internal: add OnLinux constant

Add a constant which indicates whether we are building for Linux.
This is so that we can write

	if !internal.OnLinux {

instead of

	if runtime.GOOS != "linux" {

This makes it easy to remove platform dependent code by removing the
constant and then fixing the breakage.

Signed-off-by: Lorenz Bauer <[email protected]>

internal/feature.go

@@ -93,7 +93,7 @@ func NewFeatureTest(name string, fn FeatureTestFn, versions ...string) func() er
 			break
 		}
 
-		if runtime.GOOS == "linux" && !strings.ContainsRune(version, ':') {
+		if OnLinux && !strings.ContainsRune(version, ':') {
 			// Allow version numbers without a GOOS prefix on Linux.
 			ft.Version = version
 			break

internal/feature_test.go

@@ -83,7 +83,7 @@ func TestFeatureTestNotSupportedOnOS(t *testing.T) {
 	qt.Assert(t, qt.IsNotNil(NewFeatureTest("foo", fn)()))
 	qt.Assert(t, qt.ErrorIs(NewFeatureTest("foo", fn, "froz:1.0.0")(), ErrNotSupportedOnOS))
 	qt.Assert(t, qt.ErrorIs(NewFeatureTest("foo", fn, runtime.GOOS+":1.0")(), sentinel))
-	if runtime.GOOS == "linux" {
+	if OnLinux {
 		qt.Assert(t, qt.ErrorIs(NewFeatureTest("foo", fn, "1.0")(), sentinel))
 	}
 }

internal/goos.go

@@ -0,0 +1,7 @@
+package internal
+
+import "runtime"
+
+const (
+	OnLinux = runtime.GOOS == "linux"
+)

internal/kallsyms/kallsyms.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io"
 	"os"
-	"runtime"
 	"slices"
 	"strconv"
 	"strings"
@@ -50,7 +49,7 @@ func Module(name string) (string, error) {
 // Any symbols missing in the kernel are ignored. Returns an error if multiple
 // symbols with a given name were found.
 func AssignModules(symbols map[string]string) error {
-	if runtime.GOOS != "linux" {
+	if !internal.OnLinux {
 		return fmt.Errorf("read /proc/kallsyms: %w", internal.ErrNotSupportedOnOS)
 	}
 
@@ -169,7 +168,7 @@ func Address(symbol string) (uint64, error) {
 // Any symbols missing in the kernel are ignored. Returns an error if multiple
 // addresses were found for a symbol.
 func AssignAddresses(symbols map[string]uint64) error {
-	if runtime.GOOS != "linux" {
+	if !internal.OnLinux {
 		return fmt.Errorf("read /proc/kallsyms: %w", internal.ErrNotSupportedOnOS)
 	}
 

internal/kallsyms/kallsyms_test.go

@@ -2,13 +2,12 @@ package kallsyms
 
 import (
 	"bytes"
-	"errors"
 	"os"
-	"runtime"
 	"testing"
 
 	"github.com/go-quicktest/qt"
 
+	"github.com/cilium/ebpf/internal"
 	"github.com/cilium/ebpf/internal/testutils"
 )
 
@@ -177,13 +176,11 @@ func BenchmarkAssignAddresses(b *testing.B) {
 func mustOpenProcKallsyms(tb testing.TB) *os.File {
 	tb.Helper()
 
-	if runtime.GOOS != "linux" {
+	if !internal.OnLinux {
 		tb.Skip("/proc/kallsyms is a Linux concept")
 	}
 
 	f, err := os.Open("/proc/kallsyms")
-	if runtime.GOOS != "linux" && errors.Is(err, os.ErrNotExist) {
-	}
 	qt.Assert(tb, qt.IsNil(err))
 	tb.Cleanup(func() { f.Close() })
 	return f

internal/linux/auxv.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"runtime"
 	_ "unsafe"
 
 	"github.com/cilium/ebpf/internal"
@@ -51,7 +50,7 @@ func (r *auxvRuntimeReader) ReadAuxvPair() (uint64, uint64, error) {
 }
 
 func newAuxvRuntimeReader() (auxvPairReader, error) {
-	if runtime.GOOS != "linux" {
+	if !internal.OnLinux {
 		return nil, fmt.Errorf("read auxv from runtime: %w", internal.ErrNotSupportedOnOS)
 	}
 

internal/tracefs/kprobe.go

@@ -113,7 +113,7 @@ func sanitizeTracefsPath(path ...string) (string, error) {
 // but may be also be available at /sys/kernel/debug/tracing if debugfs is mounted.
 // The available tracefs paths will depends on distribution choices.
 var getTracefsPath = sync.OnceValues(func() (string, error) {
-	if runtime.GOOS != "linux" {
+	if !internal.OnLinux {
 		return "", fmt.Errorf("tracefs: %w", internal.ErrNotSupportedOnOS)
 	}