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go/src/cmd/link/internal/ld/dwarf.go
Austin Clements 8dba66dfeb cmd/link: fix isStmt DWARF info 
When CL 147160 introduced function ABIs encoded as symbol versions in
the linker, it became slightly more complicated to look up derived
DWARF symbols. It fixed this by introducing a dwarfFuncSym function to
hide this logic, but missed one derived lookup that was done in the
object reader itself. As a result, we lost the isStmt tables from the
compiler, so every PC was marked as a statement in the DWARF info.

Fix this by moving this derived lookup out of the object reader and
into the DWARF code and calling dwarfFuncSym to get the correctly
versioned symbol.

Should fix the linux-amd64-longtest builder.

Updates #27539.

Change-Id: If40d5ba28bab1918ac4ad18fbb5103666b6d978b
Reviewed-on: https://go-review.googlesource.com/c/149605
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
2018-11-14 22:01:38 +00:00

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// 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 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/obj"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"fmt"
"log"
"sort"
"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) 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_ADDROFF
r.Add = ofs
}
func (c dwctxt) AddDWARFAddrSectionOffset(s dwarf.Sym, t interface{}, ofs int64) {
size := 4
if isDwarf64(c.linkctxt) {
size = 8
}
c.AddSectionOffset(s, size, t, ofs)
ls := s.(*sym.Symbol)
ls.R[len(ls.R)-1].Type = objabi.R_DWARFSECREF
}
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")
}
func isDwarf64(ctxt *Link) bool {
return ctxt.HeadType == objabi.Haix
}
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
}
var dwtypes 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
}
// dwarfFuncSym looks up a DWARF metadata symbol for function symbol s.
// If the symbol does not exist, it creates it if create is true,
// or returns nil otherwise.
func dwarfFuncSym(ctxt *Link, s *sym.Symbol, meta string, create bool) *sym.Symbol {
// All function ABIs use symbol version 0 for the DWARF data.
//
// TODO(austin): It may be useful to have DWARF info for ABI
// wrappers, in which case we may want these versions to
// align. Better yet, replace these name lookups with a
// general way to attach metadata to a symbol.
ver := 0
if s.IsFileLocal() {
ver = int(s.Version)
}
if create {
return ctxt.Syms.Lookup(meta+s.Name, ver)
}
return ctxt.Syms.ROLookup(meta+s.Name, ver)
}
func dotypedef(ctxt *Link, parent *dwarf.DWDie, name string, def *dwarf.DWDie) *dwarf.DWDie {
// Only emit typedefs for real names.
if strings.HasPrefix(name, "map[") {
return nil
}
if strings.HasPrefix(name, "struct {") {
return nil
}
if strings.HasPrefix(name, "chan ") {
return nil
}
if name[0] == '[' || name[0] == '*' {
return nil
}
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)
return die
}
// 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, typedefdie *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)
typedefdie = 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)
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)
typedefdie = dotypedef(ctxt, &dwtypes, name, die)
nfields := decodetypeFuncInCount(ctxt.Arch, gotype)
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)
typedefdie = dotypedef(ctxt, &dwtypes, name, die)
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)
typedefdie = 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)
typedefdie = 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)
typedefdie = 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 gotype.Attr.Reachable() {
newattr(die, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, gotype)
}
if _, ok := prototypedies[gotype.Name]; ok {
prototypedies[gotype.Name] = die
}
if typedefdie != nil {
return typedefdie
}
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)
if die := find(ctxt, ptrname); die != nil {
return die
}
pdie := newdie(ctxt, &dwtypes, dwarf.DW_ABRV_PTRTYPE, ptrname, 0)
newrefattr(pdie, dwarf.DW_AT_type, dwtype)
// The DWARF info synthesizes pointer types that don't exist at the
// language level, like *hash<...> and *bucket<...>, and the data
// pointers of slices. Link to the ones we can find.
