features: Make Main Package Feature Tests Public

Move all feature teats in the main package to a new
internal directory, "internal/features", which can be used
by the main package and also mirrored in the "features"
package for public use.

Signed-off-by: Nate Sweet <[email protected]>

collection.go

@@ -10,6 +10,7 @@ import (
 	"github.com/cilium/ebpf/asm"
 	"github.com/cilium/ebpf/btf"
 	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/features"
 	"github.com/cilium/ebpf/internal/kallsyms"
 	"github.com/cilium/ebpf/internal/kconfig"
 	"github.com/cilium/ebpf/internal/linux"
@@ -508,7 +509,7 @@ func (cl *collectionLoader) loadMap(mapName string) (*Map, error) {
 	// Defer setting the mmapable flag on maps until load time. This avoids the
 	// MapSpec having different flags on some kernel versions. Also avoid running
 	// syscalls during ELF loading, so platforms like wasm can also parse an ELF.
-	if isDataSection(mapSpec.Name) && haveMmapableMaps() == nil {
+	if isDataSection(mapSpec.Name) && features.HaveMmapableMaps() == nil {
 		mapSpec.Flags |= sys.BPF_F_MMAPABLE
 	}
 
@@ -730,7 +731,7 @@ func resolveKconfig(m *MapSpec) error {
 				return fmt.Errorf("variable %s must be an integer, got %s", n, v.Type)
 			}
 			var value uint64 = 1
-			if err := haveSyscallWrapper(); errors.Is(err, ErrNotSupported) {
+			if err := features.HaveSyscallWrapper(); errors.Is(err, ErrNotSupported) {
 				value = 0
 			} else if err != nil {
 				return fmt.Errorf("unable to derive a value for LINUX_HAS_SYSCALL_WRAPPER: %w", err)

features/syscalls.go

@@ -0,0 +1,80 @@
+package features
+
+import internalFeatures "github.com/cilium/ebpf/internal/features"
+
+// HaveNestedMaps returns a nil error if nested maps are supported.
+func HaveNestedMaps() error {
+	return internalFeatures.HaveNestedMaps()
+}
+
+// HaveMapMutabilityModifiers returns a nil error if map
+// mutability modifiers are supported.
+func HaveMapMutabilityModifiers() error {
+	return internalFeatures.HaveMapMutabilityModifiers()
+}
+
+// HaveMmapableMaps returns a nil error if mmapable maps
+// are supported.
+func HaveMmapableMaps() error {
+	return internalFeatures.HaveMmapableMaps()
+}
+
+// HaveInnerMaps returns a nil error if inner maps are supported.
+func HaveInnerMaps() error {
+	return internalFeatures.HaveInnerMaps()
+}
+
+// HaveNoPreallocMaps returns a nil error if the flag for
+// creating maps that are not pre-allocated is supported.
+func HaveNoPreallocMaps() error {
+	return internalFeatures.HaveNoPreallocMaps()
+}
+
+// HaveObjName returns a nil error if object names are supported
+func HaveObjName() error {
+	return internalFeatures.HaveObjName()
+}
+
+// ObjNameAllowsDot returns a nil error if object names support
+// the dot character, i.e. ".".
+func ObjNameAllowsDot() error {
+	return internalFeatures.ObjNameAllowsDot()
+}
+
+// HaveBatchAPI returns a nil error if batch operations are supported
+func HaveBatchAPI() error {
+	return internalFeatures.HaveBatchAPI()
+}
+
+// HaveProbeReadKernel returns a nil error if kprobes are supported.
+func HaveProbeReadKernel() error {
+	return internalFeatures.HaveProbeReadKernel()
+}
+
+// HaveBPFToBPFCalls returns a nil error if bpf programs can call other bpf
+// programs.
+func HaveBPFToBPFCalls() error {
+	return internalFeatures.HaveBPFToBPFCalls()
+}
+
+// HaveSyscallWrapper returns a nil error if syscall wrapper is not supported.
+func HaveSyscallWrapper() error {
+	return internalFeatures.HaveSyscallWrapper()
+}
+
+// HaveProgramExtInfos returns a nil error if program BTF is supported
+func HaveProgramExtInfos() error {
+	return internalFeatures.HaveProgramExtInfos()
+}
+
+// HaveProgramInfoMapIDs returns a nil error if retrieving map ids from
+// program's object info is supported.
+func HaveProgramInfoMapIDs() error {
+	return internalFeatures.HaveProgramInfoMapIDs()
+}
+
+// HaveProgTestRun returns a nil error if the bpf command
+// PROG_TEST_RUN is supported.
+func HaveProgTestRun() error {
+	return internalFeatures.HaveProgTestRun()
+}

