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// Copyright 2009 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.
package dwarf
import (
"sort"
"strconv"
)
// DWARF debug info is split into a sequence of compilation units.
// Each unit has its own abbreviation table and address size.
type unit struct {
base Offset // byte offset of header within the aggregate info
off Offset // byte offset of data within the aggregate info
data []byte
atable abbrevTable
asize int
vers int
utype uint8 // DWARF 5 unit type
is64 bool // True for 64-bit DWARF format
}
// Implement the dataFormat interface.
func (u *unit) version() int {
return u.vers
}
func (u *unit) dwarf64() (bool, bool) {
return u.is64, true
}
func (u *unit) addrsize() int {
return u.asize
}
func (d *Data) parseUnits() ([]unit, error) {
// Count units.
nunit := 0
b := makeBuf(d, unknownFormat{}, "info", 0, d.info)
for len(b.data) > 0 {
len, _ := b.unitLength()
if len != Offset(uint32(len)) {
b.error("unit length overflow")
break
}
b.skip(int(len))
if len > 0 {
nunit++
}
}
if b.err != nil {
return nil, b.err
}
// Again, this time writing them down.
b = makeBuf(d, unknownFormat{}, "info", 0, d.info)
units := make([]unit, nunit)
for i := range units {
u := &units[i]
u.base = b.off
var n Offset
if b.err != nil {
return nil, b.err
}
for n == 0 {
n, u.is64 = b.unitLength()
}
dataOff := b.off
vers := b.uint16()
if vers < 2 || vers > 5 {
b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
break
}
u.vers = int(vers)
if vers >= 5 {
u.utype = b.uint8()
u.asize = int(b.uint8())
}
var abbrevOff uint64
if u.is64 {
abbrevOff = b.uint64()
} else {
abbrevOff = uint64(b.uint32())
}
atable, err := d.parseAbbrev(abbrevOff, u.vers)
if err != nil {
if b.err == nil {
b.err = err
}
break
}
u.atable = atable
if vers < 5 {
u.asize = int(b.uint8())
}
switch u.utype {
case utSkeleton, utSplitCompile:
b.uint64() // unit ID
case utType, utSplitType:
b.uint64() // type signature
if u.is64 { // type offset
b.uint64()
} else {
b.uint32()
}
}
u.off = b.off
u.data = b.bytes(int(n - (b.off - dataOff)))
}
if b.err != nil {
return nil, b.err
}
return units, nil
}
// offsetToUnit returns the index of the unit containing offset off.
// It returns -1 if no unit contains this offset.
func (d *Data) offsetToUnit(off Offset) int {
// Find the unit after off
next := sort.Search(len(d.unit), func(i int) bool {
return d.unit[i].off > off
})
if next == 0 {
return -1
}
u := &d.unit[next-1]
if u.off <= off && off < u.off+Offset(len(u.data)) {
return next - 1
}
return -1
}
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