[dev.link] cmd/link: add loader.ExtReloc to Archreloc2

Non functional, but required by the majority of the architectures.

Change-Id: I57601016c28ce665a9d434e283a1db8bded9b133
Reviewed-on: https://go-review.googlesource.com/c/go/+/230858
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

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

@@ -253,7 +253,10 @@ func relocsym(target *Target, ldr *loader.Loader, err *ErrorReporter, syms *Arch
 			case 8:
 				o = int64(target.Arch.ByteOrder.Uint64(P[off:]))
 			}
-			if out, ok := thearch.Archreloc2(target, ldr, syms, &r, s, o); ok {
+			var out int64
+			var ok bool
+			out, needExtReloc, ok = thearch.Archreloc2(target, ldr, syms, &r, &rr, s, o)
+			if ok {
 				o = out
 			} else {
 				err.Errorf(s, "unknown reloc to %v: %d (%s)", ldr.SymName(rs), rt, sym.RelocName(target.Arch, rt))

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

@@ -235,18 +235,18 @@ type Arch struct {
 	Adddynrel      func(*Target, *loader.Loader, *ArchSyms, *sym.Symbol, *sym.Reloc) bool
 	Adddynrel2     func(*Target, *loader.Loader, *ArchSyms, loader.Sym, *loader.Reloc2, int) bool
 	Archinit       func(*Link)
-	// Archreloc is an arch-specific hook that assists in
+	// Archreloc is an arch-specific hook that assists in relocation processing
-	// relocation processing (invoked by 'relocsym'); it handles
+	// (invoked by 'relocsym'); it handles target-specific relocation tasks.
-	// target-specific relocation tasks. Here "rel" is the current
+	// Here "rel" is the current relocation being examined, "sym" is the symbol
-	// relocation being examined, "sym" is the symbol containing the
+	// containing the chunk of data to which the relocation applies, and "off"
-	// chunk of data to which the relocation applies, and "off" is the
+	// is the contents of the to-be-relocated data item (from sym.P). Return
-	// contents of the to-be-relocated data item (from sym.P). Return
+	// value is the appropriately relocated value (to be written back to the
-	// value is the appropriately relocated value (to be written back
+	// same spot in sym.P), a boolean indicating if the external relocations'
-	// to the same spot in sym.P) and a boolean indicating
+	// been used, and a boolean indicating success/failure (a failing value
-	// success/failure (a failing value indicates a fatal error).
+	// indicates a fatal error).
 	Archreloc func(target *Target, syms *ArchSyms, rel *sym.Reloc, sym *sym.Symbol,
 		offset int64) (relocatedOffset int64, success bool)
-	Archreloc2 func(*Target, *loader.Loader, *ArchSyms, *loader.Reloc2, loader.Sym, int64) (int64, bool)
+	Archreloc2 func(*Target, *loader.Loader, *ArchSyms, *loader.Reloc2, *loader.ExtReloc, loader.Sym, int64) (int64, bool, bool)
 	// Archrelocvariant is a second arch-specific hook used for
 	// relocation processing; it handles relocations where r.Type is
 	// insufficient to describe the relocation (r.Variant !=

src/cmd/link/internal/x86/asm.go

@@ -435,8 +435,8 @@ func pereloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, secto
 	return true
 }
 
-func archreloc2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r *loader.Reloc2, sym loader.Sym, val int64) (int64, bool) {
+func archreloc2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r *loader.Reloc2, rr *loader.ExtReloc, sym loader.Sym, val int64) (int64, bool, bool) {
-	return val, false
+	return val, false, false
 }
 
 func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, t int64) int64 {