// Copyright 2010 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.
// TODO/NICETOHAVE:
// - eliminate DW_CLS_ if not used
// - package info in compilation units
// - assign global variables and types to their packages
// - gdb uses c syntax, meaning clumsy quoting is needed for go identifiers. eg
// ptype struct '[]uint8' and qualifiers need to be quoted away
// - file:line info for variables
// - make strings a typedef so prettyprinters can see the underlying string type
package ld
import (
"cmd/internal/dwarf"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"fmt"
"log"
"strings"
)
type dwctxt struct {
linkctxt *Link
}
func (c dwctxt) PtrSize() int {
return c.linkctxt.Arch.PtrSize
}
func (c dwctxt) AddInt(s dwarf.Sym, size int, i int64) {
ls := s.(*sym.Symbol)
ls.AddUintXX(c.linkctxt.Arch, uint64(i), size)
}
func (c dwctxt) AddBytes(s dwarf.Sym, b []byte) {
ls := s.(*sym.Symbol)
ls.AddBytes(b)
}
func (c dwctxt) AddString(s dwarf.Sym, v string) {
Addstring(s.(*sym.Symbol), v)
}
func (c dwctxt) AddAddress(s dwarf.Sym, data interface{}, value int64) {
if value != 0 {
value -= (data.(*sym.Symbol)).Value
}
s.(*sym.Symbol).AddAddrPlus(c.linkctxt.Arch, data.(*sym.Symbol), value)
}
func (c dwctxt) AddCURelativeAddress(s dwarf.Sym, data interface{}, value int64) {
if value != 0 {
value -= (data.(*sym.Symbol)).Value
}
s.(*sym.Symbol).AddCURelativeAddrPlus(c.linkctxt.Arch, data.(*sym.Symbol), value)
}
func (c dwctxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64) {
ls := s.(*sym.Symbol)
switch size {
default:
Errorf(ls, "invalid size %d in adddwarfref\n", size)
fallthrough
case c.linkctxt.Arch.PtrSize:
ls.AddAddr(c.linkctxt.Arch, t.(*sym.Symbol))
case 4:
ls.AddAddrPlus4(t.(*sym.Symbol), 0)
}
r := &ls.R[len(ls.R)-1]
r.Type = objabi.R_DWARFSECREF
r.Add = ofs
}
func (c dwctxt) Logf(format string, args ...interface{}) {
c.linkctxt.Logf(format, args...)
}
// At the moment these interfaces are only used in the compiler.
func (c dwctxt) AddFileRef(s dwarf.Sym, f interface{}) {
panic("should be used only in the compiler")
}
func (c dwctxt) CurrentOffset(s dwarf.Sym) int64 {
panic("should be used only in the compiler")
}
func (c dwctxt) RecordDclReference(s dwarf.Sym, t dwarf.Sym, dclIdx int, inlIndex int) {
panic("should be used only in the compiler")
}
func (c dwctxt) RecordChildDieOffsets(s dwarf.Sym, vars []*dwarf.Var, offsets []int32) {
panic("should be used only in the compiler")
}
var gdbscript string
var dwarfp []*sym.Symbol
func writeabbrev(ctxt *Link) *sym.Symbol {
s := ctxt.Syms.Lookup(".debug_abbrev", 0)
s.Type = sym.SDWARFSECT
s.AddBytes(dwarf.GetAbbrev())
return s
}
/*
* Root DIEs for compilation units, types and global variables.
*/
var dwroot dwarf.DWDie
var dwtypes dwarf.DWDie
var dwglobals dwarf.DWDie
func newattr(die *dwarf.DWDie, attr uint16, cls int, value int64, data interface{}) *dwarf.DWAttr {
a := new(dwarf.DWAttr)
a.Link = die.Attr
die.Attr = a
a.Atr = attr
a.Cls = uint8(cls)
a.Value = value
a.Data = data
return a
}
// Each DIE (except the root ones) has at least 1 attribute: its
// name. getattr moves the desired one to the front so
// frequently searched ones are found faster.
func getattr(die *dwarf.DWDie, attr uint16) *dwarf.DWAttr {
if die.Attr.Atr == attr {
return die.Attr
}
a := die.Attr
b := a.Link
for b != nil {
if b.Atr == attr {
a.Link = b.Link
b.Link = die.Attr
die.Attr = b
return b
}
a = b
b = b.Link
}
return nil
}
// Every DIE manufactured by the linker has at least an AT_name
// attribute (but it will only be written out if it is listed in the abbrev).
// The compiler does create nameless DWARF DIEs (ex: concrete subprogram
// instance).
func newdie(ctxt *Link, parent *dwarf.DWDie, abbrev int, name string, version int) *dwarf.DWDie {
die := new(dwarf.DWDie)
die.Abbrev = abbrev
die.Link = parent.Child
parent.Child = die
newattr(die, dwarf.DW_AT_name, dwarf.DW_CLS_STRING, int64(len(name)), name)
if name != "" && (abbrev <= dwarf.DW_ABRV_VARIABLE || abbrev >= dwarf.DW_ABRV_NULLTYPE) {
if abbrev != dwarf.DW_ABRV_VARIABLE || version == 0 {
if abbrev == dwarf.DW_ABRV_COMPUNIT {
// Avoid collisions with "real" symbol names.
name = ".pkg." + name
}
s := ctxt.Syms.Lookup(dwarf.InfoPrefix+name, version)
s.Attr |= sym.AttrNotInSymbolTable
s.Type = sym.SDWARFINFO
die.Sym = s
}
}
return die
}
func walktypedef(die *dwarf.DWDie) *dwarf.DWDie {
if die == nil {
return nil
}
// Resolve typedef if present.
if die.Abbrev == dwarf.DW_ABRV_TYPEDECL {
for attr := die.Attr; attr != nil; attr = attr.Link {
if attr.Atr == dwarf.DW_AT_type && attr.Cls == dwarf.DW_CLS_REFERENCE && attr.Data != nil {
return attr.Data.(*dwarf.DWDie)
}
}
}
return die
}
func walksymtypedef(ctxt *Link, s *sym.Symbol) *sym.Symbol {
if t := ctxt.Syms.ROLookup(s.Name+"..def", int(s.Version)); t != nil {
return t
}
return s
}
// Find child by AT_name using hashtable if available or linear scan
// if not.
func findchild(die *dwarf.DWDie, name string) *dwarf.DWDie {
var prev *dwarf.DWDie
for ; die != prev; prev, die = die, walktypedef(die) {
for a := die.Child; a != nil; a = a.Link {
if name == getattr(a, dwarf.DW_AT_name).Data {
return a
}
}
continue
}
return nil
}
// Used to avoid string allocation when looking up dwarf symbols
var prefixBuf = []byte(dwarf.InfoPrefix)
func find(ctxt *Link, name string) *sym.Symbol {
n := append(prefixBuf, name...)
// The string allocation below is optimized away because it is only used in a map lookup.
s := ctxt.Syms.ROLookup(string(n), 0)
prefixBuf = n[:len(dwarf.InfoPrefix)]
if s != nil && s.Type == sym.SDWARFINFO {
return s
}
return nil
}
func mustFind(ctxt *Link, name string) *sym.Symbol {
r := find(ctxt, name)
if r == nil {
Exitf("dwarf find: cannot find %s", name)
}
return r
}
func adddwarfref(ctxt *Link, s *sym.Symbol, t *sym.Symbol, size int) int64 {
var result int64
switch size {
default:
Errorf(s, "invalid size %d in adddwarfref\n", size)
fallthrough
case ctxt.Arch.PtrSize:
result = s.AddAddr(ctxt.Arch, t)
case 4:
result = s.AddAddrPlus4(t, 0)
}
r := &s.R[len(s.R)-1]
r.Type = objabi.R_DWARFSECREF
return result
}
func newrefattr(die *dwarf.DWDie, attr uint16, ref *sym.Symbol) *dwarf.DWAttr {
if ref == nil {
return nil
}
return newattr(die, attr, dwarf.DW_CLS_REFERENCE, 0, ref)
}
func putdies(linkctxt *Link, ctxt dwarf.Context, syms []*sym.Symbol, die *dwarf.DWDie) []*sym.Symbol {
for ; die != nil; die = die.Link {
syms = putdie(linkctxt, ctxt, syms, die)
}
syms[len(syms)-1].AddUint8(0)
return syms
}
func dtolsym(s dwarf.Sym) *sym.Symbol {
if s == nil {
return nil
}
return s.(*sym.Symbol)
}
func putdie(linkctxt *Link, ctxt dwarf.Context, syms []*sym.Symbol, die *dwarf.DWDie) []*sym.Symbol {
s := dtolsym(die.Sym)
if s == nil {
s = syms[len(syms)-1]
} else {
if s.Attr.OnList() {
log.Fatalf("symbol %s listed multiple times", s.Name)
}
s.Attr |= sym.AttrOnList
syms = append(syms, s)
}
dwarf.Uleb128put(ctxt, s, int64(die.Abbrev))
dwarf.PutAttrs(ctxt, s, die.Abbrev, die.Attr)
if dwarf.HasChildren(die) {
return putdies(linkctxt, ctxt, syms, die.Child)
}
return syms
}
func reverselist(list **dwarf.DWDie) {
curr := *list
var prev *dwarf.DWDie
for curr != nil {
next := curr.Link
curr.Link = prev
prev = curr
curr = next
}
*list = prev
}
func reversetree(list **dwarf.DWDie) {
reverselist(list)
for die := *list; die != nil; die = die.Link {
if dwarf.HasChildren(die) {
reversetree(&die.Child)
}
}
}
func newmemberoffsetattr(die *dwarf.DWDie, offs int32) {
newattr(die, dwarf.DW_AT_data_member_location, dwarf.DW_CLS_CONSTANT, int64(offs), nil)
}
// GDB doesn't like FORM_addr for AT_location, so emit a
// location expression that evals to a const.
