runtime, cmd/link: tighten search for stackObjectRecord

A stackObjectRecord should always be in funcdata, between gofunc
and the end of pclntab, except for the special case of
methodValueCallFrameObjs, which should always be in noptrbss.
Adjust the two loops that look for the moduledata corresponding
to a stackObjectRecord to search more precisely, rather than
relying on datap.end.

Closely based on a patch by Michael Stapelberg.

For #76038

Change-Id: I751801d8fd030af751825a67905b2a343280e7d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/728840
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: ianlancetaylor

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

@@ -656,6 +656,7 @@ func (ctxt *Link) symtab(pcln *pclntab) []sym.SymKind {
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.etypes", 0))
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.rodata", 0))
 	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("go:func.*", 0))
+	moduledata.AddAddr(ctxt.Arch, ldr.Lookup("runtime.epclntab", 0))
 
 	if ctxt.IsAIX() && ctxt.IsExternal() {
 		// Add R_XCOFFREF relocation to prevent ld's garbage collection of

src/runtime/stack.go

@@ -1357,7 +1357,13 @@ func (r *stackObjectRecord) gcdata() (uintptr, *byte) {
 	ptr := uintptr(unsafe.Pointer(r))
 	var mod *moduledata
 	for datap := &firstmoduledata; datap != nil; datap = datap.next {
-		if datap.gofunc <= ptr && ptr < datap.end {
+		// The normal case: stackObjectRecord is in funcdata.
+		if datap.gofunc <= ptr && ptr < datap.epclntab {
+			mod = datap
+			break
+		}
+		// A special case: methodValueCallFrameObjs.
+		if datap.noptrbss <= ptr && ptr < datap.enoptrbss {
 			mod = datap
 			break
 		}

src/runtime/stkframe.go

@@ -269,7 +269,7 @@ func stkobjinit() {
 	ptr := uintptr(unsafe.Pointer(&methodValueCallFrameObjs[0]))
 	var mod *moduledata
 	for datap := &firstmoduledata; datap != nil; datap = datap.next {
-		if datap.gofunc <= ptr && ptr < datap.end {
+		if datap.noptrbss <= ptr && ptr < datap.enoptrbss {
 			mod = datap
 			break
 		}

src/runtime/symtab.go

@@ -422,6 +422,7 @@ type moduledata struct {
 	types, etypes         uintptr
 	rodata                uintptr
 	gofunc                uintptr // go.func.*
+	epclntab              uintptr
 
 	textsectmap []textsect
 	typelinks   []int32 // offsets from types