From 36be5cba99f6f9984a9a9f0454f95a38f4184d3e Mon Sep 17 00:00:00 2001
From: Marco Elver <elver@google.com>
Date: Fri, 24 Feb 2023 09:59:40 +0100
Subject: [PATCH] kasan: treat meminstrinsic as builtins in uninstrumented
files
Where the compiler instruments meminstrinsics by generating calls to
__asan/__hwasan_ prefixed functions, let the compiler consider
memintrinsics as builtin again.
To do so, never override memset/memmove/memcpy if the compiler does the
correct instrumentation - even on !GENERIC_ENTRY architectures.
[elver@google.com: powerpc: don't rename memintrinsics if compiler adds prefixes]
Link: https://lore.kernel.org/all/20230224085942.1791837-1-elver@google.com/ [1]
Link: https://lkml.kernel.org/r/20230227094726.3833247-1-elver@google.com
Link: https://lkml.kernel.org/r/20230224085942.1791837-2-elver@google.com
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
lib/Kconfig.kasan | 9 +++++++++
mm/kasan/shadow.c | 5 ++++-
scripts/Makefile.kasan | 9 +++++++++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index be6ee60202908..fdca89c057452 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -49,6 +49,15 @@ menuconfig KASAN
if KASAN
+config CC_HAS_KASAN_MEMINTRINSIC_PREFIX
+ def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=kernel-address -mllvm -asan-kernel-mem-intrinsic-prefix=1)) || \
+ (CC_IS_GCC && $(cc-option,-fsanitize=kernel-address --param asan-kernel-mem-intrinsic-prefix=1))
+ # Don't define it if we don't need it: compilation of the test uses
+ # this variable to decide how the compiler should treat builtins.
+ depends on !KASAN_HW_TAGS
+ help
+ The compiler is able to prefix memintrinsics with __asan or __hwasan.
+
choice
prompt "KASAN mode"
default KASAN_GENERIC
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 90186122b21b0..c8b86f3273b50 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -38,11 +38,14 @@ bool __kasan_check_write(const volatile void *p, unsigned int size)
}
EXPORT_SYMBOL(__kasan_check_write);
-#ifndef CONFIG_GENERIC_ENTRY
+#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY)
/*
* CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be
* instrumented. KASAN enabled toolchains should emit __asan_mem*() functions
* for the sites they want to instrument.
+ *
+ * If we have a compiler that can instrument meminstrinsics, never override
+ * these, so that non-instrumented files can safely consider them as builtins.
*/
#undef memset
void *memset(void *addr, int c, size_t len)
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index fa9f836f8039d..c186110ffa209 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -1,5 +1,14 @@
# SPDX-License-Identifier: GPL-2.0
+
+ifdef CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX
+# Safe for compiler to generate meminstrinsic calls in uninstrumented files.
+CFLAGS_KASAN_NOSANITIZE :=
+else
+# Don't let compiler generate memintrinsic calls in uninstrumented files
+# because they are instrumented.
CFLAGS_KASAN_NOSANITIZE := -fno-builtin
+endif
+
KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
--
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