8
 const BPF_OBJ_NAME_LEN = 16
 
-// wrappedErrno wraps syscall.Errno to prevent direct comparisons with
+// wrappedErrno wraps [unix.Errno] to prevent direct comparisons with
 // syscall.E* or unix.E* constants.
 //
 // You should never export an error of this type.
 type wrappedErrno struct {
-	syscall.Errno
+	unix.Errno
 }
 
 func (we wrappedErrno) Unwrap() error {
@@ -200,10 +199,10 @@ func (we wrappedErrno) Error() string {
 
 type syscallError struct {
 	error
-	errno syscall.Errno
+	errno unix.Errno
 }
 
-func Error(err error, errno syscall.Errno) error {
+func Error(err error, errno unix.Errno) error {
 	return &syscallError{err, errno}
 }
 

internal/unix/errno_linux.go

@@ -0,0 +1,29 @@
+package unix
+
+import (
+	"syscall"
+
+	linux "golang.org/x/sys/unix"
+)
+
+type Errno = syscall.Errno
+
+const (
+	E2BIG      = linux.E2BIG
+	EACCES     = linux.EACCES
+	EAGAIN     = linux.EAGAIN
+	EBADF      = linux.EBADF
+	EEXIST     = linux.EEXIST
+	EFAULT     = linux.EFAULT
+	EILSEQ     = linux.EILSEQ
+	EINTR      = linux.EINTR
+	EINVAL     = linux.EINVAL
+	ENODEV     = linux.ENODEV
+	ENOENT     = linux.ENOENT
+	ENOSPC     = linux.ENOSPC
+	EOPNOTSUPP = linux.EOPNOTSUPP
+	EPERM      = linux.EPERM
+	EPOLLIN    = linux.EPOLLIN
+	ESRCH      = linux.ESRCH
+	ESTALE     = linux.ESTALE
+)

internal/unix/errno_linux_test.go

@@ -0,0 +1,13 @@
+package unix
+
+import (
+	"testing"
+
+	"github.com/go-quicktest/qt"
+	"golang.org/x/sys/unix"
+)
+
+func TestErrnoIsUnix(t *testing.T) {
+	qt.Assert(t, qt.ErrorIs(EPERM, unix.EPERM))
+	qt.Assert(t, qt.ErrorIs(ENOENT, unix.ENOENT))
+}

internal/unix/errno_other.go

@@ -0,0 +1,29 @@
+//go:build !linux && !windows
+
+package unix
+
+import "syscall"
+
+type Errno = syscall.Errno
+
+// Errnos are distinct and non-zero.
+const (
+	E2BIG Errno = iota + 1
+	EACCES
+	EAGAIN
+	EBADF
+	EEXIST
+	EFAULT
+	EILSEQ
+	EINTR
+	EINVAL
+	ENODEV
+	ENOENT
+	ENOSPC
+	ENOTSUP
+	ENOTSUPP
+	EOPNOTSUPP
+	EPERM
+	ESRCH
+	ESTALE
+)

internal/unix/errno_test.go

@@ -0,0 +1,12 @@
+package unix
+
+import (
+	"os"
+	"testing"
+
+	"github.com/go-quicktest/qt"
+)
+
+func TestErrno(t *testing.T) {
+	qt.Assert(t, qt.ErrorIs(ENOENT, os.ErrNotExist))
+}

