delve/pkg/dwarf/frame/parser.go
Alessandro Arzilli a3c7ba8808
proc: add workaround for debug_frame bug on macOS (#2374)
This adds a workaround for the bug described at:

https://github.com/golang/go/issues/25841

Because dsymutil running on PIE does not adjust the address of
debug_frame entries (but adjusts debug_info entries) we try to do the
adjustment ourselves.

Updates #2346
2021-03-09 11:35:24 +01:00

287 lines
8.6 KiB
Go

// Package frame contains data structures and
// related functions for parsing and searching
// through Dwarf .debug_frame data.
package frame
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"github.com/go-delve/delve/pkg/dwarf/util"
)
type parsefunc func(*parseContext) parsefunc
type parseContext struct {
staticBase uint64
buf *bytes.Buffer
totalLen int
entries FrameDescriptionEntries
ciemap map[int]*CommonInformationEntry
common *CommonInformationEntry
frame *FrameDescriptionEntry
length uint32
ptrSize int
ehFrameAddr uint64
err error
}
// Parse takes in data (a byte slice) and returns FrameDescriptionEntries,
// which is a slice of FrameDescriptionEntry. Each FrameDescriptionEntry
// has a pointer to CommonInformationEntry.
// If ehFrameAddr is not zero the .eh_frame format will be used, a minor variant of DWARF described at https://www.airs.com/blog/archives/460.
// The value of ehFrameAddr will be used as the address at which eh_frame will be mapped into memory
func Parse(data []byte, order binary.ByteOrder, staticBase uint64, ptrSize int, ehFrameAddr uint64) (FrameDescriptionEntries, error) {
var (
buf = bytes.NewBuffer(data)
pctx = &parseContext{buf: buf, totalLen: len(data), entries: newFrameIndex(), staticBase: staticBase, ptrSize: ptrSize, ehFrameAddr: ehFrameAddr, ciemap: map[int]*CommonInformationEntry{}}
)
for fn := parselength; buf.Len() != 0; {
fn = fn(pctx)
if pctx.err != nil {
return nil, pctx.err
}
}
for i := range pctx.entries {
pctx.entries[i].order = order
}
return pctx.entries, nil
}
func (ctx *parseContext) parsingEHFrame() bool {
return ctx.ehFrameAddr > 0
}
func (ctx *parseContext) cieEntry(cieid uint32) bool {
if ctx.parsingEHFrame() {
return cieid == 0x00
}
return cieid == 0xffffffff
}
func (ctx *parseContext) offset() int {
return ctx.totalLen - ctx.buf.Len()
}
func parselength(ctx *parseContext) parsefunc {
start := ctx.offset()
binary.Read(ctx.buf, binary.LittleEndian, &ctx.length) //TODO(aarzilli): this does not support 64bit DWARF
if ctx.length == 0 {
// ZERO terminator
return parselength
}
var cieid uint32
binary.Read(ctx.buf, binary.LittleEndian, &cieid)
ctx.length -= 4 // take off the length of the CIE id / CIE pointer.
if ctx.cieEntry(cieid) {
ctx.common = &CommonInformationEntry{Length: ctx.length, staticBase: ctx.staticBase, CIE_id: cieid}
ctx.ciemap[start] = ctx.common
return parseCIE
}
if ctx.ehFrameAddr > 0 {
cieid = uint32(start - int(cieid) + 4)
}
common := ctx.ciemap[int(cieid)]
if common == nil {
ctx.err = fmt.Errorf("unknown CIE_id %#x at %#x", cieid, start)
}
ctx.frame = &FrameDescriptionEntry{Length: ctx.length, CIE: common}
return parseFDE
}
func parseFDE(ctx *parseContext) parsefunc {
startOff := ctx.offset()
r := ctx.buf.Next(int(ctx.length))
reader := bytes.NewReader(r)
num := ctx.readEncodedPtr(addrSum(ctx.ehFrameAddr+uint64(startOff), reader), reader, ctx.frame.CIE.ptrEncAddr)
ctx.frame.begin = num + ctx.staticBase
// For the size field in .eh_frame only the size encoding portion of the
// address pointer encoding is considered.
// See decode_frame_entry_1 in gdb/dwarf2-frame.c.
// For .debug_frame ptrEncAddr is always ptrEncAbs and never has flags.
sizePtrEnc := ctx.frame.CIE.ptrEncAddr & 0x0f
ctx.frame.size = ctx.readEncodedPtr(0, reader, sizePtrEnc)
// Insert into the tree after setting address range begin
// otherwise compares won't work.
ctx.entries = append(ctx.entries, ctx.frame)
if ctx.parsingEHFrame() && len(ctx.frame.CIE.Augmentation) > 0 {
// If we are parsing a .eh_frame and we saw an agumentation string then we
// need to read the augmentation data, which are encoded as a ULEB128
// size followed by 'size' bytes.
n, _ := util.DecodeULEB128(reader)
reader.Seek(int64(n), io.SeekCurrent)
}
// The rest of this entry consists of the instructions
// so we can just grab all of the data from the buffer
// cursor to length.
off, _ := reader.Seek(0, io.SeekCurrent)
ctx.frame.Instructions = r[off:]
ctx.length = 0
return parselength
