internal/linux: skip some tests on non-Linux platforms

Skip most tests in the package, with the exception of the vdso
tests that use testdata. For those we need to make the string
manipulation functions in package unix work on Windows.

Signed-off-by: Lorenz Bauer <lmb@isovalent.com>

internal/linux/auxv.go

@@ -2,8 +2,12 @@ package linux
 
 import (
 	"errors"
+	"fmt"
 	"io"
+	"runtime"
 	_ "unsafe"
+
+	"github.com/cilium/ebpf/internal"
 )
 
 type auxvPairReader interface {
@@ -47,6 +51,10 @@ func (r *auxvRuntimeReader) ReadAuxvPair() (uint64, uint64, error) {
 }
 
 func newAuxvRuntimeReader() (auxvPairReader, error) {
+	if runtime.GOOS != "linux" {
+		return nil, fmt.Errorf("read auxv from runtime: %w", internal.ErrNotSupportedOnOS)
+	}
+
 	data := runtime_getAuxv()
 
 	if len(data)%2 != 0 {

internal/linux/auxv_test.go

@@ -72,6 +72,7 @@ func newDefaultAuxvFileReader() (auxvPairReader, error) {
 
 func TestAuxvBothSourcesEqual(t *testing.T) {
 	runtimeBased, err := newAuxvRuntimeReader()
+	skipIfNotSupportedOnOS(t, err)
 	if err != nil {
 		t.Fatal(err)
 	}

internal/linux/helper_test.go

@@ -0,0 +1,22 @@
+package linux
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/cilium/ebpf/internal"
+)
+
+// skipIfNotSupportedOnOS is a copy of testutils.SkipIfNotSupported to avoid
+// a circular dependency.
+func skipIfNotSupportedOnOS(tb testing.TB, err error) {
+	tb.Helper()
+
+	if err == internal.ErrNotSupportedOnOS {
+		tb.Fatal("Unwrapped ErrNotSupportedOnOS")
+	}
+
+	if errors.Is(err, internal.ErrNotSupportedOnOS) {
+		tb.Skip(err.Error())
+	}
+}

internal/linux/statfs_test.go

@@ -17,6 +17,7 @@ func TestFSType(t *testing.T) {
 		{"/sys/fs/bpf", unix.BPF_FS_MAGIC},
 	} {
 		fst, err := FSType(fs.path)
+		skipIfNotSupportedOnOS(t, err)
 		qt.Assert(t, qt.IsNil(err))
 		qt.Assert(t, qt.Equals(fst, fs.magic))
 	}

internal/linux/vdso_test.go

@@ -53,6 +53,7 @@ func TestAuxvNoVDSO(t *testing.T) {
 
 func TestVDSOVersion(t *testing.T) {
 	_, err := vdsoVersion()
+	skipIfNotSupportedOnOS(t, err)
 	qt.Assert(t, qt.IsNil(err))
 }
 

internal/linux/version_test.go

@@ -8,11 +8,13 @@ import (
 
 func TestCurrentKernelVersion(t *testing.T) {
 	_, err := KernelVersion()
+	skipIfNotSupportedOnOS(t, err)
 	qt.Assert(t, qt.IsNil(err))
 }
 
 func TestKernelRelease(t *testing.T) {
 	r, err := KernelRelease()
+	skipIfNotSupportedOnOS(t, err)
 	if err != nil {
 		t.Fatal(err)
 	}

internal/unix/strings_other.go

@@ -0,0 +1,11 @@
+//go:build !linux && !windows
+
+package unix
+
+func BytePtrFromString(s string) (*byte, error) {
+	return nil, errNonLinux()
+}
+
+func ByteSliceToString(s []byte) string {
+	return ""
+}

internal/unix/strings_windows.go

@@ -0,0 +1,19 @@
+package unix
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+func BytePtrFromString(s string) (*byte, error) {
+	p, err := windows.BytePtrFromString(s)
+	if err == syscall.EINVAL {
+		err = EINVAL
+	}
+	return p, err
+}
+
+func ByteSliceToString(s []byte) string {
+	return windows.ByteSliceToString(s)
+}

internal/unix/types_other.go

@@ -267,14 +267,6 @@ func Tgkill(tgid int, tid int, sig syscall.Signal) (err error) {
 	return errNonLinux()
 }
 
-func BytePtrFromString(s string) (*byte, error) {
-	return nil, errNonLinux()
-}
-
-func ByteSliceToString(s []byte) string {
-	return ""
-}
-
 func Renameat2(olddirfd int, oldpath string, newdirfd int, newpath string, flags uint) error {
 	return errNonLinux()
 }