func newabslocexprattr(die *dwarf.DWDie, addr int64, sym *sym.Symbol) {
newattr(die, dwarf.DW_AT_location, dwarf.DW_CLS_ADDRESS, addr, sym)
// below
}
// Lookup predefined types
func lookupOrDiag(ctxt *Link, n string) *sym.Symbol {
s := ctxt.Syms.ROLookup(n, 0)
if s == nil || s.Size == 0 {
Exitf("dwarf: missing type: %s", n)
}
return s
}
func dotypedef(ctxt *Link, parent *dwarf.DWDie, name string, def *dwarf.DWDie) {
// Only emit typedefs for real names.
if strings.HasPrefix(name, "map[") {
return
}
if strings.HasPrefix(name, "struct {") {
return
}
if strings.HasPrefix(name, "chan ") {
return
}
if name[0] == '[' || name[0] == '*' {
return
}
if def == nil {
Errorf(nil, "dwarf: bad def in dotypedef")
}
s := ctxt.Syms.Lookup(dtolsym(def.Sym).Name+"..def", 0)
s.Attr |= sym.AttrNotInSymbolTable
s.Type = sym.SDWARFINFO
def.Sym = s
// The typedef entry must be created after the def,
// so that future lookups will find the typedef instead
// of the real definition. This hooks the typedef into any
// circular definition loops, so that gdb can understand them.
die := newdie(ctxt, parent, dwarf.DW_ABRV_TYPEDECL, name, 0)
newrefattr(die, dwarf.DW_AT_type, s)
}
// Define gotype, for composite ones recurse into constituents.
func defgotype(ctxt *Link, gotype *sym.Symbol) *sym.Symbol {
if gotype == nil {
return mustFind(ctxt, "<unspecified>")
}
if !strings.HasPrefix(gotype.Name, "type.") {
Errorf(gotype, "dwarf: type name doesn't start with \"type.\"")
return mustFind(ctxt, "<unspecified>")
}
name := gotype.Name[5:] // could also decode from Type.string
sdie := find(ctxt, name)
if sdie != nil {
return sdie
}
return newtype(ctxt, gotype).Sym.(*sym.Symbol)
}
func newtype(ctxt *Link, gotype *sym.Symbol) *dwarf.DWDie {
name := gotype.Name[5:] // could also decode from Type.string
kind := decodetypeKind(ctxt.Arch, gotype)
bytesize := decodetypeSize(ctxt.Arch, gotype)
var die *dwarf.DWDie
switch kind {
case objabi.KindBool:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, name, 0)
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_boolean, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindInt,
objabi.KindInt8,
objabi.KindInt16,
objabi.KindInt32,
objabi.KindInt64:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, name, 0)
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_signed, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindUint,
objabi.KindUint8,
objabi.KindUint16,
objabi.KindUint32,
objabi.KindUint64,
objabi.KindUintptr:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, name, 0)
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_unsigned, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindFloat32,
objabi.KindFloat64:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, name, 0)
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_float, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindComplex64,
objabi.KindComplex128:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, name, 0)
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_complex_float, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindArray:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_ARRAYTYPE, name, 0)
dotypedef(ctxt, &dwtypes, name, die)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
s := decodetypeArrayElem(ctxt.Arch, gotype)
newrefattr(die, dwarf.DW_AT_type, defgotype(ctxt, s))
fld := newdie(ctxt, die, dwarf.DW_ABRV_ARRAYRANGE, "range", 0)
// use actual length not upper bound; correct for 0-length arrays.
newattr(fld, dwarf.DW_AT_count, dwarf.DW_CLS_CONSTANT, decodetypeArrayLen(ctxt.Arch, gotype), 0)
newrefattr(fld, dwarf.DW_AT_type, mustFind(ctxt, "uintptr"))
case objabi.KindChan:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_CHANTYPE, name, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
s := decodetypeChanElem(ctxt.Arch, gotype)
newrefattr(die, dwarf.DW_AT_go_elem, defgotype(ctxt, s))
// Save elem type for synthesizechantypes. We could synthesize here
// but that would change the order of DIEs we output.
newrefattr(die, dwarf.DW_AT_type, s)
case objabi.KindFunc:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_FUNCTYPE, name, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
dotypedef(ctxt, &dwtypes, name, die)
newrefattr(die, dwarf.DW_AT_type, mustFind(ctxt, "void"))
nfields := decodetypeFuncInCount(ctxt.Arch, gotype)
var fld *dwarf.DWDie
var s *sym.Symbol
for i := 0; i < nfields; i++ {
s = decodetypeFuncInType(ctxt.Arch, gotype, i)
fld = newdie(ctxt, die, dwarf.DW_ABRV_FUNCTYPEPARAM, s.Name[5:], 0)
newrefattr(fld, dwarf.DW_AT_type, defgotype(ctxt, s))
}
if decodetypeFuncDotdotdot(ctxt.Arch, gotype) {
newdie(ctxt, die, dwarf.DW_ABRV_DOTDOTDOT, "...", 0)
}
nfields = decodetypeFuncOutCount(ctxt.Arch, gotype)
for i := 0; i < nfields; i++ {
s = decodetypeFuncOutType(ctxt.Arch, gotype, i)
fld = newdie(ctxt, die, dwarf.DW_ABRV_FUNCTYPEPARAM, s.Name[5:], 0)
newrefattr(fld, dwarf.DW_AT_type, defptrto(ctxt, defgotype(ctxt, s)))
}
case objabi.KindInterface:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_IFACETYPE, name, 0)
dotypedef(ctxt, &dwtypes, name, die)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
nfields := int(decodetypeIfaceMethodCount(ctxt.Arch, gotype))
var s *sym.Symbol
if nfields == 0 {
s = lookupOrDiag(ctxt, "type.runtime.eface")
} else {
s = lookupOrDiag(ctxt, "type.runtime.iface")
}
newrefattr(die, dwarf.DW_AT_type, defgotype(ctxt, s))
case objabi.KindMap:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_MAPTYPE, name, 0)
s := decodetypeMapKey(ctxt.Arch, gotype)
newrefattr(die, dwarf.DW_AT_go_key, defgotype(ctxt, s))
s = decodetypeMapValue(ctxt.Arch, gotype)
newrefattr(die, dwarf.DW_AT_go_elem, defgotype(ctxt, s))
// Save gotype for use in synthesizemaptypes. We could synthesize here,
// but that would change the order of the DIEs.
newrefattr(die, dwarf.DW_AT_type, gotype)
case objabi.KindPtr:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_PTRTYPE, name, 0)
dotypedef(ctxt, &dwtypes, name, die)
s := decodetypePtrElem(ctxt.Arch, gotype)
newrefattr(die, dwarf.DW_AT_type, defgotype(ctxt, s))
case objabi.KindSlice:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_SLICETYPE, name, 0)
dotypedef(ctxt, &dwtypes, name, die)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
s := decodetypeArrayElem(ctxt.Arch, gotype)
elem := defgotype(ctxt, s)
newrefattr(die, dwarf.DW_AT_go_elem, elem)
case objabi.KindString:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_STRINGTYPE, name, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
case objabi.KindStruct:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_STRUCTTYPE, name, 0)
dotypedef(ctxt, &dwtypes, name, die)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, bytesize, 0)
nfields := decodetypeStructFieldCount(ctxt.Arch, gotype)
for i := 0; i < nfields; i++ {
f := decodetypeStructFieldName(ctxt.Arch, gotype, i)
s := decodetypeStructFieldType(ctxt.Arch, gotype, i)
if f == "" {
f = s.Name[5:] // skip "type."
