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cmd/link: pass-through undefined call targets in external link mode

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Allows Go asm calls referencing a function in a .syso file to be
passed through to the external linker, that would have otherwise
raised a "relocation target X not defined" error in cmd/link.

Fixes #33139

Change-Id: I2a8eb6063ebcd05fac96f141acf7652cf9189766
Reviewed-on: https://go-review.googlesource.com/c/go/+/198798
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
John Papandriopoulos 2019-09-29 16:59:56 -07:00 • committed by Ian Lance Taylor
parent 81d6ec204f
commit 59a6847039
12 changed files with 97 additions and 18 deletions
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43
src/cmd/go/testdata/script/link_syso_issue33139.txt vendored Normal file
View file

@ -0,0 +1,43 @@
# Test that we can use the external linker with a host syso file that is
# embedded in a package, that is referenced by a Go assembly function.
# See issue 33139.
[!gc] skip
[!exec:cc] skip
# External linking is not supported on linux/ppc64.
# See: https://github.com/golang/go/issues/8912
[linux] [ppc64] skip
# External linking is not supported on darwin/386 (10.14+).
# See: https://github.com/golang/go/issues/31751
[darwin] [386] skip
cc -c -o syso/objTestImpl.syso syso/src/objTestImpl.c
go build -ldflags='-linkmode=external' ./cmd/main.go
-- syso/objTest.s --
#include "textflag.h"
TEXT ·ObjTest(SB), NOSPLIT, $0
// We do not actually execute this function in the test above, thus
// there is no stack frame setup here.
// We only care about Go build and/or link errors when referencing
// the objTestImpl symbol in the syso file.
JMP objTestImpl(SB)
-- syso/pkg.go --
package syso
func ObjTest()
-- syso/src/objTestImpl.c --
void objTestImpl() { /* Empty */ }
-- cmd/main.go --
package main
import "syso"
func main() {
syso.ObjTest()
}

2
src/cmd/link/internal/arm/asm.go
View file

@ -613,7 +613,7 @@ func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bo
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
ld.Errorf(s, "missing section for %s", rs.Name)
}
r.Xsym = rs

15
src/cmd/link/internal/ld/data.go
View file

@ -96,7 +96,7 @@ func trampoline(ctxt *Link, s *sym.Symbol) {
if !r.Type.IsDirectJump() {
continue
}
if Symaddr(r.Sym) == 0 && r.Sym.Type != sym.SDYNIMPORT {
if Symaddr(r.Sym) == 0 && (r.Sym.Type != sym.SDYNIMPORT && r.Sym.Type != sym.SUNDEFEXT) {
if r.Sym.File != s.File {
if !isRuntimeDepPkg(s.File) || !isRuntimeDepPkg(r.Sym.File) {
ctxt.ErrorUnresolved(s, r)
@ -298,7 +298,7 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
Errorf(s, "missing section for relocation target %s", rs.Name)
}
r.Xsym = rs
@ -418,6 +418,17 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
}
fallthrough
case objabi.R_CALL, objabi.R_PCREL:
if ctxt.LinkMode == LinkExternal && r.Sym != nil && r.Sym.Type == sym.SUNDEFEXT {
// pass through to the external linker.
r.Done = false
r.Xadd = 0
if ctxt.IsELF {
r.Xadd -= int64(r.Siz)
}
r.Xsym = r.Sym
o = 0
break
}
if ctxt.LinkMode == LinkExternal && r.Sym != nil && r.Sym.Type != sym.SCONST && (r.Sym.Sect != s.Sect || r.Type == objabi.R_GOTPCREL) {
r.Done = false

18
src/cmd/link/internal/ld/go.go
View file

@ -334,6 +334,24 @@ func fieldtrack(ctxt *Link) {
}
func (ctxt *Link) addexport() {
// Track undefined external symbols during external link.
if ctxt.LinkMode == LinkExternal {
for _, s := range ctxt.Syms.Allsym {
if !s.Attr.Reachable() || s.Attr.Special() || s.Attr.SubSymbol() {
continue
}
if s.Type != sym.STEXT {
continue
}
for i := range s.R {
r := &s.R[i]
if r.Sym != nil && r.Sym.Type == sym.Sxxx {
r.Sym.Type = sym.SUNDEFEXT
}
}
}
}
// TODO(aix)
if ctxt.HeadType == objabi.Hdarwin || ctxt.HeadType == objabi.Haix {
return

5
src/cmd/link/internal/ld/lib.go
View file

@ -2369,6 +2369,11 @@ func genasmsym(ctxt *Link, put func(*Link, *sym.Symbol, string, SymbolType, int6
}
put(ctxt, s, s.Name, BSSSym, Symaddr(s), s.Gotype)
case sym.SUNDEFEXT:
if ctxt.HeadType == objabi.Hwindows || ctxt.HeadType == objabi.Haix || ctxt.IsELF {
put(ctxt, s, s.Name, UndefinedSym, s.Value, nil)
}
case sym.SHOSTOBJ:
if ctxt.HeadType == objabi.Hwindows || ctxt.IsELF {
put(ctxt, s, s.Name, UndefinedSym, s.Value, nil)

