linux-kernel - [PATCH 1/2] kasan: mark !__SANITIZE_ADDRESS__ stubs __always

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Message-ID: <20251208-gcov-inline-noinstr-v1-1-623c48ca5714@google.com>
Date: Mon, 08 Dec 2025 01:34:58 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, 
	Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Vincenzo Frascino <vincenzo.frascino@....com>, Marco Elver <elver@...gle.com>, 
	Ard Biesheuvel <ardb@...nel.org>
Cc: kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, 
	Brendan Jackman <jackmanb@...gle.com>
Subject: [PATCH 1/2] kasan: mark !__SANITIZE_ADDRESS__ stubs __always_inline

The x86 instrumented bitops in
include/asm-generic/bitops/instrumented-non-atomic.h are
KASAN-instrumented via explicit calls to instrument_* functions from
include/linux/instrumented.h.

This bitops are used from noinstr code in __sev_es_nmi_complete(). This
code avoids noinstr violations by disabling __SANITIZE_ADDRESS__ etc for
the compilation unit.

However, when GCOV is enabled, there can still be violations caused by
the stub versions of these functions, since coverage instrumentation is
injected that causes them to be out-of-lined.

(Note: the GCOV isntrumentation itself also appears to violate noinstr
in principle, but it appears to be harmless - basically just an inc
instruction).

Fix this by just applying __always_inline.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 include/linux/kasan-checks.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/kasan-checks.h b/include/linux/kasan-checks.h
index 3d6d22a25bdc391c0015a6daf2249d6bea752dcb..9aa0f1cc90133ca334afa478b5f762aef9e5d79c 100644
--- a/include/linux/kasan-checks.h
+++ b/include/linux/kasan-checks.h
@@ -37,11 +37,11 @@ static inline bool __kasan_check_write(const volatile void *p, unsigned int size
 #define kasan_check_read __kasan_check_read
 #define kasan_check_write __kasan_check_write
 #else
-static inline bool kasan_check_read(const volatile void *p, unsigned int size)
+static __always_inline bool kasan_check_read(const volatile void *p, unsigned int size)
 {
 	return true;
 }
-static inline bool kasan_check_write(const volatile void *p, unsigned int size)
+static __always_inline bool kasan_check_write(const volatile void *p, unsigned int size)
 {
 	return true;
 }

-- 
2.50.1