cmd/link/internal/ld: remove R_ADDR relocations inside XCOFF text sections

On XCOFF, it is forbidden relocation of a DATA pointer to a text
section. It happens when a RODATA symbol needs a DATA symbol's address.
This commit moves every RODATA symbols with a R_ADDR on a data symbol to
.data sections to avoid these relocations.

Change-Id: I7f34d8e0ebdc8352a74e6b40e4c893d8d9419f4d
Reviewed-on: https://go-review.googlesource.com/c/146977Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -318,8 +318,7 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
 			// must be done by the loader, as the section .data will be moved.
 			// The "default" symbol address is still needed by the loader so
 			// the current relocation can't be skipped.
-			// runtime.algarray is different because it will end up in .rodata section
-			if ctxt.HeadType == objabi.Haix && r.Sym.Sect.Seg == &Segdata && r.Sym.Name != "runtime.algarray" {
+			if ctxt.HeadType == objabi.Haix && r.Sym.Sect.Seg == &Segdata {
 				// It's not possible to make a loader relocation to a DWARF section.
 				// FIXME
 				if s.Sect.Seg != &Segdwarf {

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

@@ -878,6 +878,38 @@ func (ctxt *Link) doxcoff() {
 	toc := ctxt.Syms.Lookup("TOC", 0)
 	toc.Type = sym.SXCOFFTOC
 	toc.Attr |= sym.AttrReachable
+
+	// XCOFF does not allow relocations of data symbol address to a text symbol.
+	// Such case occurs when a RODATA symbol retrieves a data symbol address.
+	// When it happens, this RODATA symbol is moved to .data section.
+	// runtime.algarray is a readonly symbol but stored inside .data section.
+	// If it stays in .data, all type symbols will be moved to .data which
+	// cannot be done.
+	algarray := ctxt.Syms.Lookup("runtime.algarray", 0)
+	algarray.Type = sym.SRODATA
+	for {
+		again := false
+		for _, s := range ctxt.Syms.Allsym {
+			if s.Type != sym.SRODATA {
+				continue
+			}
+			for ri := range s.R {
+				r := &s.R[ri]
+				if r.Type != objabi.R_ADDR {
+					continue
+				}
+				if r.Sym.Type != sym.Sxxx && r.Sym.Type != sym.STEXT && r.Sym.Type != sym.SRODATA {
+					s.Type = sym.SDATA
+					again = true
+					break
+				}
+			}
+
+		}
+		if !again {
+			break
+		}
+	}
 }
 
 // Loader section

src/runtime/alg.go

@@ -301,6 +301,10 @@ func alginit() {
 }
 
 func initAlgAES() {
+	if GOOS == "aix" {
+		// runtime.algarray is immutable on AIX: see cmd/link/internal/ld/xcoff.go
+		return
+	}
 	useAeshash = true
 	algarray[alg_MEM32].hash = aeshash32
 	algarray[alg_MEM64].hash = aeshash64