internal/unix/errno_windows.go

@@ -0,0 +1,78 @@
+package unix
+
+// The code in this file is derived from syscall_unix.go in the Go source code,
+// licensed under the MIT license.
+
+import (
+	"errors"
+	"os"
+	"syscall"
+)
+
+//go:generate go run golang.org/x/tools/cmd/stringer@latest -type=Errno -tags=windows -output=errno_string_windows.go
+
+// Windows specific constants for Unix errnos.
+//
+// The values do not always match Linux, for example EILSEQ and EOPNOTSUPP.
+//
+// See https://learn.microsoft.com/en-us/cpp/c-runtime-library/errno-constants?view=msvc-170
+const (
+	EPERM       Errno = 1
+	ENOENT      Errno = 2
+	ESRCH       Errno = 3
+	EINTR       Errno = 4
+	E2BIG       Errno = 7
+	EBADF       Errno = 9
+	EAGAIN      Errno = 11
+	EACCES      Errno = 13
+	EFAULT      Errno = 14
+	EEXIST      Errno = 17
+	ENODEV      Errno = 19
+	EINVAL      Errno = 22
+	ENFILE      Errno = 23
+	EMFILE      Errno = 24
+	ENOSPC      Errno = 28
+	ENOSYS      Errno = 40
+	ENOTEMPTY   Errno = 41
+	EILSEQ      Errno = 42
+	ENOTSUP     Errno = 129
+	EOPNOTSUPP  Errno = 130
+	ETIMEDOUT   Errno = 138
+	EWOULDBLOCK Errno = 140
+)
+
+// These constants do not exist on Windows and therefore have a non-zero
+// dummy value.
+const (
+	ENOTSUPP Errno = Errno(syscall.APPLICATION_ERROR) + iota
+	ESTALE
+)
+
+// Errno is a Windows compatibility shim for Unix errnos.
+type Errno uintptr
+
+func (e Errno) Error() string {
+	return e.String()
+}
+
+func (e Errno) Is(target error) bool {
+	switch target {
+	case os.ErrPermission:
+		return e == EACCES || e == EPERM
+	case os.ErrExist:
+		return e == EEXIST || e == ENOTEMPTY
+	case os.ErrNotExist:
+		return e == ENOENT
+	case errors.ErrUnsupported:
+		return e == ENOSYS || e == ENOTSUP || e == EOPNOTSUPP
+	}
+	return false
+}
+
+func (e Errno) Temporary() bool {
+	return e == EINTR || e == EMFILE || e == ENFILE || e.Timeout()
+}
+
+func (e Errno) Timeout() bool {
+	return e == EAGAIN || e == EWOULDBLOCK || e == ETIMEDOUT
+}

internal/unix/types_linux.go

@@ -8,26 +8,6 @@ import (
 	linux "golang.org/x/sys/unix"
 )
 
-const (
-	ENOENT     = linux.ENOENT
-	EEXIST     = linux.EEXIST
-	EAGAIN     = linux.EAGAIN
-	ENOSPC     = linux.ENOSPC
-	EINVAL     = linux.EINVAL
-	EPOLLIN    = linux.EPOLLIN
-	EINTR      = linux.EINTR
-	EPERM      = linux.EPERM
-	ESRCH      = linux.ESRCH
-	ENODEV     = linux.ENODEV
-	EBADF      = linux.EBADF
-	E2BIG      = linux.E2BIG
-	EFAULT     = linux.EFAULT
-	EACCES     = linux.EACCES
-	EILSEQ     = linux.EILSEQ
-	EOPNOTSUPP = linux.EOPNOTSUPP
-	ESTALE     = linux.ESTALE
-)
-
 const (
 	BPF_F_NO_PREALLOC         = linux.BPF_F_NO_PREALLOC
 	BPF_F_NUMA_NODE           = linux.BPF_F_NUMA_NODE

internal/unix/types_other.go

@@ -6,26 +6,6 @@ import (
 	"syscall"
 )
 
-// Errnos are distinct and non-zero.
-const (
-	ENOENT syscall.Errno = iota + 1
-	EEXIST
-	EAGAIN
-	ENOSPC
-	EINVAL
-	EINTR
-	EPERM
-	ESRCH
-	ENODEV
-	EBADF
-	E2BIG
-	EFAULT
-	EACCES
-	EILSEQ
-	EOPNOTSUPP
-	ESTALE
-)
-
 // Constants are distinct to avoid breaking switch statements.
 const (
 	BPF_F_NO_PREALLOC = iota
@@ -133,8 +113,8 @@ type Sigset_t struct {
 	Val [4]uint64
 }
 
-func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err syscall.Errno) {
-	return 0, 0, syscall.ENOTSUP
+func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
+	return 0, 0, ENOTSUP
 }
 
 func PthreadSigmask(how int, set, oldset *Sigset_t) error {