cmd/internal/objabi,cmd/link: initial linker support for riscv64

Provide initial linker support for riscv64.

Based on riscv-go port.

Updates #27532

Change-Id: I8a881ce41cd49efef0358bad9171d4d18aaf7ab2
Reviewed-on: https://go-review.googlesource.com/c/go/+/204624
Run-TryBot: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/dist/buildtool.go

@@ -82,6 +82,7 @@ var bootstrapDirs = []string{
 	"cmd/link/internal/mips64",
 	"cmd/link/internal/objfile",
 	"cmd/link/internal/ppc64",
+	"cmd/link/internal/riscv64",
 	"cmd/link/internal/s390x",
 	"cmd/link/internal/sym",
 	"cmd/link/internal/x86",

src/cmd/internal/objabi/reloctype.go

@@ -64,6 +64,8 @@ const (
 	// R_CALLMIPS (only used on mips64) resolves to non-PC-relative target address
 	// of a CALL (JAL) instruction, by encoding the address into the instruction.
 	R_CALLMIPS
+	// R_CALLRISCV marks RISC-V CALLs for stack checking.
+	R_CALLRISCV
 	R_CONST
 	R_PCREL
 	// R_TLS_LE, used on 386, amd64, and ARM, resolves to the offset of the
@@ -200,6 +202,16 @@ const (
 	// relocated symbol rather than the symbol's address.
 	R_ADDRPOWER_TOCREL_DS
 
+	// RISC-V.
+
+	// R_RISCV_PCREL_ITYPE resolves a 32-bit PC-relative address using an
+	// AUIPC + I-type instruction pair.
+	R_RISCV_PCREL_ITYPE
+
+	// R_RISCV_PCREL_STYPE resolves a 32-bit PC-relative address using an
+	// AUIPC + S-type instruction pair.
+	R_RISCV_PCREL_STYPE
+
 	// R_PCRELDBL relocates s390x 2-byte aligned PC-relative addresses.
 	// TODO(mundaym): remove once variants can be serialized - see issue 14218.
 	R_PCRELDBL
@@ -210,6 +222,7 @@ const (
 	// R_ADDRMIPSTLS (only used on mips64) resolves to the low 16 bits of a TLS
 	// address (offset from thread pointer), by encoding it into the instruction.
 	R_ADDRMIPSTLS
+
 	// R_ADDRCUOFF resolves to a pointer-sized offset from the start of the
 	// symbol's DWARF compile unit.
 	R_ADDRCUOFF
@@ -230,7 +243,7 @@ const (
 // the target address in register or memory.
 func (r RelocType) IsDirectCall() bool {
 	switch r {
-	case R_CALL, R_CALLARM, R_CALLARM64, R_CALLMIPS, R_CALLPOWER:
+	case R_CALL, R_CALLARM, R_CALLARM64, R_CALLMIPS, R_CALLPOWER, R_CALLRISCV:
 		return true
 	}
 	return false

src/cmd/internal/objabi/reloctype_string.go

@@ -4,9 +4,9 @@ package objabi
 
 import "strconv"
 
