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126 lines
3.2 KiB
Go
126 lines
3.2 KiB
Go
// Package frame contains data structures and
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// related functions for parsing and searching
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// through Dwarf .debug_frame data.
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package frame
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import (
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"bytes"
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"encoding/binary"
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"github.com/derekparker/delve/dwarf/util"
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)
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type parsefunc func(*parseContext) parsefunc
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type parseContext struct {
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buf *bytes.Buffer
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entries FrameDescriptionEntries
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common *CommonInformationEntry
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frame *FrameDescriptionEntry
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length uint32
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}
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// Parse takes in data (a byte slice) and returns a slice of
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// commonInformationEntry structures. Each commonInformationEntry
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// has a slice of frameDescriptionEntry structures.
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func Parse(data []byte, order binary.ByteOrder) FrameDescriptionEntries {
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var (
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buf = bytes.NewBuffer(data)
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pctx = &parseContext{buf: buf, entries: NewFrameIndex()}
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)
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for fn := parselength; buf.Len() != 0; {
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fn = fn(pctx)
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}
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for i := range pctx.entries {
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pctx.entries[i].order = order
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}
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return pctx.entries
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}
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func cieEntry(data []byte) bool {
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return bytes.Equal(data, []byte{0xff, 0xff, 0xff, 0xff})
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}
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func parselength(ctx *parseContext) parsefunc {
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var data = ctx.buf.Next(8)
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ctx.length = binary.LittleEndian.Uint32(data[:4]) - 4 // take off the length of the CIE id / CIE pointer.
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if cieEntry(data[4:]) {
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ctx.common = &CommonInformationEntry{Length: ctx.length}
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return parseCIE
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}
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ctx.frame = &FrameDescriptionEntry{Length: ctx.length, CIE: ctx.common}
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return parseFDE
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}
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func parseFDE(ctx *parseContext) parsefunc {
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r := ctx.buf.Next(int(ctx.length))
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ctx.frame.begin = binary.LittleEndian.Uint64(r[:8])
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ctx.frame.end = binary.LittleEndian.Uint64(r[8:16])
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// Insert into the tree after setting address range begin
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// otherwise compares won't work.
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ctx.entries = append(ctx.entries, ctx.frame)
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// The rest of this entry consists of the instructions
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// so we can just grab all of the data from the buffer
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// cursor to length.
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ctx.frame.Instructions = r[16:]
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ctx.length = 0
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return parselength
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}
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func parseCIE(ctx *parseContext) parsefunc {
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data := ctx.buf.Next(int(ctx.length))
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buf := bytes.NewBuffer(data)
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// parse version
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ctx.common.Version = data[0]
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// parse augmentation
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ctx.common.Augmentation, _ = util.ParseString(buf)
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// parse code alignment factor
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ctx.common.CodeAlignmentFactor, _ = util.DecodeULEB128(buf)
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// parse data alignment factor
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ctx.common.DataAlignmentFactor, _ = util.DecodeSLEB128(buf)
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// parse return address register
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ctx.common.ReturnAddressRegister, _ = util.DecodeULEB128(buf)
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// parse initial instructions
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// The rest of this entry consists of the instructions
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// so we can just grab all of the data from the buffer
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// cursor to length.
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ctx.common.InitialInstructions = buf.Bytes() //ctx.buf.Next(int(ctx.length))
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ctx.length = 0
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return parselength
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}
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// DwarfEndian determines the endianness of the DWARF by using the version number field in the debug_info section
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// Trick borrowed from "debug/dwarf".New()
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func DwarfEndian(infoSec []byte) binary.ByteOrder {
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if len(infoSec) < 6 {
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return binary.BigEndian
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}
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x, y := infoSec[4], infoSec[5]
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switch {
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case x == 0 && y == 0:
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return binary.BigEndian
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case x == 0:
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return binary.BigEndian
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case y == 0:
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return binary.LittleEndian
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default:
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return binary.BigEndian
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}
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}
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