cmd/link: add windows/arm64 support

This CL is part of a stack adding windows/arm64
support (#36439), intended to land in the Go 1.17 cycle.

Change-Id: I397c1d238bb18cbe78b3fca00910660cf1d66b8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/288822
Trust: Russ Cox <rsc@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>

src/cmd/link/internal/arm64/asm.go

@@ -568,6 +568,40 @@ func machoreloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sy
 	return true
 }
 
+func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym, r loader.ExtReloc, sectoff int64) bool {
+	var v uint32
+
+	rs := r.Xsym
+	rt := r.Type
+
+	if ldr.SymDynid(rs) < 0 {
+		ldr.Errorf(s, "reloc %d (%s) to non-coff symbol %s type=%d (%s)", rt, sym.RelocName(arch, rt), ldr.SymName(rs), ldr.SymType(rs), ldr.SymType(rs))
+		return false
+	}
+
+	out.Write32(uint32(sectoff))
+	out.Write32(uint32(ldr.SymDynid(rs)))
+
+	switch rt {
+	default:
+		return false
+
+	case objabi.R_DWARFSECREF:
+		v = ld.IMAGE_REL_ARM64_SECREL
+
+	case objabi.R_ADDR:
+		if r.Size == 8 {
+			v = ld.IMAGE_REL_ARM64_ADDR64
+		} else {
+			v = ld.IMAGE_REL_ARM64_ADDR32
+		}
+	}
+
+	out.Write16(uint16(v))
+
+	return true
+}
+
 func archreloc(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, r loader.Reloc, s loader.Sym, val int64) (int64, int, bool) {
 	const noExtReloc = 0
 	const isOk = true

src/cmd/link/internal/arm64/obj.go

@@ -58,6 +58,7 @@ func Init() (*sys.Arch, ld.Arch) {
 		GenSymsLate:      gensymlate,
 		Machoreloc1:      machoreloc1,
 		MachorelocSize:   8,
+		PEreloc1:         pereloc1,
 
 		Androiddynld: "/system/bin/linker64",
 		Linuxdynld:   "/lib/ld-linux-aarch64.so.1",
@@ -108,5 +109,9 @@ func archinit(ctxt *ld.Link) {
 		if *ld.FlagRound == -1 {
 			*ld.FlagRound = 16384 // 16K page alignment
 		}
+
+	case objabi.Hwindows: /* PE executable */
+		// ld.HEADR, ld.FlagTextAddr, ld.FlagRound are set in ld.Peinit
+		return
 	}
 }

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

@@ -36,7 +36,7 @@ func (mode *BuildMode) Set(s string) error {
 		return fmt.Errorf("invalid buildmode: %q", s)
 	case "exe":
 		switch objabi.GOOS + "/" + objabi.GOARCH {
-		case "darwin/arm64", "windows/arm": // On these platforms, everything is PIE
+		case "darwin/arm64", "windows/arm", "windows/arm64": // On these platforms, everything is PIE
 			*mode = BuildModePIE
 		default:
 			*mode = BuildModeExe
@@ -65,7 +65,7 @@ func (mode *BuildMode) Set(s string) error {
 			}
 		case "windows":
 			switch objabi.GOARCH {
-			case "amd64", "386", "arm":
+			case "amd64", "386", "arm", "arm64":
 			default:
 				return badmode()
 			}
@@ -220,7 +220,7 @@ func mustLinkExternal(ctxt *Link) (res bool, reason string) {
 	case BuildModePIE:
 		switch objabi.GOOS + "/" + objabi.GOARCH {
 		case "linux/amd64", "linux/arm64", "android/arm64":
-		case "windows/386", "windows/amd64", "windows/arm":
+		case "windows/386", "windows/amd64", "windows/arm", "windows/arm64":
 		case "darwin/amd64", "darwin/arm64":
 		default:
 			// Internal linking does not support TLS_IE.

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

@@ -69,6 +69,7 @@ const (
 	IMAGE_SCN_ALIGN_32BYTES          = 0x600000
 )
 
+// See https://docs.microsoft.com/en-us/windows/win32/debug/pe-format.
 // TODO(crawshaw): add these constants to debug/pe.
 const (
 	// TODO: the Microsoft doco says IMAGE_SYM_DTYPE_ARRAY is 3 and IMAGE_SYM_DTYPE_FUNCTION is 2
@@ -95,6 +96,25 @@ const (
 	IMAGE_REL_ARM_BRANCH11 = 0x0004
 	IMAGE_REL_ARM_SECREL   = 0x000F
 
+	IMAGE_REL_ARM64_ABSOLUTE       = 0x0000
+	IMAGE_REL_ARM64_ADDR32         = 0x0001
+	IMAGE_REL_ARM64_ADDR32NB       = 0x0002
+	IMAGE_REL_ARM64_BRANCH26       = 0x0003
+	IMAGE_REL_ARM64_PAGEBASE_REL21 = 0x0004
+	IMAGE_REL_ARM64_REL21          = 0x0005
+	IMAGE_REL_ARM64_PAGEOFFSET_12A = 0x0006
+	IMAGE_REL_ARM64_PAGEOFFSET_12L = 0x0007
+	IMAGE_REL_ARM64_SECREL         = 0x0008
+	IMAGE_REL_ARM64_SECREL_LOW12A  = 0x0009
+	IMAGE_REL_ARM64_SECREL_HIGH12A = 0x000A
+	IMAGE_REL_ARM64_SECREL_LOW12L  = 0x000B
+	IMAGE_REL_ARM64_TOKEN          = 0x000C
+	IMAGE_REL_ARM64_SECTION        = 0x000D
+	IMAGE_REL_ARM64_ADDR64         = 0x000E
+	IMAGE_REL_ARM64_BRANCH19       = 0x000F
+	IMAGE_REL_ARM64_BRANCH14       = 0x0010
+	IMAGE_REL_ARM64_REL32          = 0x0011
+
 	IMAGE_REL_BASED_HIGHLOW = 3
 	IMAGE_REL_BASED_DIR64   = 10
 )
@@ -465,6 +485,8 @@ func (f *peFile) addInitArray(ctxt *Link) *peSection {
 		size = 8
 	case "arm":
 		size = 4
+	case "arm64":
+		size = 8
 	}
 	sect := f.addSection(".ctors", size, size)
 	sect.characteristics = IMAGE_SCN_CNT_INITIALIZED_DATA | IMAGE_SCN_MEM_READ
@@ -477,7 +499,7 @@ func (f *peFile) addInitArray(ctxt *Link) *peSection {
 	switch objabi.GOARCH {
 	case "386", "arm":
 		ctxt.Out.Write32(uint32(addr))
-	case "amd64":
+	case "amd64", "arm64":
 		ctxt.Out.Write64(addr)
 	}
 	return sect
@@ -594,6 +616,8 @@ dwarfLoop:
 			ctxt.Out.Write16(IMAGE_REL_AMD64_ADDR64)
 		case "arm":
 			ctxt.Out.Write16(IMAGE_REL_ARM_ADDR32)
+		case "arm64":
+			ctxt.Out.Write16(IMAGE_REL_ARM64_ADDR64)
 		}
 		return 1
 	})
@@ -788,6 +812,8 @@ func (f *peFile) writeFileHeader(ctxt *Link) {
 		fh.Machine = pe.IMAGE_FILE_MACHINE_I386
 	case sys.ARM:
 		fh.Machine = pe.IMAGE_FILE_MACHINE_ARMNT
+	case sys.ARM64:
+		fh.Machine = pe.IMAGE_FILE_MACHINE_ARM64
 	}
 
 	fh.NumberOfSections = uint16(len(f.sections))