gotype := ctxt.Syms.ROLookup("type."+ptrname, 0)
if gotype != nil && gotype.Attr.Reachable() {
newattr(pdie, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_GO_TYPEREF, 0, gotype)
}
return dtolsym(pdie.Sym)
}
// 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 {
if arg2 == "" {
return fmt.Sprintf("%s<%s>", base, arg1)
}
return fmt.Sprintf("%s<%s,%s>", base, arg1, arg2)
}
// 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))
}
}
func dwarfDefineGlobal(ctxt *Link, s *sym.Symbol, str string, v int64, gotype *sym.Symbol) {
lib := s.Lib
if lib == nil {
lib = ctxt.LibraryByPkg["runtime"]
}
dv := newdie(ctxt, ctxt.compUnitByPackage[lib].dwinfo, dwarf.DW_ABRV_VARIABLE, str, int(s.Version))
newabslocexprattr(dv, v, s)
if !s.IsFileLocal() {
newattr(dv, dwarf.DW_AT_external, dwarf.DW_CLS_FLAG, 1, 0)
}
dt := defgotype(ctxt, gotype)
newrefattr(dv, dwarf.DW_AT_type, dt)
}
// 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
}
switch t {
case DataSym, BSSSym:
switch s.Type {
case sym.SDATA, sym.SNOPTRDATA, sym.STYPE, sym.SBSS, sym.SNOPTRBSS, sym.STLSBSS:
// ok
case sym.SRODATA:
if gotype != nil {
defgotype(ctxt, gotype)
}
return
default:
return
}
if ctxt.LinkMode != LinkExternal && isStaticTemp(s.Name) {
return
}
dwarfDefineGlobal(ctxt, s, str, v, gotype)
case AutoSym, ParamSym, DeletedAutoSym:
defgotype(ctxt, gotype)
}
}
// createUnitLength creates the initial length field with value v and update
// offset of unit_length if needed.
func createUnitLength(ctxt *Link, s *sym.Symbol, v uint64) {
if isDwarf64(ctxt) {
s.AddUint32(ctxt.Arch, 0xFFFFFFFF)
}
addDwarfAddrField(ctxt, s, v)
}
// addDwarfAddrField adds a DWARF field in DWARF 64bits or 32bits.
func addDwarfAddrField(ctxt *Link, s *sym.Symbol, v uint64) {
if isDwarf64(ctxt) {
s.AddUint(ctxt.Arch, v)
} else {
s.AddUint32(ctxt.Arch, uint32(v))
}
}
// addDwarfAddrRef adds a DWARF pointer in DWARF 64bits or 32bits.
func addDwarfAddrRef(ctxt *Link, s *sym.Symbol, t *sym.Symbol) {
if isDwarf64(ctxt) {
adddwarfref(ctxt, s, t, 8)
} else {
adddwarfref(ctxt, s, t, 4)
}
}
// 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
rangeSyms []*sym.Symbol // symbols for debug_range
}
// calcCompUnitRanges calculates the PC ranges of the compilation units.
func calcCompUnitRanges(ctxt *Link) {
var prevUnit *compilationUnit
for _, s := range ctxt.Textp {
if s.FuncInfo == nil {
continue
}
unit := ctxt.compUnitByPackage[s.Lib]
// 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
}
}
func movetomodule(ctxt *Link, parent *dwarf.DWDie) {
runtimelib := ctxt.LibraryByPkg["runtime"]
die := ctxt.compUnitByPackage[runtimelib].dwinfo.Child
if die == nil {
ctxt.compUnitByPackage[runtimelib].dwinfo.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 = 11
)
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 -= (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 i := range dsym.R {
r := &dsym.R[i] // Copying sym.Reloc has measurable impact on performance
if r.Type == objabi.R_DWARFSECREF && r.Sym.Size == 0 {
n := nameFromDIESym(r.Sym)
defgotype(ctxt, ctxt.Syms.Lookup("type."+n, 0))
}
}
}
func writelines(ctxt *Link, unit *compilationUnit, ls *sym.Symbol) {
var dwarfctxt dwarf.Context = dwctxt{ctxt}
is_stmt := uint8(1) // initially = recommended default_is_stmt = 1, tracks is_stmt toggles.
