runtime: use 2*regSize for saved frame pointer check
Previously, we checked for a saved frame pointer by looking for a
2*ptrSize gap between the argument pointer and the locals pointer.
The intent of this check was to look for a two stack slot gap (caller
IP and saved frame pointer), but stack slots are regSize, not ptrSize.
Correct this by checking instead for a 2*regSize gap.
On most platforms, this made no difference because ptrSize==regSize.
However, on amd64p32 (nacl), the saved frame pointer check incorrectly
fired when there was no saved frame pointer because the one stack slot
for the caller IP left an 8 byte gap, which is 2*ptrSize (but not
2*regSize) on amd64p32.
Fixes #9760.
Change-Id: I6eedcf681fe5bf2bf924dde8a8f2d9860a4d758e
Reviewed-on: https://go-review.googlesource.com/3781
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go
index c813453..4f63502 100644
--- a/src/runtime/traceback.go
+++ b/src/runtime/traceback.go
@@ -235,7 +235,7 @@
// If framepointer_enabled and there's a frame, then
// there's a saved bp here.
if GOARCH == "amd64" && frame.varp > frame.sp && framepointer_enabled {
- frame.varp -= ptrSize
+ frame.varp -= regSize
}
// Derive size of arguments.
