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path: root/go-patches/0005-cmd-link-handle-grouped-resource-sections.patch
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From 5d5d74f35dd3375cda8ef2ba8257547aad107ecb Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sun, 8 Nov 2020 11:57:42 +0100
Subject: [PATCH 05/10] cmd/link: handle grouped resource sections

The Go PE linker does not support enough generalized PE logic to
properly handle .rsrc sections gracefully. Instead a few things are
special cased for these. The linker also does not support PE's "grouped
sections" features, in which input objects have several named sections
that are sorted, merged, and renamed in the output file. In the past,
more sophisticated support for resources or for PE features like grouped
sections have not been necessary, as Go's own object formats are pretty
vanilla, and GNU binutils also produces pretty vanilla objects where all
sections are already merged.

However, GNU binutils is lagging with arm support, and here LLVM has
picked up the slack. In particular, LLVM has its own rc/cvtres combo,
which are glued together in mingw LLVM distributions as windres, a
command line compatible tool with binutils' windres, which supports arm
and arm64. But there's a key difference between binutils' windres and
LLVM's windres: the LLVM one uses proper grouped sections.

So, this commit adds grouped sections support for resource sections to
the linker. We don't attempt to plumb generic support for grouped
sections, just as there isn't generic support already for what resources
require. Instead we augment the resource handling logic to deal with
standard two-section resource objects.

Change-Id: I059450021405cdf2ef1c195ddbab3960764ad711
---
 src/cmd/link/internal/ld/lib.go      |  2 +-
 src/cmd/link/internal/ld/pe.go       | 50 ++++++++++++++--------------
 src/cmd/link/internal/loadpe/ldpe.go | 47 ++++++++++++++------------
 3 files changed, 52 insertions(+), 47 deletions(-)

diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index f98668a7dc..f09b5910b9 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -1900,7 +1900,7 @@ func ldobj(ctxt *Link, f *bio.Reader, lib *sym.Library, length int64, pn string,
 				Errorf(nil, "%v", err)
 				return
 			}
-			if rsrc != 0 {
+			if rsrc != nil {
 				setpersrc(ctxt, rsrc)
 			}
 			ctxt.Textp2 = append(ctxt.Textp2, textp...)
diff --git a/src/cmd/link/internal/ld/pe.go b/src/cmd/link/internal/ld/pe.go
index ec5b6d5f52..29094fe8ed 100644
--- a/src/cmd/link/internal/ld/pe.go
+++ b/src/cmd/link/internal/ld/pe.go
@@ -253,7 +253,7 @@ type Dll struct {
 }
 
 var (
-	rsrcsym     loader.Sym
+	rsrcsyms    []loader.Sym
 	PESECTHEADR int32
 	PEFILEHEADR int32
 	pe64        int
@@ -1464,47 +1464,47 @@ func (ctxt *Link) dope() {
 	initdynexport(ctxt)
 }
 
-func setpersrc(ctxt *Link, sym loader.Sym) {
-	if rsrcsym != 0 {
+func setpersrc(ctxt *Link, syms []loader.Sym) {
+	if rsrcsyms != nil {
 		Errorf(nil, "too many .rsrc sections")
 	}
-
-	rsrcsym = sym
-	ctxt.loader.SetAttrReachable(rsrcsym, true)
+	rsrcsyms = syms
+	for i := range rsrcsyms {
+		ctxt.loader.SetAttrReachable(rsrcsyms[i], true)
+	}
 }
 
 func addpersrc(ctxt *Link) {
-	if rsrcsym == 0 {
+	if rsrcsyms == nil {
 		return
 	}
 
-	rsrc := ctxt.loader.Syms[rsrcsym]
-	data := rsrc.P
-	size := len(data)
+	var size int
+	for i := range rsrcsyms {
+		size += len(ctxt.loader.Syms[rsrcsyms[i]].P)
+	}
 	h := pefile.addSection(".rsrc", size, size)
 	h.characteristics = IMAGE_SCN_MEM_READ | IMAGE_SCN_CNT_INITIALIZED_DATA
 	h.checkOffset(ctxt.Out.Offset())
 
