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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// DWARF line number information.
package dwarf
import (
"errors"
"path/filepath"
"sort"
"strconv"
)
// A Line holds all the available information about the source code
// corresponding to a specific program counter address.
type Line struct {
Filename string // source file name
OpIndex int // index of operation in VLIW instruction
Line int // line number
Column int // column number
ISA int // instruction set code
Discriminator int // block discriminator
Stmt bool // instruction starts statement
Block bool // instruction starts basic block
EndPrologue bool // instruction ends function prologue
BeginEpilogue bool // instruction begins function epilogue
}
// LineForPc returns the line number information for a program counter
// address, if any. When this returns multiple Line structures in a
// context where only one can be used, the last one is the best.
func (d *Data) LineForPC(pc uint64) ([]*Line, error) {
for i := range d.unit {
u := &d.unit[i]
if u.pc == nil {
if err := d.readUnitLine(i, u); err != nil {
return nil, err
}
}
for _, ar := range u.pc {
if pc >= ar.low && pc < ar.high {
return d.findLine(u, pc)
}
}
}
return nil, nil
}
// readUnitLine reads in the line number information for a compilation
// unit.
func (d *Data) readUnitLine(i int, u *unit) error {
r := d.unitReader(i)
setLineOff := false
for {
e, err := r.Next()
if err != nil {
return err
}
if e == nil {
break
}
if r.unit != i {
break
}
switch e.Tag {
case TagCompileUnit, TagSubprogram, TagEntryPoint, TagInlinedSubroutine:
low, lowok := e.Val(AttrLowpc).(uint64)
var high uint64
var highok bool
switch v := e.Val(AttrHighpc).(type) {
case uint64:
high = v
highok = true
case int64:
high = low + uint64(v)
highok = true
}
if lowok && highok {
u.pc = append(u.pc, addrRange{low, high})
} else if off, ok := e.Val(AttrRanges).(Offset); ok {
if err := d.readAddressRanges(off, low, u); err != nil {
return err
}
}
val := e.Val(AttrStmtList)
if val != nil {
if off, ok := val.(int64); ok {
u.lineoff = Offset(off)
setLineOff = true
} else if off, ok := val.(Offset); ok {
u.lineoff = off
setLineOff = true
} else {
return errors.New("unrecognized format for DW_ATTR_stmt_list")
}
}
if dir, ok := e.Val(AttrCompDir).(string); ok {
u.dir = dir
}
}
}
if !setLineOff {
u.lineoff = Offset(0)
u.lineoff--
}
return nil
}
// readAddressRanges adds address ranges to a unit.
func (d *Data) readAddressRanges(off Offset, base uint64, u *unit) error {
b := makeBuf(d, u, "ranges", off, d.ranges[off:])
var highest uint64
switch u.addrsize() {
case 1:
highest = 0xff
case 2:
highest = 0xffff
case 4:
highest = 0xffffffff
case 8:
highest = 0xffffffffffffffff
default:
return errors.New("unknown address size")
}
for {
if b.err != nil {
return b.err
}
low := b.addr()
high := b.addr()
if low == 0 && high == 0 {
return b.err
} else if low == highest {
base = high
} else {
u.pc = append(u.pc, addrRange{low + base, high + base})
}
}
}
// findLine finds the line information for a PC value, given the unit
// containing the information.
func (d *Data) findLine(u *unit, pc uint64) ([]*Line, error) {
if u.lines == nil {
if err := d.parseLine(u); err != nil {
return nil, err
}
}
for _, ln := range u.lines {
if pc < ln.addrs[0].pc || pc > ln.addrs[len(ln.addrs)-1].pc {
continue
}
i := sort.Search(len(ln.addrs),
func(i int) bool { return ln.addrs[i].pc > pc })
i--
p := new(Line)
*p = ln.line
p.Line = ln.addrs[i].line
ret := []*Line{p}
for i++; i < len(ln.addrs) && ln.addrs[i].pc == pc; i++ {
p = new(Line)
*p = ln.line
p.Line = ln.addrs[i].line
ret = append(ret, p)
}
return ret, nil
}
return nil, nil
}
// FileLine returns the file name and line number for a program
// counter address, or "", 0 if unknown.
func (d *Data) FileLine(pc uint64) (string, int, error) {
r, err := d.LineForPC(pc)
if err != nil {
return "", 0, err
}
if r == nil {
return "", 0, nil
}
ln := r[len(r)-1]
return ln.Filename, ln.Line, nil
}
// A mapLineInfo holds the PC values and line numbers associated with
// a single Line structure. This representation is chosen to reduce
// memory usage based on typical debug info.