}
fld := newdie(ctxt, die, dwarf.DW_ABRV_STRUCTFIELD, f, 0)
newrefattr(fld, dwarf.DW_AT_type, defgotype(ctxt, s))
offsetAnon := decodetypeStructFieldOffsAnon(ctxt.Arch, gotype, i)
newmemberoffsetattr(fld, int32(offsetAnon>>1))
if offsetAnon&1 != 0 { // is embedded field
newattr(fld, dwarf.DW_AT_go_embedded_field, dwarf.DW_CLS_FLAG, 1, 0)
}
}
case objabi.KindUnsafePointer:
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BARE_PTRTYPE, name, 0)
default:
Errorf(gotype, "dwarf: definition of unknown kind %d", kind)
die = newdie(ctxt, &dwtypes, dwarf.DW_ABRV_TYPEDECL, name, 0)
newrefattr(die, dwarf.DW_AT_type, mustFind(ctxt, "<unspecified>"))
}
newattr(die, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, int64(kind), 0)
if _, ok := prototypedies[gotype.Name]; ok {
prototypedies[gotype.Name] = die
}
return die
}
func nameFromDIESym(dwtype *sym.Symbol) string {
return strings.TrimSuffix(dwtype.Name[len(dwarf.InfoPrefix):], "..def")
}
// Find or construct *T given T.
func defptrto(ctxt *Link, dwtype *sym.Symbol) *sym.Symbol {
ptrname := "*" + nameFromDIESym(dwtype)
die := find(ctxt, ptrname)
if die == nil {
pdie := newdie(ctxt, &dwtypes, dwarf.DW_ABRV_PTRTYPE, ptrname, 0)
newrefattr(pdie, dwarf.DW_AT_type, dwtype)
return dtolsym(pdie.Sym)
}
return die
}
// Copies src's children into dst. Copies attributes by value.
// DWAttr.data is copied as pointer only. If except is one of
// the top-level children, it will not be copied.
func copychildrenexcept(ctxt *Link, dst *dwarf.DWDie, src *dwarf.DWDie, except *dwarf.DWDie) {
for src = src.Child; src != nil; src = src.Link {
if src == except {
continue
}
c := newdie(ctxt, dst, src.Abbrev, getattr(src, dwarf.DW_AT_name).Data.(string), 0)
for a := src.Attr; a != nil; a = a.Link {
newattr(c, a.Atr, int(a.Cls), a.Value, a.Data)
}
copychildrenexcept(ctxt, c, src, nil)
}
reverselist(&dst.Child)
}
func copychildren(ctxt *Link, dst *dwarf.DWDie, src *dwarf.DWDie) {
copychildrenexcept(ctxt, dst, src, nil)
}
// Search children (assumed to have TAG_member) for the one named
// field and set its AT_type to dwtype
func substitutetype(structdie *dwarf.DWDie, field string, dwtype *sym.Symbol) {
child := findchild(structdie, field)
if child == nil {
Exitf("dwarf substitutetype: %s does not have member %s",
getattr(structdie, dwarf.DW_AT_name).Data, field)
return
}
a := getattr(child, dwarf.DW_AT_type)
if a != nil {
a.Data = dwtype
} else {
newrefattr(child, dwarf.DW_AT_type, dwtype)
}
}
func findprotodie(ctxt *Link, name string) *dwarf.DWDie {
die, ok := prototypedies[name]
if ok && die == nil {
defgotype(ctxt, lookupOrDiag(ctxt, name))
die = prototypedies[name]
}
return die
}
func synthesizestringtypes(ctxt *Link, die *dwarf.DWDie) {
prototype := walktypedef(findprotodie(ctxt, "type.runtime.stringStructDWARF"))
if prototype == nil {
return
}
for ; die != nil; die = die.Link {
if die.Abbrev != dwarf.DW_ABRV_STRINGTYPE {
continue
}
copychildren(ctxt, die, prototype)
}
}
func synthesizeslicetypes(ctxt *Link, die *dwarf.DWDie) {
prototype := walktypedef(findprotodie(ctxt, "type.runtime.slice"))
if prototype == nil {
return
}
for ; die != nil; die = die.Link {
if die.Abbrev != dwarf.DW_ABRV_SLICETYPE {
continue
}
copychildren(ctxt, die, prototype)
elem := getattr(die, dwarf.DW_AT_go_elem).Data.(*sym.Symbol)
substitutetype(die, "array", defptrto(ctxt, elem))
}
}
func mkinternaltypename(base string, arg1 string, arg2 string) string {
var buf string
if arg2 == "" {
buf = fmt.Sprintf("%s<%s>", base, arg1)
} else {
buf = fmt.Sprintf("%s<%s,%s>", base, arg1, arg2)
}
n := buf
return n
}
// synthesizemaptypes is way too closely married to runtime/hashmap.c
const (
MaxKeySize = 128
MaxValSize = 128
BucketSize = 8
)
func mkinternaltype(ctxt *Link, abbrev int, typename, keyname, valname string, f func(*dwarf.DWDie)) *sym.Symbol {
name := mkinternaltypename(typename, keyname, valname)
symname := dwarf.InfoPrefix + name
s := ctxt.Syms.ROLookup(symname, 0)
if s != nil && s.Type == sym.SDWARFINFO {
return s
}
die := newdie(ctxt, &dwtypes, abbrev, name, 0)
f(die)
return dtolsym(die.Sym)
}
func synthesizemaptypes(ctxt *Link, die *dwarf.DWDie) {
hash := walktypedef(findprotodie(ctxt, "type.runtime.hmap"))
bucket := walktypedef(findprotodie(ctxt, "type.runtime.bmap"))
if hash == nil {
return
}
for ; die != nil; die = die.Link {
if die.Abbrev != dwarf.DW_ABRV_MAPTYPE {
continue
}
gotype := getattr(die, dwarf.DW_AT_type).Data.(*sym.Symbol)
keytype := decodetypeMapKey(ctxt.Arch, gotype)
valtype := decodetypeMapValue(ctxt.Arch, gotype)
keysize, valsize := decodetypeSize(ctxt.Arch, keytype), decodetypeSize(ctxt.Arch, valtype)
keytype, valtype = walksymtypedef(ctxt, defgotype(ctxt, keytype)), walksymtypedef(ctxt, defgotype(ctxt, valtype))
// compute size info like hashmap.c does.
indirectKey, indirectVal := false, false
if keysize > MaxKeySize {
keysize = int64(ctxt.Arch.PtrSize)
indirectKey = true
}
if valsize > MaxValSize {
valsize = int64(ctxt.Arch.PtrSize)
indirectVal = true
}
// Construct type to represent an array of BucketSize keys
keyname := nameFromDIESym(keytype)
dwhks := mkinternaltype(ctxt, dwarf.DW_ABRV_ARRAYTYPE, "[]key", keyname, "", func(dwhk *dwarf.DWDie) {
newattr(dwhk, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, BucketSize*keysize, 0)
t := keytype
if indirectKey {
t = defptrto(ctxt, keytype)
}
newrefattr(dwhk, dwarf.DW_AT_type, t)
fld := newdie(ctxt, dwhk, dwarf.DW_ABRV_ARRAYRANGE, "size", 0)
newattr(fld, dwarf.DW_AT_count, dwarf.DW_CLS_CONSTANT, BucketSize, 0)
newrefattr(fld, dwarf.DW_AT_type, mustFind(ctxt, "uintptr"))
})
// Construct type to represent an array of BucketSize values
valname := nameFromDIESym(valtype)
dwhvs := mkinternaltype(ctxt, dwarf.DW_ABRV_ARRAYTYPE, "[]val", valname, "", func(dwhv *dwarf.DWDie) {
newattr(dwhv, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, BucketSize*valsize, 0)
t := valtype
if indirectVal {
t = defptrto(ctxt, valtype)
}
newrefattr(dwhv, dwarf.DW_AT_type, t)
fld := newdie(ctxt, dwhv, dwarf.DW_ABRV_ARRAYRANGE, "size", 0)
newattr(fld, dwarf.DW_AT_count, dwarf.DW_CLS_CONSTANT, BucketSize, 0)
newrefattr(fld, dwarf.DW_AT_type, mustFind(ctxt, "uintptr"))
})
// Construct bucket<K,V>
dwhbs := mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "bucket", keyname, valname, func(dwhb *dwarf.DWDie) {
// Copy over all fields except the field "data" from the generic
// bucket. "data" will be replaced with keys/values below.
