cmd/internal/ld, cmd/6l: external linking for windows/amd64

Change-Id: I2d2ea233f976aab3f356f9b508cdd246d5013e30
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/7534
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/6l/asm.go

@@ -204,10 +204,16 @@ func adddynrel(s *ld.LSym, r *ld.Reloc) {
 	switch r.Type {
 	case ld.R_CALL,
 		ld.R_PCREL:
+		if ld.HEADTYPE == ld.Hwindows {
+			// nothing to do, the relocation will be laid out in pereloc1
+			return
+		} else {
+			// for both ELF and Mach-O
 			addpltsym(targ)
 			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
 			r.Add = int64(targ.Plt)
 			return
+		}
 
 	case ld.R_ADDR:
 		if s.Type == ld.STEXT && ld.Iself {
@@ -262,6 +268,11 @@ func adddynrel(s *ld.LSym, r *ld.Reloc) {
 			r.Type = 256 // ignore during relocsym
 			return
 		}
+
+		if ld.HEADTYPE == ld.Hwindows {
+			// nothing to do, the relocation will be laid out in pereloc1
+			return
+		}
 	}
 
 	ld.Ctxt.Cursym = s
@@ -393,6 +404,40 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 	return 0
 }
 
+func pereloc1(r *ld.Reloc, sectoff int64) bool {
+	var v uint32
+
+	rs := r.Xsym
+
+	if rs.Dynid < 0 {
+		ld.Diag("reloc %d to non-coff symbol %s type=%d", r.Type, rs.Name, rs.Type)
+		return false
+	}
+
+	ld.Thearch.Lput(uint32(sectoff))
+	ld.Thearch.Lput(uint32(rs.Dynid))
+
+	switch r.Type {
+	default:
+		return false
+
+	case ld.R_ADDR:
+		if r.Siz == 8 {
+			v = ld.IMAGE_REL_AMD64_ADDR64
+		} else {
+			v = ld.IMAGE_REL_AMD64_ADDR32
+		}
+
+	case ld.R_CALL,
+		ld.R_PCREL:
+		v = ld.IMAGE_REL_AMD64_REL32
+	}
+
+	ld.Thearch.Wput(uint16(v))
+
+	return true
+}
+
 func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 	return -1
 }

src/cmd/6l/obj.go

@@ -71,6 +71,7 @@ func linkarchinit() {
 	ld.Thearch.Elfsetupplt = elfsetupplt
 	ld.Thearch.Gentext = gentext
 	ld.Thearch.Machoreloc1 = machoreloc1
+	ld.Thearch.PEreloc1 = pereloc1
 	ld.Thearch.Lput = ld.Lputl
 	ld.Thearch.Wput = ld.Wputl
 	ld.Thearch.Vput = ld.Vputl
@@ -110,7 +111,8 @@ func archinit() {
 		ld.Hnacl,
 		ld.Hnetbsd,
 		ld.Hopenbsd,
-		ld.Hsolaris:
+		ld.Hsolaris,
+		ld.Hwindows:
 		break
 	}
 

src/cmd/internal/ld/data.go

@@ -499,8 +499,13 @@ func relocsym(s *LSym) {
 					} else {
 						o += int64(r.Siz)
 					}
-				} else if HEADTYPE == Hwindows {
+				} else if HEADTYPE == Hwindows && Thearch.Thechar == '6' { // only amd64 needs PCREL
-					// nothing to do
+					// PE/COFF's PC32 relocation uses the address after the relocated
+					// bytes as the base. Compensate by skewing the addend.
+					o += int64(r.Siz)
+					// GNU ld always add VirtualAddress of the .text section to the
+					// relocated address, compensate that.
+					o -= int64(s.Sect.(*Section).Vaddr - PEBASE)
 				} else {
 					Diag("unhandled pcrel relocation for %s", headstring)
 				}

src/cmd/internal/ld/pe.go

@@ -532,7 +532,8 @@ func initdynimport() *Dll {
 				m.s.Type = SDATA
 				Symgrow(Ctxt, m.s, int64(Thearch.Ptrsize))
 				dynName := m.s.Extname
-				if m.argsize >= 0 {
+				// only windows/386 requires stdcall decoration
+				if Thearch.Thechar == '8' && m.argsize >= 0 {
 					dynName += fmt.Sprintf("@%d", m.argsize)
 				}
 				dynSym := Linklookup(Ctxt, dynName, 0)
@@ -955,7 +956,8 @@ func addpesym(s *LSym, name string, type_ int, addr int64, size int64, ver int,
 	}
 
 	if coffsym != nil {
-		if Linkmode == LinkExternal && (s.Type == SHOSTOBJ || s.Cgoexport != 0) && s.Name == s.Extname {
+		// only windows/386 requires underscore prefix on external symbols
+		if Thearch.Thechar == '8' && Linkmode == LinkExternal && (s.Type == SHOSTOBJ || s.Cgoexport != 0) && s.Name == s.Extname {
 			s.Name = "_" + s.Name
 		}
 		cs := &coffsym[ncoffsym]
@@ -963,7 +965,9 @@ func addpesym(s *LSym, name string, type_ int, addr int64, size int64, ver int,
 		if len(s.Name) > 8 {
 			cs.strtbloff = strtbladd(s.Name)
 		}
-		if uint64(s.Value) >= Segdata.Vaddr+Segdata.Filelen && Linkmode == LinkExternal {
+		// Note: although address of runtime.edata (type SDATA) is at the start of .bss section
+		// it still belongs to the .data section, not the .bss section.
+		if uint64(s.Value) >= Segdata.Vaddr+Segdata.Filelen && s.Type != SDATA && Linkmode == LinkExternal {
 			cs.value = int64(uint64(s.Value) - Segdata.Vaddr - Segdata.Filelen)
 			cs.sect = bsssect
 		} else if uint64(s.Value) >= Segdata.Vaddr {