108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
package loclist
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import (
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"encoding/binary"
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"github.com/go-delve/delve/pkg/dwarf/godwarf"
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)
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// Reader represents a loclist reader.
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type Reader interface {
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Find(off int, staticBase, base, pc uint64, debugAddr *godwarf.DebugAddr) (*Entry, error)
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Empty() bool
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}
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// Dwarf2Reader parses and presents DWARF loclist information for DWARF versions 2 through 4.
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type Dwarf2Reader struct {
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data []byte
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cur int
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ptrSz int
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}
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// NewDwarf2Reader returns an initialized loclist Reader for DWARF versions 2 through 4.
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func NewDwarf2Reader(data []byte, ptrSz int) *Dwarf2Reader {
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return &Dwarf2Reader{data: data, ptrSz: ptrSz}
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}
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// Empty returns true if this reader has no data.
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func (rdr *Dwarf2Reader) Empty() bool {
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return rdr.data == nil
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}
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// Seek moves the data pointer to the specified offset.
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func (rdr *Dwarf2Reader) Seek(off int) {
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rdr.cur = off
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}
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// Next advances the reader to the next loclist entry, returning
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// the entry and true if successful, or nil, false if not.
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func (rdr *Dwarf2Reader) Next(e *Entry) bool {
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e.LowPC = rdr.oneAddr()
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e.HighPC = rdr.oneAddr()
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if e.LowPC == 0 && e.HighPC == 0 {
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return false
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}
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if e.BaseAddressSelection() {
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e.Instr = nil
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return true
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}
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instrlen := binary.LittleEndian.Uint16(rdr.read(2))
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e.Instr = rdr.read(int(instrlen))
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return true
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}
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// Find returns the loclist entry for the specified PC address, inside the
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// loclist stating at off. Base is the base address of the compile unit and
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// staticBase is the static base at which the image is loaded.
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func (rdr *Dwarf2Reader) Find(off int, staticBase, base, pc uint64, debugAddr *godwarf.DebugAddr) (*Entry, error) {
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rdr.Seek(off)
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var e Entry
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for rdr.Next(&e) {
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if e.BaseAddressSelection() {
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base = e.HighPC + staticBase
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continue
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}
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if pc >= e.LowPC+base && pc < e.HighPC+base {
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return &e, nil
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}
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}
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return nil, nil
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}
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func (rdr *Dwarf2Reader) read(sz int) []byte {
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r := rdr.data[rdr.cur : rdr.cur+sz]
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rdr.cur += sz
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return r
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}
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func (rdr *Dwarf2Reader) oneAddr() uint64 {
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switch rdr.ptrSz {
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case 4:
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addr := binary.LittleEndian.Uint32(rdr.read(rdr.ptrSz))
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if addr == ^uint32(0) {
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return ^uint64(0)
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}
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return uint64(addr)
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case 8:
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addr := uint64(binary.LittleEndian.Uint64(rdr.read(rdr.ptrSz)))
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return addr
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default:
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panic("bad address size")
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}
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}
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// Entry represents a single entry in the loclist section.
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type Entry struct {
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LowPC, HighPC uint64
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Instr []byte
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}
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// BaseAddressSelection returns true if entry.highpc should
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// be used as the base address for subsequent entries.
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func (e *Entry) BaseAddressSelection() bool {
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return e.LowPC == ^uint64(0)
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}
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