forked from go-delve/delve
/
reader.go
executable file
·328 lines (276 loc) · 7.96 KB
/
reader.go
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package reader
import (
"debug/dwarf"
"errors"
"fmt"
"github.com/derekparker/delve/dwarf/op"
)
type Reader struct {
*dwarf.Reader
depth int
}
// New returns a reader for the specified dwarf data.
func New(data *dwarf.Data) *Reader {
return &Reader{data.Reader(), 0}
}
// Seek moves the reader to an arbitrary offset.
func (reader *Reader) Seek(off dwarf.Offset) {
reader.depth = 0
reader.Reader.Seek(off)
}
// SeekToEntry moves the reader to an arbitrary entry.
func (reader *Reader) SeekToEntry(entry *dwarf.Entry) error {
reader.Seek(entry.Offset)
// Consume the current entry so .Next works as intended
_, err := reader.Next()
return err
}
// SeekToFunctionEntry moves the reader to the function that includes the
// specified program counter.
func (reader *Reader) SeekToFunction(pc uint64) (*dwarf.Entry, error) {
reader.Seek(0)
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
if entry.Tag != dwarf.TagSubprogram {
continue
}
lowpc, ok := entry.Val(dwarf.AttrLowpc).(uint64)
if !ok {
continue
}
highpc, ok := entry.Val(dwarf.AttrHighpc).(uint64)
if !ok {
continue
}
if lowpc <= pc && highpc > pc {
return entry, nil
}
}
return nil, fmt.Errorf("unable to find function context")
}
// 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
}
// 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
}
}
// 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, fmt.Errorf("no type entry found")
}
// SeekToTypeNamed moves the reader to the type specified by the name.
// If the reader is set to a struct type the NextMemberVariable call
// can be used to walk all member data.
func (reader *Reader) SeekToTypeNamed(name string) (*dwarf.Entry, error) {
// Walk the types to the base
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
n, ok := entry.Val(dwarf.AttrName).(string)
if !ok {
continue
}
if n == name {
return entry, nil
}
}
return nil, errors.New("no type entry found")
}
// Finds the entry for 'name'.
func (reader *Reader) FindEntryNamed(name string, member bool) (*dwarf.Entry, error) {
depth := 1
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
if entry.Children {
depth++
}
if entry.Tag == 0 {
depth--
if depth <= 0 {
return nil, fmt.Errorf("could not find symbol value for %s", name)
}
}
if member {
if entry.Tag != dwarf.TagMember {
continue
}
} else {
if entry.Tag != dwarf.TagVariable && entry.Tag != dwarf.TagFormalParameter && entry.Tag != dwarf.TagStructType {
continue
}
}
n, ok := entry.Val(dwarf.AttrName).(string)
if !ok || n != name {
continue
}
return entry, nil
}
return nil, fmt.Errorf("could not find symbol value for %s", name)
}
func (reader *Reader) InstructionsForEntryNamed(name string, member bool) ([]byte, error) {
entry, err := reader.FindEntryNamed(name, member)
if err != nil {
return nil, err
}
var attr dwarf.Attr
if member {
attr = dwarf.AttrDataMemberLoc
} else {
attr = dwarf.AttrLocation
}
instr, ok := entry.Val(attr).([]byte)
if !ok {
return nil, errors.New("invalid typecast for Dwarf instructions")
}
return instr, nil
}
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
}
// NextScopeVariable moves the reader to the next debug entry that describes a local variable and returns the entry.
func (reader *Reader) NextScopeVariable() (*dwarf.Entry, error) {
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
// All scope variables will be at the same depth
reader.SkipChildren()
// End of the current depth
if entry.Tag == 0 {
break
}
if entry.Tag == dwarf.TagVariable || entry.Tag == dwarf.TagFormalParameter {
return entry, nil
}
}
// No more items
return nil, nil
}
// NextMememberVariable moves the reader to the next debug entry that describes a member variable and returns the entry.
func (reader *Reader) NextMemberVariable() (*dwarf.Entry, error) {
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
// All member variables will be at the same depth
reader.SkipChildren()
// End of the current depth
if entry.Tag == 0 {
break
}
if entry.Tag == dwarf.TagMember {
return entry, nil
}
}
// No more items
return nil, nil
}
// NextPackageVariable moves the reader to the next debug entry that describes a package variable.
// Any TagVariable entry that is not inside a sub prgram entry and is marked external is considered a package variable.
func (reader *Reader) NextPackageVariable() (*dwarf.Entry, error) {
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
if entry.Tag == dwarf.TagVariable {
ext, ok := entry.Val(dwarf.AttrExternal).(bool)
if ok && ext {
return entry, nil
}
}
// Ignore everything inside sub programs
if entry.Tag == dwarf.TagSubprogram {
reader.SkipChildren()
}
}
// No more items
return nil, nil
}
func (reader *Reader) NextCompileUnit() (*dwarf.Entry, error) {
for entry, err := reader.Next(); entry != nil; entry, err = reader.Next() {
if err != nil {
return nil, err
}
if entry.Tag == dwarf.TagCompileUnit {
return entry, nil
}
}
return nil, nil
}