The patch titled
Subject: kasan: treat meminstrinsic as builtins in uninstrumented files
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Marco Elver <elver@xxxxxxxxxx>
Subject: kasan: treat meminstrinsic as builtins in uninstrumented files
Date: Fri, 24 Feb 2023 09:59:40 +0100
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.
Link: https://lkml.kernel.org/r/20230224085942.1791837-2-elver@xxxxxxxxxx
Fixes: 69d4c0d32186 ("entry, kasan, x86: Disallow overriding mem*() functions")
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Tested-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
Tested-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jakub Jelinek <jakub@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Nicolas Schier <nicolas@xxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/lib/Kconfig.kasan~kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files
+++ 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
--- a/mm/kasan/shadow.c~kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files
+++ 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)
--- a/scripts/Makefile.kasan~kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files
+++ 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)))
_
Patches currently in -mm which might be from elver@xxxxxxxxxx are
kasan-emit-different-calls-for-instrumentable-memintrinsics.patch
kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files.patch
kasan-test-fix-test-for-new-meminstrinsic-instrumentation.patch
kasan-x86-dont-rename-memintrinsics-in-uninstrumented-files.patch
