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[dev.link] cmd/link: stop emitting .debug_pubnames/.debug_pubtypes

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Don't emit the .debug_pubnames/.debug_pubtypes sections. These sections
are not used by either GDB or Delve, and C++ compilers [notably GCC
and Clang] no longer emit the sections by default.

Change-Id: Ic3309755e88c8e1aa28a29366bc7f0df1748fe64
Reviewed-on: https://go-review.googlesource.com/c/go/+/237426
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2020-06-10 10:05:37 -04:00
parent 188e995ae9
commit bc1dbe58cf
1 changed files with 6 additions and 95 deletions
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101
src/cmd/link/internal/ld/dwarf.go
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@ -1518,7 +1518,7 @@ func appendSyms(syms []loader.Sym, src []sym.LoaderSym) []loader.Sym {
return syms
}
func (d *dwctxt) writeinfo(units []*sym.CompilationUnit, abbrevsym loader.Sym, pubNames, pubTypes *pubWriter) dwarfSecInfo {
func (d *dwctxt) writeinfo(units []*sym.CompilationUnit, abbrevsym loader.Sym) dwarfSecInfo {
infosec := d.ldr.LookupOrCreateSym(".debug_info", 0)
disu := d.ldr.MakeSymbolUpdater(infosec)
@ -1535,9 +1535,6 @@ func (d *dwctxt) writeinfo(units []*sym.CompilationUnit, abbrevsym loader.Sym, p
continue
}
pubNames.beginCompUnit(compunit)
pubTypes.beginCompUnit(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.
@ -1568,12 +1565,6 @@ func (d *dwctxt) writeinfo(units []*sym.CompilationUnit, abbrevsym loader.Sym, p
l := len(cu)
lastSymSz := int64(len(d.ldr.Data(cu[l-1])))
cu = d.putdie(cu, die)
if ispubname(die) {
pubNames.add(die, cusize)
}
if ispubtype(die) {
pubTypes.add(die, cusize)
}
if lastSymSz != int64(len(d.ldr.Data(cu[l-1]))) {
// putdie will sometimes append directly to the last symbol of the list
cusize = cusize - lastSymSz + int64(len(d.ldr.Data(cu[l-1])))
@ -1598,87 +1589,12 @@ func (d *dwctxt) writeinfo(units []*sym.CompilationUnit, abbrevsym loader.Sym, p
cusize -= 4 // exclude the length field.
su.SetUint32(d.arch, 0, uint32(cusize))
}
pubNames.endCompUnit(compunit, uint32(cusize)+4)
pubTypes.endCompUnit(compunit, uint32(cusize)+4)
syms = append(syms, cu...)
}
return dwarfSecInfo{syms: syms}
}
/*
* Emit .debug_pubnames/_types. _info must have been written before,
* because we need die->offs and infoo/infosize;
*/
type pubWriter struct {
d *dwctxt
s loader.Sym
su *loader.SymbolBuilder
sname string
sectionstart int64
culengthOff int64
}
func newPubWriter(d *dwctxt, sname string) *pubWriter {
s := d.ldr.LookupOrCreateSym(sname, 0)
u := d.ldr.MakeSymbolUpdater(s)
u.SetType(sym.SDWARFSECT)
return &pubWriter{d: d, s: s, su: u, sname: sname}
}
func (pw *pubWriter) beginCompUnit(compunit *dwarf.DWDie) {
pw.sectionstart = pw.su.Size()
// Write .debug_pubnames/types Header (sec 6.1.1)
pw.d.createUnitLength(pw.su, 0) // unit_length (*), will be filled in later.
pw.su.AddUint16(pw.d.arch, 2) // dwarf version (appendix F)
pw.d.addDwarfAddrRef(pw.su, pw.d.dtolsym(compunit.Sym)) // debug_info_offset (of the Comp unit Header)
pw.culengthOff = pw.su.Size()
pw.d.addDwarfAddrField(pw.su, uint64(0)) // debug_info_length, will be filled in later.
}
func (pw *pubWriter) add(die *dwarf.DWDie, offset int64) {
dwa := getattr(die, dwarf.DW_AT_name)
name := dwa.Data.(string)
if pw.d.dtolsym(die.Sym) == 0 {
fmt.Println("Missing sym for ", name)
}
pw.d.addDwarfAddrField(pw.su, uint64(offset))
pw.su.Addstring(name)
}
func (pw *pubWriter) endCompUnit(compunit *dwarf.DWDie, culength uint32) {
pw.d.addDwarfAddrField(pw.su, 0) // Null offset
// On AIX, save the current size of this compilation unit.
if pw.d.linkctxt.HeadType == objabi.Haix {
saveDwsectCUSize(pw.sname, pw.d.getPkgFromCUSym(pw.d.dtolsym(compunit.Sym)), uint64(pw.su.Size()-pw.sectionstart))
}
if isDwarf64(pw.d.linkctxt) {
pw.su.SetUint(pw.d.arch, pw.sectionstart+4, uint64(pw.su.Size()-pw.sectionstart)-12) // exclude the length field.
pw.su.SetUint(pw.d.arch, pw.culengthOff, uint64(culength))
} else {
pw.su.SetUint32(pw.d.arch, pw.sectionstart, uint32(pw.su.Size()-pw.sectionstart)-4) // exclude the length field.
pw.su.SetUint32(pw.d.arch, pw.culengthOff, culength)
}
}
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 (d *dwctxt) writegdbscript() dwarfSecInfo {
// TODO (aix): make it available
if d.linkctxt.HeadType == objabi.Haix {
@ -2019,9 +1935,9 @@ func dwarfGenerateDebugInfo(ctxt *Link) {
// every DIE constructed and convert the symbols.
}
// 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 dwarfGenerateDebugInfo2.
// dwarfGenerateDebugSyms constructs debug_line, debug_frame, and
// debug_loc. It also writes out the debug_info section using symbols
// generated in dwarfGenerateDebugInfo2.
func dwarfGenerateDebugSyms(ctxt *Link) {
if !dwarfEnabled(ctxt) {
return
@ -2070,15 +1986,10 @@ func (d *dwctxt) dwarfGenerateDebugSyms() {
reversetree(&dwtypes.Child)
movetomodule(d.linkctxt, &dwtypes)
pubNames := newPubWriter(d, ".debug_pubnames")
pubTypes := newPubWriter(d, ".debug_pubtypes")
infoSec := d.writeinfo(d.linkctxt.compUnits, abbrevSec.secSym(), pubNames, pubTypes)
infoSec := d.writeinfo(d.linkctxt.compUnits, abbrevSec.secSym())
framesSec := d.writeframes()
dwarfp = append(dwarfp, framesSec)
dwarfp = append(dwarfp, dwarfSecInfo{syms: []loader.Sym{pubNames.s}})
dwarfp = append(dwarfp, dwarfSecInfo{syms: []loader.Sym{pubTypes.s}})
gdbScriptSec := d.writegdbscript()
if gdbScriptSec.secSym() != 0 {
dwarfp = append(dwarfp, gdbScriptSec)
@ -2142,7 +2053,7 @@ func dwarfaddshstrings(ctxt *Link, shstrtab *loader.SymbolBuilder) {
return
}
secs := []string{"abbrev", "frame", "info", "loc", "line", "pubnames", "pubtypes", "gdb_scripts", "ranges"}
secs := []string{"abbrev", "frame", "info", "loc", "line", "gdb_scripts", "ranges"}
for _, sec := range secs {
shstrtab.Addstring(".debug_" + sec)
if ctxt.IsExternal() {