linux-kernel - [PATCH -tip] kasan: Emit different calls for instrumentable memintrinsics

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Date:   Wed,  8 Feb 2023 19:42:03 +0100
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, Peter Zijlstra <peterz@...radead.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        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>,
        linux-kbuild@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-toolchains@...r.kernel.org
Subject: [PATCH -tip] kasan: Emit different calls for instrumentable memintrinsics

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

GCC does not yet have similar support.

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@...gle.com>
---

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..78336b04c077 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)
+endif
+
 endif # CONFIG_KASAN_GENERIC
 
 ifdef CONFIG_KASAN_SW_TAGS
-- 
2.39.1.519.gcb327c4b5f-goog