4
src/cmd/link/internal/ld/macho.go
View file

@ -809,7 +809,7 @@ func machogenasmsym(ctxt *Link) {
}
}
if s.Type == sym.SDYNIMPORT || s.Type == sym.SHOSTOBJ {
if s.Type == sym.SDYNIMPORT || s.Type == sym.SHOSTOBJ || s.Type == sym.SUNDEFEXT {
if s.Attr.Reachable() {
addsym(ctxt, s, "", DataSym, 0, nil)
}
@ -886,7 +886,7 @@ func machosymtab(ctxt *Link) {
// replace "·" as ".", because DTrace cannot handle it.
Addstring(symstr, strings.Replace(s.Extname(), "·", ".", -1))
if s.Type == sym.SDYNIMPORT || s.Type == sym.SHOSTOBJ {
if s.Type == sym.SDYNIMPORT || s.Type == sym.SHOSTOBJ || s.Type == sym.SUNDEFEXT {
symtab.AddUint8(0x01) // type N_EXT, external symbol
symtab.AddUint8(0) // no section
symtab.AddUint16(ctxt.Arch, 0) // desc

2
src/cmd/link/internal/ld/pe.go
View file

@ -685,7 +685,7 @@ func (f *peFile) writeSymbols(ctxt *Link) {
// Only windows/386 requires underscore prefix on external symbols.
if ctxt.Arch.Family == sys.I386 &&
ctxt.LinkMode == LinkExternal &&
(s.Type == sym.SHOSTOBJ || s.Attr.CgoExport()) {
(s.Type == sym.SHOSTOBJ || s.Type == sym.SUNDEFEXT || s.Attr.CgoExport()) {
s.Name = "_" + s.Name
}

2
src/cmd/link/internal/ld/symtab.go
View file

@ -110,7 +110,7 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go
}
var elfshnum int
if xo.Type == sym.SDYNIMPORT || xo.Type == sym.SHOSTOBJ {
if xo.Type == sym.SDYNIMPORT || xo.Type == sym.SHOSTOBJ || xo.Type == sym.SUNDEFEXT {
elfshnum = SHN_UNDEF
} else {
if xo.Sect == nil {

2
src/cmd/link/internal/ld/xcoff.go
View file

@ -955,7 +955,7 @@ func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64,
syms = append(syms, a4)
case UndefinedSym:
if x.Type != sym.SDYNIMPORT && x.Type != sym.SHOSTOBJ {
if x.Type != sym.SDYNIMPORT && x.Type != sym.SHOSTOBJ && x.Type != sym.SUNDEFEXT {
return
}
s := &XcoffSymEnt64{

2
src/cmd/link/internal/ppc64/asm.go
View file

@ -801,7 +801,7 @@ func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bo
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
ld.Errorf(s, "missing section for %s", rs.Name)
}
r.Xsym = rs

1
src/cmd/link/internal/sym/symkind.go
View file

@ -104,6 +104,7 @@ const (
SCONST
SDYNIMPORT
SHOSTOBJ
SUNDEFEXT // Undefined symbol for resolution by external linker
// Sections for debugging information
SDWARFSECT

19
src/cmd/link/internal/sym/symkind_string.go
View file

@ -1,4 +1,4 @@
// Code generated by "stringer -type=SymKind"; DO NOT EDIT.
// Code generated by "stringer -type=SymKind symkind.go"; DO NOT EDIT.
package sym
@ -54,17 +54,18 @@ func _() {
_ = x[SCONST-43]
_ = x[SDYNIMPORT-44]
_ = x[SHOSTOBJ-45]
_ = x[SDWARFSECT-46]
_ = x[SDWARFINFO-47]
_ = x[SDWARFRANGE-48]
_ = x[SDWARFLOC-49]
_ = x[SDWARFLINES-50]
_ = x[SABIALIAS-51]
_ = x[SUNDEFEXT-46]
_ = x[SDWARFSECT-47]
_ = x[SDWARFINFO-48]
_ = x[SDWARFRANGE-49]
_ = x[SDWARFLOC-50]
_ = x[SDWARFLINES-51]
_ = x[SABIALIAS-52]
}
const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFOSDWARFRANGESDWARFLOCSDWARFLINESSABIALIAS"
const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSMACHOPLTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSCONSTSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFINFOSDWARFRANGESDWARFLOCSDWARFLINESSABIALIAS"
var _SymKind_index = [...]uint16{0, 4, 9, 19, 24, 31, 40, 47, 54, 61, 69, 79, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 320, 325, 337, 349, 366, 383, 392, 398, 408, 416, 426, 436, 447, 456, 467, 476}
var _SymKind_index = [...]uint16{0, 4, 9, 19, 24, 31, 40, 47, 54, 61, 69, 79, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 320, 325, 337, 349, 366, 383, 392, 398, 408, 416, 425, 435, 445, 456, 465, 476, 485}
func (i SymKind) String() string {
if i >= SymKind(len(_SymKind_index)-1) {