Fix GS cookie check on ARM in functions with stackalloc (#25628)

* Fix GS cookie check on ARM in functions with stackalloc

The GC cookie check was failing during GC stack walking on ARM for frames
of functions using stackalloc and pinvoke. The InlinedCallFrame stores
only the SP after the stackalloc adjustment and unwinder needs R9
that contains SP before the stackalloc to be able to unwind the frame
to get caller SP. The caller SP is used as a base for getting the GS
cookie address. We were incorrectly setting the R9 in the CONTEXT
to the same value as SP and so the unwinding was getting an incorrect
caller SP.

The fix is to store R9 in the InlinedCallFrame for ARM.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/inc/corinfo.h b/src/inc/corinfo.h
index 083450b016..9cc849043e 100644
--- a/src/inc/corinfo.h
+++ b/src/inc/corinfo.h
@@ -1813,6 +1813,8 @@ struct CORINFO_EE_INFO
         unsigned    offsetOfCalleeSavedFP;
         unsigned    offsetOfCallTarget;
         unsigned    offsetOfReturnAddress;
+        // This offset is used only for ARM
+        unsigned    offsetOfSPAfterProlog;
     }
     inlinedCallFrameInfo;