cmd/link, runtime: allow external linking for aix/ppc64

This commit adds external linking in cmd/link for aix/ppc64.
As relocations on .text data aren't possible on AIX, Segrelrodata is
used to move all these datas to .data section.

Change-Id: I4d1361c1fc9290e11e6f5560864460c76551dbeb
Reviewed-on: https://go-review.googlesource.com/c/go/+/164003
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -247,7 +247,7 @@ func determineLinkMode(ctxt *Link) {
 			}
 			ctxt.LinkMode = LinkInternal
 		case "1":
-			if objabi.GOARCH == "ppc64" {
+			if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" {
 				Exitf("external linking requested via GO_EXTLINK_ENABLED but not supported for %s/ppc64", objabi.GOOS)
 			}
 			ctxt.LinkMode = LinkExternal
@@ -261,7 +261,7 @@ func determineLinkMode(ctxt *Link) {
 			} else {
 				ctxt.LinkMode = LinkInternal
 			}
-			if objabi.GOARCH == "ppc64" && ctxt.LinkMode == LinkExternal {
+			if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" && ctxt.LinkMode == LinkExternal {
 				Exitf("external linking is not supported for %s/ppc64", objabi.GOOS)
 			}
 		}
@@ -270,7 +270,7 @@ func determineLinkMode(ctxt *Link) {
 			Exitf("internal linking requested but external linking required: %s", reason)
 		}
 	case LinkExternal:
-		if objabi.GOARCH == "ppc64" {
+		if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" {
 			Exitf("external linking not supported for %s/ppc64", objabi.GOOS)
 		}
 	}

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

@@ -308,6 +308,8 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
 					}
 				} else if ctxt.HeadType == objabi.Hwindows {
 					// nothing to do
+				} else if ctxt.HeadType == objabi.Haix {
+					o = Symaddr(r.Sym) + r.Add
 				} else {
 					Errorf(s, "unhandled pcrel relocation to %s on %v", rs.Name, ctxt.HeadType)
 				}
@@ -1400,7 +1402,7 @@ func (ctxt *Link) dodata() {
 
 	if len(data[sym.STLSBSS]) > 0 {
 		var sect *sym.Section
-		if ctxt.IsELF && (ctxt.LinkMode == LinkExternal || !*FlagD) {
+		if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && (ctxt.LinkMode == LinkExternal || !*FlagD) {
 			sect = addsection(ctxt.Arch, &Segdata, ".tbss", 06)
 			sect.Align = int32(ctxt.Arch.PtrSize)
 			sect.Vaddr = 0
@@ -1538,7 +1540,7 @@ func (ctxt *Link) dodata() {
 	if ctxt.UseRelro() {
 		addrelrosection = func(suffix string) *sym.Section {
 			seg := &Segrelrodata
-			if ctxt.LinkMode == LinkExternal {
+			if ctxt.LinkMode == LinkExternal && ctxt.HeadType != objabi.Haix {
 				// Using a separate segment with an external
 				// linker results in some programs moving
 				// their data sections unexpectedly, which
@@ -2046,6 +2048,10 @@ func (ctxt *Link) address() []*sym.Segment {
 		// align to page boundary so as not to mix
 		// rodata, rel-ro data, and executable text.
 		va = uint64(Rnd(int64(va), int64(*FlagRound)))
+		if ctxt.HeadType == objabi.Haix {
+			// Relro data are inside data segment on AIX.
+			va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
+		}
 
 		order = append(order, &Segrelrodata)
 		Segrelrodata.Rwx = 06
@@ -2060,9 +2066,10 @@ func (ctxt *Link) address() []*sym.Segment {
 	}
 
 	va = uint64(Rnd(int64(va), int64(*FlagRound)))
-	if ctxt.HeadType == objabi.Haix {
+	if ctxt.HeadType == objabi.Haix && len(Segrelrodata.Sections) == 0 {
 		// Data sections are moved to an unreachable segment
 		// to ensure that they are position-independent.
+		// Already done if relro sections exist.
 		va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
 	}
 	order = append(order, &Segdata)
@@ -2073,11 +2080,11 @@ func (ctxt *Link) address() []*sym.Segment {
 	var bss *sym.Section
 	var noptrbss *sym.Section
 	for i, s := range Segdata.Sections {
-		if ctxt.IsELF && s.Name == ".tbss" {
+		if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && s.Name == ".tbss" {
 			continue
 		}
 		vlen := int64(s.Length)
-		if i+1 < len(Segdata.Sections) && !(ctxt.IsELF && Segdata.Sections[i+1].Name == ".tbss") {
+		if i+1 < len(Segdata.Sections) && !((ctxt.IsELF || ctxt.HeadType == objabi.Haix) && Segdata.Sections[i+1].Name == ".tbss") {
 			vlen = int64(Segdata.Sections[i+1].Vaddr - s.Vaddr)
 		}
 		s.Vaddr = va

