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fix: find ret offset #96

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Merged
merged 1 commit into from
Jun 4, 2025
Merged

fix: find ret offset #96

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42 changes: 33 additions & 9 deletions internal/elfreader/retoffsets.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,20 +13,30 @@ import (
// This code was taken from here:
// https://github.com/cfc4n/go_uretprobe_demo/blob/master/ret_offset.go#L22
func GetFunctionRetOffsets(elfFile string, fnName string) ([]uint64, error) {
var err error
var allSymbs []elf.Symbol
var goSymbs []elf.Symbol
var goElf *elf.File

goElf, err := elf.Open(elfFile)
if err != nil {
return []uint64{}, err
}
goSymbs, err = goElf.Symbols()
if err != nil {
return nil, err
if len(goSymbs) > 0 {
allSymbs = append(allSymbs, goSymbs...)
}
goDynamicSymbs, _ := goElf.DynamicSymbols()
if len(goDynamicSymbs) > 0 {
allSymbs = append(allSymbs, goDynamicSymbs...)
}

if len(allSymbs) == 0 {
return nil, fmt.Errorf("symbol is empty")
}

var found bool
var symbol elf.Symbol
for _, s := range goSymbs {
for _, s := range allSymbs {
if s.Name == fnName {
symbol = s
found = true
Expand All @@ -49,16 +59,30 @@ func GetFunctionRetOffsets(elfFile string, fnName string) ([]uint64, error) {
start := symbol.Value - section.Addr
end := start + symbol.Size

instHex := elfText[start:end]
var offsets []uint64
offsets, err = decodeInstruction(instHex)
if err != nil {
return nil, fmt.Errorf("error decoding instruction: %v", err)
}
var instHex []byte
instHex = elfText[start:end]
offsets, _ = decodeInstruction(instHex)
if len(offsets) == 0 {
return offsets, fmt.Errorf("no RET instructions found")
}

address := symbol.Value
for _, prog := range goElf.Progs {
// Skip uninteresting segments.
if prog.Type != elf.PT_LOAD || (prog.Flags&elf.PF_X) == 0 {
continue
}

if prog.Vaddr <= symbol.Value && symbol.Value < (prog.Vaddr+prog.Memsz) {
// stackoverflow.com/a/40249502
address = symbol.Value - prog.Vaddr + prog.Off
break
}
}
for i, offset := range offsets {
offsets[i] = address + offset
}
return offsets, nil
}

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