copychildrenexcept(ctxt, dwhb, bucket, findchild(bucket, "data"))
fld := newdie(ctxt, dwhb, dwarf.DW_ABRV_STRUCTFIELD, "keys", 0)
newrefattr(fld, dwarf.DW_AT_type, dwhks)
newmemberoffsetattr(fld, BucketSize)
fld = newdie(ctxt, dwhb, dwarf.DW_ABRV_STRUCTFIELD, "values", 0)
newrefattr(fld, dwarf.DW_AT_type, dwhvs)
newmemberoffsetattr(fld, BucketSize+BucketSize*int32(keysize))
fld = newdie(ctxt, dwhb, dwarf.DW_ABRV_STRUCTFIELD, "overflow", 0)
newrefattr(fld, dwarf.DW_AT_type, defptrto(ctxt, dtolsym(dwhb.Sym)))
newmemberoffsetattr(fld, BucketSize+BucketSize*(int32(keysize)+int32(valsize)))
if ctxt.Arch.RegSize > ctxt.Arch.PtrSize {
fld = newdie(ctxt, dwhb, dwarf.DW_ABRV_STRUCTFIELD, "pad", 0)
newrefattr(fld, dwarf.DW_AT_type, mustFind(ctxt, "uintptr"))
newmemberoffsetattr(fld, BucketSize+BucketSize*(int32(keysize)+int32(valsize))+int32(ctxt.Arch.PtrSize))
}
newattr(dwhb, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, BucketSize+BucketSize*keysize+BucketSize*valsize+int64(ctxt.Arch.RegSize), 0)
})
// Construct hash<K,V>
dwhs := mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "hash", keyname, valname, func(dwh *dwarf.DWDie) {
copychildren(ctxt, dwh, hash)
substitutetype(dwh, "buckets", defptrto(ctxt, dwhbs))
substitutetype(dwh, "oldbuckets", defptrto(ctxt, dwhbs))
newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(hash, dwarf.DW_AT_byte_size).Value, nil)
})
// make map type a pointer to hash<K,V>
newrefattr(die, dwarf.DW_AT_type, defptrto(ctxt, dwhs))
}
}
func synthesizechantypes(ctxt *Link, die *dwarf.DWDie) {
sudog := walktypedef(findprotodie(ctxt, "type.runtime.sudog"))
waitq := walktypedef(findprotodie(ctxt, "type.runtime.waitq"))
hchan := walktypedef(findprotodie(ctxt, "type.runtime.hchan"))
if sudog == nil || waitq == nil || hchan == nil {
return
}
sudogsize := int(getattr(sudog, dwarf.DW_AT_byte_size).Value)
for ; die != nil; die = die.Link {
if die.Abbrev != dwarf.DW_ABRV_CHANTYPE {
continue
}
elemgotype := getattr(die, dwarf.DW_AT_type).Data.(*sym.Symbol)
elemname := elemgotype.Name[5:]
elemtype := walksymtypedef(ctxt, defgotype(ctxt, elemgotype))
// sudog<T>
dwss := mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "sudog", elemname, "", func(dws *dwarf.DWDie) {
copychildren(ctxt, dws, sudog)
substitutetype(dws, "elem", defptrto(ctxt, elemtype))
newattr(dws, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, int64(sudogsize), nil)
})
// waitq<T>
dwws := mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "waitq", elemname, "", func(dww *dwarf.DWDie) {
copychildren(ctxt, dww, waitq)
substitutetype(dww, "first", defptrto(ctxt, dwss))
substitutetype(dww, "last", defptrto(ctxt, dwss))
newattr(dww, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(waitq, dwarf.DW_AT_byte_size).Value, nil)
})
// hchan<T>
dwhs := mkinternaltype(ctxt, dwarf.DW_ABRV_STRUCTTYPE, "hchan", elemname, "", func(dwh *dwarf.DWDie) {
copychildren(ctxt, dwh, hchan)
substitutetype(dwh, "recvq", dwws)
substitutetype(dwh, "sendq", dwws)
newattr(dwh, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, getattr(hchan, dwarf.DW_AT_byte_size).Value, nil)
})
newrefattr(die, dwarf.DW_AT_type, defptrto(ctxt, dwhs))
}
}
// For use with pass.c::genasmsym
func defdwsymb(ctxt *Link, s *sym.Symbol, str string, t SymbolType, v int64, gotype *sym.Symbol) {
if strings.HasPrefix(str, "go.string.") {
return
}
if strings.HasPrefix(str, "runtime.gcbits.") {
return
}
if strings.HasPrefix(str, "type.") && str != "type.*" && !strings.HasPrefix(str, "type..") {
defgotype(ctxt, s)
return
}
var dv *dwarf.DWDie
var dt *sym.Symbol
switch t {
default:
return
case DataSym, BSSSym:
dv = newdie(ctxt, &dwglobals, dwarf.DW_ABRV_VARIABLE, str, int(s.Version))
newabslocexprattr(dv, v, s)
if s.Version == 0 {
newattr(dv, dwarf.DW_AT_external, dwarf.DW_CLS_FLAG, 1, 0)
}
fallthrough
case AutoSym, ParamSym, DeletedAutoSym:
dt = defgotype(ctxt, gotype)
}
if dv != nil {
newrefattr(dv, dwarf.DW_AT_type, dt)
}
}
// compilationUnit is per-compilation unit (equivalently, per-package)
// debug-related data.
type compilationUnit struct {
lib *sym.Library
consts *sym.Symbol // Package constants DIEs
pcs []dwarf.Range // PC ranges, relative to textp[0]
dwinfo *dwarf.DWDie // CU root DIE
funcDIEs []*sym.Symbol // Function DIE subtrees
absFnDIEs []*sym.Symbol // Abstract function DIE subtrees
}
// getCompilationUnits divides the symbols in ctxt.Textp by package.
func getCompilationUnits(ctxt *Link) []*compilationUnit {
units := []*compilationUnit{}
index := make(map[*sym.Library]*compilationUnit)
var prevUnit *compilationUnit
for _, s := range ctxt.Textp {
if s.FuncInfo == nil {
continue
}
unit := index[s.Lib]
if unit == nil {
unit = &compilationUnit{lib: s.Lib}
if s := ctxt.Syms.ROLookup(dwarf.ConstInfoPrefix+s.Lib.Pkg, 0); s != nil {
importInfoSymbol(ctxt, s)
unit.consts = s
}
units = append(units, unit)
index[s.Lib] = unit
}
// Update PC ranges.
//
// We don't simply compare the end of the previous
// symbol with the start of the next because there's
// often a little padding between them. Instead, we
// only create boundaries between symbols from
// different units.
if prevUnit != unit {
unit.pcs = append(unit.pcs, dwarf.Range{Start: s.Value - unit.lib.Textp[0].Value})
prevUnit = unit
}
unit.pcs[len(unit.pcs)-1].End = s.Value - unit.lib.Textp[0].Value + s.Size
}
return units
}
func movetomodule(parent *dwarf.DWDie) {
die := dwroot.Child.Child
if die == nil {
dwroot.Child.Child = parent.Child
return
}
for die.Link != nil {
die = die.Link
}
die.Link = parent.Child
}
// If the pcln table contains runtime/proc.go, use that to set gdbscript path.
func finddebugruntimepath(s *sym.Symbol) {
if gdbscript != "" {
return
}
for i := range s.FuncInfo.File {
f := s.FuncInfo.File[i]
// We can't use something that may be dead-code
// eliminated from a binary here. proc.go contains
// main and the scheduler, so it's not going anywhere.
if i := strings.Index(f.Name, "runtime/proc.go"); i >= 0 {
gdbscript = f.Name[:i] + "runtime/runtime-gdb.py"
break
}
}
}
/*
* Generate a sequence of opcodes that is as short as possible.
* See section 6.2.5
*/
const (
LINE_BASE = -4
LINE_RANGE = 10
PC_RANGE = (255 - OPCODE_BASE) / LINE_RANGE
OPCODE_BASE = 10
)
func putpclcdelta(linkctxt *Link, ctxt dwarf.Context, s *sym.Symbol, deltaPC uint64, deltaLC int64) {
// Choose a special opcode that minimizes the number of bytes needed to
// encode the remaining PC delta and LC delta.
var opcode int64
if deltaLC < LINE_BASE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE * PC_RANGE)
} else {
opcode = OPCODE_BASE + (LINE_RANGE * int64(deltaPC))
}
} else if deltaLC < LINE_BASE+LINE_RANGE {
if deltaPC >= PC_RANGE {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * PC_RANGE)
if opcode > 255 {
opcode -= LINE_RANGE
}
} else {
opcode = OPCODE_BASE + (deltaLC - LINE_BASE) + (LINE_RANGE * int64(deltaPC))
}
} else {
if deltaPC <= PC_RANGE {
opcode = OPCODE_BASE + (LINE_RANGE - 1) + (LINE_RANGE * int64(deltaPC))
if opcode > 255 {
opcode = 255
}
} else {
// Use opcode 249 (pc+=23, lc+=5) or 255 (pc+=24, lc+=1).