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

@@ -1683,6 +1683,7 @@ func dwarfEnabled(ctxt *Link) bool {
 	}
 
 	if ctxt.LinkMode == LinkExternal {
+		// TODO(aix): enable DWARF
 		switch {
 		case ctxt.IsELF:
 		case ctxt.HeadType == objabi.Hdarwin:

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

@@ -133,6 +133,7 @@ type Arch struct {
 	Gentext     func(*Link)
 	Machoreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool
 	PEreloc1    func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool
+	Xcoffreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool
 
 	// TLSIEtoLE converts a TLS Initial Executable relocation to
 	// a TLS Local Executable relocation.
@@ -179,7 +180,7 @@ func (ctxt *Link) UseRelro() bool {
 	case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePIE, BuildModePlugin:
 		return ctxt.IsELF
 	default:
-		return ctxt.linkShared
+		return ctxt.linkShared || (ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal)
 	}
 }
 
@@ -405,7 +406,7 @@ func (ctxt *Link) loadlib() {
 		*FlagTextAddr = 0
 	}
 
-	if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 {
+	if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && objabi.GOOS != "aix" {
 		toc := ctxt.Syms.Lookup(".TOC.", 0)
 		toc.Type = sym.SDYNIMPORT
 	}
@@ -1145,6 +1146,11 @@ func (ctxt *Link) hostlink() {
 		} else {
 			argv = append(argv, "-mconsole")
 		}
+	case objabi.Haix:
+		argv = append(argv, "-pthread")
+		// prevent ld to reorder .text functions to keep the same
+		// first/last functions for moduledata.
+		argv = append(argv, "-Wl,-bnoobjreorder")
 	}
 
 	switch ctxt.BuildMode {
@@ -1493,7 +1499,7 @@ func hostlinkArchArgs(arch *sys.Arch) []string {
 	switch arch.Family {
 	case sys.I386:
 		return []string{"-m32"}
-	case sys.AMD64, sys.PPC64, sys.S390X:
+	case sys.AMD64, sys.S390X:
 		return []string{"-m64"}
 	case sys.ARM:
 		return []string{"-marm"}
@@ -1503,6 +1509,13 @@ func hostlinkArchArgs(arch *sys.Arch) []string {
 		return []string{"-mabi=64"}
 	case sys.MIPS:
 		return []string{"-mabi=32"}
+	case sys.PPC64:
+		if objabi.GOOS == "aix" {
+			return []string{"-maix64"}
+		} else {
+			return []string{"-m64"}
+		}
+
 	}
 	return nil
 }

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

@@ -382,6 +382,43 @@ func addelfdynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 	return false
 }
 
+func xcoffreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
+	rs := r.Xsym
+
+	emitReloc := func(v uint16, off uint64) {
+		out.Write64(uint64(sectoff) + off)
+		out.Write32(uint32(rs.Dynid))
+		out.Write16(v)
+	}
+
+	var v uint16
+	switch r.Type {
+	default:
+		return false
+	case objabi.R_ADDR:
+		v = ld.XCOFF_R_POS
+		if r.Siz == 4 {
+			v |= 0x1F << 8
+		} else {
+			v |= 0x3F << 8
+		}
+		emitReloc(v, 0)
+	case objabi.R_ADDRPOWER_TOCREL:
+	case objabi.R_ADDRPOWER_TOCREL_DS:
+		emitReloc(ld.XCOFF_R_TOCU|(0x0F<<8), 2)
+		emitReloc(ld.XCOFF_R_TOCL|(0x0F<<8), 6)
+	case objabi.R_POWER_TLS_LE:
+		emitReloc(ld.XCOFF_R_TLS_LE|0x0F<<8, 2)
+	case objabi.R_CALLPOWER:
+		if r.Siz != 4 {
+			return false
+		}
+		emitReloc(ld.XCOFF_R_RBR|0x19<<8, 0)
+	}
+	return true
+
+}
+
 func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
 	// Beware that bit0~bit15 start from the third byte of a instruction in Big-Endian machines.
 	if r.Type == objabi.R_ADDR || r.Type == objabi.R_POWER_TLS || r.Type == objabi.R_CALLPOWER {
@@ -514,7 +551,7 @@ func archreloctoc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) int64 {
 		ld.Errorf(s, "archreloctoc called for a symbol without TOC anchor")
 	}
 