info.go

@@ -16,6 +16,7 @@ import (
 	"github.com/cilium/ebpf/asm"
 	"github.com/cilium/ebpf/btf"
 	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/features"
 	"github.com/cilium/ebpf/internal/sys"
 	"github.com/cilium/ebpf/internal/unix"
 )
@@ -277,7 +278,7 @@ func newProgramInfoFromFd(fd *sys.FD) (*ProgramInfo, error) {
 		info2.NrMapIds = info.NrMapIds
 		info2.MapIds = sys.NewSlicePointer(pi.maps)
 		makeSecondCall = true
-	} else if haveProgramInfoMapIDs() == nil {
+	} else if features.HaveProgramInfoMapIDs() == nil {
 		// This program really has no associated maps.
 		pi.maps = make([]MapID, 0)
 	} else {
@@ -766,30 +767,3 @@ func EnableStats(which uint32) (io.Closer, error) {
 	}
 	return fd, nil
 }
-
-var haveProgramInfoMapIDs = internal.NewFeatureTest("map IDs in program info", func() error {
-	prog, err := progLoad(asm.Instructions{
-		asm.LoadImm(asm.R0, 0, asm.DWord),
-		asm.Return(),
-	}, SocketFilter, "MIT")
-	if err != nil {
-		return err
-	}
-	defer prog.Close()
-
-	err = sys.ObjInfo(prog, &sys.ProgInfo{
-		// NB: Don't need to allocate MapIds since the program isn't using
-		// any maps.
-		NrMapIds: 1,
-	})
-	if errors.Is(err, unix.EINVAL) {
-		// Most likely the syscall doesn't exist.
-		return internal.ErrNotSupported
-	}
-	if errors.Is(err, unix.E2BIG) {
-		// We've hit check_uarg_tail_zero on older kernels.
-		return internal.ErrNotSupported
-	}
-
-	return err
-}, "4.15")

info_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/cilium/ebpf/asm"
 	"github.com/cilium/ebpf/btf"
 	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/features"
 	"github.com/cilium/ebpf/internal/sys"
 	"github.com/cilium/ebpf/internal/testutils"
 )
@@ -461,7 +462,7 @@ func testStats(prog *Program) error {
 }
 
 func TestHaveProgramInfoMapIDs(t *testing.T) {
-	testutils.CheckFeatureTest(t, haveProgramInfoMapIDs)
+	testutils.CheckFeatureTest(t, features.HaveProgramInfoMapIDs)
 }
 
 func TestProgInfoExtBTF(t *testing.T) {

internal/elf.go

@@ -100,3 +100,22 @@ func (se *SafeELFFile) SectionsByType(typ elf.SectionType) []*elf.Section {
 	}
 	return sections
 }
+
+// InvalidBPFObjNameChar returns true if char may not appear in
+// a BPF object name.
+func InvalidBPFObjNameChar(char rune, dotAllowed bool) bool {
+	switch {
+	case char >= 'A' && char <= 'Z':
+		return false
+	case char >= 'a' && char <= 'z':
+		return false
+	case char >= '0' && char <= '9':
+		return false
+	case dotAllowed && char == '.':
+		return false
+	case char == '_':
+		return false
+	default:
+		return true
+	}
+}