// 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
}
// parseParameterOrLocal parses the entry for a function parameter or local
// variable, which are both specified the same way. fp contains the frame
// pointer, which is used to calculate the variable location.
func (s *Server) parseParameterOrLocal(entry *dwarf.Entry, fp uint64) (program.LocalVar, error) {
var v program.LocalVar
v.Name, _ = entry.Val(dwarf.AttrName).(string)
if off, err := s.dwarfData.EntryTypeOffset(entry); err != nil {
return v, err
} else {
v.Var.TypeID = uint64(off)
}
if i := entry.Val(dwarf.AttrLocation); i == nil {
return v, fmt.Errorf("missing location description")
} else if locationDescription, ok := i.([]uint8); !ok {
return v, fmt.Errorf("unsupported location description")
} else if offset, err := evalLocation(locationDescription); err != nil {
return v, err
} else {
v.Var.Address = fp + uint64(offset)
}
return v, nil
}
// printEntryValueAt pretty-prints the data at the specified address.
// using the type information in the Entry.
func (p *Printer) printEntryValueAt(entry *dwarf.Entry, a uint64) {
if a == 0 {
p.printf("<nil>")
return
}
switch entry.Tag {
case dwarf.TagVariable, dwarf.TagFormalParameter:
// OK
default:
p.errorf("unrecognized entry type %s", entry.Tag)
return
}
iface := entry.Val(dwarf.AttrType)
if iface == nil {
p.errorf("no type")
return
}
typ, err := p.dwarf.Type(iface.(dwarf.Offset))
if err != nil {
p.errorf("type lookup: %v", err)
return
}
p.printValueAt(typ, a)
}
// 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
}