}
func addrSum(base uint64, buf *bytes.Reader) uint64 {
n, _ := buf.Seek(0, io.SeekCurrent)
return base + uint64(n)
}
func parseCIE(ctx *parseContext) parsefunc {
data := ctx.buf.Next(int(ctx.length))
buf := bytes.NewBuffer(data)
// parse version
ctx.common.Version, _ = buf.ReadByte()
// parse augmentation
ctx.common.Augmentation, _ = util.ParseString(buf)
if ctx.parsingEHFrame() {
if ctx.common.Augmentation == "eh" {
ctx.err = fmt.Errorf("unsupported 'eh' augmentation at %#x", ctx.offset())
}
if len(ctx.common.Augmentation) > 0 && ctx.common.Augmentation[0] != 'z' {
ctx.err = fmt.Errorf("unsupported augmentation at %#x (does not start with 'z')", ctx.offset())
}
}
// parse code alignment factor
ctx.common.CodeAlignmentFactor, _ = util.DecodeULEB128(buf)
// parse data alignment factor
ctx.common.DataAlignmentFactor, _ = util.DecodeSLEB128(buf)
// parse return address register
if ctx.parsingEHFrame() && ctx.common.Version == 1 {
b, _ := buf.ReadByte()
ctx.common.ReturnAddressRegister = uint64(b)
} else {
ctx.common.ReturnAddressRegister, _ = util.DecodeULEB128(buf)
}
ctx.common.ptrEncAddr = ptrEncAbs
if ctx.parsingEHFrame() && len(ctx.common.Augmentation) > 0 {
_, _ = util.DecodeULEB128(buf) // augmentation data length
for i := 1; i < len(ctx.common.Augmentation); i++ {
switch ctx.common.Augmentation[i] {
case 'L':
_, _ = buf.ReadByte() // LSDA pointer encoding, we don't support this.
case 'R':
// Pointer encoding, describes how begin and size fields of FDEs are encoded.
b, _ := buf.ReadByte()
ctx.common.ptrEncAddr = ptrEnc(b)
if !ctx.common.ptrEncAddr.Supported() {
ctx.err = fmt.Errorf("pointer encoding not supported %#x at %#x", ctx.common.ptrEncAddr, ctx.offset())
return nil
}
case 'S':
// Signal handler invocation frame, we don't support this but there is no associated data to read.
case 'P':
// Personality function encoded as a pointer encoding byte followed by
// the pointer to the personality function encoded as specified by the
// pointer encoding.
// We don't support this but have to read it anyway.
e, _ := buf.ReadByte()
if !ptrEnc(e).Supported() {
ctx.err = fmt.Errorf("pointer encoding not supported %#x at %#x", e, ctx.offset())
return nil
}
ctx.readEncodedPtr(0, buf, ptrEnc(e))
default:
ctx.err = fmt.Errorf("unsupported augmentation character %c at %#x", ctx.common.Augmentation[i], ctx.offset())
return nil
}
}
}
// parse initial instructions
// The rest of this entry consists of the instructions
// so we can just grab all of the data from the buffer
// cursor to length.
ctx.common.InitialInstructions = buf.Bytes() //ctx.buf.Next(int(ctx.length))
ctx.length = 0
return parselength
}
// readEncodedPtr reads a pointer from buf encoded as specified by ptrEnc.
// This function is used to read pointers from a .eh_frame section, when
// used to parse a .debug_frame section ptrEnc will always be ptrEncAbs.
// The parameter addr is the address that the current byte of 'buf' will be
// mapped to when the executable file containing the eh_frame section being
// parse is loaded in memory.
func (ctx *parseContext) readEncodedPtr(addr uint64, buf util.ByteReaderWithLen, ptrEnc ptrEnc) uint64 {
if ptrEnc == ptrEncOmit {
return 0
}
var ptr uint64
switch ptrEnc & 0xf {
case ptrEncAbs, ptrEncSigned:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, ctx.ptrSize)
case ptrEncUleb:
ptr, _ = util.DecodeULEB128(buf)
case ptrEncUdata2:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, 2)
case ptrEncSdata2:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, 2)
ptr = uint64(int16(ptr))
case ptrEncUdata4:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, 4)
case ptrEncSdata4:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, 4)
ptr = uint64(int32(ptr))
case ptrEncUdata8, ptrEncSdata8:
ptr, _ = util.ReadUintRaw(buf, binary.LittleEndian, 8)
case ptrEncSleb:
n, _ := util.DecodeSLEB128(buf)
ptr = uint64(n)
}
if ptrEnc&0xf0 == ptrEncPCRel {
ptr += addr
}
return ptr
}
// DwarfEndian determines the endianness of the DWARF by using the version number field in the debug_info section
// Trick borrowed from "debug/dwarf".New()
func DwarfEndian(infoSec []byte) binary.ByteOrder {
if len(infoSec) < 6 {
return binary.BigEndian
}
x, y := infoSec[4], infoSec[5]
switch {
case x == 0 && y == 0:
return binary.BigEndian
case x == 0:
return binary.BigEndian
case y == 0:
return binary.LittleEndian
default:
return binary.BigEndian
}
}