//
// Let x=deltaPC-PC_RANGE. If we use opcode 255, x will be the remaining
// deltaPC that we need to encode separately before emitting 255. If we
// use opcode 249, we will need to encode x+1. If x+1 takes one more
// byte to encode than x, then we use opcode 255.
//
// In all other cases x and x+1 take the same number of bytes to encode,
// so we use opcode 249, which may save us a byte in encoding deltaLC,
// for similar reasons.
switch deltaPC - PC_RANGE {
// PC_RANGE is the largest deltaPC we can encode in one byte, using
// DW_LNS_const_add_pc.
//
// (1<<16)-1 is the largest deltaPC we can encode in three bytes, using
// DW_LNS_fixed_advance_pc.
//
// (1<<(7n))-1 is the largest deltaPC we can encode in n+1 bytes for
// n=1,3,4,5,..., using DW_LNS_advance_pc.
case PC_RANGE, (1 << 7) - 1, (1 << 16) - 1, (1 << 21) - 1, (1 << 28) - 1,
(1 << 35) - 1, (1 << 42) - 1, (1 << 49) - 1, (1 << 56) - 1, (1 << 63) - 1:
opcode = 255
default:
opcode = OPCODE_BASE + LINE_RANGE*PC_RANGE - 1 // 249
}
}
}
if opcode < OPCODE_BASE || opcode > 255 {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
// Subtract from deltaPC and deltaLC the amounts that the opcode will add.
deltaPC -= uint64((opcode - OPCODE_BASE) / LINE_RANGE)
deltaLC -= int64((opcode-OPCODE_BASE)%LINE_RANGE + LINE_BASE)
// Encode deltaPC.
if deltaPC != 0 {
if deltaPC <= PC_RANGE {
// Adjust the opcode so that we can use the 1-byte DW_LNS_const_add_pc
// instruction.
opcode -= LINE_RANGE * int64(PC_RANGE-deltaPC)
if opcode < OPCODE_BASE {
panic(fmt.Sprintf("produced invalid special opcode %d", opcode))
}
s.AddUint8(dwarf.DW_LNS_const_add_pc)
} else if (1<<14) <= deltaPC && deltaPC < (1<<16) {
s.AddUint8(dwarf.DW_LNS_fixed_advance_pc)
s.AddUint16(linkctxt.Arch, uint16(deltaPC))
} else {
s.AddUint8(dwarf.DW_LNS_advance_pc)
dwarf.Uleb128put(ctxt, s, int64(deltaPC))
}
}
// Encode deltaLC.
if deltaLC != 0 {
s.AddUint8(dwarf.DW_LNS_advance_line)
dwarf.Sleb128put(ctxt, s, deltaLC)
}
// Output the special opcode.
s.AddUint8(uint8(opcode))
}
/*
* Walk prog table, emit line program and build DIE tree.
*/
func getCompilationDir() string {
// OSX requires this be set to something, but it's not easy to choose
// a value. Linking takes place in a temporary directory, so there's
// no point including it here. Paths in the file table are usually
// absolute, in which case debuggers will ignore this value. -trimpath
// produces relative paths, but we don't know where they start, so
// all we can do here is try not to make things worse.
return "."
}
func importInfoSymbol(ctxt *Link, dsym *sym.Symbol) {
dsym.Attr |= sym.AttrNotInSymbolTable | sym.AttrReachable
dsym.Type = sym.SDWARFINFO
for _, r := range dsym.R {
if r.Type == objabi.R_DWARFSECREF && r.Sym.Size == 0 {
if ctxt.BuildMode == BuildModeShared {
// These type symbols may not be present in BuildModeShared. Skip.
continue
}
n := nameFromDIESym(r.Sym)
defgotype(ctxt, ctxt.Syms.Lookup("type."+n, 0))
}
}
}
// For the specified function, collect symbols corresponding to any
// "abstract" subprogram DIEs referenced. The first case of interest
// is a concrete subprogram DIE, which will refer to its corresponding
// abstract subprogram DIE, and then there can be references from a
// non-abstract subprogram DIE to the abstract subprogram DIEs for any
// functions inlined into this one.
//
// A given abstract subprogram DIE can be referenced in numerous
// places (even within the same DIE), so it is important to make sure
// it gets imported and added to the absfuncs lists only once.
func collectAbstractFunctions(ctxt *Link, fn *sym.Symbol, dsym *sym.Symbol, absfuncs []*sym.Symbol) []*sym.Symbol {
var newabsfns []*sym.Symbol
// Walk the relocations on the primary subprogram DIE and look for
// references to abstract funcs.
for _, reloc := range dsym.R {
candsym := reloc.Sym
if reloc.Type != objabi.R_DWARFSECREF {
continue
}
if !strings.HasPrefix(candsym.Name, dwarf.InfoPrefix) {
continue
}
if !strings.HasSuffix(candsym.Name, dwarf.AbstractFuncSuffix) {
continue
}
if candsym.Attr.OnList() {
continue
}
candsym.Attr |= sym.AttrOnList
newabsfns = append(newabsfns, candsym)
}
// Import any new symbols that have turned up.
for _, absdsym := range newabsfns {
importInfoSymbol(ctxt, absdsym)
absfuncs = append(absfuncs, absdsym)
}
return absfuncs
}
func writelines(ctxt *Link, lib *sym.Library, textp []*sym.Symbol, ls *sym.Symbol) (dwinfo *dwarf.DWDie, funcs []*sym.Symbol, absfuncs []*sym.Symbol) {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
unitstart := int64(-1)
headerstart := int64(-1)
headerend := int64(-1)
lang := dwarf.DW_LANG_Go
dwinfo = newdie(ctxt, &dwroot, dwarf.DW_ABRV_COMPUNIT, lib.Pkg, 0)
newattr(dwinfo, dwarf.DW_AT_language, dwarf.DW_CLS_CONSTANT, int64(lang), 0)
newattr(dwinfo, dwarf.DW_AT_stmt_list, dwarf.DW_CLS_PTR, ls.Size, ls)
// OS X linker requires compilation dir or absolute path in comp unit name to output debug info.
compDir := getCompilationDir()
// TODO: Make this be the actual compilation directory, not
// the linker directory. If we move CU construction into the
// compiler, this should happen naturally.
newattr(dwinfo, dwarf.DW_AT_comp_dir, dwarf.DW_CLS_STRING, int64(len(compDir)), compDir)
producerExtra := ctxt.Syms.Lookup(dwarf.CUInfoPrefix+"producer."+lib.Pkg, 0)
producer := "Go cmd/compile " + objabi.Version
if len(producerExtra.P) > 0 {
// We put a semicolon before the flags to clearly
// separate them from the version, which can be long
// and have lots of weird things in it in development
// versions. We promise not to put a semicolon in the
// version, so it should be safe for readers to scan
// forward to the semicolon.
producer += "; " + string(producerExtra.P)
}
newattr(dwinfo, dwarf.DW_AT_producer, dwarf.DW_CLS_STRING, int64(len(producer)), producer)
// Write .debug_line Line Number Program Header (sec 6.2.4)
// Fields marked with (*) must be changed for 64-bit dwarf
unitLengthOffset := ls.Size
ls.AddUint32(ctxt.Arch, 0) // unit_length (*), filled in at end.
unitstart = ls.Size
ls.AddUint16(ctxt.Arch, 2) // dwarf version (appendix F)
headerLengthOffset := ls.Size
ls.AddUint32(ctxt.Arch, 0) // header_length (*), filled in at end.
headerstart = ls.Size
// cpos == unitstart + 4 + 2 + 4
ls.AddUint8(1) // minimum_instruction_length
ls.AddUint8(1) // default_is_stmt
ls.AddUint8(LINE_BASE & 0xFF) // line_base
ls.AddUint8(LINE_RANGE) // line_range
ls.AddUint8(OPCODE_BASE) // opcode_base
ls.AddUint8(0) // standard_opcode_lengths[1]
ls.AddUint8(1) // standard_opcode_lengths[2]
ls.AddUint8(1) // standard_opcode_lengths[3]
ls.AddUint8(1) // standard_opcode_lengths[4]
ls.AddUint8(1) // standard_opcode_lengths[5]
ls.AddUint8(0) // standard_opcode_lengths[6]
ls.AddUint8(0) // standard_opcode_lengths[7]
ls.AddUint8(0) // standard_opcode_lengths[8]
ls.AddUint8(1) // standard_opcode_lengths[9]
ls.AddUint8(0) // include_directories (empty)
// Create the file table. fileNums maps from global file
// indexes (created by numberfile) to CU-local indexes.
