xtensa, kasan: define KASAN_SHADOW_END

Common KASAN code might rely on the definitions of the shadow mapping
start, end, and size. Define KASAN_SHADOW_END in addition to
KASAN_SHADOW_START and KASAN_SHADOW_SIZE.

Link: https://lkml.kernel.org/r/20231225151924.5422-1-andrey.konovalov@linux.dev
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312240755.MqsWuTno-lkp@intel.com/
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

xtensa: fix build with KASAN

The commit 917538e212a2 ("kasan: clean up KASAN_SHADOW_SCALE_SHIFT
usage") removed KASAN_SHADOW_SCALE_SHIFT definition from
include/linux/kasan.h and added it to architecture-specific headers,
except for xtensa. This broke the xtensa build with KASAN enabled.
Define KASAN_SHADOW_SCALE_SHIFT in arch/xtensa/include/asm/kasan.h

Reported by: kbuild test robot <fengguang.wu@intel.com>
Fixes: 917538e212a2 ("kasan: clean up KASAN_SHADOW_SCALE_SHIFT usage")
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa: add support for KASAN

Cover kernel addresses above 0x90000000 by the shadow map. Enable
HAVE_ARCH_KASAN when MMU is enabled. Provide kasan_early_init that fills
shadow map with writable copies of kasan_zero_page. Call
kasan_early_init right after mmu initialization in the setup_arch.
Provide kasan_init that allocates proper shadow map pages from the
memblock and puts these pages into the shadow map for addresses from
VMALLOC area to the end of KSEG. Call kasan_init right after memblock
initialization. Don't use KASAN for the boot code, MMU and KASAN
initialization and page fault handler. Make kernel stack size 4 times
larger when KASAN is enabled to avoid stack overflows.
GCC 7.3, 8 or newer is required to build the xtensa kernel with KASAN.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>