-	// relocation
-	for ri := range rsrc.R {
-		r := &rsrc.R[ri]
-		p := data[r.Off:]
-		val := uint32(int64(h.virtualAddress) + r.Add)
-
-		// 32-bit little-endian
-		p[0] = byte(val)
-
-		p[1] = byte(val >> 8)
-		p[2] = byte(val >> 16)
-		p[3] = byte(val >> 24)
+	for i := range rsrcsyms {
+		rsrc := ctxt.loader.Syms[rsrcsyms[i]]
+		splitResources := strings.Contains(rsrc.Name, ".rsrc$")
+		for ri := range rsrc.R {
+			r := &rsrc.R[ri]
+			p := rsrc.P[r.Off:]
+			val := uint32(int64(h.virtualAddress) + r.Add)
+			if splitResources {
+				val += uint32(len(rsrc.P))
+			}
+			binary.LittleEndian.PutUint32(p, val)
+		}
+		ctxt.Out.Write(rsrc.P)
 	}
-
-	ctxt.Out.Write(data)
 	h.pad(ctxt.Out, uint32(size))
 
 	// update data directory
 	pefile.dataDirectory[pe.IMAGE_DIRECTORY_ENTRY_RESOURCE].VirtualAddress = h.virtualAddress
-
 	pefile.dataDirectory[pe.IMAGE_DIRECTORY_ENTRY_RESOURCE].Size = h.virtualSize
 }
 
diff --git a/src/cmd/link/internal/loadpe/ldpe.go b/src/cmd/link/internal/loadpe/ldpe.go
index b60b84ce9f..08832ba552 100644
--- a/src/cmd/link/internal/loadpe/ldpe.go
+++ b/src/cmd/link/internal/loadpe/ldpe.go
@@ -158,7 +158,7 @@ func makeUpdater(l *loader.Loader, bld *loader.SymbolBuilder, s loader.Sym) *loa
 // Load loads the PE file pn from input.
 // Symbols are written into syms, and a slice of the text symbols is returned.
 // If an .rsrc section is found, its symbol is returned as rsrc.
-func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Reader, pkg string, length int64, pn string) (textp []loader.Sym, rsrc loader.Sym, err error) {
+func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Reader, pkg string, length int64, pn string) (textp []loader.Sym, rsrc []loader.Sym, err error) {
 	lookup := func(name string, version int) (*loader.SymbolBuilder, loader.Sym) {
 		s := l.LookupOrCreateSym(name, version)
 		sb := l.MakeSymbolUpdater(s)
@@ -176,7 +176,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 	// TODO: replace pe.NewFile with pe.Load (grep for "add Load function" in debug/pe for details)
 	f, err := pe.NewFile(sr)
 	if err != nil {
-		return nil, 0, err
+		return nil, nil, err
 	}
 	defer f.Close()
 
@@ -211,21 +211,21 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			bld.SetType(sym.STEXT)
 
 		default:
-			return nil, 0, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
+			return nil, nil, fmt.Errorf("unexpected flags %#06x for PE section %s", sect.Characteristics, sect.Name)
 		}
 
 		if bld.Type() != sym.SNOPTRBSS {
 			data, err := sect.Data()
 			if err != nil {
-				return nil, 0, err
+				return nil, nil, err
 			}
 			sectdata[sect] = data
 			bld.SetData(data)
 		}
 		bld.SetSize(int64(sect.Size))
 		sectsyms[sect] = s
-		if sect.Name == ".rsrc" {
-			rsrc = s
+		if sect.Name == ".rsrc" || strings.HasPrefix(sect.Name, ".rsrc$") {
+			rsrc = append(rsrc, s)
 		}
 	}
 
@@ -246,22 +246,23 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			continue
 		}
 
+		splitResources := strings.HasPrefix(rsect.Name, ".rsrc$")
 		sb := l.MakeSymbolUpdater(sectsyms[rsect])
 		for j, r := range rsect.Relocs {
 			if int(r.SymbolTableIndex) >= len(f.COFFSymbols) {
-				return nil, 0, fmt.Errorf("relocation number %d symbol index idx=%d cannot be large then number of symbols %d", j, r.SymbolTableIndex, len(f.COFFSymbols))
+				return nil, nil, fmt.Errorf("relocation number %d symbol index idx=%d cannot be large then number of symbols %d", j, r.SymbolTableIndex, len(f.COFFSymbols))
 			}
 			pesym := &f.COFFSymbols[r.SymbolTableIndex]
 			_, gosym, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 			if err != nil {
-				return nil, 0, err
+				return nil, nil, err
 			}
 			if gosym == 0 {
 				name, err := pesym.FullName(f.StringTable)
 				if err != nil {
 					name = string(pesym.Name[:])
 				}
-				return nil, 0, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
+				return nil, nil, fmt.Errorf("reloc of invalid sym %s idx=%d type=%d", name, r.SymbolTableIndex, pesym.Type)
 			}
 
