cmd/link: sort .pdata by function start address

Loosely based on CL 678795.

The PE/COFF spec requires RUNTIME_FUNCTION entries in the .pdata
section to be ordered by their function start address. Previously
the linker emitted them in symbol order.

An unsorted table triggers the MSVC linker error:

    fatal error LNK1223: invalid or corrupt file: file contains invalid
    .pdata contributions

Fixes #65116.

Change-Id: I589cb4e6787a9edb34400b56e60fe23065b59162
Reviewed-on: https://go-review.googlesource.com/c/go/+/743820
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

src/cmd/cgo/internal/test/seh_internal_windows_test.go

@@ -1,16 +0,0 @@
-// Copyright 2024 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.
-
-//go:build cgo && windows && internal
-
-package cgotest
-
-import (
-	"internal/testenv"
-	"testing"
-)
-
-func TestCallbackCallersSEH(t *testing.T) {
-	testenv.SkipFlaky(t, 65116)
-}

src/cmd/cgo/internal/test/seh_windows_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build cgo && windows && !internal
+//go:build cgo && windows
 
 package cgotest
 

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

@@ -2777,6 +2777,11 @@ func (ctxt *Link) textaddress() {
 		ldr.SetSymValue(etext, int64(va))
 		ldr.SetSymValue(text, int64(Segtext.Sections[0].Vaddr))
 	}
+	if ctxt.IsWindows() {
+		// .pdata entries should be sorted by address, so process them now
+		// that we have final addresses for the text symbols.
+		collectSEH(ctxt)
+	}
 }
 
 // assigns address for a text symbol, returns (possibly new) section, its number, and the address.

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

@@ -1635,7 +1635,6 @@ func addPEBaseReloc(ctxt *Link) {
 func (ctxt *Link) dope() {
 	initdynimport(ctxt)
 	initdynexport(ctxt)
-	writeSEH(ctxt)
 }
 
 func setpersrc(ctxt *Link, syms []loader.Sym) {

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

@@ -8,6 +8,8 @@ import (
 	"cmd/internal/sys"
 	"cmd/link/internal/loader"
 	"cmd/link/internal/sym"
+	"cmp"
+	"slices"
 )
 
 var sehp struct {
@@ -15,14 +17,16 @@ var sehp struct {
 	xdata []sym.LoaderSym
 }
 
-func writeSEH(ctxt *Link) {
+// collectSEH collects the SEH unwind information for all functions and organizes
+// it into .pdata and .xdata sections.
+func collectSEH(ctxt *Link) {
 	switch ctxt.Arch.Family {
 	case sys.AMD64:
-		writeSEHAMD64(ctxt)
+		collectSEHAMD64(ctxt)
 	}
 }
 
-func writeSEHAMD64(ctxt *Link) {
+func collectSEHAMD64(ctxt *Link) {
 	ldr := ctxt.loader
 	mkSecSym := func(name string, kind sym.SymKind) *loader.SymbolBuilder {
 		s := ldr.CreateSymForUpdate(name, 0)
@@ -39,6 +43,11 @@ func writeSEHAMD64(ctxt *Link) {
 	// an RVA, so it is possible, and binary-size wise,
 	// to deduplicate .xdata entries.
 	uwcache := make(map[string]int64) // aux symbol name --> .xdata offset
+	type pdataEntry struct {
+		start    sym.LoaderSym
+		xdataOff int64
+	}
+	var entries []pdataEntry
 	for _, s := range ctxt.Textp {
 		if fi := ldr.FuncInfo(s); !fi.Valid() {
 			continue
@@ -66,12 +75,22 @@ func writeSEHAMD64(ctxt *Link) {
 			}
 		}
 
+		entries = append(entries, pdataEntry{start: s, xdataOff: off})
+	}
+	slices.SortFunc(entries, func(a, b pdataEntry) int {
+		return cmp.Compare(ldr.SymAddr(a.start), ldr.SymAddr(b.start))
+	})
+	for _, ent := range entries {
 		// Reference:
 		// https://learn.microsoft.com/en-us/cpp/build/exception-handling-x64#struct-runtime_function
-		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, 0)
-		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, s, ldr.SymSize(s))
-		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, xdata.Sym(), off)
+		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, ent.start, 0)                      // function start address
+		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, ent.start, ldr.SymSize(ent.start)) // function end address
+		pdata.AddPEImageRelativeAddrPlus(ctxt.Arch, xdata.Sym(), ent.xdataOff)         // xdata symbol offset
+	}
+	if pdata.Size() > 0 {
+		sehp.pdata = append(sehp.pdata, pdata.Sym())
+	}
+	if xdata.Size() > 0 {
+		sehp.xdata = append(sehp.xdata, xdata.Sym())
 	}
-	sehp.pdata = append(sehp.pdata, pdata.Sym())
-	sehp.xdata = append(sehp.xdata, xdata.Sym())
 }