Fix exception handlers in BL31: Use DSB to synchronize pending EA
For SoCs which do not implement RAS, use DSB as a barrier to
synchronize pending external aborts at the entry and exit of
exception handlers. This is needed to isolate the SErrors to
appropriate context.
However, this introduces an unintended side effect as discussed
in the https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/3440
A summary of the side effect and a quick workaround is provided as
part of this patch and summarized here:
The explicit DSB at the entry of various exception vectors in BL31
for handling exceptions from lower ELs can inadvertently trigger an
SError exception in EL3 due to pending asyncrhonouus aborts in lower
ELs. This will end up being handled by serror_sp_elx in EL3 which will
ultimately panic and die.
The way to workaround is to update a flag to indicate if the exception
truly came from EL3. This flag is allocated in the cpu_context
structure. This is not a bullet proof solution to the problem at hand
because we assume the instructions following "isb" that help to update
the flag (lines 100-102 & 139-141) execute without causing further
exceptions.
Change-Id: I4d345b07d746a727459435ddd6abb37fda24a9bf
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/include/lib/el3_runtime/aarch64/context.h b/include/lib/el3_runtime/aarch64/context.h
index 3490414..3135fb4 100644
--- a/include/lib/el3_runtime/aarch64/context.h
+++ b/include/lib/el3_runtime/aarch64/context.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2021, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -60,7 +60,8 @@
#define CTX_SPSR_EL3 U(0x18)
#define CTX_ELR_EL3 U(0x20)
#define CTX_PMCR_EL0 U(0x28)
-#define CTX_EL3STATE_END U(0x30)
+#define CTX_IS_IN_EL3 U(0x30)
+#define CTX_EL3STATE_END U(0x40) /* Align to the next 16 byte boundary */
/*******************************************************************************
* Constants that allow assembler code to access members of and the