cmd/link: fix XCOFF sections

XCOFF files can't have multiples text or data sections. The name
of each type section must be .text, .data and .bss.

This commit also updates cmd/internal/objfile/xcoff.go to retrieve Go
sections using runtime symbols.

Change-Id: Ib6315f19dad2d154a4531fc6508e7cbd8bc94743
Reviewed-on: https://go-review.googlesource.com/c/151037
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/objfile/xcoff.go

@@ -91,15 +91,11 @@ func (f *xcoffFile) pcln() (textStart uint64, symtab, pclntab []byte, err error)
 	if sect := f.xcoff.Section(".text"); sect != nil {
 		textStart = sect.VirtualAddress
 	}
-	if sect := f.xcoff.Section(".gosymtab"); sect != nil {
-		if symtab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
-		}
+	if pclntab, err = loadXCOFFTable(f.xcoff, "runtime.pclntab", "runtime.epclntab"); err != nil {
+		return 0, nil, nil, err
 	}
-	if sect := f.xcoff.Section(".gopclntab"); sect != nil {
-		if pclntab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
-		}
+	if symtab, err = loadXCOFFTable(f.xcoff, "runtime.symtab", "runtime.esymtab"); err != nil {
+		return 0, nil, nil, err
 	}
 	return textStart, symtab, pclntab, nil
 }
@@ -114,6 +110,42 @@ func (f *xcoffFile) text() (textStart uint64, text []byte, err error) {
 	return
 }
 
+func findXCOFFSymbol(f *xcoff.File, name string) (*xcoff.Symbol, error) {
+	for _, s := range f.Symbols {
+		if s.Name != name {
+			continue
+		}
+		if s.SectionNumber <= 0 {
+			return nil, fmt.Errorf("symbol %s: invalid section number %d", name, s.SectionNumber)
+		}
+		if len(f.Sections) < int(s.SectionNumber) {
+			return nil, fmt.Errorf("symbol %s: section number %d is larger than max %d", name, s.SectionNumber, len(f.Sections))
+		}
+		return s, nil
+	}
+	return nil, fmt.Errorf("no %s symbol found", name)
+}
+
+func loadXCOFFTable(f *xcoff.File, sname, ename string) ([]byte, error) {
+	ssym, err := findXCOFFSymbol(f, sname)
+	if err != nil {
+		return nil, err
+	}
+	esym, err := findXCOFFSymbol(f, ename)
+	if err != nil {
+		return nil, err
+	}
+	if ssym.SectionNumber != esym.SectionNumber {
+		return nil, fmt.Errorf("%s and %s symbols must be in the same section", sname, ename)
+	}
+	sect := f.Sections[ssym.SectionNumber-1]
+	data, err := sect.Data()
+	if err != nil {
+		return nil, err
+	}
+	return data[ssym.Value:esym.Value], nil
+}
+
 func (f *xcoffFile) goarch() string {
 	switch f.xcoff.TargetMachine {
 	case xcoff.U802TOCMAGIC:

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

@@ -1708,10 +1708,6 @@ func (ctxt *Link) dodata() {
 	}
 	for _, sect := range Segdata.Sections {
 		sect.Extnum = int16(n)
-		if ctxt.HeadType == objabi.Haix && (sect.Name == ".noptrdata" || sect.Name == ".bss") {
-			// On AIX, "noptr" sections are merged with their "ptr" section
-			continue
-		}
 		n++
 	}
 	for _, sect := range Segdwarf.Sections {

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

@@ -953,13 +953,6 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
 	ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
 
-	loadersize := uint64(0)
-	if ctxt.HeadType == objabi.Haix && ctxt.BuildMode == ld.BuildModeExe {
-		loadero := uint64(ld.Rnd(int64(ld.Segdwarf.Fileoff+ld.Segdwarf.Filelen), int64(*ld.FlagRound)))
-		ctxt.Out.SeekSet(int64(loadero))
-		loadersize = ld.Loaderblk(ctxt, loadero)
-	}
-
 	/* output symbol table */
 	ld.Symsize = 0
 
@@ -981,14 +974,7 @@ func asmb(ctxt *ld.Link) {
 			symo = uint32(ld.Segdata.Fileoff + ld.Segdata.Filelen)
 
 		case objabi.Haix:
-			symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
-
-			// Add loader size if needed
-			if ctxt.BuildMode == ld.BuildModeExe {
-				symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
-				symo += uint32(loadersize)
-			}
-			symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
+			// Nothing to do
 		}
 
 		ctxt.Out.SeekSet(int64(symo))
@@ -1019,7 +1005,7 @@ func asmb(ctxt *ld.Link) {
 			}
 
 		case objabi.Haix:
-			ld.Asmaixsym(ctxt)
+			// symtab must be added once sections have been created in ld.Asmbxcoff
 			ctxt.Out.Flush()
 		}
 	}
@@ -1048,7 +1034,9 @@ func asmb(ctxt *ld.Link) {
 		ld.Asmbelf(ctxt, int64(symo))
 
 	case objabi.Haix:
-		ld.Asmbxcoff(ctxt)
+		fileoff := uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
+		fileoff = uint32(ld.Rnd(int64(fileoff), int64(*ld.FlagRound)))
+		ld.Asmbxcoff(ctxt, int64(fileoff))
 	}
 
 	ctxt.Out.Flush()