[patch 004/159] kasan: fix kasan_check_read/write definitions

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From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: kasan: fix kasan_check_read/write definitions

Building little-endian allmodconfig kernels on arm64 started failing with
the generated atomic.h implementation, since we now try to call kasan
helpers from the EFI stub:

aarch64-linux-gnu-ld: drivers/firmware/efi/libstub/arm-stub.stub.o: in function `atomic_set':
include/generated/atomic-instrumented.h:44: undefined reference to `__efistub_kasan_check_write'

I suspect that we get similar problems in other files that explicitly
disable KASAN for some reason but call atomic_t based helper functions.

We can fix this by checking the predefined __SANITIZE_ADDRESS__ macro that
the compiler sets instead of checking CONFIG_KASAN, but this in turn
requires a small hack in mm/kasan/common.c so we do see the extern
declaration there instead of the inline function.

Link: http://lkml.kernel.org/r/20181211133453.2835077-1-arnd@xxxxxxxx
Fixes: b1864b828644 ("locking/atomics: build atomic headers as required")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Reported-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
Acked-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>,
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 include/linux/kasan-checks.h |    2 +-
 mm/kasan/common.c            |    2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/include/linux/kasan-checks.h~kasan-fix-kasan_check_read-write-definitions
+++ a/include/linux/kasan-checks.h
@@ -2,7 +2,7 @@
 #ifndef _LINUX_KASAN_CHECKS_H
 #define _LINUX_KASAN_CHECKS_H
 
-#ifdef CONFIG_KASAN
+#if defined(__SANITIZE_ADDRESS__) || defined(__KASAN_INTERNAL)
 void kasan_check_read(const volatile void *p, unsigned int size);
 void kasan_check_write(const volatile void *p, unsigned int size);
 #else
--- a/mm/kasan/common.c~kasan-fix-kasan_check_read-write-definitions
+++ a/mm/kasan/common.c
@@ -14,6 +14,8 @@
  *
  */
 
+#define __KASAN_INTERNAL
+
 #include <linux/export.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
_



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