type mapLineInfo struct {
line Line // line.Line will be zero
addrs lineAddrs // sorted by PC
}
// A list of lines. This will be sorted by PC.
type lineAddrs []oneLineInfo
func (p lineAddrs) Len() int { return len(p) }
func (p lineAddrs) Less(i, j int) bool { return p[i].pc < p[j].pc }
func (p lineAddrs) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// A oneLineInfo is a single PC and line number.
type oneLineInfo struct {
pc uint64
line int
}
// A lineHdr holds the relevant information from a line number
// program header.
type lineHdr struct {
version uint16 // version of line number encoding
minInsnLen uint8 // minimum instruction length
maxOpsPerInsn uint8 // maximum number of ops per instruction
defStmt bool // initial value of stmt register
lineBase int8 // line adjustment base
lineRange uint8 // line adjustment step
opBase uint8 // base of special opcode values
opLen []uint8 // lengths of standard opcodes
dirs []string // directories
files []string // file names
}
// parseLine parses the line number information for a compilation unit
func (d *Data) parseLine(u *unit) error {
if u.lineoff+1 == 0 {
return errors.New("unknown line offset")
}
b := makeBuf(d, u, "line", u.lineoff, d.line[u.lineoff:])
len := uint64(b.uint32())
dwarf64 := false
if len == 0xffffffff {
len = b.uint64()
dwarf64 = true
}
end := b.off + Offset(len)
hdr := d.parseLineHdr(u, &b, dwarf64)
if b.err == nil {
d.parseLineProgram(u, &b, hdr, end)
}
return b.err
}
// parseLineHdr parses a line number program header.
func (d *Data) parseLineHdr(u *unit, b *buf, dwarf64 bool) (hdr lineHdr) {
hdr.version = b.uint16()
if hdr.version < 2 || hdr.version > 4 {
b.error("unsupported DWARF version " + strconv.Itoa(int(hdr.version)))
return
}
var hlen Offset
if dwarf64 {
hlen = Offset(b.uint64())
} else {
hlen = Offset(b.uint32())
}
end := b.off + hlen
hdr.minInsnLen = b.uint8()
if hdr.version < 4 {
hdr.maxOpsPerInsn = 1
} else {
hdr.maxOpsPerInsn = b.uint8()
}
if b.uint8() == 0 {
hdr.defStmt = false
} else {
hdr.defStmt = true
}
hdr.lineBase = int8(b.uint8())
hdr.lineRange = b.uint8()
hdr.opBase = b.uint8()
hdr.opLen = b.bytes(int(hdr.opBase - 1))
for d := b.string(); len(d) > 0; d = b.string() {
hdr.dirs = append(hdr.dirs, d)
}
for f := b.string(); len(f) > 0; f = b.string() {
d := b.uint()
if !filepath.IsAbs(f) {
if d > 0 {
if d > uint64(len(hdr.dirs)) {
b.error("DWARF directory index out of range")
return
}
f = filepath.Join(hdr.dirs[d-1], f)
} else if u.dir != "" {
f = filepath.Join(u.dir, f)
}
}
b.uint() // file's last mtime
b.uint() // file length
hdr.files = append(hdr.files, f)
}
if end > b.off {
b.bytes(int(end - b.off))
}
return
}
// parseLineProgram parses a line program, adding information to
// d.lineInfo as it goes.
func (d *Data) parseLineProgram(u *unit, b *buf, hdr lineHdr, end Offset) {
address := uint64(0)
line := 1
resetLineInfo := Line{
Filename: "",
OpIndex: 0,
Line: 0,
Column: 0,
ISA: 0,
Discriminator: 0,
Stmt: hdr.defStmt,
Block: false,
EndPrologue: false,
BeginEpilogue: false,
}
if len(hdr.files) > 0 {
resetLineInfo.Filename = hdr.files[0]
}
lineInfo := resetLineInfo
var lines []mapLineInfo
minInsnLen := uint64(hdr.minInsnLen)
maxOpsPerInsn := uint64(hdr.maxOpsPerInsn)
lineBase := int(hdr.lineBase)
lineRange := hdr.lineRange
newLineInfo := true
for b.off < end && b.err == nil {
op := b.uint8()
if op >= hdr.opBase {
// This is a special opcode.
