runtime: identify special functions by flag instead of address

When there are plugins, there may not be a unique copy of runtime
functions like goexit, mcall, etc.  So identifying them by entry
address is problematic.  Instead, keep track of each special function
using a field in the symbol table.  That way, multiple copies of
the same runtime function will be treated identically.

Fixes #24351
Fixes #23133

Change-Id: Iea3232df8a6af68509769d9ca618f530cc0f84fd
Reviewed-on: https://go-review.googlesource.com/100739
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 8f10508a7d..2dc7001e38 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -619,7 +619,7 @@ func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
 	if stackDebug >= 2 {
 		print("    adjusting ", funcname(f), " frame=[", hex(frame.sp), ",", hex(frame.fp), "] pc=", hex(frame.pc), " continpc=", hex(frame.continpc), "\n")
 	}
-	if f.entry == systemstack_switchPC {
+	if f.funcID == funcID_systemstack_switch {
 		// A special routine at the bottom of stack of a goroutine that does an systemstack call.
 		// We will allow it to be copied even though we don't
 		// have full GC info for it (because it is written in asm).
@@ -1110,7 +1110,8 @@ func shrinkstack(gp *g) {
 	if debug.gcshrinkstackoff > 0 {
 		return
 	}
-	if gp.startpc == gcBgMarkWorkerPC {
+	f := findfunc(gp.startpc)
+	if f.valid() && f.funcID == funcID_gcBgMarkWorker {
 		// We're not allowed to shrink the gcBgMarkWorker
 		// stack (see gcBgMarkWorker for explanation).
 		return