Date:   Mon, 13 Feb 2023 21:13:35 +0100
Mime-Version: 1.0
Message-ID: <20230213201334.1494626-1-elver@google.com>
Subject: [PATCH -tip v3] kasan: Emit different calls for instrumentable memintrinsics
From:   Marco Elver <elver@google.com>
To:     elver@google.com, Peter Zijlstra <peterz@infradead.org>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com,
        linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Tony Lindgren <tony@atomide.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Jakub Jelinek <jakub@redhat.com>,
        linux-toolchains@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Clang 15 will provide an option to prefix calls to memcpy/memset/memmove
with __asan_ in instrumented functions: https://reviews.llvm.org/D122724

GCC will add support in future:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108777

Use it to regain KASAN instrumentation of memcpy/memset/memmove on
architectures that require noinstr to be really free from instrumented
mem*() functions (all GENERIC_ENTRY architectures).

Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <elver@google.com>
---
v3:
* Resend with actual fix.

v2:
* Use asan-kernel-mem-intrinsic-prefix=1, so that once GCC supports the
  param, it also works there (it needs the =1).

The Fixes tag is just there to show the dependency, and that people
shouldn't apply this patch without 69d4c0d32186.
---
 scripts/Makefile.kasan | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index b9e94c5e7097..3b35a88af60d 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -38,6 +38,13 @@ endif
 
 CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
 
+ifdef CONFIG_GENERIC_ENTRY
+# Instrument memcpy/memset/memmove calls by using instrumented __asan_mem*()
+# instead. With compilers that don't support this option, compiler-inserted
+# memintrinsics won't be checked by KASAN.
+CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)
+endif
+
 endif # CONFIG_KASAN_GENERIC
 
 ifdef CONFIG_KASAN_SW_TAGS
-- 
2.39.1.581.gbfd45094c4-goog