op -= hdr.opBase
advance := uint64(op / hdr.lineRange)
opIndex := uint64(lineInfo.OpIndex)
address += minInsnLen * ((opIndex + advance) / maxOpsPerInsn)
newOpIndex := int((opIndex + advance) % maxOpsPerInsn)
line += lineBase + int(op%lineRange)
if newOpIndex != lineInfo.OpIndex {
lineInfo.OpIndex = newOpIndex
newLineInfo = true
}
lines, lineInfo, newLineInfo = d.addLine(lines, lineInfo, address, line, newLineInfo)
} else if op == LineExtendedOp {
c := b.uint()
op = b.uint8()
switch op {
case LineExtEndSequence:
u.lines = append(u.lines, lines...)
lineInfo = resetLineInfo
lines = nil
newLineInfo = true
case LineExtSetAddress:
address = b.addr()
case LineExtDefineFile:
f := b.string()
d := b.uint()
b.uint() // mtime
b.uint() // length
if d > 0 && !filepath.IsAbs(f) {
if d >= uint64(len(hdr.dirs)) {
b.error("DWARF directory index out of range")
return
}
f = filepath.Join(hdr.dirs[d-1], f)
}
hdr.files = append(hdr.files, f)
case LineExtSetDiscriminator:
lineInfo.Discriminator = int(b.uint())
newLineInfo = true
default:
if c > 0 {
b.bytes(int(c) - 1)
}
}
} else {
switch op {
case LineCopy:
lines, lineInfo, newLineInfo = d.addLine(lines, lineInfo, address, line, newLineInfo)
case LineAdvancePC:
advance := b.uint()
opIndex := uint64(lineInfo.OpIndex)
address += minInsnLen * ((opIndex + advance) / maxOpsPerInsn)
newOpIndex := int((opIndex + advance) % maxOpsPerInsn)
if newOpIndex != lineInfo.OpIndex {
lineInfo.OpIndex = newOpIndex
newLineInfo = true
}
case LineAdvanceLine:
line += int(b.int())
case LineSetFile:
i := b.uint()
if i > uint64(len(hdr.files)) {
b.error("DWARF file number out of range")
return
}
lineInfo.Filename = hdr.files[i-1]
newLineInfo = true
case LineSetColumn:
lineInfo.Column = int(b.uint())
newLineInfo = true
case LineNegateStmt:
lineInfo.Stmt = !lineInfo.Stmt
newLineInfo = true
case LineSetBasicBlock:
lineInfo.Block = true
newLineInfo = true
case LineConstAddPC:
op = 255 - hdr.opBase
advance := uint64(op / hdr.lineRange)
opIndex := uint64(lineInfo.OpIndex)
address += minInsnLen * ((opIndex + advance) / maxOpsPerInsn)
newOpIndex := int((opIndex + advance) % maxOpsPerInsn)
if newOpIndex != lineInfo.OpIndex {
lineInfo.OpIndex = newOpIndex
newLineInfo = true
}
case LineFixedAdvancePC:
address += uint64(b.uint16())
if lineInfo.OpIndex != 0 {
lineInfo.OpIndex = 0
newLineInfo = true
}
case LineSetPrologueEnd:
lineInfo.EndPrologue = true
newLineInfo = true
case LineSetEpilogueBegin:
lineInfo.BeginEpilogue = true
newLineInfo = true
case LineSetISA:
lineInfo.ISA = int(b.uint())
newLineInfo = true
default:
if int(op) >= len(hdr.opLen) {
b.error("DWARF line opcode has unknown length")
return
}
for i := hdr.opLen[op-1]; i > 0; i-- {
b.int()
}
}
}
}
}
// addLine adds the current address and line to lines using lineInfo.
// If newLineInfo is true this is a new lineInfo. This returns the
// updated lines, lineInfo, and newLineInfo.
func (d *Data) addLine(lines []mapLineInfo, lineInfo Line, address uint64, line int, newLineInfo bool) ([]mapLineInfo, Line, bool) {
if newLineInfo {
if len(lines) > 0 {
sort.Sort(lines[len(lines)-1].addrs)
p := &lines[len(lines)-1]
if len(p.addrs) > 0 && address > p.addrs[len(p.addrs)-1].pc {
p.addrs = append(p.addrs, oneLineInfo{address, p.addrs[len(p.addrs)-1].line})
}
}
lines = append(lines, mapLineInfo{line: lineInfo})
}
p := &lines[len(lines)-1]
p.addrs = append(p.addrs, oneLineInfo{address, line})
if lineInfo.Block || lineInfo.EndPrologue || lineInfo.BeginEpilogue || lineInfo.Discriminator != 0 {
lineInfo.Block = false
lineInfo.EndPrologue = false
lineInfo.BeginEpilogue = false
lineInfo.Discriminator = 0
newLineInfo = true
} else {
newLineInfo = false
}
return lines, lineInfo, newLineInfo
}
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