fileNums := make(map[int]int)
for _, s := range textp {
for _, f := range s.FuncInfo.File {
if _, ok := fileNums[int(f.Value)]; ok {
continue
}
// File indexes are 1-based.
fileNums[int(f.Value)] = len(fileNums) + 1
Addstring(ls, f.Name)
ls.AddUint8(0)
ls.AddUint8(0)
ls.AddUint8(0)
}
// Look up the .debug_info sym for the function. We do this
// now so that we can walk the sym's relocations to discover
// files that aren't mentioned in S.FuncInfo.File (for
// example, files mentioned only in an inlined subroutine).
dsym := ctxt.Syms.Lookup(dwarf.InfoPrefix+s.Name, int(s.Version))
importInfoSymbol(ctxt, dsym)
for ri := 0; ri < len(dsym.R); ri++ {
r := &dsym.R[ri]
if r.Type != objabi.R_DWARFFILEREF {
continue
}
_, ok := fileNums[int(r.Sym.Value)]
if !ok {
fileNums[int(r.Sym.Value)] = len(fileNums) + 1
Addstring(ls, r.Sym.Name)
ls.AddUint8(0)
ls.AddUint8(0)
ls.AddUint8(0)
}
}
}
// 4 zeros: the string termination + 3 fields.
ls.AddUint8(0)
// terminate file_names.
headerend = ls.Size
ls.AddUint8(0) // start extended opcode
dwarf.Uleb128put(dwarfctxt, ls, 1+int64(ctxt.Arch.PtrSize))
ls.AddUint8(dwarf.DW_LNE_set_address)
s := textp[0]
pc := s.Value
line := 1
file := 1
ls.AddAddr(ctxt.Arch, s)
var pcfile Pciter
var pcline Pciter
for _, s := range textp {
dsym := ctxt.Syms.Lookup(dwarf.InfoPrefix+s.Name, int(s.Version))
funcs = append(funcs, dsym)
absfuncs = collectAbstractFunctions(ctxt, s, dsym, absfuncs)
finddebugruntimepath(s)
pciterinit(ctxt, &pcfile, &s.FuncInfo.Pcfile)
pciterinit(ctxt, &pcline, &s.FuncInfo.Pcline)
epc := pc
for pcfile.done == 0 && pcline.done == 0 {
if epc-s.Value >= int64(pcfile.nextpc) {
pciternext(&pcfile)
continue
}
if epc-s.Value >= int64(pcline.nextpc) {
pciternext(&pcline)
continue
}
if int32(file) != pcfile.value {
ls.AddUint8(dwarf.DW_LNS_set_file)
idx, ok := fileNums[int(pcfile.value)]
if !ok {
Exitf("pcln table file missing from DWARF line table")
}
dwarf.Uleb128put(dwarfctxt, ls, int64(idx))
file = int(pcfile.value)
}
putpclcdelta(ctxt, dwarfctxt, ls, uint64(s.Value+int64(pcline.pc)-pc), int64(pcline.value)-int64(line))
pc = s.Value + int64(pcline.pc)
line = int(pcline.value)
if pcfile.nextpc < pcline.nextpc {
epc = int64(pcfile.nextpc)
} else {
epc = int64(pcline.nextpc)
}
epc += s.Value
}
}
ls.AddUint8(0) // start extended opcode
dwarf.Uleb128put(dwarfctxt, ls, 1)
ls.AddUint8(dwarf.DW_LNE_end_sequence)
ls.SetUint32(ctxt.Arch, unitLengthOffset, uint32(ls.Size-unitstart))
ls.SetUint32(ctxt.Arch, headerLengthOffset, uint32(headerend-headerstart))
// Apply any R_DWARFFILEREF relocations, since we now know the
// line table file indices for this compilation unit. Note that
// this loop visits only subprogram DIEs: if the compiler is
// changed to generate DW_AT_decl_file attributes for other
// DIE flavors (ex: variables) then those DIEs would need to
// be included below.
missing := make(map[int]interface{})
for fidx := 0; fidx < len(funcs); fidx++ {
f := funcs[fidx]
for ri := 0; ri < len(f.R); ri++ {
r := &f.R[ri]
if r.Type != objabi.R_DWARFFILEREF {
continue
}
// Mark relocation as applied (signal to relocsym)
r.Done = true
idx, ok := fileNums[int(r.Sym.Value)]
if ok {
if int(int32(idx)) != idx {
Errorf(f, "bad R_DWARFFILEREF relocation: file index overflow")
}
if r.Siz != 4 {
Errorf(f, "bad R_DWARFFILEREF relocation: has size %d, expected 4", r.Siz)
}
if r.Off < 0 || r.Off+4 > int32(len(f.P)) {
Errorf(f, "bad R_DWARFFILEREF relocation offset %d + 4 would write past length %d", r.Off, len(s.P))
continue
}
ctxt.Arch.ByteOrder.PutUint32(f.P[r.Off:r.Off+4], uint32(idx))
} else {
_, found := missing[int(r.Sym.Value)]
if !found {
Errorf(f, "R_DWARFFILEREF relocation file missing: %v idx %d", r.Sym, r.Sym.Value)
missing[int(r.Sym.Value)] = nil
}
}
}
}
return dwinfo, funcs, absfuncs
}
// writepcranges generates the DW_AT_ranges table for compilation unit cu.
func writepcranges(ctxt *Link, cu *dwarf.DWDie, base *sym.Symbol, pcs []dwarf.Range, ranges *sym.Symbol) {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
// Create PC ranges for this CU.
newattr(cu, dwarf.DW_AT_ranges, dwarf.DW_CLS_PTR, ranges.Size, ranges)
newattr(cu, dwarf.DW_AT_low_pc, dwarf.DW_CLS_ADDRESS, base.Value, base)
dwarf.PutRanges(dwarfctxt, ranges, nil, pcs)
}
/*
* Emit .debug_frame
*/
const (
dataAlignmentFactor = -4
)
// appendPCDeltaCFA appends per-PC CFA deltas to b and returns the final slice.
func appendPCDeltaCFA(arch *sys.Arch, b []byte, deltapc, cfa int64) []byte {
b = append(b, dwarf.DW_CFA_def_cfa_offset_sf)
b = dwarf.AppendSleb128(b, cfa/dataAlignmentFactor)
switch {
case deltapc < 0x40:
b = append(b, uint8(dwarf.DW_CFA_advance_loc+deltapc))
case deltapc < 0x100:
b = append(b, dwarf.DW_CFA_advance_loc1)
b = append(b, uint8(deltapc))
case deltapc < 0x10000:
b = append(b, dwarf.DW_CFA_advance_loc2, 0, 0)
arch.ByteOrder.PutUint16(b[len(b)-2:], uint16(deltapc))
default:
b = append(b, dwarf.DW_CFA_advance_loc4, 0, 0, 0, 0)
arch.ByteOrder.PutUint32(b[len(b)-4:], uint32(deltapc))
}
return b
}
func writeframes(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
fs := ctxt.Syms.Lookup(".debug_frame", 0)
fs.Type = sym.SDWARFSECT
syms = append(syms, fs)
// Emit the CIE, Section 6.4.1
cieReserve := uint32(16)
if haslinkregister(ctxt) {
cieReserve = 32
}
fs.AddUint32(ctxt.Arch, cieReserve) // initial length, must be multiple of thearch.ptrsize
fs.AddUint32(ctxt.Arch, 0xffffffff) // cid.
fs.AddUint8(3) // dwarf version (appendix F)
fs.AddUint8(0) // augmentation ""
dwarf.Uleb128put(dwarfctxt, fs, 1) // code_alignment_factor
dwarf.Sleb128put(dwarfctxt, fs, dataAlignmentFactor) // all CFI offset calculations include multiplication with this factor
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr)) // return_address_register
fs.AddUint8(dwarf.DW_CFA_def_cfa) // Set the current frame address..
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfregsp)) // ...to use the value in the platform's SP register (defined in l.go)...
if haslinkregister(ctxt) {
dwarf.Uleb128put(dwarfctxt, fs, int64(0)) // ...plus a 0 offset.
fs.AddUint8(dwarf.DW_CFA_same_value) // The platform's link register is unchanged during the prologue.
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr))
fs.AddUint8(dwarf.DW_CFA_val_offset) // The previous value...
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfregsp)) // ...of the platform's SP register...
dwarf.Uleb128put(dwarfctxt, fs, int64(0)) // ...is CFA+0.
