cmd/link: set correct sizes for XCOFF outer symbols

This commit fixes the size of outer symbols like type.*.
Outer symbols cannot have a nil size on AIX or they will be
removed by ld as long as all their sub-symbols.

Change-Id: I68ff3ce5a3a034e3c3eb23431aba31245073cf20
Reviewed-on: https://go-review.googlesource.com/c/163999
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -1475,6 +1475,7 @@ func (ctxt *Link) dodata() {
 	}
 	datsize = Rnd(datsize, int64(sect.Align))
 	for _, symn := range sym.ReadOnly {
+		symnStartValue := datsize
 		for _, s := range data[symn] {
 			datsize = aligndatsize(datsize, s)
 			s.Sect = sect
@@ -1483,6 +1484,13 @@ func (ctxt *Link) dodata() {
 			datsize += s.Size
 		}
 		checkdatsize(ctxt, datsize, symn)
+		if ctxt.HeadType == objabi.Haix {
+			// Read-only symbols might be wrapped inside their outer
+			// symbol.
+			// XCOFF symbol table needs to know the size of
+			// these outer symbols.
+			xcoffUpdateOuterSize(ctxt, datsize-symnStartValue, symn)
+		}
 	}
 	sect.Length = uint64(datsize) - sect.Vaddr
 
@@ -1557,6 +1565,7 @@ func (ctxt *Link) dodata() {
 		datsize = Rnd(datsize, int64(sect.Align))
 		for _, symnro := range sym.ReadOnly {
 			symn := sym.RelROMap[symnro]
+			symnStartValue := datsize
 			for _, s := range data[symn] {
 				datsize = aligndatsize(datsize, s)
 				if s.Outer != nil && s.Outer.Sect != nil && s.Outer.Sect != sect {
@@ -1568,6 +1577,13 @@ func (ctxt *Link) dodata() {
 				datsize += s.Size
 			}
 			checkdatsize(ctxt, datsize, symn)
+			if ctxt.HeadType == objabi.Haix {
+				// Read-only symbols might be wrapped inside their outer
+				// symbol.
+				// XCOFF symbol table needs to know the size of
+				// these outer symbols.
+				xcoffUpdateOuterSize(ctxt, datsize-symnStartValue, symn)
+			}
 		}
 
 		sect.Length = uint64(datsize) - sect.Vaddr
@@ -1601,6 +1617,11 @@ func (ctxt *Link) dodata() {
 	}
 	checkdatsize(ctxt, datsize, sym.SITABLINK)
 	sect.Length = uint64(datsize) - sect.Vaddr
+	if ctxt.HeadType == objabi.Haix {
+		// Store .itablink size because its symbols are wrapped
+		// under an outer symbol: runtime.itablink.
+		xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SITABLINK)
+	}
 
 	/* gosymtab */
 	sect = addrelrosection(".gosymtab")

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

@@ -529,8 +529,48 @@ type xcoffSymSrcFile struct {
 var (
 	currDwscnoff   = make(map[string]uint64) // Needed to create C_DWARF symbols
 	currSymSrcFile xcoffSymSrcFile
+	outerSymSize   = make(map[string]int64)
 )
 
+// xcoffUpdateOuterSize stores the size of outer symbols in order to have it
+// in the symbol table.
+func xcoffUpdateOuterSize(ctxt *Link, size int64, stype sym.SymKind) {
+	if size == 0 {
+		return
+	}
+
+	switch stype {
+	default:
+		Errorf(nil, "unknown XCOFF outer symbol for type %s", stype.String())
+	case sym.SRODATA, sym.SRODATARELRO, sym.SFUNCTAB, sym.SSTRING:
+		// Nothing to do
+	case sym.STYPERELRO:
+		if ctxt.UseRelro() && (ctxt.BuildMode == BuildModeCArchive || ctxt.BuildMode == BuildModeCShared || ctxt.BuildMode == BuildModePIE) {
+			outerSymSize["typerel.*"] = size
+			return
+		}
+		fallthrough
+	case sym.STYPE:
+		if !ctxt.DynlinkingGo() {
+			outerSymSize["type.*"] = size
+		}
+	case sym.SGOSTRING:
+		outerSymSize["go.string.*"] = size
+	case sym.SGOFUNC:
+		if !ctxt.DynlinkingGo() {
+			outerSymSize["go.func.*"] = size
+		}
+	case sym.SGOFUNCRELRO:
+		outerSymSize["go.funcrel.*"] = size
+	case sym.SGCBITS:
+		outerSymSize["runtime.gcbits.*"] = size
+	case sym.SITABLINK:
+		outerSymSize["runtime.itablink"] = size
+
+	}
+
+}
+
 // addSymbol writes a symbol or an auxiliary symbol entry on ctxt.out.
 func (f *xcoffFile) addSymbol(sym xcoffSym) {
 	f.symtabSym = append(f.symtabSym, sym)
@@ -888,6 +928,17 @@ func putaixsym(ctxt *Link, x *sym.Symbol, str string, t SymbolType, addr int64,
 // It will be written in out file in Asmbxcoff, because it must be
 // at the very end, especially after relocation sections which needs symbols' index.
 func (f *xcoffFile) asmaixsym(ctxt *Link) {
+	// Get correct size for symbols wrapping others symbols like go.string.*
+	// sym.Size can be used directly as the symbols have already been written.
+	for name, size := range outerSymSize {
+		sym := ctxt.Syms.ROLookup(name, 0)
+		if sym == nil {
+			Errorf(nil, "unknown outer symbol with name %s", name)
+		} else {
+			sym.Size = size
+		}
+	}
+
 	genasmsym(ctxt, putaixsym)
 	xfile.updatePreviousFile(ctxt, true)
 }