unitstart := int64(-1)
headerstart := int64(-1)
headerend := int64(-1)
newattr(unit.dwinfo, dwarf.DW_AT_stmt_list, dwarf.DW_CLS_PTR, ls.Size, ls)
// Write .debug_line Line Number Program Header (sec 6.2.4)
// Fields marked with (*) must be changed for 64-bit dwarf
unitLengthOffset := ls.Size
createUnitLength(ctxt, ls, 0) // unit_length (*), filled in at end
unitstart = ls.Size
ls.AddUint16(ctxt.Arch, 2) // dwarf version (appendix F) -- version 3 is incompatible w/ XCode 9.0's dsymutil, latest supported on OSX 10.12 as of 2018-05
headerLengthOffset := ls.Size
addDwarfAddrField(ctxt, ls, 0) // header_length (*), filled in at end
headerstart = ls.Size
// cpos == unitstart + 4 + 2 + 4
ls.AddUint8(1) // minimum_instruction_length
ls.AddUint8(is_stmt) // 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) // standard_opcode_lengths[10]
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 unit.lib.Textp { // textp has been dead-code-eliminated already.
dsym := dwarfFuncSym(ctxt, s, dwarf.InfoPrefix, true)
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)
}
for ri := 0; ri < len(dsym.R); ri++ {
r := &dsym.R[ri]
if r.Type != objabi.R_DWARFFILEREF {
continue
}
// A file that is only mentioned in an inlined subroutine will appear
// as a R_DWARFFILEREF but not in s.FuncInfo.File
if _, ok := fileNums[int(r.Sym.Value)]; ok {
continue
}
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 := unit.lib.Textp[0]
pc := s.Value
line := 1
file := 1
ls.AddAddr(ctxt.Arch, s)
var pcfile Pciter
var pcline Pciter
var pcstmt Pciter
for i, s := range unit.lib.Textp {
finddebugruntimepath(s)
pciterinit(ctxt, &pcfile, &s.FuncInfo.Pcfile)
pciterinit(ctxt, &pcline, &s.FuncInfo.Pcline)
isStmtSym := dwarfFuncSym(ctxt, s, dwarf.IsStmtPrefix, false)
if isStmtSym != nil && len(isStmtSym.P) > 0 {
pciterinit(ctxt, &pcstmt, &sym.Pcdata{P: isStmtSym.P})
} else {
// Assembly files lack a pcstmt section, we assume that every instruction
// is a valid statement.
pcstmt.done = 1
pcstmt.value = 1
}
var thispc uint32
// TODO this loop looks like it could exit with work remaining.
for pcfile.done == 0 && pcline.done == 0 {
// Only changed if it advanced
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)
}
// Only changed if it advanced
if is_stmt != uint8(pcstmt.value) {
new_stmt := uint8(pcstmt.value)
switch new_stmt &^ 1 {
case obj.PrologueEnd:
ls.AddUint8(uint8(dwarf.DW_LNS_set_prologue_end))
case obj.EpilogueBegin:
// TODO if there is a use for this, add it.
// Don't forget to increase OPCODE_BASE by 1 and add entry for standard_opcode_lengths[11]
}
new_stmt &= 1
if is_stmt != new_stmt {
is_stmt = new_stmt
ls.AddUint8(uint8(dwarf.DW_LNS_negate_stmt))
}
}
// putpcldelta makes a row in the DWARF matrix, always, even if line is unchanged.
putpclcdelta(ctxt, dwarfctxt, ls, uint64(s.Value+int64(thispc)-pc), int64(pcline.value)-int64(line))
pc = s.Value + int64(thispc)
line = int(pcline.value)
// Take the minimum step forward for the three iterators
thispc = pcfile.nextpc
if pcline.nextpc < thispc {
thispc = pcline.nextpc
}
if pcstmt.done == 0 && pcstmt.nextpc < thispc {
thispc = pcstmt.nextpc
}
if pcfile.nextpc == thispc {
pciternext(&pcfile)
}
if pcstmt.done == 0 && pcstmt.nextpc == thispc {
pciternext(&pcstmt)
}
if pcline.nextpc == thispc {
pciternext(&pcline)
}
}
if is_stmt == 0 && i < len(unit.lib.Textp)-1 {
// If there is more than one function, ensure default value is established.