} else {
dwarf.Uleb128put(dwarfctxt, fs, int64(ctxt.Arch.PtrSize)) // ...plus the word size (because the call instruction implicitly adds one word to the frame).
fs.AddUint8(dwarf.DW_CFA_offset_extended) // The previous value...
dwarf.Uleb128put(dwarfctxt, fs, int64(Thearch.Dwarfreglr)) // ...of the return address...
dwarf.Uleb128put(dwarfctxt, fs, int64(-ctxt.Arch.PtrSize)/dataAlignmentFactor) // ...is saved at [CFA - (PtrSize/4)].
}
// 4 is to exclude the length field.
pad := int64(cieReserve) + 4 - fs.Size
if pad < 0 {
Exitf("dwarf: cieReserve too small by %d bytes.", -pad)
}
fs.AddBytes(zeros[:pad])
var deltaBuf []byte
var pcsp Pciter
for _, s := range ctxt.Textp {
if s.FuncInfo == nil {
continue
}
// Emit a FDE, Section 6.4.1.
// First build the section contents into a byte buffer.
deltaBuf = deltaBuf[:0]
for pciterinit(ctxt, &pcsp, &s.FuncInfo.Pcsp); pcsp.done == 0; pciternext(&pcsp) {
nextpc := pcsp.nextpc
// pciterinit goes up to the end of the function,
// but DWARF expects us to stop just before the end.
if int64(nextpc) == s.Size {
nextpc--
if nextpc < pcsp.pc {
continue
}
}
if haslinkregister(ctxt) {
// TODO(bryanpkc): This is imprecise. In general, the instruction
// that stores the return address to the stack frame is not the
// same one that allocates the frame.
if pcsp.value > 0 {
// The return address is preserved at (CFA-frame_size)
// after a stack frame has been allocated.
deltaBuf = append(deltaBuf, dwarf.DW_CFA_offset_extended_sf)
deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(Thearch.Dwarfreglr))
deltaBuf = dwarf.AppendSleb128(deltaBuf, -int64(pcsp.value)/dataAlignmentFactor)
} else {
// The return address is restored into the link register
// when a stack frame has been de-allocated.
deltaBuf = append(deltaBuf, dwarf.DW_CFA_same_value)
deltaBuf = dwarf.AppendUleb128(deltaBuf, uint64(Thearch.Dwarfreglr))
}
deltaBuf = appendPCDeltaCFA(ctxt.Arch, deltaBuf, int64(nextpc)-int64(pcsp.pc), int64(pcsp.value))
} else {
deltaBuf = appendPCDeltaCFA(ctxt.Arch, deltaBuf, int64(nextpc)-int64(pcsp.pc), int64(ctxt.Arch.PtrSize)+int64(pcsp.value))
}
}
pad := int(Rnd(int64(len(deltaBuf)), int64(ctxt.Arch.PtrSize))) - len(deltaBuf)
deltaBuf = append(deltaBuf, zeros[:pad]...)
// Emit the FDE header, Section 6.4.1.
// 4 bytes: length, must be multiple of thearch.ptrsize
// 4 bytes: Pointer to the CIE above, at offset 0
// ptrsize: initial location
// ptrsize: address range
fs.AddUint32(ctxt.Arch, uint32(4+2*ctxt.Arch.PtrSize+len(deltaBuf))) // length (excludes itself)
if ctxt.LinkMode == LinkExternal {
adddwarfref(ctxt, fs, fs, 4)
} else {
fs.AddUint32(ctxt.Arch, 0) // CIE offset
}
fs.AddAddr(ctxt.Arch, s)
fs.AddUintXX(ctxt.Arch, uint64(s.Size), ctxt.Arch.PtrSize) // address range
fs.AddBytes(deltaBuf)
}
return syms
}
func writeranges(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
for _, s := range ctxt.Textp {
rangeSym := ctxt.Syms.ROLookup(dwarf.RangePrefix+s.Name, int(s.Version))
if rangeSym == nil || rangeSym.Size == 0 {
continue
}
rangeSym.Attr |= sym.AttrReachable | sym.AttrNotInSymbolTable
rangeSym.Type = sym.SDWARFRANGE
syms = append(syms, rangeSym)
}
return syms
}
/*
* Walk DWarfDebugInfoEntries, and emit .debug_info
*/
const (
COMPUNITHEADERSIZE = 4 + 2 + 4 + 1
)
func writeinfo(ctxt *Link, syms []*sym.Symbol, units []*compilationUnit, abbrevsym *sym.Symbol) []*sym.Symbol {
infosec := ctxt.Syms.Lookup(".debug_info", 0)
infosec.Type = sym.SDWARFINFO
infosec.Attr |= sym.AttrReachable
syms = append(syms, infosec)
var dwarfctxt dwarf.Context = dwctxt{ctxt}
// Re-index per-package information by its CU die.
unitByDIE := make(map[*dwarf.DWDie]*compilationUnit)
for _, u := range units {
unitByDIE[u.dwinfo] = u
}
for compunit := dwroot.Child; compunit != nil; compunit = compunit.Link {
s := dtolsym(compunit.Sym)
u := unitByDIE[compunit]
// Write .debug_info Compilation Unit Header (sec 7.5.1)
// Fields marked with (*) must be changed for 64-bit dwarf
// This must match COMPUNITHEADERSIZE above.
s.AddUint32(ctxt.Arch, 0) // unit_length (*), will be filled in later.
s.AddUint16(ctxt.Arch, 4) // dwarf version (appendix F)
// debug_abbrev_offset (*)
adddwarfref(ctxt, s, abbrevsym, 4)
s.AddUint8(uint8(ctxt.Arch.PtrSize)) // address_size
dwarf.Uleb128put(dwarfctxt, s, int64(compunit.Abbrev))
dwarf.PutAttrs(dwarfctxt, s, compunit.Abbrev, compunit.Attr)
cu := []*sym.Symbol{s}
cu = append(cu, u.absFnDIEs...)
cu = append(cu, u.funcDIEs...)
if u.consts != nil {
cu = append(cu, u.consts)
}
cu = putdies(ctxt, dwarfctxt, cu, compunit.Child)
var cusize int64
for _, child := range cu {
cusize += child.Size
}
cusize -= 4 // exclude the length field.
s.SetUint32(ctxt.Arch, 0, uint32(cusize))
// Leave a breadcrumb for writepub. This does not
// appear in the DWARF output.
newattr(compunit, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, cusize, 0)
syms = append(syms, cu...)
}
return syms
}
/*
* Emit .debug_pubnames/_types. _info must have been written before,
* because we need die->offs and infoo/infosize;
*/
func ispubname(die *dwarf.DWDie) bool {
switch die.Abbrev {
case dwarf.DW_ABRV_FUNCTION, dwarf.DW_ABRV_VARIABLE:
a := getattr(die, dwarf.DW_AT_external)
return a != nil && a.Value != 0
}
return false
}
func ispubtype(die *dwarf.DWDie) bool {
return die.Abbrev >= dwarf.DW_ABRV_NULLTYPE
}
func writepub(ctxt *Link, sname string, ispub func(*dwarf.DWDie) bool, syms []*sym.Symbol) []*sym.Symbol {
s := ctxt.Syms.Lookup(sname, 0)
s.Type = sym.SDWARFSECT
syms = append(syms, s)
for compunit := dwroot.Child; compunit != nil; compunit = compunit.Link {
sectionstart := s.Size
culength := uint32(getattr(compunit, dwarf.DW_AT_byte_size).Value) + 4
// Write .debug_pubnames/types Header (sec 6.1.1)
s.AddUint32(ctxt.Arch, 0) // unit_length (*), will be filled in later.
s.AddUint16(ctxt.Arch, 2) // dwarf version (appendix F)
adddwarfref(ctxt, s, dtolsym(compunit.Sym), 4) // debug_info_offset (of the Comp unit Header)
s.AddUint32(ctxt.Arch, culength) // debug_info_length
for die := compunit.Child; die != nil; die = die.Link {
if !ispub(die) {
continue
}
dwa := getattr(die, dwarf.DW_AT_name)
name := dwa.Data.(string)
if die.Sym == nil {
fmt.Println("Missing sym for ", name)
}
adddwarfref(ctxt, s, dtolsym(die.Sym), 4)
Addstring(s, name)
}
s.AddUint32(ctxt.Arch, 0)
s.SetUint32(ctxt.Arch, sectionstart, uint32(s.Size-sectionstart)-4) // exclude the length field.
