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Date:   Fri,  1 Jul 2022 16:23:00 +0200
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Subject: [PATCH v4 35/45] x86: kmsan: handle open-coded assembly in lib/iomem.c
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

KMSAN cannot intercept memory accesses within asm() statements.
That's why we add kmsan_unpoison_memory() and kmsan_check_memory() to
hint it how to handle memory copied from/to I/O memory.

Signed-off-by: Alexander Potapenko <glider@google.com>
---
Link: https://linux-review.googlesource.com/id/Icb16bf17269087e475debf07a7fe7d4bebc3df23
---
 arch/x86/lib/iomem.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
index 3e2f33fc33de2..e0411a3774d49 100644
--- a/arch/x86/lib/iomem.c
+++ b/arch/x86/lib/iomem.c
@@ -1,6 +1,7 @@
 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/io.h>
+#include <linux/kmsan-checks.h>
 
 #define movs(type,to,from) \
 	asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")
@@ -37,6 +38,8 @@ static void string_memcpy_fromio(void *to, const volatile void __iomem *from, si
 		n-=2;
 	}
 	rep_movs(to, (const void *)from, n);
+	/* KMSAN must treat values read from devices as initialized. */
+	kmsan_unpoison_memory(to, n);
 }
 
 static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
@@ -44,6 +47,8 @@ static void string_memcpy_toio(volatile void __iomem *to, const void *from, size
 	if (unlikely(!n))
 		return;
 
+	/* Make sure uninitialized memory isn't copied to devices. */
+	kmsan_check_memory(from, n);
 	/* Align any unaligned destination IO */
 	if (unlikely(1 & (unsigned long)to)) {
 		movs("b", to, from);
-- 
2.37.0.rc0.161.g10f37bed90-goog