is_stmt = 1
ls.AddUint8(uint8(dwarf.DW_LNS_negate_stmt))
}
}
ls.AddUint8(0) // start extended opcode
dwarf.Uleb128put(dwarfctxt, ls, 1)
ls.AddUint8(dwarf.DW_LNE_end_sequence)
if ctxt.HeadType == objabi.Haix {
saveDwsectCUSize(".debug_line", unit.lib.String(), uint64(ls.Size-unitLengthOffset))
}
if isDwarf64(ctxt) {
ls.SetUint(ctxt.Arch, unitLengthOffset+4, uint64(ls.Size-unitstart)) // +4 because of 0xFFFFFFFF
ls.SetUint(ctxt.Arch, headerLengthOffset, uint64(headerend-headerstart))
} else {
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 _, f := range unit.funcDIEs {
for ri := range f.R {
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
}
}
}
}
}
// 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
}
createUnitLength(ctxt, fs, uint64(cieReserve)) // initial length, must be multiple of thearch.ptrsize
addDwarfAddrField(ctxt, fs, 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 {
addDwarfAddrRef(ctxt, fs, fs)
} else {
addDwarfAddrField(ctxt, fs, 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
}
/*
* 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}
for _, u := range units {
compunit := u.dwinfo
s := dtolsym(compunit.Sym)
if len(u.lib.Textp) == 0 && u.dwinfo.Child == nil {
continue
}
// 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.
createUnitLength(ctxt, s, 0) // unit_length (*), will be filled in later.
s.AddUint16(ctxt.Arch, 4) // dwarf version (appendix F)
// debug_abbrev_offset (*)
addDwarfAddrRef(ctxt, s, abbrevsym)
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
}
// Save size for AIX symbol table.
if ctxt.HeadType == objabi.Haix {
saveDwsectCUSize(".debug_info", getPkgFromCUSym(s), uint64(cusize))
}
if isDwarf64(ctxt) {
cusize -= 12 // exclude the length field.
s.SetUint(ctxt.Arch, 4, uint64(cusize)) // 4 because of 0XFFFFFFFF
} else {
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 _, u := range ctxt.compUnits {
if len(u.lib.Textp) == 0 && u.dwinfo.Child == nil {
continue
}
compunit := u.dwinfo
sectionstart := s.Size
culength := uint32(getattr(compunit, dwarf.DW_AT_byte_size).Value) + 4
// Write .debug_pubnames/types Header (sec 6.1.1)
createUnitLength(ctxt, s, 0) // unit_length (*), will be filled in later.
s.AddUint16(ctxt.Arch, 2) // dwarf version (appendix F)
addDwarfAddrRef(ctxt, s, dtolsym(compunit.Sym)) // debug_info_offset (of the Comp unit Header)
addDwarfAddrField(ctxt, s, uint64(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)
}
addDwarfAddrRef(ctxt, s, dtolsym(die.Sym))
Addstring(s, name)
}
addDwarfAddrField(ctxt, s, 0) // Null offset
// On AIX, save the current size of this compilation unit.
if ctxt.HeadType == objabi.Haix {
saveDwsectCUSize(sname, getPkgFromCUSym(dtolsym(compunit.Sym)), uint64(s.Size-sectionstart))
}
if isDwarf64(ctxt) {
s.SetUint(ctxt.Arch, sectionstart+4, uint64(s.Size-sectionstart)-12) // exclude the length field.
} else {
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 {
// TODO (aix): make it available
if ctxt.HeadType == objabi.Haix {
return syms
}
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
func dwarfEnabled(ctxt *Link) bool {
if *FlagW { // disable dwarf
return false
}
if *FlagS && ctxt.HeadType != objabi.Hdarwin {
return false
}
if ctxt.HeadType == objabi.Hplan9 || ctxt.HeadType == objabi.Hjs {
return false
}
if ctxt.LinkMode == LinkExternal {
switch {
case ctxt.IsELF:
case ctxt.HeadType == objabi.Hdarwin:
case ctxt.HeadType == objabi.Hwindows:
default:
return false
}
}
return true
}
// dwarfGenerateDebugInfo generated debug info entries for all types,
// variables and functions in the program.
