dma: kmsan: unpoison DMA mappings

KMSAN doesn't know about DMA memory writes performed by devices.  We
unpoison such memory when it's mapped to avoid false positive reports.

Link: https://lkml.kernel.org/r/20220915150417.722975-22-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/kmsan.h

@@ -9,6 +9,7 @@
 #ifndef _LINUX_KMSAN_H
 #define _LINUX_KMSAN_H
 
+#include <linux/dma-direction.h>
 #include <linux/gfp.h>
 #include <linux/kmsan-checks.h>
 #include <linux/types.h>
@@ -16,6 +17,7 @@
 struct page;
 struct kmem_cache;
 struct task_struct;
+struct scatterlist;
 
 #ifdef CONFIG_KMSAN
 
@@ -172,6 +174,35 @@ void kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
  */
 void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
 
+/**
+ * kmsan_handle_dma() - Handle a DMA data transfer.
+ * @page:   first page of the buffer.
+ * @offset: offset of the buffer within the first page.
+ * @size:   buffer size.
+ * @dir:    one of possible dma_data_direction values.
+ *
+ * Depending on @direction, KMSAN:
+ * * checks the buffer, if it is copied to device;
+ * * initializes the buffer, if it is copied from device;
+ * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ */
+void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+		      enum dma_data_direction dir);
+
+/**
+ * kmsan_handle_dma_sg() - Handle a DMA transfer using scatterlist.
+ * @sg:    scatterlist holding DMA buffers.
+ * @nents: number of scatterlist entries.
+ * @dir:   one of possible dma_data_direction values.
+ *
+ * Depending on @direction, KMSAN:
+ * * checks the buffers in the scatterlist, if they are copied to device;
+ * * initializes the buffers, if they are copied from device;
+ * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ */
+void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
+			 enum dma_data_direction dir);
+
 #else
 
 static inline void kmsan_init_shadow(void)
@@ -254,6 +285,16 @@ static inline void kmsan_iounmap_page_range(unsigned long start,
 {
 }
 
+static inline void kmsan_handle_dma(struct page *page, size_t offset,
+				    size_t size, enum dma_data_direction dir)
+{
+}
+
+static inline void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
+				       enum dma_data_direction dir)
+{
+}
+
 #endif
 
 #endif /* _LINUX_KMSAN_H */