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Date:   Fri,  1 Jul 2022 16:23:03 +0200
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Subject: [PATCH v4 38/45] x86: kasan: kmsan: support CONFIG_GENERIC_CSUM on
 x86, enable it for KASAN/KMSAN
From:   Alexander Potapenko <glider@google.com>
To:     glider@google.com
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>, Borislav Petkov <bp@alien8.de>,
        Christoph Hellwig <hch@lst.de>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Ilya Leoshkevich <iii@linux.ibm.com>,
        Ingo Molnar <mingo@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Kees Cook <keescook@chromium.org>,
        Marco Elver <elver@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Matthew Wilcox <willy@infradead.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Pekka Enberg <penberg@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Vlastimil Babka <vbabka@suse.cz>, kasan-dev@googlegroups.com,
        linux-mm@kvack.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Precedence: bulk

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>

---

Link: https://linux-review.googlesource.com/id/I3e95247be55b1112af59dbba07e8cbf34e50a581
---
 arch/x86/Kconfig                |  4 ++++
 arch/x86/include/asm/checksum.h | 16 ++++++++++------
 arch/x86/lib/Makefile           |  2 ++
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index be0b95e51df66..4a5d0a0f54dea 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -324,6 +324,10 @@ 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 bca625a60186c..6df6ece8a28ec 100644
--- a/arch/x86/include/asm/checksum.h
+++ b/arch/x86/include/asm/checksum.h
@@ -1,9 +1,13 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#define  _HAVE_ARCH_COPY_AND_CSUM_FROM_USER 1
-#define HAVE_CSUM_COPY_USER
-#define _HAVE_ARCH_CSUM_AND_COPY
-#ifdef CONFIG_X86_32
-# include <asm/checksum_32.h>
+#ifdef CONFIG_GENERIC_CSUM
+# include <asm-generic/checksum.h>
 #else
-# include <asm/checksum_64.h>
+# define  _HAVE_ARCH_COPY_AND_CSUM_FROM_USER 1
+# define HAVE_CSUM_COPY_USER
+# define _HAVE_ARCH_CSUM_AND_COPY
+# 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 f76747862bd2e..7ba5f61d72735 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -65,7 +65,9 @@ ifneq ($(CONFIG_X86_CMPXCHG64),y)
 endif
 else
         obj-y += iomap_copy_64.o
+ifneq ($(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
-- 
2.37.0.rc0.161.g10f37bed90-goog