// Along with dwarfGenerateDebugSyms they are the two main entry points into
// dwarf generation: dwarfGenerateDebugInfo does all the work that should be
// done before symbol names are mangled while dwarfgeneratedebugsyms does
// all the work that can only be done after addresses have been assigned to
// text symbols.
func dwarfGenerateDebugInfo(ctxt *Link) {
if !dwarfEnabled(ctxt) {
return
}
ctxt.compUnitByPackage = make(map[*sym.Library]*compilationUnit)
// 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)
newattr(die, dwarf.DW_AT_go_runtime_type, dwarf.DW_CLS_ADDRESS, 0, lookupOrDiag(ctxt, "type.uintptr"))
// 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))
}
// fake root DIE for compile unit DIEs
var dwroot dwarf.DWDie
for _, lib := range ctxt.Library {
unit := &compilationUnit{lib: lib}
if s := ctxt.Syms.ROLookup(dwarf.ConstInfoPrefix+lib.Pkg, 0); s != nil {
importInfoSymbol(ctxt, s)
unit.consts = s
}
ctxt.compUnits = append(ctxt.compUnits, unit)
ctxt.compUnitByPackage[lib] = unit
unit.dwinfo = newdie(ctxt, &dwroot, dwarf.DW_ABRV_COMPUNIT, unit.lib.Pkg, 0)
newattr(unit.dwinfo, dwarf.DW_AT_language, dwarf.DW_CLS_CONSTANT, int64(dwarf.DW_LANG_Go), 0)
// 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(unit.dwinfo, dwarf.DW_AT_comp_dir, dwarf.DW_CLS_STRING, int64(len(compDir)), compDir)
producerExtra := ctxt.Syms.Lookup(dwarf.CUInfoPrefix+"producer."+unit.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(unit.dwinfo, dwarf.DW_AT_producer, dwarf.DW_CLS_STRING, int64(len(producer)), producer)
if len(lib.Textp) == 0 {
unit.dwinfo.Abbrev = dwarf.DW_ABRV_COMPUNIT_TEXTLESS
}
// Scan all functions in this compilation unit, create DIEs for all
// referenced types, create the file table for debug_line, find all
// referenced abstract functions.
// Collect all debug_range symbols in unit.rangeSyms
for _, s := range lib.Textp { // textp has been dead-code-eliminated already.
dsym := dwarfFuncSym(ctxt, s, dwarf.InfoPrefix, false)
dsym.Attr |= sym.AttrNotInSymbolTable | sym.AttrReachable
dsym.Type = sym.SDWARFINFO
unit.funcDIEs = append(unit.funcDIEs, dsym)
rangeSym := dwarfFuncSym(ctxt, s, dwarf.RangePrefix, false)
if rangeSym != nil && rangeSym.Size > 0 {
rangeSym.Attr |= sym.AttrReachable | sym.AttrNotInSymbolTable
rangeSym.Type = sym.SDWARFRANGE
// LLVM doesn't support base address entries. Strip them out so LLDB and dsymutil don't get confused.
if ctxt.HeadType == objabi.Hdarwin {
removeDwarfAddrListBaseAddress(ctxt, dsym, rangeSym, false)
}
unit.rangeSyms = append(unit.rangeSyms, rangeSym)
}
for ri := 0; ri < len(dsym.R); ri++ {
r := &dsym.R[ri]
if r.Type == objabi.R_DWARFSECREF {
rsym := r.Sym
if strings.HasPrefix(rsym.Name, dwarf.InfoPrefix) && strings.HasSuffix(rsym.Name, dwarf.AbstractFuncSuffix) && !rsym.Attr.OnList() {
// abstract function
rsym.Attr |= sym.AttrOnList
unit.absFnDIEs = append(unit.absFnDIEs, rsym)
importInfoSymbol(ctxt, rsym)
} else if rsym.Size == 0 {
// a type we do not have a DIE for
n := nameFromDIESym(rsym)
defgotype(ctxt, ctxt.Syms.Lookup("type."+n, 0))
}
}
}
}
}
// Create DIEs for global variables and the types they use.
genasmsym(ctxt, defdwsymb)
synthesizestringtypes(ctxt, dwtypes.Child)
synthesizeslicetypes(ctxt, dwtypes.Child)
synthesizemaptypes(ctxt, dwtypes.Child)
synthesizechantypes(ctxt, dwtypes.Child)
}
// dwarfGenerateDebugSyms constructs debug_line, debug_frame, debug_loc,
// debug_pubnames and debug_pubtypes. It also writes out the debug_info
// section using symbols generated in dwarfGenerateDebugInfo.
