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btf,info: Fix bad instruction offset when parsing infos from kernel #1169

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merged 1 commit into from
Oct 19, 2023
Merged

btf,info: Fix bad instruction offset when parsing infos from kernel #1169

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42 changes: 24 additions & 18 deletions btf/ext_info.go
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Original file line number Diff line number Diff line change
Expand Up @@ -391,13 +391,14 @@ func newFuncInfos(bfis []bpfFuncInfo, spec *Spec) (FuncInfos, error) {
return fis, nil
}

// LoadFuncInfos parses btf func info in wire format.
// LoadFuncInfos parses BTF func info in kernel wire format.
func LoadFuncInfos(reader io.Reader, bo binary.ByteOrder, recordNum uint32, spec *Spec) (FuncInfos, error) {
fis, err := parseFuncInfoRecords(
reader,
bo,
FuncInfoSize,
recordNum,
false,
)
if err != nil {
return FuncInfos{}, fmt.Errorf("parsing BTF func info: %w", err)
Expand Down Expand Up @@ -441,7 +442,7 @@ func parseFuncInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map
return nil, err
}

records, err := parseFuncInfoRecords(r, bo, recordSize, infoHeader.NumInfo)
records, err := parseFuncInfoRecords(r, bo, recordSize, infoHeader.NumInfo, true)
if err != nil {
return nil, fmt.Errorf("section %v: %w", secName, err)
}
Expand All @@ -453,7 +454,7 @@ func parseFuncInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map
// parseFuncInfoRecords parses a stream of func_infos into a funcInfos.
// These records appear after a btf_ext_info_sec header in the func_info
// sub-section of .BTF.ext.
func parseFuncInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32) ([]bpfFuncInfo, error) {
func parseFuncInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32, offsetInBytes bool) ([]bpfFuncInfo, error) {
var out []bpfFuncInfo
var fi bpfFuncInfo

Expand All @@ -467,13 +468,15 @@ func parseFuncInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, r
return nil, fmt.Errorf("can't read function info: %v", err)
}

if fi.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", fi.InsnOff)
}
if offsetInBytes {
if fi.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", fi.InsnOff)
}

// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
fi.InsnOff /= asm.InstructionSize
// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
fi.InsnOff /= asm.InstructionSize
}

out = append(out, fi)
}
Expand Down Expand Up @@ -537,13 +540,14 @@ type bpfLineInfo struct {
LineCol uint32
}

// LoadLineInfos parses btf line info in wire format.
// LoadLineInfos parses BTF line info in kernel wire format.
func LoadLineInfos(reader io.Reader, bo binary.ByteOrder, recordNum uint32, spec *Spec) (LineInfos, error) {
lis, err := parseLineInfoRecords(
reader,
bo,
LineInfoSize,
recordNum,
false,
)
if err != nil {
return LineInfos{}, fmt.Errorf("parsing BTF line info: %w", err)
Expand Down Expand Up @@ -649,7 +653,7 @@ func parseLineInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map
return nil, err
}

records, err := parseLineInfoRecords(r, bo, recordSize, infoHeader.NumInfo)
records, err := parseLineInfoRecords(r, bo, recordSize, infoHeader.NumInfo, true)
if err != nil {
return nil, fmt.Errorf("section %v: %w", secName, err)
}
Expand All @@ -661,7 +665,7 @@ func parseLineInfos(r io.Reader, bo binary.ByteOrder, strings *stringTable) (map
// parseLineInfoRecords parses a stream of line_infos into a lineInfos.
// These records appear after a btf_ext_info_sec header in the line_info
// sub-section of .BTF.ext.
func parseLineInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32) ([]bpfLineInfo, error) {
func parseLineInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, recordNum uint32, offsetInBytes bool) ([]bpfLineInfo, error) {
var out []bpfLineInfo
var li bpfLineInfo

Expand All @@ -675,13 +679,15 @@ func parseLineInfoRecords(r io.Reader, bo binary.ByteOrder, recordSize uint32, r
return nil, fmt.Errorf("can't read line info: %v", err)
}

if li.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", li.InsnOff)
}
if offsetInBytes {
if li.InsnOff%asm.InstructionSize != 0 {
return nil, fmt.Errorf("offset %v is not aligned with instruction size", li.InsnOff)
}

// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
li.InsnOff /= asm.InstructionSize
// ELF tracks offset in bytes, the kernel expects raw BPF instructions.
// Convert as early as possible.
li.InsnOff /= asm.InstructionSize
}

out = append(out, li)
}
Expand Down
46 changes: 34 additions & 12 deletions info_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -370,18 +370,23 @@ func TestHaveProgramInfoMapIDs(t *testing.T) {
func TestProgInfoExtBTF(t *testing.T) {
testutils.SkipOnOldKernel(t, "5.0", "Program BTF (func/line_info)")

spec, err := LoadCollectionSpec("testdata/raw_tracepoint-el.elf")
spec, err := LoadCollectionSpec(fmt.Sprintf("testdata/loader-%s.elf", internal.ClangEndian))
if err != nil {
t.Fatal(err)
}

coll, err := NewCollection(spec)
var obj struct {
Main *Program `ebpf:"xdp_prog"`
}

err = spec.LoadAndAssign(&obj, nil)
testutils.SkipIfNotSupported(t, err)
if err != nil {
t.Fatal(err)
}
defer coll.Close()
defer obj.Main.Close()

info, err := coll.Programs["sched_process_exec"].Info()
info, err := obj.Main.Info()
if err != nil {
t.Fatal(err)
}
Expand All @@ -391,17 +396,34 @@ func TestProgInfoExtBTF(t *testing.T) {
t.Fatal(err)
}

const expectedSource = "\treturn 0;"
if inst[0].Source().String() != expectedSource {
t.Fatalf("Source of first instruction incorrect. Got '%s', expected: '%s'", inst[0].Source().String(), expectedSource)
expectedLineInfoCount := 26
expectedFuncInfo := map[string]bool{
"xdp_prog": false,
"static_fn": false,
"global_fn2": false,
"global_fn3": false,
}

lineInfoCount := 0

for _, ins := range inst {
if ins.Source() != nil {
lineInfoCount++
}

fn := btf.FuncMetadata(&ins)
if fn != nil {
expectedFuncInfo[fn.Name] = true
}
}

fn := btf.FuncMetadata(&inst[0])
if fn == nil {
t.Fatal("Func metadata missing")
if lineInfoCount != expectedLineInfoCount {
t.Errorf("expected %d line info entries, got %d", expectedLineInfoCount, lineInfoCount)
}

if fn.Name != "sched_process_exec" {
t.Fatalf("Func metadata incorrect. Got '%s', expected: 'sched_process_exec'", fn.Name)
for fn, found := range expectedFuncInfo {
if !found {
t.Errorf("func %q not found", fn)
}
}
}