 			rSym := gosym
@@ -271,11 +272,11 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			var rType objabi.RelocType
 			switch arch.Family {
 			default:
-				return nil, 0, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
+				return nil, nil, fmt.Errorf("%s: unsupported arch %v", pn, arch.Family)
 			case sys.I386, sys.AMD64:
 				switch r.Type {
 				default:
-					return nil, 0, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
+					return nil, nil, fmt.Errorf("%s: %v: unknown relocation type %v", pn, sectsyms[rsect], r.Type)
 
 				case IMAGE_REL_I386_REL32, IMAGE_REL_AMD64_REL32,
 					IMAGE_REL_AMD64_ADDR32, // R_X86_64_PC32
@@ -302,7 +303,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			case sys.ARM:
 				switch r.Type {
 				default:
-					return nil, 0, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
+					return nil, nil, fmt.Errorf("%s: %v: unknown ARM relocation type %v", pn, sectsyms[rsect], r.Type)
 
 				case IMAGE_REL_ARM_SECREL:
 					rType = objabi.R_PCREL
@@ -324,7 +325,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			// ld -r could generate multiple section symbols for the
 			// same section but with different values, we have to take
 			// that into account
-			if issect(pesym) {
+			if issect(pesym) || splitResources {
 				rAdd += int64(pesym.Value)
 			}
 
@@ -333,6 +334,10 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			rel.SetSiz(rSize)
 			rel.SetSym(rSym)
 			rel.SetAdd(rAdd)
+
+			if splitResources {
+				l.SetAttrReachable(rSym, true)
+			}
 		}
 
 		sb.SortRelocs()
@@ -346,7 +351,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 
 		name, err := pesym.FullName(f.StringTable)
 		if err != nil {
-			return nil, 0, err
+			return nil, nil, err
 		}
 		if name == "" {
 			continue
@@ -373,7 +378,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 
 		bld, s, err := readpesym(l, arch, l.LookupOrCreateSym, f, pesym, sectsyms, localSymVersion)
 		if err != nil {
-			return nil, 0, err
+			return nil, nil, err
 		}
 
 		if pesym.SectionNumber == 0 { // extern
@@ -391,14 +396,14 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 		} else if pesym.SectionNumber > 0 && int(pesym.SectionNumber) <= len(f.Sections) {
 			sect = f.Sections[pesym.SectionNumber-1]
 			if _, found := sectsyms[sect]; !found {
-				return nil, 0, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
+				return nil, nil, fmt.Errorf("%s: %v: missing sect.sym", pn, s)
 			}
 		} else {
-			return nil, 0, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
+			return nil, nil, fmt.Errorf("%s: %v: sectnum < 0!", pn, s)
 		}
 
 		if sect == nil {
-			return nil, 0, nil
+			return nil, nil, nil
 		}
 
 		if l.OuterSym(s) != 0 {
@@ -407,7 +412,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 			}
 			outerName := l.SymName(l.OuterSym(s))
 			sectName := l.SymName(sectsyms[sect])
-			return nil, 0, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
+			return nil, nil, fmt.Errorf("%s: duplicate symbol reference: %s in both %s and %s", pn, l.SymName(s), outerName, sectName)
 		}
 
 		bld = makeUpdater(l, bld, s)
@@ -418,7 +423,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 		bld.SetSize(4)
 		if l.SymType(sectsym) == sym.STEXT {
 			if bld.External() && !bld.DuplicateOK() {
-				return nil, 0, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
+				return nil, nil, fmt.Errorf("%s: duplicate symbol definition", l.SymName(s))
 			}
 			bld.SetExternal(true)
 		}
@@ -435,7 +440,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, input *bio.Read
 		if l.SymType(s) == sym.STEXT {
 			for ; s != 0; s = l.SubSym(s) {
 				if l.AttrOnList(s) {
-					return nil, 0, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
+					return nil, nil, fmt.Errorf("symbol %s listed multiple times", l.SymName(s))
 				}
 				l.SetAttrOnList(s, true)
 				textp = append(textp, s)
-- 
2.29.2