-const _RelocType_name = "R_ADDRR_ADDRPOWERR_ADDRARM64R_ADDRMIPSR_ADDROFFR_WEAKADDROFFR_SIZER_CALLR_CALLARMR_CALLARM64R_CALLINDR_CALLPOWERR_CALLMIPSR_CONSTR_PCRELR_TLS_LER_TLS_IER_GOTOFFR_PLT0R_PLT1R_PLT2R_USEFIELDR_USETYPER_METHODOFFR_POWER_TOCR_GOTPCRELR_JMPMIPSR_DWARFSECREFR_DWARFFILEREFR_ARM64_TLS_LER_ARM64_TLS_IER_ARM64_GOTPCRELR_ARM64_GOTR_ARM64_PCRELR_ARM64_LDST8R_ARM64_LDST32R_ARM64_LDST64R_ARM64_LDST128R_POWER_TLS_LER_POWER_TLS_IER_POWER_TLSR_ADDRPOWER_DSR_ADDRPOWER_GOTR_ADDRPOWER_PCRELR_ADDRPOWER_TOCRELR_ADDRPOWER_TOCREL_DSR_PCRELDBLR_ADDRMIPSUR_ADDRMIPSTLSR_ADDRCUOFFR_WASMIMPORTR_XCOFFREF"
+const _RelocType_name = "R_ADDRR_ADDRPOWERR_ADDRARM64R_ADDRMIPSR_ADDROFFR_WEAKADDROFFR_SIZER_CALLR_CALLARMR_CALLARM64R_CALLINDR_CALLPOWERR_CALLMIPSR_CALLRISCVR_CONSTR_PCRELR_TLS_LER_TLS_IER_GOTOFFR_PLT0R_PLT1R_PLT2R_USEFIELDR_USETYPER_METHODOFFR_POWER_TOCR_GOTPCRELR_JMPMIPSR_DWARFSECREFR_DWARFFILEREFR_ARM64_TLS_LER_ARM64_TLS_IER_ARM64_GOTPCRELR_ARM64_GOTR_ARM64_PCRELR_ARM64_LDST8R_ARM64_LDST32R_ARM64_LDST64R_ARM64_LDST128R_POWER_TLS_LER_POWER_TLS_IER_POWER_TLSR_ADDRPOWER_DSR_ADDRPOWER_GOTR_ADDRPOWER_PCRELR_ADDRPOWER_TOCRELR_ADDRPOWER_TOCREL_DSR_RISCV_PCREL_ITYPER_RISCV_PCREL_STYPER_PCRELDBLR_ADDRMIPSUR_ADDRMIPSTLSR_ADDRCUOFFR_WASMIMPORTR_XCOFFREF"
 
-var _RelocType_index = [...]uint16{0, 6, 17, 28, 38, 47, 60, 66, 72, 81, 92, 101, 112, 122, 129, 136, 144, 152, 160, 166, 172, 178, 188, 197, 208, 219, 229, 238, 251, 265, 279, 293, 309, 320, 333, 346, 360, 374, 389, 403, 417, 428, 442, 457, 474, 492, 513, 523, 534, 547, 558, 570, 580}
+var _RelocType_index = [...]uint16{0, 6, 17, 28, 38, 47, 60, 66, 72, 81, 92, 101, 112, 122, 133, 140, 147, 155, 163, 171, 177, 183, 189, 199, 208, 219, 230, 240, 249, 262, 276, 290, 304, 320, 331, 344, 357, 371, 385, 400, 414, 428, 439, 453, 468, 485, 503, 524, 543, 562, 572, 583, 596, 607, 619, 629}
 
 func (i RelocType) String() string {
 	i -= 1

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

@@ -258,7 +258,10 @@ func determineLinkMode(ctxt *Link) {
 			Exitf("internal linking requested %sbut external linking required: %s", via, extReason)
 		}
 	case LinkExternal:
-		if objabi.GOARCH == "ppc64" && objabi.GOOS != "aix" {
+		switch {
+		case objabi.GOARCH == "riscv64":
+			Exitf("external linking not supported for %s/riscv64", objabi.GOOS)
+		case objabi.GOARCH == "ppc64" && objabi.GOOS != "aix":
 			Exitf("external linking not supported for %s/ppc64", objabi.GOOS)
 		}
 	}

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

@@ -176,6 +176,7 @@ const (
 	EM_MIPS_RS4_BE       = 10
 	EM_ALPHA_STD         = 41
 	EM_ALPHA             = 0x9026
+	EM_RISCV             = 243
 	SHN_UNDEF            = 0
 	SHN_LORESERVE        = 0xff00
 	SHN_LOPROC           = 0xff00
@@ -485,7 +486,7 @@ var buildinfo []byte
 func Elfinit(ctxt *Link) {
 	ctxt.IsELF = true
 
