// SeekToType moves the reader to the type specified by the entry,
// optionally resolving typedefs and pointer types. If the reader is set
// to a struct type the NextMemberVariable call can be used to walk all member data.
func (reader *Reader) SeekToType(entry *dwarf.Entry, resolveTypedefs bool, resolvePointerTypes bool) (*dwarf.Entry, error) {
offset, ok := entry.Val(dwarf.AttrType).(dwarf.Offset)
if !ok {
return nil, fmt.Errorf("entry does not have a type attribute")
}
// Seek to the first type offset
reader.Seek(offset)
// Walk the types to the base
for typeEntry, err := reader.Next(); typeEntry != nil; typeEntry, err = reader.Next() {
if err != nil {
return nil, err
}
if typeEntry.Tag == dwarf.TagTypedef && !resolveTypedefs {
return typeEntry, nil
}
if typeEntry.Tag == dwarf.TagPointerType && !resolvePointerTypes {
return typeEntry, nil
}
offset, ok = typeEntry.Val(dwarf.AttrType).(dwarf.Offset)
if !ok {
return typeEntry, nil
}
reader.Seek(offset)
}
return nil, TypeNotFoundErr
}
func (reader *Reader) InstructionsForEntry(entry *dwarf.Entry) ([]byte, error) {
if entry.Tag == dwarf.TagMember {
instructions, ok := entry.Val(dwarf.AttrDataMemberLoc).([]byte)
if !ok {
return nil, fmt.Errorf("member data has no data member location attribute")
}
// clone slice to prevent stomping on the dwarf data
return append([]byte{}, instructions...), nil
}
// non-member
instructions, ok := entry.Val(dwarf.AttrLocation).([]byte)
if !ok {
return nil, fmt.Errorf("entry has no location attribute")
}
// clone slice to prevent stomping on the dwarf data
return append([]byte{}, instructions...), nil
}
// 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
}