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>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/xtensa/include/asm/string.h b/arch/xtensa/include/asm/string.h
index 8d5d9dfadb09..586bad9fe187 100644
--- a/arch/xtensa/include/asm/string.h
+++ b/arch/xtensa/include/asm/string.h
@@ -108,14 +108,33 @@ static inline int strncmp(const char *__cs, const char *__ct, size_t __n)
 
 #define __HAVE_ARCH_MEMSET
 extern void *memset(void *__s, int __c, size_t __count);
+extern void *__memset(void *__s, int __c, size_t __count);
 
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *__to, __const__ void *__from, size_t __n);
+extern void *__memcpy(void *__to, __const__ void *__from, size_t __n);
 
 #define __HAVE_ARCH_MEMMOVE
 extern void *memmove(void *__dest, __const__ void *__src, size_t __n);
+extern void *__memmove(void *__dest, __const__ void *__src, size_t __n);
 
 /* Don't build bcopy at all ...  */
 #define __HAVE_ARCH_BCOPY
 
+#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
+
+/*
+ * For files that are not instrumented (e.g. mm/slub.c) we
+ * should use not instrumented version of mem* functions.
+ */
+
+#define memcpy(dst, src, len) __memcpy(dst, src, len)
+#define memmove(dst, src, len) __memmove(dst, src, len)
+#define memset(s, c, n) __memset(s, c, n)
+
+#ifndef __NO_FORTIFY
+#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
+#endif
+#endif
+
 #endif	/* _XTENSA_STRING_H */