+ kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files.patch added to mm-hotfixes-unstable branch

+ kasan-treat-meminstrinsic-as-builtins-in-uninstrumented-files.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

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

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Marco Elver <elver@google.com>
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@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>
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>
---


--- 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@google.com 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