func dwarfGenerateDebugSyms(ctxt *Link) {
if !dwarfEnabled(ctxt) {
return
}
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f dwarf\n", Cputime())
}
abbrev := writeabbrev(ctxt)
syms := []*sym.Symbol{abbrev}
calcCompUnitRanges(ctxt)
sort.Sort(compilationUnitByStartPC(ctxt.compUnits))
// 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 ctxt.compUnits {
reversetree(&u.dwinfo.Child)
if u.dwinfo.Abbrev == dwarf.DW_ABRV_COMPUNIT_TEXTLESS {
continue
}
writelines(ctxt, u, debugLine)
writepcranges(ctxt, u.dwinfo, u.lib.Textp[0], u.pcs, debugRanges)
}
// 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(&dwtypes.Child)
movetomodule(ctxt, &dwtypes)
// Need to reorder symbols so sym.SDWARFINFO is after all sym.SDWARFSECT
// (but we need to generate dies before writepub)
infosyms := writeinfo(ctxt, nil, ctxt.compUnits, 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, ctxt.compUnits)
syms = append(syms, debugRanges)
for _, unit := range ctxt.compUnits {
syms = append(syms, unit.rangeSyms...)
}
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 i := range fn.R {
reloc := &fn.R[i] // Copying sym.Reloc has measurable impact on performance
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
// LLVM doesn't support base address entries. Strip them out so LLDB and dsymutil don't get confused.
if ctxt.HeadType == objabi.Hdarwin {
removeDwarfAddrListBaseAddress(ctxt, fn, reloc.Sym, true)
}
// 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
}
// removeDwarfAddrListBaseAddress removes base address selector entries from
// DWARF location lists and range lists.
func removeDwarfAddrListBaseAddress(ctxt *Link, info, list *sym.Symbol, isloclist bool) {
// The list symbol contains multiple lists, but they're all for the
// same function, and it's not empty.
fn := list.R[0].Sym
// Discard the relocations for the base address entries.
list.R = list.R[:0]
// Add relocations for each location entry's start and end addresses,
// so that the base address entries aren't necessary.
// We could remove them entirely, but that's more work for a relatively
// small size win. If dsymutil runs it'll throw them away anyway.
// relocate adds a CU-relative relocation to fn+addr at offset.
relocate := func(addr uint64, offset int) {
list.R = append(list.R, sym.Reloc{
Off: int32(offset),
Siz: uint8(ctxt.Arch.PtrSize),
Type: objabi.R_ADDRCUOFF,
Add: int64(addr),
Sym: fn,
})
}
for i := 0; i < len(list.P); {
first := readPtr(ctxt, list.P[i:])
second := readPtr(ctxt, list.P[i+ctxt.Arch.PtrSize:])
if (first == 0 && second == 0) ||
first == ^uint64(0) ||
(ctxt.Arch.PtrSize == 4 && first == uint64(^uint32(0))) {
// Base address selection entry or end of list. Ignore.
i += ctxt.Arch.PtrSize * 2
continue
}
relocate(first, i)
relocate(second, i+ctxt.Arch.PtrSize)
// Skip past the actual location.
i += ctxt.Arch.PtrSize * 2
if isloclist {
i += 2 + int(ctxt.Arch.ByteOrder.Uint16(list.P[i:]))
}
}
// Rewrite the DIE's relocations to point to the first location entry,
// not the now-useless base address selection entry.
for i := range info.R {
r := &info.R[i]
if r.Sym != list {
continue
}
r.Add += int64(2 * ctxt.Arch.PtrSize)
}
}
// Read a pointer-sized uint from the beginning of buf.
func readPtr(ctxt *Link, buf []byte) uint64 {
switch ctxt.Arch.PtrSize {
case 4:
return uint64(ctxt.Arch.ByteOrder.Uint32(buf))
case 8:
return ctxt.Arch.ByteOrder.Uint64(buf)
default:
panic("unexpected pointer size")
}
}
/*
* Elf.