-	if tarSym != nil && tarSym.Attr.Reachable() && (tarSym.Sect.Seg == &ld.Segdata) {
+	if ctxt.LinkMode == ld.LinkInternal && tarSym != nil && tarSym.Attr.Reachable() && (tarSym.Sect.Seg == &ld.Segdata) {
 		t = ld.Symaddr(tarSym) + r.Add - ctxt.Syms.ROLookup("TOC", 0).Value
 		// change ld to addi in the second instruction
 		o2 = (o2 & 0x03FF0000) | 0xE<<26
@@ -704,9 +741,13 @@ func gentramp(arch *sys.Arch, linkmode ld.LinkMode, tramp, target *sym.Symbol, o
 
 func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bool) {
 	if ctxt.LinkMode == ld.LinkExternal {
+		// On AIX, relocations (except TLS ones) must be also done to the
+		// value with the current addresses.
 		switch r.Type {
 		default:
-			return val, false
+			if ctxt.HeadType != objabi.Haix {
+				return val, false
+			}
 		case objabi.R_POWER_TLS, objabi.R_POWER_TLS_LE, objabi.R_POWER_TLS_IE:
 			r.Done = false
 			// check Outer is nil, Type is TLSBSS?
@@ -734,12 +775,16 @@ func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bo
 			}
 			r.Xsym = rs
 
-			return val, true
+			if ctxt.HeadType != objabi.Haix {
+				return val, true
+			}
 		case objabi.R_CALLPOWER:
 			r.Done = false
 			r.Xsym = r.Sym
 			r.Xadd = r.Add
-			return val, true
+			if ctxt.HeadType != objabi.Haix {
+				return val, true
+			}
 		}
 	}
 

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

@@ -59,6 +59,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		Gentext:          gentext,
 		Trampoline:       trampoline,
 		Machoreloc1:      machoreloc1,
+		Xcoffreloc1:      xcoffreloc1,
 
 		// TODO(austin): ABI v1 uses /usr/lib/ld.so.1,
 		Linuxdynld: "/lib64/ld64.so.1",

src/runtime/asm_ppc64x.s

@@ -784,11 +784,18 @@ TEXT runtime·setg(SB), NOSPLIT, $0-8
 	RET
 
 #ifdef GOARCH_ppc64
+#ifdef GOOS_aix
+DATA    setg_gcc<>+0(SB)/8, $_setg_gcc<>(SB)
+DATA    setg_gcc<>+8(SB)/8, $TOC(SB)
+DATA    setg_gcc<>+16(SB)/8, $0
+GLOBL   setg_gcc<>(SB), NOPTR, $24
+#else
 TEXT setg_gcc<>(SB),NOSPLIT|NOFRAME,$0-0
 	DWORD	$_setg_gcc<>(SB)
 	DWORD	$0
 	DWORD	$0
 #endif
+#endif
 
 // void setg_gcc(G*); set g in C TLS.
 // Must obey the gcc calling convention.

src/runtime/rt0_aix_ppc64.s

@@ -34,6 +34,15 @@ TEXT __start<>(SB),NOSPLIT,$-8
 	MOVD 40(R1), R2
 	MOVD R14, R3 // argc
 	MOVD R15, R4 // argv
+	BL _main(SB)
+
+
+DATA	main+0(SB)/8, $_main(SB)
+DATA	main+8(SB)/8, $TOC(SB)
+DATA	main+16(SB)/8, $0
+GLOBL	main(SB), NOPTR, $24
+
+TEXT _main(SB),NOSPLIT,$-8
 	MOVD $runtime·rt0_go(SB), R12
 	MOVD R12, CTR
 	BR (CTR)