core: asan: KASAN and ASLR are incompatible

The address sanitizer shadow offset address is given at compile time
(CFG_ASAN_SHADOW_OFFSET) and is hard-coded by the compiler into the
prologue of instrumented functions, for the purpose of initializing
the shadow area for the stack (local variables). With ASLR turned on,
this offset becomes invalid because of the random ASLR offset.

For KASAN to work with ASLR, we would need to either keep the shadow
area at the expected offset (which may not be very easy, I have not
investigated in more details) or provide the shadow offset dynamically.
An attempt was made three years ago to extend the GCC compiler with
such a feature [1] but there was no feedback from the maintainers [2].

Add a check in mk/config.mk so that KASAN and ASLR may not be enabled
simultaneously.

Link: https://blogs.coreboot.org/blog/2020/08/31/gsoc-address-sanitizer-wrap-up/ [1]
Link: https://gcc.gnu.org/pipermail/gcc-patches/2020-July/550176.html [2]
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

.github/workflows/ci.yml

@@ -92,7 +92,7 @@ jobs:
           _make CFG_TEE_CORE_LOG_LEVEL=4 CFG_TEE_CORE_DEBUG=y CFG_TEE_TA_LOG_LEVEL=4 CFG_CC_OPT_LEVEL=0 CFG_DEBUG_INFO=y
           _make CFG_TEE_CORE_LOG_LEVEL=0 CFG_TEE_CORE_DEBUG=n CFG_TEE_TA_LOG_LEVEL=0 CFG_DEBUG_INFO=n CFG_ENABLE_EMBEDDED_TESTS=n
           _make CFG_TEE_CORE_MALLOC_DEBUG=y CFG_CORE_DEBUG_CHECK_STACKS=y
-          _make CFG_CORE_SANITIZE_KADDRESS=y
+          _make CFG_CORE_SANITIZE_KADDRESS=y CFG_CORE_ASLR=n
           _make CFG_LOCKDEP=y
           _make CFG_CRYPTO=n
           _make CFG_CRYPTO_{AES,DES}=n

mk/config.mk

@@ -444,6 +444,10 @@ CFG_CORE_SANITIZE_UNDEFINED ?= n
 # default
 CFG_CORE_SANITIZE_KADDRESS ?= n
 
+ifeq (y-y,$(CFG_CORE_SANITIZE_KADDRESS)-$(CFG_CORE_ASLR))
+$(error CFG_CORE_SANITIZE_KADDRESS and CFG_CORE_ASLR are not compatible)
+endif
+
 # Add stack guards before/after stacks and periodically check them
 CFG_WITH_STACK_CANARIES ?= y