-	if ctxt.Arch.InFamily(sys.AMD64, sys.ARM64, sys.MIPS64, sys.PPC64, sys.S390X) {
+	if ctxt.Arch.InFamily(sys.AMD64, sys.ARM64, sys.MIPS64, sys.PPC64, sys.RISCV64, sys.S390X) {
 		elfRelType = ".rela"
 	} else {
 		elfRelType = ".rel"
@@ -500,7 +501,7 @@ func Elfinit(ctxt *Link) {
 			ehdr.flags = 2 /* Version 2 ABI */
 		}
 		fallthrough
-	case sys.AMD64, sys.ARM64, sys.MIPS64:
+	case sys.AMD64, sys.ARM64, sys.MIPS64, sys.RISCV64:
 		if ctxt.Arch.Family == sys.MIPS64 {
 			ehdr.flags = 0x20000004 /* MIPS 3 CPIC */
 		}
@@ -1758,6 +1759,8 @@ func Asmbelf(ctxt *Link, symo int64) {
 		eh.machine = EM_386
 	case sys.PPC64:
 		eh.machine = EM_PPC64
+	case sys.RISCV64:
+		eh.machine = EM_RISCV
 	case sys.S390X:
 		eh.machine = EM_S390
 	}

src/cmd/link/internal/riscv64/asm.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"cmd/link/internal/ld"
+	"cmd/link/internal/sym"
+	"fmt"
+	"log"
+)
+
+func gentext(ctxt *ld.Link) {
+}
+
+func adddynrela(ctxt *ld.Link, rel *sym.Symbol, s *sym.Symbol, r *sym.Reloc) {
+	log.Fatalf("adddynrela not implemented")
+}
+
+func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
+	log.Fatalf("adddynrel not implemented")
+	return false
+}
+
+func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
+	log.Fatalf("elfreloc1")
+	return false
+}
+
+func elfsetupplt(ctxt *ld.Link) {
+	log.Fatalf("elfsetuplt")
+}
+
+func machoreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
+	log.Fatalf("machoreloc1 not implemented")
+	return false
+}
+
+func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bool) {
+	// TODO(jsing): Implement.
+	log.Fatalf("archreloc not implemented")
+	return val, false
+}
+
+func archrelocvariant(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, t int64) int64 {
+	log.Fatalf("archrelocvariant")
+	return -1
+}
+
+func asmb(ctxt *ld.Link) {
+	if ctxt.IsELF {
+		ld.Asmbelfsetup()
+	}
+
+	sect := ld.Segtext.Sections[0]
+	ctxt.Out.SeekSet(int64(sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff))
+	ld.Codeblk(ctxt, int64(sect.Vaddr), int64(sect.Length))
+	for _, sect = range ld.Segtext.Sections[1:] {
+		ctxt.Out.SeekSet(int64(sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff))
+		ld.Datblk(ctxt, int64(sect.Vaddr), int64(sect.Length))
+	}
+
+	if ld.Segrodata.Filelen > 0 {
+		ctxt.Out.SeekSet(int64(ld.Segrodata.Fileoff))
+		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
+	}
+	if ld.Segrelrodata.Filelen > 0 {
+		ctxt.Out.SeekSet(int64(ld.Segrelrodata.Fileoff))
+		ld.Datblk(ctxt, int64(ld.Segrelrodata.Vaddr), int64(ld.Segrelrodata.Filelen))
+	}
+
+	ctxt.Out.SeekSet(int64(ld.Segdata.Fileoff))
+	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
+
+	ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
+	ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+
+func asmb2(ctxt *ld.Link) {
+	ld.Symsize = 0
+	ld.Lcsize = 0
+	symo := uint32(0)
+
+	if !*ld.FlagS {
+		if !ctxt.IsELF {
+			ld.Errorf(nil, "unsupported executable format")
+		}
+
+		symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
+		symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
+		ctxt.Out.SeekSet(int64(symo))
+
+		ld.Asmelfsym(ctxt)
+		ctxt.Out.Flush()
+		ctxt.Out.Write(ld.Elfstrdat)
+
+		if ctxt.LinkMode == ld.LinkExternal {
+			ld.Elfemitreloc(ctxt)
+		}
+	}
+
+	ctxt.Out.SeekSet(0)
+	switch ctxt.HeadType {
+	case objabi.Hlinux:
+		ld.Asmbelf(ctxt, int64(symo))
+	default:
+		ld.Errorf(nil, "unsupported operating system")
+	}
+	ctxt.Out.Flush()
+
+	if *ld.FlagC {
+		fmt.Printf("textsize=%d\n", ld.Segtext.Filelen)
+		fmt.Printf("datsize=%d\n", ld.Segdata.Filelen)
+		fmt.Printf("bsssize=%d\n", ld.Segdata.Length-ld.Segdata.Filelen)
+		fmt.Printf("symsize=%d\n", ld.Symsize)
+		fmt.Printf("lcsize=%d\n", ld.Lcsize)
+		fmt.Printf("total=%d\n", ld.Segtext.Filelen+ld.Segdata.Length+uint64(ld.Symsize)+uint64(ld.Lcsize))
+	}
+}

