cmd/internal/obj, cmd/link: generate position independent loads of static data

Change-Id: I0a8448c2b69f5cfa6f099d772f5eb3412f853045
Reviewed-on: https://go-review.googlesource.com/15969Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/internal/obj/link.go

@@ -491,6 +491,16 @@ const (
 	// inserts the displacement from the place being relocated to the address of the
 	// the relocated symbol instead of just its address.
 	R_ADDRPOWER_PCREL
+
+	// R_ADDRPOWER_TOCREL relocates two D-form instructions like R_ADDRPOWER, but
+	// inserts the offset from the TOC to the address of the the relocated symbol
+	// rather than the symbol's address.
+	R_ADDRPOWER_TOCREL
+
+	// R_ADDRPOWER_TOCREL relocates a D-form, DS-form instruction sequence like
+	// R_ADDRPOWER_DS but inserts the offset from the TOC to the address of the the
+	// relocated symbol rather than the symbol's address.
+	R_ADDRPOWER_TOCREL_DS
 )
 
 type Auto struct {

src/cmd/internal/obj/ppc64/asm9.go

@@ -1417,19 +1417,35 @@ func opform(ctxt *obj.Link, insn int32) int {
 // Encode instructions and create relocation for accessing s+d according to the
 // instruction op with source or destination (as appropriate) register reg.
 func symbolAccess(ctxt *obj.Link, s *obj.LSym, d int64, reg int16, op int32) (o1, o2 uint32) {
+	var base uint32
 	form := opform(ctxt, op)
-	o1 = AOP_IRR(OP_ADDIS, REGTMP, REGZERO, 0)
+	if ctxt.Flag_shared != 0 {
+		base = REG_R2
+	} else {
+		base = REG_R0
+	}
+	o1 = AOP_IRR(OP_ADDIS, REGTMP, base, 0)
 	o2 = AOP_IRR(uint32(op), uint32(reg), REGTMP, 0)
 	rel := obj.Addrel(ctxt.Cursym)
 	rel.Off = int32(ctxt.Pc)
 	rel.Siz = 8
 	rel.Sym = s
 	rel.Add = d
-	switch form {
-	case D_FORM:
-		rel.Type = obj.R_ADDRPOWER
-	case DS_FORM:
-		rel.Type = obj.R_ADDRPOWER_DS
+	if ctxt.Flag_shared != 0 {
+		switch form {
+		case D_FORM:
+			rel.Type = obj.R_ADDRPOWER_TOCREL
+		case DS_FORM:
+			rel.Type = obj.R_ADDRPOWER_TOCREL_DS
+		}
+
+	} else {
+		switch form {
+		case D_FORM:
+			rel.Type = obj.R_ADDRPOWER
+		case DS_FORM:
+			rel.Type = obj.R_ADDRPOWER_DS
+		}
 	}
 	return
 }

src/cmd/link/internal/ppc64/asm.go

@@ -332,6 +332,18 @@ func elfreloc1(r *ld.Reloc, sectoff int64) int {
 		ld.Thearch.Vput(ld.R_PPC64_REL16_LO | uint64(elfsym)<<32)
 		r.Xadd += 4
 
+	case obj.R_ADDRPOWER_TOCREL:
+		ld.Thearch.Vput(ld.R_PPC64_TOC16_HA | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_PPC64_TOC16_LO | uint64(elfsym)<<32)
+
+	case obj.R_ADDRPOWER_TOCREL_DS:
+		ld.Thearch.Vput(ld.R_PPC64_TOC16_HA | uint64(elfsym)<<32)
+		ld.Thearch.Vput(uint64(r.Xadd))
+		ld.Thearch.Vput(uint64(sectoff + 4))
+		ld.Thearch.Vput(ld.R_PPC64_TOC16_LO_DS | uint64(elfsym)<<32)
+
 	case obj.R_CALLPOWER:
 		if r.Siz != 4 {
 			return -1
@@ -441,6 +453,8 @@ func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 
 		case obj.R_ADDRPOWER,
 			obj.R_ADDRPOWER_DS,
+			obj.R_ADDRPOWER_TOCREL,
+			obj.R_ADDRPOWER_TOCREL_DS,
 			obj.R_ADDRPOWER_PCREL:
 			r.Done = 0