cmd/link,cmd/internal/objabi: support ADDR32NB relocations on windows

This CL updates the linker to support
IMAGE_REL_[I386|AMD64|ARM|ARM64]_ADDR32NB relocations via the new
R_PEIMAGEOFF relocation type. This relocation type references symbols
using RVAs instead of VA, so it can use 4-byte offsets to reference
symbols that would normally require 8-byte offsets.

This new relocation is still not used, but will be useful when
generating Structured Exception Handling (SEH) metadata, which
needs to reference functions only using 4-byte addresses, thus
using RVAs instead of VA is of great help.

Updates #57302

Change-Id: I28d73e97d5cb78a3bc7194dc7d2fcb4a03f9f4d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/461737
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Davis Goodin <dagood@microsoft.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/internal/objabi/reloctype.go

@@ -333,6 +333,10 @@ const (
 	// in a symbol and target any symbols.
 	R_XCOFFREF
 
+	// R_PEIMAGEOFF resolves to a 32-bit offset from the start address of where
+	// the executable file is mapped in memory.
+	R_PEIMAGEOFF
+
 	// R_WEAK marks the relocation as a weak reference.
 	// A weak relocation does not make the symbol it refers to reachable,
 	// and is only honored by the linker if the symbol is in some other way

src/cmd/link/internal/amd64/asm.go

@@ -532,6 +532,9 @@ func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 			v = ld.IMAGE_REL_AMD64_ADDR32
 		}
 
+	case objabi.R_PEIMAGEOFF:
+		v = ld.IMAGE_REL_AMD64_ADDR32NB
+
 	case objabi.R_CALL,
 		objabi.R_PCREL:
 		v = ld.IMAGE_REL_AMD64_REL32

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

@@ -356,6 +356,9 @@ func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 
 	case objabi.R_ADDR:
 		v = ld.IMAGE_REL_ARM_ADDR32
+
+	case objabi.R_PEIMAGEOFF:
+		v = ld.IMAGE_REL_ARM_ADDR32NB
 	}
 
 	out.Write16(uint16(v))

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

@@ -679,6 +679,9 @@ func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 			out.Write16(ld.IMAGE_REL_ARM64_ADDR32)
 		}
 
+	case objabi.R_PEIMAGEOFF:
+		out.Write16(ld.IMAGE_REL_ARM64_ADDR32NB)
+
 	case objabi.R_ADDRARM64:
 		// Note: r.Xadd has been taken care of below, in archreloc.
 		out.Write32(uint32(sectoff))

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

@@ -345,7 +345,7 @@ func (st *relocSymState) relocsym(s loader.Sym, P []byte) {
 			} else {
 				log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", ldr.SymName(s))
 			}
-		case objabi.R_ADDR:
+		case objabi.R_ADDR, objabi.R_PEIMAGEOFF:
 			if weak && !ldr.AttrReachable(rs) {
 				// Redirect it to runtime.unreachableMethod, which will throw if called.
 				rs = syms.unreachableMethod
@@ -398,6 +398,11 @@ func (st *relocSymState) relocsym(s loader.Sym, P []byte) {
 			}
 
 			o = ldr.SymValue(rs) + r.Add()
+			if rt == objabi.R_PEIMAGEOFF {
+				// The R_PEIMAGEOFF offset is a RVA, so subtract
+				// the base address for the executable.
+				o -= PEBASE
+			}
 
 			// On amd64, 4-byte offsets will be sign-extended, so it is impossible to
 			// access more than 2GB of static data; fail at link time is better than
@@ -639,7 +644,7 @@ func extreloc(ctxt *Link, ldr *loader.Loader, s loader.Sym, r loader.Reloc) (loa
 		}
 		return rr, false
 
-	case objabi.R_ADDR:
+	case objabi.R_ADDR, objabi.R_PEIMAGEOFF:
 		// set up addend for eventual relocation via outer symbol.
 		rs := r.Sym()
 		if r.Weak() && !ldr.AttrReachable(rs) {

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

@@ -105,14 +105,16 @@ const (
 	IMAGE_SYM_CLASS_EXTERNAL = 2
 	IMAGE_SYM_CLASS_STATIC   = 3
 
-	IMAGE_REL_I386_DIR32  = 0x0006
-	IMAGE_REL_I386_SECREL = 0x000B
-	IMAGE_REL_I386_REL32  = 0x0014
-
-	IMAGE_REL_AMD64_ADDR64 = 0x0001
-	IMAGE_REL_AMD64_ADDR32 = 0x0002
-	IMAGE_REL_AMD64_REL32  = 0x0004
-	IMAGE_REL_AMD64_SECREL = 0x000B
+	IMAGE_REL_I386_DIR32   = 0x0006
+	IMAGE_REL_I386_DIR32NB = 0x0007
+	IMAGE_REL_I386_SECREL  = 0x000B
+	IMAGE_REL_I386_REL32   = 0x0014
+
+	IMAGE_REL_AMD64_ADDR64   = 0x0001
+	IMAGE_REL_AMD64_ADDR32   = 0x0002
+	IMAGE_REL_AMD64_ADDR32NB = 0x0003
+	IMAGE_REL_AMD64_REL32    = 0x0004
+	IMAGE_REL_AMD64_SECREL   = 0x000B
 
 	IMAGE_REL_ARM_ABSOLUTE = 0x0000
 	IMAGE_REL_ARM_ADDR32   = 0x0001

src/cmd/link/internal/loader/loader_test.go

@@ -338,6 +338,17 @@ func TestAddDataMethods(t *testing.T) {
 			expKind: sym.SDATA,
 			expRel:  []Reloc{mkReloc(ldr, objabi.R_ADDRCUOFF, 0, 8, 7, 8)},
 		},
+		{
+			which: "AddPEImageRelativeAddrPlus",
+			addDataFunc: func(l *Loader, s Sym, s2 Sym) Sym {
+				sb := l.MakeSymbolUpdater(s)
+				sb.AddPEImageRelativeAddrPlus(arch, s2, 3)
+				return s
+			},
+			expData: []byte{0, 0, 0, 0},
+			expKind: sym.SDATA,
+			expRel:  []Reloc{mkReloc(ldr, objabi.R_PEIMAGEOFF, 0, 4, 3, 9)},
+		},
 	}
 
 	var pmi Sym

src/cmd/link/internal/loader/symbolbuilder.go

@@ -387,6 +387,10 @@ func (sb *SymbolBuilder) AddAddr(arch *sys.Arch, tgt Sym) int64 {
 	return sb.AddAddrPlus(arch, tgt, 0)
 }
 
+func (sb *SymbolBuilder) AddPEImageRelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
+	return sb.addSymRef(tgt, add, objabi.R_PEIMAGEOFF, 4)
+}
+
 func (sb *SymbolBuilder) AddPCRelPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
 	return sb.addSymRef(tgt, add, objabi.R_PCREL, 4)
 }

src/cmd/link/internal/x86/asm.go

@@ -399,6 +399,9 @@ func pereloc1(arch *sys.Arch, out *ld.OutBuf, ldr *loader.Loader, s loader.Sym,
 	case objabi.R_ADDR:
 		v = ld.IMAGE_REL_I386_DIR32
 
+	case objabi.R_PEIMAGEOFF:
+		v = ld.IMAGE_REL_I386_DIR32NB
+
 	case objabi.R_CALL,
 		objabi.R_PCREL:
 		v = ld.IMAGE_REL_I386_REL32