[PATCH RFC v4 41/42] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN

[glider@google.com]

This is needed to allow memory tools like KASAN and KMSAN see the
memory accesses from the checksum code. Without CONFIG_GENERIC_CSUM the
tools can't see memory accesses originating from handwritten assembly
code.
For KASAN it's a question of detecting more bugs, for KMSAN using the C
implementation also helps avoid false positives originating from
seemingly uninitialized checksum values.

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Alexander Potapenko <glider@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-mm@kvack.org
---

v2:
 - dropped the "default n" (as requested by Randy Dunlap)

v4:
 - changed "net:" to "x86:" in the patch name

Change-Id: I645e2c097253a8d5717ad87e2e2df6f6f67251f3
---
 arch/x86/Kconfig                |  4 ++++
 arch/x86/include/asm/checksum.h | 10 +++++++---
 arch/x86/lib/Makefile           |  2 ++
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8081bc31d5f0..dd4a6c233d18 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -273,6 +273,10 @@ config GENERIC_ISA_DMA
 	def_bool y
 	depends on ISA_DMA_API
 
+config GENERIC_CSUM
+	bool
+	default y if KMSAN || KASAN
+
 config GENERIC_BUG
 	def_bool y
 	depends on BUG
diff --git a/arch/x86/include/asm/checksum.h b/arch/x86/include/asm/checksum.h
index d79d1e622dcf..ab3464cbce26 100644
--- a/arch/x86/include/asm/checksum.h
+++ b/arch/x86/include/asm/checksum.h
@@ -1,6 +1,10 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifdef CONFIG_X86_32
-# include <asm/checksum_32.h>
+#ifdef CONFIG_GENERIC_CSUM
+# include <asm-generic/checksum.h>
 #else
-# include <asm/checksum_64.h>
+# ifdef CONFIG_X86_32
+#  include <asm/checksum_32.h>
+# else
+#  include <asm/checksum_64.h>
+# endif
 #endif
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 5246db42de45..bca9031de9ff 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -55,7 +55,9 @@ endif
         lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o
 else
         obj-y += iomap_copy_64.o
+ifneq ($(CONFIG_GENERIC_CSUM),y)
         lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
+endif
         lib-y += clear_page_64.o copy_page_64.o
         lib-y += memmove_64.o memset_64.o
         lib-y += copy_user_64.o
-- 
2.24.1.735.g03f4e72817-goog