ebpf: export PossibleCPU

Make PossibleCPU available to users of the package. This allows pre-allocating per-CPU slices.

Signed-off-by: Alun Evans <alun@badgerous.net>

internal/cpu.go → cpu.go

@@ -1,17 +1,33 @@
-package internal
+package ebpf
 
 import (
 	"fmt"
 	"os"
 	"strings"
+
+	"github.com/cilium/ebpf/internal"
 )
 
-// PossibleCPUs returns the max number of CPUs a system may possibly have
-// Logical CPU numbers must be of the form 0-n
-var PossibleCPUs = Memoize(func() (int, error) {
+var possibleCPU = internal.Memoize(func() (int, error) {
 	return parseCPUsFromFile("/sys/devices/system/cpu/possible")
 })
 
+// PossibleCPU returns the max number of CPUs a system may possibly have
+// Logical CPU numbers must be of the form 0-n
+func PossibleCPU() (int, error) {
+	return possibleCPU()
+}
+
+// MustPossibleCPU is a helper that wraps a call to PossibleCPU and panics if
+// the error is non-nil.
+func MustPossibleCPU() int {
+	cpus, err := PossibleCPU()
+	if err != nil {
+		panic(err)
+	}
+	return cpus
+}
+
 func parseCPUsFromFile(path string) (int, error) {
 	spec, err := os.ReadFile(path)
 	if err != nil {

internal/cpu_test.go → cpu_test.go

@@ -1,4 +1,4 @@
-package internal
+package ebpf
 
 import (
 	"testing"

map.go

@@ -133,7 +133,7 @@ func (spec *MapSpec) fixupMagicFields() (*MapSpec, error) {
 		spec.KeySize = 4
 		spec.ValueSize = 4
 
-		n, err := internal.PossibleCPUs()
+		n, err := PossibleCPU()
 		if err != nil {
 			return nil, fmt.Errorf("fixup perf event array: %w", err)
 		}
@@ -515,7 +515,7 @@ func newMap(fd *sys.FD, name string, typ MapType, keySize, valueSize, maxEntries
 		return m, nil
 	}
 
-	possibleCPUs, err := internal.PossibleCPUs()
+	possibleCPUs, err := PossibleCPU()
 	if err != nil {
 		return nil, err
 	}

map_test.go

@@ -1314,10 +1314,7 @@ func TestIterateMapInMap(t *testing.T) {
 func TestPerCPUMarshaling(t *testing.T) {
 	for _, typ := range []MapType{PerCPUHash, PerCPUArray, LRUCPUHash} {
 		t.Run(typ.String(), func(t *testing.T) {
-			numCPU, err := internal.PossibleCPUs()
-			if err != nil {
-				t.Fatal(err)
-			}
+			numCPU := MustPossibleCPU()
 			if numCPU < 2 {
 				t.Skip("Test requires at least two CPUs")
 			}
@@ -1372,10 +1369,7 @@ type bpfCgroupStorageKey struct {
 }
 
 func TestCgroupPerCPUStorageMarshaling(t *testing.T) {
-	numCPU, err := internal.PossibleCPUs()
-	if err != nil {
-		t.Fatal(err)
-	}
+	numCPU := MustPossibleCPU()
 	if numCPU < 2 {
 		t.Skip("Test requires at least two CPUs")
 	}

marshalers.go

@@ -53,7 +53,7 @@ func marshalPerCPUValue(slice any, elemLength int) (sys.Pointer, error) {
 		return sys.Pointer{}, errors.New("per-CPU value requires slice")
 	}
 
-	possibleCPUs, err := internal.PossibleCPUs()
+	possibleCPUs, err := PossibleCPU()
 	if err != nil {
 		return sys.Pointer{}, err
 	}
@@ -91,7 +91,7 @@ func unmarshalPerCPUValue(slicePtr any, elemLength int, buf []byte) error {
 		return fmt.Errorf("per-cpu value requires pointer to slice")
 	}
 
-	possibleCPUs, err := internal.PossibleCPUs()
+	possibleCPUs, err := PossibleCPU()
 	if err != nil {
 		return err
 	}