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148 lines
3.4 KiB
Go
148 lines
3.4 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/dbg/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) FrameDescriptionEntries {
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var (
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buf = bytes.NewBuffer(data)
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pctx = &parseContext{Buf: buf}
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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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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 fn parsefunc
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ctx.Length = binary.LittleEndian.Uint32(ctx.Buf.Next(4))
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cieid := ctx.Buf.Next(4)
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if cieEntry(cieid) {
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ctx.Common = &CommonInformationEntry{Length: ctx.Length}
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fn = parseVersion
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} else {
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ctx.Frame = &FrameDescriptionEntry{Length: ctx.Length, CIE: ctx.Common, AddressRange: &addrange{}}
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fn = parseInitialLocation
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}
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// Take off the length of the CIE id / CIE pointer.
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ctx.Length -= 4
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return fn
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}
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func parseInitialLocation(ctx *parseContext) parsefunc {
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ctx.Frame.AddressRange.begin = binary.LittleEndian.Uint64(ctx.Buf.Next(8))
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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.Put(ctx.Frame)
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ctx.Length -= 8
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return parseAddressRange
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}
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func parseAddressRange(ctx *parseContext) parsefunc {
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ctx.Frame.AddressRange.end = binary.LittleEndian.Uint64(ctx.Buf.Next(8))
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ctx.Length -= 8
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return parseFrameInstructions
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}
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func parseFrameInstructions(ctx *parseContext) parsefunc {
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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 = 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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func parseVersion(ctx *parseContext) parsefunc {
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version, err := ctx.Buf.ReadByte()
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if err != nil {
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panic(err)
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}
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ctx.Common.Version = version
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ctx.Length -= 1
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return parseAugmentation
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}
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func parseAugmentation(ctx *parseContext) parsefunc {
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var str, c = util.ParseString(ctx.Buf)
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ctx.Common.Augmentation = str
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ctx.Length -= c
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return parseCodeAlignmentFactor
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}
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func parseCodeAlignmentFactor(ctx *parseContext) parsefunc {
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var caf, c = util.DecodeULEB128(ctx.Buf)
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ctx.Common.CodeAlignmentFactor = caf
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ctx.Length -= c
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return parseDataAlignmentFactor
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}
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func parseDataAlignmentFactor(ctx *parseContext) parsefunc {
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var daf, c = util.DecodeSLEB128(ctx.Buf)
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ctx.Common.DataAlignmentFactor = daf
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ctx.Length -= c
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return parseReturnAddressRegister
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}
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func parseReturnAddressRegister(ctx *parseContext) parsefunc {
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reg, c := util.DecodeULEB128(ctx.Buf)
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ctx.Common.ReturnAddressRegister = reg
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ctx.Length -= c
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return parseInitialInstructions
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}
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func parseInitialInstructions(ctx *parseContext) parsefunc {
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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 = 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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