}
return syms
}
func writegdbscript(ctxt *Link, syms []*sym.Symbol) []*sym.Symbol {
if ctxt.LinkMode == LinkExternal && ctxt.HeadType == objabi.Hwindows && ctxt.BuildMode == BuildModeCArchive {
// gcc on Windows places .debug_gdb_scripts in the wrong location, which
// causes the program not to run. See https://golang.org/issue/20183
// Non c-archives can avoid this issue via a linker script
// (see fix near writeGDBLinkerScript).
// c-archive users would need to specify the linker script manually.
// For UX it's better not to deal with this.
return syms
}
if gdbscript != "" {
s := ctxt.Syms.Lookup(".debug_gdb_scripts", 0)
s.Type = sym.SDWARFSECT
syms = append(syms, s)
s.AddUint8(1) // magic 1 byte?
Addstring(s, gdbscript)
}
return syms
}
var prototypedies map[string]*dwarf.DWDie
/*
* This is the main entry point for generating dwarf. After emitting
* the mandatory debug_abbrev section, it calls writelines() to set up
* the per-compilation unit part of the DIE tree, while simultaneously
* emitting the debug_line section. When the final tree contains
* forward references, it will write the debug_info section in 2
* passes.
*
*/
func dwarfgeneratedebugsyms(ctxt *Link) {
if *FlagW { // disable dwarf
return
}
if *FlagS && ctxt.HeadType != objabi.Hdarwin {
return
}
if ctxt.HeadType == objabi.Hplan9 {
return
}
if ctxt.LinkMode == LinkExternal {
switch {
case ctxt.IsELF:
case ctxt.HeadType == objabi.Hdarwin:
case ctxt.HeadType == objabi.Hwindows:
default:
return
}
}
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f dwarf\n", Cputime())
}
// Forctxt.Diagnostic messages.
newattr(&dwtypes, dwarf.DW_AT_name, dwarf.DW_CLS_STRING, int64(len("dwtypes")), "dwtypes")
// Some types that must exist to define other ones.
newdie(ctxt, &dwtypes, dwarf.DW_ABRV_NULLTYPE, "<unspecified>", 0)
newdie(ctxt, &dwtypes, dwarf.DW_ABRV_NULLTYPE, "void", 0)
newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BARE_PTRTYPE, "unsafe.Pointer", 0)
die := newdie(ctxt, &dwtypes, dwarf.DW_ABRV_BASETYPE, "uintptr", 0) // needed for array size
newattr(die, dwarf.DW_AT_encoding, dwarf.DW_CLS_CONSTANT, dwarf.DW_ATE_unsigned, 0)
newattr(die, dwarf.DW_AT_byte_size, dwarf.DW_CLS_CONSTANT, int64(ctxt.Arch.PtrSize), 0)
newattr(die, dwarf.DW_AT_go_kind, dwarf.DW_CLS_CONSTANT, objabi.KindUintptr, 0)
// Prototypes needed for type synthesis.
prototypedies = map[string]*dwarf.DWDie{
"type.runtime.stringStructDWARF": nil,
"type.runtime.slice": nil,
"type.runtime.hmap": nil,
"type.runtime.bmap": nil,
"type.runtime.sudog": nil,
"type.runtime.waitq": nil,
"type.runtime.hchan": nil,
}
// Needed by the prettyprinter code for interface inspection.
for _, typ := range []string{
"type.runtime._type",
"type.runtime.arraytype",
"type.runtime.chantype",
"type.runtime.functype",
"type.runtime.maptype",
"type.runtime.ptrtype",
"type.runtime.slicetype",
"type.runtime.structtype",
"type.runtime.interfacetype",
"type.runtime.itab",
"type.runtime.imethod"} {
defgotype(ctxt, lookupOrDiag(ctxt, typ))
}
genasmsym(ctxt, defdwsymb)
abbrev := writeabbrev(ctxt)
syms := []*sym.Symbol{abbrev}
units := getCompilationUnits(ctxt)
// Write per-package line and range tables and start their CU DIEs.
debugLine := ctxt.Syms.Lookup(".debug_line", 0)
debugLine.Type = sym.SDWARFSECT
debugRanges := ctxt.Syms.Lookup(".debug_ranges", 0)
debugRanges.Type = sym.SDWARFRANGE
debugRanges.Attr |= sym.AttrReachable
syms = append(syms, debugLine)
for _, u := range units {
u.dwinfo, u.funcDIEs, u.absFnDIEs = writelines(ctxt, u.lib, u.lib.Textp, debugLine)
writepcranges(ctxt, u.dwinfo, u.lib.Textp[0], u.pcs, debugRanges)
}
synthesizestringtypes(ctxt, dwtypes.Child)
synthesizeslicetypes(ctxt, dwtypes.Child)
synthesizemaptypes(ctxt, dwtypes.Child)
synthesizechantypes(ctxt, dwtypes.Child)
// newdie adds DIEs to the *beginning* of the parent's DIE list.
// Now that we're done creating DIEs, reverse the trees so DIEs
// appear in the order they were created.
reversetree(&dwroot.Child)
reversetree(&dwtypes.Child)
reversetree(&dwglobals.Child)
movetomodule(&dwtypes)
movetomodule(&dwglobals)
// Need to reorder symbols so sym.SDWARFINFO is after all sym.SDWARFSECT
// (but we need to generate dies before writepub)
infosyms := writeinfo(ctxt, nil, units, abbrev)
syms = writeframes(ctxt, syms)
syms = writepub(ctxt, ".debug_pubnames", ispubname, syms)
syms = writepub(ctxt, ".debug_pubtypes", ispubtype, syms)
syms = writegdbscript(ctxt, syms)
// Now we're done writing SDWARFSECT symbols, so we can write
// other SDWARF* symbols.
syms = append(syms, infosyms...)
syms = collectlocs(ctxt, syms, units)
syms = append(syms, debugRanges)
syms = writeranges(ctxt, syms)
dwarfp = syms
}
func collectlocs(ctxt *Link, syms []*sym.Symbol, units []*compilationUnit) []*sym.Symbol {
empty := true
for _, u := range units {
for _, fn := range u.funcDIEs {
for _, reloc := range fn.R {
if reloc.Type == objabi.R_DWARFSECREF && strings.HasPrefix(reloc.Sym.Name, dwarf.LocPrefix) {
reloc.Sym.Attr |= sym.AttrReachable | sym.AttrNotInSymbolTable
syms = append(syms, reloc.Sym)
empty = false
// One location list entry per function, but many relocations to it. Don't duplicate.
break
}
}
}
}
// Don't emit .debug_loc if it's empty -- it makes the ARM linker mad.
if !empty {
locsym := ctxt.Syms.Lookup(".debug_loc", 0)
locsym.Type = sym.SDWARFLOC
locsym.Attr |= sym.AttrReachable
syms = append(syms, locsym)
}
return syms
}
/*
* Elf.
*/
func dwarfaddshstrings(ctxt *Link, shstrtab *sym.Symbol) {
if *FlagW { // disable dwarf
return
}
Addstring(shstrtab, ".debug_abbrev")
Addstring(shstrtab, ".debug_frame")
Addstring(shstrtab, ".debug_info")
Addstring(shstrtab, ".debug_loc")
Addstring(shstrtab, ".debug_line")
Addstring(shstrtab, ".debug_pubnames")
Addstring(shstrtab, ".debug_pubtypes")
Addstring(shstrtab, ".debug_gdb_scripts")
Addstring(shstrtab, ".debug_ranges")
if ctxt.LinkMode == LinkExternal {
Addstring(shstrtab, elfRelType+".debug_info")
Addstring(shstrtab, elfRelType+".debug_loc")
Addstring(shstrtab, elfRelType+".debug_line")
Addstring(shstrtab, elfRelType+".debug_frame")
Addstring(shstrtab, elfRelType+".debug_pubnames")
Addstring(shstrtab, elfRelType+".debug_pubtypes")
Addstring(shstrtab, elfRelType+".debug_ranges")
}
}
// Add section symbols for DWARF debug info. This is called before
// dwarfaddelfheaders.
func dwarfaddelfsectionsyms(ctxt *Link) {
if *FlagW { // disable dwarf
return
}
if ctxt.LinkMode != LinkExternal {
return
}
s := ctxt.Syms.Lookup(".debug_info", 0)
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
s = ctxt.Syms.Lookup(".debug_abbrev", 0)
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
s = ctxt.Syms.Lookup(".debug_line", 0)
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
s = ctxt.Syms.Lookup(".debug_frame", 0)
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
s = ctxt.Syms.Lookup(".debug_loc", 0)
if s.Sect != nil {
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
}
s = ctxt.Syms.Lookup(".debug_ranges", 0)
if s.Sect != nil {
putelfsectionsym(ctxt.Out, s, s.Sect.Elfsect.(*ElfShdr).shnum)
}
}