cmd/link: move .rel symbol from .rdata into .text

.rel symbol type is sym.SELFROSECT, and that makes .rel written
into .rdata section. But .rel stores code - jump table used for
external C functions. So we have to mark whole .rdata section
as executable (IMAGE_SCN_MEM_EXECUTE), because of .rel presence
in it.

Move .rel into .text section, and make .rdata section non executable.

I also had to move code that adjusted the size of .rel symbol
before calling textaddress, otherwise textaddress would not
calculate size of .text section correctly.

Fixes #25926

Change-Id: I4962f5de7b367410154c8709adfcd8472de9ac1a
Reviewed-on: https://go-review.googlesource.com/c/125455
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/link/internal/ld/data.go

@@ -529,11 +529,7 @@ func (ctxt *Link) reloc() {
 	}
 }
 
-func windynrelocsym(ctxt *Link, s *sym.Symbol) {
-	rel := ctxt.Syms.Lookup(".rel", 0)
-	if s == rel {
-		return
-	}
+func windynrelocsym(ctxt *Link, rel, s *sym.Symbol) {
 	for ri := range s.R {
 		r := &s.R[ri]
 		targ := r.Sym
@@ -576,14 +572,31 @@ func windynrelocsym(ctxt *Link, s *sym.Symbol) {
 	}
 }
 
-func dynrelocsym(ctxt *Link, s *sym.Symbol) {
-	if ctxt.HeadType == objabi.Hwindows {
-		if ctxt.LinkMode == LinkInternal {
-			windynrelocsym(ctxt, s)
-		}
+// windynrelocsyms generates jump table to C library functions that will be
+// added later. windynrelocsyms writes the table into .rel symbol.
+func (ctxt *Link) windynrelocsyms() {
+	if !(ctxt.HeadType == objabi.Hwindows && iscgo && ctxt.LinkMode == LinkInternal) {
 		return
 	}
+	if ctxt.Debugvlog != 0 {
+		ctxt.Logf("%5.2f windynrelocsyms\n", Cputime())
+	}
+
+	/* relocation table */
+	rel := ctxt.Syms.Lookup(".rel", 0)
+	rel.Attr |= sym.AttrReachable
+	rel.Type = sym.STEXT
+	ctxt.Textp = append(ctxt.Textp, rel)
+
+	for _, s := range ctxt.Textp {
+		if s == rel {
+			continue
+		}
+		windynrelocsym(ctxt, rel, s)
+	}
+}
 
+func dynrelocsym(ctxt *Link, s *sym.Symbol) {
 	for ri := range s.R {
 		r := &s.R[ri]
 		if ctxt.BuildMode == BuildModePIE && ctxt.LinkMode == LinkInternal {
@@ -605,9 +618,12 @@ func dynrelocsym(ctxt *Link, s *sym.Symbol) {
 }
 
 func dynreloc(ctxt *Link, data *[sym.SXREF][]*sym.Symbol) {
+	if ctxt.HeadType == objabi.Hwindows {
+		return
+	}
 	// -d suppresses dynamic loader format, so we may as well not
 	// compute these sections or mark their symbols as reachable.
-	if *FlagD && ctxt.HeadType != objabi.Hwindows {
+	if *FlagD {
 		return
 	}
 	if ctxt.Debugvlog != 0 {

src/cmd/link/internal/ld/main.go

@@ -222,6 +222,7 @@ func Main(arch *sys.Arch, theArch Arch) {
 	ctxt.dostkcheck()
 	if ctxt.HeadType == objabi.Hwindows {
 		ctxt.dope()
+		ctxt.windynrelocsyms()
 	}
 	ctxt.addexport()
 	thearch.Gentext(ctxt) // trampolines, call stubs, etc.

src/cmd/link/internal/ld/pe.go

@@ -1461,12 +1461,6 @@ func addPEBaseReloc(ctxt *Link) {
 }
 
 func (ctxt *Link) dope() {
-	/* relocation table */
-	rel := ctxt.Syms.Lookup(".rel", 0)
-
-	rel.Attr |= sym.AttrReachable
-	rel.Type = sym.SELFROSECT
-
 	initdynimport(ctxt)
 	initdynexport(ctxt)
 }
@@ -1534,9 +1528,6 @@ func Asmbpe(ctxt *Link) {
 		// some data symbols (e.g. masks) end up in the .rdata section, and they normally
 		// expect larger alignment requirement than the default text section alignment.
 		ro.characteristics |= IMAGE_SCN_ALIGN_32BYTES
-	} else {
-		// TODO(brainman): should not need IMAGE_SCN_MEM_EXECUTE, but I do not know why it carshes without it
-		ro.characteristics |= IMAGE_SCN_MEM_EXECUTE
 	}
 	ro.checkSegment(&Segrodata)
 	pefile.rdataSect = ro