[dev.link] cmd/link: stream external relocations on ARM and on Windows

Do them in the same CL so ARM's archreloc doesn't need to support
both streaming and non-streaming.

TODO: we haven't switched to using mmap to emit external
relocations on Windows.

Change-Id: Ica2ee89c03fc74839efd6b9e26c80585fcdce45c
Reviewed-on: https://go-review.googlesource.com/c/go/+/244357
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

src/cmd/link/internal/arm/asm.go

@@ -535,23 +535,13 @@ func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loade
 		switch r.Type() {
 		case objabi.R_CALLARM:
 			// set up addend for eventual relocation via outer symbol.
-			rs, off := ld.FoldSubSymbolOffset(ldr, rs)
+			_, off := ld.FoldSubSymbolOffset(ldr, rs)
-			rr.Xadd = int64(signext24(r.Add() & 0xffffff))
+			xadd := int64(signext24(r.Add()&0xffffff))*4 + off
-			rr.Xadd *= 4
+			if xadd/4 > 0x7fffff || xadd/4 < -0x800000 {
-			rr.Xadd += off
+				ldr.Errorf(s, "direct call too far %d", xadd/4)
-			rst := ldr.SymType(rs)
-			if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
-				ldr.Errorf(s, "missing section for %s", ldr.SymName(rs))
 			}
-			rr.Xsym = rs
+			return int64(braddoff(int32(0xff000000&uint32(r.Add())), int32(0xffffff&uint32(xadd/4)))), 1, true
-
-			if rr.Xadd/4 > 0x7fffff || rr.Xadd/4 < -0x800000 {
-				ldr.Errorf(s, "direct call too far %d", rr.Xadd/4)
-			}
-
-			return int64(braddoff(int32(0xff000000&uint32(r.Add())), int32(0xffffff&uint32(rr.Xadd/4)))), 1, true
 		}
-
 		return -1, 0, false
 	}
 
@@ -587,6 +577,24 @@ func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc2, sym.RelocVarian
 	return -1
 }
 
+func extreloc(target *ld.Target, ldr *loader.Loader, r loader.Reloc2, s loader.Sym) (loader.ExtReloc, bool) {
+	rs := ldr.ResolveABIAlias(r.Sym())
+	var rr loader.ExtReloc
+	switch r.Type() {
+	case objabi.R_CALLARM:
+		// set up addend for eventual relocation via outer symbol.
+		rs, off := ld.FoldSubSymbolOffset(ldr, rs)
+		rr.Xadd = int64(signext24(r.Add()&0xffffff))*4 + off
+		rst := ldr.SymType(rs)
+		if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
+			ldr.Errorf(s, "missing section for %s", ldr.SymName(rs))
+		}
+		rr.Xsym = rs
+		return rr, true
+	}
+	return rr, false
+}
+
 func addpltreloc(ldr *loader.Loader, plt *loader.SymbolBuilder, got *loader.SymbolBuilder, s loader.Sym, typ objabi.RelocType) {
 	r, _ := plt.AddRel(typ)
 	r.SetSym(got.Sym())

src/cmd/link/internal/arm/obj.go

@@ -52,6 +52,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Archinit:         archinit,
 		Archreloc:        archreloc,
 		Archrelocvariant: archrelocvariant,
+		Extreloc:         extreloc,
 		Trampoline:       trampoline,
 		Elfreloc1:        elfreloc1,
 		ElfrelocSize:     8,

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

@@ -517,17 +517,24 @@ func (f *peFile) emitRelocations(ctxt *Link) {
 			if ldr.SymValue(s) >= int64(eaddr) {
 				break
 			}
-			relocs := ldr.ExtRelocs(s)
+			// Compute external relocations on the go, and pass to PEreloc1
+			// to stream out.
+			relocs := ldr.Relocs(s)
 			for ri := 0; ri < relocs.Count(); ri++ {
-				r := relocs.At(ri)
+				r := relocs.At2(ri)
-				if r.Xsym == 0 {
+				rr, ok := extreloc(ctxt, ldr, s, r, ri)
+				if !ok {
+					continue
+				}
+				if rr.Xsym == 0 {
 					ctxt.Errorf(s, "missing xsym in relocation")
 					continue
 				}
-				if ldr.SymDynid(r.Xsym) < 0 {
+				if ldr.SymDynid(rr.Xsym) < 0 {
-					ctxt.Errorf(s, "reloc %d to non-coff symbol %s (outer=%s) %d", r.Type(), ldr.SymName(r.Sym()), ldr.SymName(r.Xsym), ldr.SymType(r.Sym()))
+					ctxt.Errorf(s, "reloc %d to non-coff symbol %s (outer=%s) %d", r.Type(), ldr.SymName(r.Sym()), ldr.SymName(rr.Xsym), ldr.SymType(r.Sym()))
 				}
-				if !thearch.PEreloc1(ctxt.Arch, ctxt.Out, ldr, s, r, int64(uint64(ldr.SymValue(s)+int64(r.Off()))-base)) {
+				rv := loader.ExtRelocView{Reloc2: r, ExtReloc: rr}
+				if !thearch.PEreloc1(ctxt.Arch, ctxt.Out, ldr, s, rv, int64(uint64(ldr.SymValue(s)+int64(r.Off()))-base)) {
 					ctxt.Errorf(s, "unsupported obj reloc %d/%d to %s", r.Type(), r.Siz(), ldr.SymName(r.Sym()))
 				}
 				nrelocs++

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

@@ -184,6 +184,6 @@ func (t *Target) IsBigEndian() bool {
 
 // Temporary helper.
 func (t *Target) StreamExtRelocs() bool {
-	return (t.IsELF || t.IsDarwin()) &&
+	return (t.IsELF || t.IsDarwin() || t.IsWindows()) &&
-		(t.IsAMD64() || t.Is386() || t.IsARM64() || t.IsMIPS() || t.IsMIPS64() || t.IsS390X())
+		(t.IsAMD64() || t.Is386() || t.IsARM() || t.IsARM64() || t.IsMIPS() || t.IsMIPS64() || t.IsS390X())
 }