src/cmd/link/internal/riscv64/l.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+const (
+	maxAlign  = 32 // max data alignment
+	minAlign  = 1
+	funcAlign = 8
+
+	dwarfRegLR = 1
+	dwarfRegSP = 2
+)

src/cmd/link/internal/riscv64/obj.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package riscv64
+
+import (
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"cmd/link/internal/ld"
+)
+
+func Init() (*sys.Arch, ld.Arch) {
+	arch := sys.ArchRISCV64
+
+	theArch := ld.Arch{
+		Funcalign:  funcAlign,
+		Maxalign:   maxAlign,
+		Minalign:   minAlign,
+		Dwarfregsp: dwarfRegSP,
+		Dwarfreglr: dwarfRegLR,
+
+		Adddynrel:        adddynrel,
+		Archinit:         archinit,
+		Archreloc:        archreloc,
+		Archrelocvariant: archrelocvariant,
+		Asmb:             asmb,
+		Asmb2:            asmb2,
+		Elfreloc1:        elfreloc1,
+		Elfsetupplt:      elfsetupplt,
+		Gentext:          gentext,
+		Machoreloc1:      machoreloc1,
+
+		Linuxdynld: "/lib/ld.so.1",
+
+		Freebsddynld:   "XXX",
+		Netbsddynld:    "XXX",
+		Openbsddynld:   "XXX",
+		Dragonflydynld: "XXX",
+		Solarisdynld:   "XXX",
+	}
+
+	return arch, theArch
+}
+
+func archinit(ctxt *ld.Link) {
+	switch ctxt.HeadType {
+	case objabi.Hlinux:
+		ld.Elfinit(ctxt)
+		ld.HEADR = ld.ELFRESERVE
+		if *ld.FlagTextAddr == -1 {
+			*ld.FlagTextAddr = 0x10000 + int64(ld.HEADR)
+		}
+		if *ld.FlagRound == -1 {
+			*ld.FlagRound = 0x10000
+		}
+	default:
+		ld.Exitf("unknown -H option: %v", ctxt.HeadType)
+	}
+}

src/cmd/link/main.go

@@ -14,6 +14,7 @@ import (
 	"cmd/link/internal/mips"
 	"cmd/link/internal/mips64"
 	"cmd/link/internal/ppc64"
+	"cmd/link/internal/riscv64"
 	"cmd/link/internal/s390x"
 	"cmd/link/internal/wasm"
 	"cmd/link/internal/x86"
@@ -57,6 +58,8 @@ func main() {
 		arch, theArch = mips64.Init()
 	case "ppc64", "ppc64le":
 		arch, theArch = ppc64.Init()
+	case "riscv64":
+		arch, theArch = riscv64.Init()
 	case "s390x":
 		arch, theArch = s390x.Init()
 	case "wasm":