*/
func dwarfaddshstrings(ctxt *Link, shstrtab *sym.Symbol) {
if *FlagW { // disable dwarf
return
}
secs := []string{"abbrev", "frame", "info", "loc", "line", "pubnames", "pubtypes", "gdb_scripts", "ranges"}
for _, sec := range secs {
Addstring(shstrtab, ".debug_"+sec)
if ctxt.LinkMode == LinkExternal {
Addstring(shstrtab, elfRelType+".debug_"+sec)
} else {
Addstring(shstrtab, ".zdebug_"+sec)
}
}
}
// 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)
}
}
// dwarfcompress compresses the DWARF sections. This must happen after
// relocations are applied. After this, dwarfp will contain a
// different (new) set of symbols, and sections may have been replaced.
func dwarfcompress(ctxt *Link) {
supported := ctxt.IsELF || ctxt.HeadType == objabi.Hwindows || ctxt.HeadType == objabi.Hdarwin
if !ctxt.compressDWARF || !supported || ctxt.LinkMode != LinkInternal {
return
}
var start int
var newDwarfp []*sym.Symbol
Segdwarf.Sections = Segdwarf.Sections[:0]
for i, s := range dwarfp {
// Find the boundaries between sections and compress
// the whole section once we've found the last of its
// symbols.
if i+1 >= len(dwarfp) || s.Sect != dwarfp[i+1].Sect {
s1 := compressSyms(ctxt, dwarfp[start:i+1])
if s1 == nil {
// Compression didn't help.
newDwarfp = append(newDwarfp, dwarfp[start:i+1]...)
Segdwarf.Sections = append(Segdwarf.Sections, s.Sect)
} else {
compressedSegName := ".zdebug_" + s.Sect.Name[len(".debug_"):]
sect := addsection(ctxt.Arch, &Segdwarf, compressedSegName, 04)
sect.Length = uint64(len(s1))
newSym := ctxt.Syms.Lookup(compressedSegName, 0)
newSym.P = s1
newSym.Size = int64(len(s1))
newSym.Sect = sect
newDwarfp = append(newDwarfp, newSym)
}
start = i + 1
}
}
dwarfp = newDwarfp
// Re-compute the locations of the compressed DWARF symbols
// and sections, since the layout of these within the file is
// based on Section.Vaddr and Symbol.Value.
pos := Segdwarf.Vaddr
var prevSect *sym.Section
for _, s := range dwarfp {
s.Value = int64(pos)
if s.Sect != prevSect {
s.Sect.Vaddr = uint64(s.Value)
prevSect = s.Sect
}
if s.Sub != nil {
log.Fatalf("%s: unexpected sub-symbols", s)
}
pos += uint64(s.Size)
if ctxt.HeadType == objabi.Hwindows {
pos = uint64(Rnd(int64(pos), PEFILEALIGN))
}
}
Segdwarf.Length = pos - Segdwarf.Vaddr
}
type compilationUnitByStartPC []*compilationUnit
func (v compilationUnitByStartPC) Len() int { return len(v) }
func (v compilationUnitByStartPC) Swap(i, j int) { v[i], v[j] = v[j], v[i] }
func (v compilationUnitByStartPC) Less(i, j int) bool {
switch {
case len(v[i].lib.Textp) == 0 && len(v[j].lib.Textp) == 0:
return v[i].lib.Pkg < v[j].lib.Pkg
case len(v[i].lib.Textp) != 0 && len(v[j].lib.Textp) == 0:
return true
case len(v[i].lib.Textp) == 0 && len(v[j].lib.Textp) != 0:
return false
default:
return v[i].lib.Textp[0].Value < v[j].lib.Textp[0].Value
}
}
// On AIX, the symbol table needs to know where are the compilation units parts
// for a specific package in each .dw section.
// dwsectCUSize map will save the size of a compilation unit for
// the corresponding .dw section.
// This size can later be retrieved with the index "sectionName.pkgName".
var dwsectCUSize map[string]uint64
// getDwsectCUSize retrieves the corresponding package size inside the current section.
func getDwsectCUSize(sname string, pkgname string) uint64 {
return dwsectCUSize[sname+"."+pkgname]
}
func saveDwsectCUSize(sname string, pkgname string, size uint64) {
dwsectCUSize[sname+"."+pkgname] = size
}
// getPkgFromCUSym returns the package name for the compilation unit
// represented by s.
// The prefix dwarf.InfoPrefix+".pkg." needs to be removed in order to get
// the package name.
func getPkgFromCUSym(s *sym.Symbol) string {
return strings.TrimPrefix(s.Name, dwarf.InfoPrefix+".pkg.")
}
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