feat(elfunwindinfo): allow capturing an FDE during deltas extraction

nativeunwind/elfunwindinfo/stackdeltaextraction.go

@@ -11,6 +11,7 @@ import (
 
 	"go.opentelemetry.io/ebpf-profiler/libpf/pfelf"
 	sdtypes "go.opentelemetry.io/ebpf-profiler/nativeunwind/stackdeltatypes"
+	"go.opentelemetry.io/ebpf-profiler/util"
 )
 
 const (
@@ -20,6 +21,18 @@ const (
 	numIntervalsToOmitDebugLink = 20
 )
 
+type Option func(*elfExtractor, *extractionFilter)
+
+// WithCaptureFDEHook configures ExtractELF to capture FDE information for a specific address.
+// When an FDE contains the given address 'at', the hook function is called with the address
+// range covered by that FDE.
+func WithCaptureFDEHook(at uintptr, hook func(p util.Range)) Option {
+	return func(ee *elfExtractor, f *extractionFilter) {
+		f.captureFDEAt = at
+		f.capturedFDEHook = hook
+	}
+}
+
 // extractionFilter is used to filter in .eh_frame data when a better source
 // is available (.gopclntab).
 type extractionFilter struct {
@@ -35,12 +48,23 @@ type extractionFilter struct {
 
 	// unsortedFrames is set if stack deltas from unsorted source are found
 	unsortedFrames bool
+
+	captureFDEAt    uintptr
+	capturedFDEHook func(util.Range)
 }
 
 var _ ehframeHooks = &extractionFilter{}
 
 // fdeHook filters out .eh_frame data that is superseded by .gopclntab data
 func (f *extractionFilter) fdeHook(_ *cieInfo, fde *fdeInfo) bool {
+	if f.captureFDEAt != 0 &&
+		f.captureFDEAt >= fde.ipStart &&
+		f.captureFDEAt < fde.ipStart+fde.ipLen {
+		f.capturedFDEHook(util.Range{
+			Start: uint64(fde.ipStart),
+			End:   uint64(fde.ipStart + fde.ipLen),
+		})
+	}
 	if !fde.sorted {
 		// Seems .debug_frame sometimes has broken FDEs for zero address
 		if fde.ipStart == 0 {
@@ -117,7 +141,7 @@ func Extract(filename string, interval *sdtypes.IntervalData) error {
 
 // ExtractELF takes a pfelf.Reference and provides the stack delta
 // intervals for it in the interval parameter.
-func ExtractELF(elfRef *pfelf.Reference, interval *sdtypes.IntervalData) error {
+func ExtractELF(elfRef *pfelf.Reference, interval *sdtypes.IntervalData, opt ...Option) error {
 	elfFile, err := elfRef.GetELF()
 	if err != nil {
 		return err
@@ -133,6 +157,9 @@ func ExtractELF(elfRef *pfelf.Reference, interval *sdtypes.IntervalData) error {
 		hooks:            &filter,
 		allowGenericRegs: isLibCrypto(elfFile),
 	}
+	for _, o := range opt {
+		o(&ee, &filter)
+	}
 
 	if err = ee.parseGoPclntab(); err != nil {
 		return fmt.Errorf("failure to parse golang stack deltas: %v", err)

nativeunwind/elfunwindinfo/stackdeltaextraction_test.go

@@ -6,9 +6,12 @@ package elfunwindinfo
 import (
 	"encoding/base64"
 	"os"
+	"path/filepath"
 	"testing"
 
+	"go.opentelemetry.io/ebpf-profiler/libpf/pfelf"
 	sdtypes "go.opentelemetry.io/ebpf-profiler/nativeunwind/stackdeltatypes"
+	"go.opentelemetry.io/ebpf-profiler/util"
 
 	"github.com/stretchr/testify/require"
 )
@@ -157,3 +160,22 @@ func TestExtractStackDeltasFromFilename(t *testing.T) {
 	}
 	require.Equal(t, data.Deltas[:len(firstDeltas)], firstDeltas)
 }
+
+func TestCaptureFDE(t *testing.T) {
+	buffer, err := base64.StdEncoding.DecodeString(usrBinVolname)
+	require.NoError(t, err)
+	filename := filepath.Join(t.TempDir(), "dwarf_extract_elf_")
+	err = os.WriteFile(filename, buffer, 0o600)
+	require.NoError(t, err)
+	elfRef := pfelf.NewReference(filename, pfelf.SystemOpener)
+	defer elfRef.Close()
+	expected := util.Range{Start: 0x8d0, End: 0x9EF}
+	actual := util.Range{}
+	err = ExtractELF(elfRef, new(sdtypes.IntervalData),
+		WithCaptureFDEHook(0x973, func(p util.Range) {
+			actual = p
+		}),
+	)
+	require.NoError(t, err)
+	require.Equal(t, expected, actual)
+}