// Extracts the address of a variable, dereferencing any pointers
func (scope *EvalScope) extractVariableDataAddress(entry *dwarf.Entry, rdr *reader.Reader) (int64, error) {
instructions, err := rdr.InstructionsForEntry(entry)
if err != nil {
return 0, err
}
address, err := op.ExecuteStackProgram(scope.CFA, instructions)
if err != nil {
return 0, err
}
// Dereference pointers to get down the concrete type
for typeEntry, err := rdr.SeekToType(entry, true, false); typeEntry != nil; typeEntry, err = rdr.SeekToType(typeEntry, true, false) {
if err != nil {
return 0, err
}
if typeEntry.Tag != dwarf.TagPointerType {
break
}
ptraddress := uintptr(address)
ptr, err := scope.Thread.readMemory(ptraddress, scope.PtrSize())
if err != nil {
return 0, err
}
address = int64(binary.LittleEndian.Uint64(ptr))
}
return address, nil
}
// Returns the address for the named entry.
func (reader *Reader) AddrFor(name string) (uint64, error) {
entry, err := reader.FindEntryNamed(name, false)
if err != nil {
return 0, err
}
instructions, ok := entry.Val(dwarf.AttrLocation).([]byte)
if !ok {
return 0, fmt.Errorf("type assertion failed")
}
addr, err := op.ExecuteStackProgram(0, instructions)
if err != nil {
return 0, err
}
return uint64(addr), nil
}
// Execute the stack program taking into account the current stack frame
func (thread *Thread) executeStackProgram(instructions []byte) (int64, error) {
regs, err := thread.Registers()
if err != nil {
return 0, err
}
var cfa int64 = 0
fde, err := thread.dbp.frameEntries.FDEForPC(regs.PC())
if err == nil {
fctx := fde.EstablishFrame(regs.PC())
cfa = fctx.CFAOffset() + int64(regs.SP())
}
address, err := op.ExecuteStackProgram(cfa, instructions)
if err != nil {
return 0, err
}
return address, nil
}
// Returns the address for the named struct member. Expects the reader to be at the parent entry
// or one of the parents children, thus does not seek to parent by itself.
func (reader *Reader) AddrForMember(member string, initialInstructions []byte) (uint64, error) {
for {
entry, err := reader.NextMemberVariable()
if err != nil {
return 0, err
}
if entry == nil {
return 0, fmt.Errorf("nil entry for member named %s", member)
}
name, ok := entry.Val(dwarf.AttrName).(string)
if !ok || name != member {
continue
}
instructions, ok := entry.Val(dwarf.AttrDataMemberLoc).([]byte)
if !ok {
continue
}
addr, err := op.ExecuteStackProgram(0, append(initialInstructions, instructions...))
return uint64(addr), err
}
}
// Extracts the name and type of a variable from a dwarf entry
// then executes the instructions given in the DW_AT_location attribute to grab the variable's address
func (scope *EvalScope) extractVarInfoFromEntry(entry *dwarf.Entry, rdr *reader.Reader) (*Variable, error) {
if entry == nil {
return nil, fmt.Errorf("invalid entry")
}
if entry.Tag != dwarf.TagFormalParameter && entry.Tag != dwarf.TagVariable {
return nil, fmt.Errorf("invalid entry tag, only supports FormalParameter and Variable, got %s", entry.Tag.String())
}
n, ok := entry.Val(dwarf.AttrName).(string)
if !ok {
return nil, fmt.Errorf("type assertion failed")
}
offset, ok := entry.Val(dwarf.AttrType).(dwarf.Offset)
if !ok {
return nil, fmt.Errorf("type assertion failed")
}
t, err := scope.Type(offset)
if err != nil {
return nil, err
}
instructions, ok := entry.Val(dwarf.AttrLocation).([]byte)
if !ok {
return nil, fmt.Errorf("type assertion failed")
}
addr, err := op.ExecuteStackProgram(scope.CFA, instructions)
if err != nil {
return nil, err
}
return scope.newVariable(n, uintptr(addr), t), nil
}
func (scope *EvalScope) extractValueInternal(instructions []byte, addr int64, typ interface{}, printStructName bool, recurseLevel int) (string, error) {
var err error
if addr == 0 {
addr, err = op.ExecuteStackProgram(scope.CFA, instructions)
if err != nil {
return "", err
}
}
// If we have a user defined type, find the
// underlying concrete type and use that.
for {
if tt, ok := typ.(*dwarf.TypedefType); ok {
typ = tt.Type
} else {
break
}
}
ptraddress := uintptr(addr)
switch t := typ.(type) {
case *dwarf.PtrType:
ptr, err := scope.Thread.readMemory(ptraddress, scope.PtrSize())
if err != nil {
return "", err
}
intaddr := int64(binary.LittleEndian.Uint64(ptr))
if intaddr == 0 {
return fmt.Sprintf("%s nil", t.String()), nil
}
// Don't increase the recursion level when dereferencing pointers
val, err := scope.extractValueInternal(nil, intaddr, t.Type, printStructName, recurseLevel)
if err != nil {
return "", err
}
return fmt.Sprintf("*%s", val), nil
case *dwarf.StructType:
switch {
case t.StructName == "string":
return scope.Thread.readString(ptraddress)
case strings.HasPrefix(t.StructName, "[]"):
return scope.readSlice(ptraddress, t, recurseLevel)
default:
// Recursively call extractValue to grab
// the value of all the members of the struct.
if recurseLevel <= maxVariableRecurse {
fields := make([]string, 0, len(t.Field))
for _, field := range t.Field {
val, err := scope.extractValueInternal(nil, field.ByteOffset+addr, field.Type, printStructName, recurseLevel+1)
if err != nil {
return "", err
}
fields = append(fields, fmt.Sprintf("%s: %s", field.Name, val))
}
if printStructName {
return fmt.Sprintf("%s {%s}", t.StructName, strings.Join(fields, ", ")), nil
}
return fmt.Sprintf("{%s}", strings.Join(fields, ", ")), nil
}
// no fields
if printStructName {
return fmt.Sprintf("%s {...}", t.StructName), nil
}
return "{...}", nil
}
case *dwarf.ArrayType:
return scope.readArray(ptraddress, t, recurseLevel)
case *dwarf.ComplexType:
return scope.Thread.readComplex(ptraddress, t.ByteSize)
case *dwarf.IntType:
return scope.Thread.readInt(ptraddress, t.ByteSize)
case *dwarf.UintType:
return scope.Thread.readUint(ptraddress, t.ByteSize)
case *dwarf.FloatType:
return scope.Thread.readFloat(ptraddress, t.ByteSize)
case *dwarf.BoolType:
return scope.Thread.readBool(ptraddress)
case *dwarf.FuncType:
return scope.Thread.readFunctionPtr(ptraddress)
case *dwarf.VoidType:
return "(void)", nil
case *dwarf.UnspecifiedType:
return "(unknown)", nil
default:
fmt.Printf("Unknown type: %T\n", t)
}
return "", fmt.Errorf("could not find value for type %s", typ)
}
