kmemcheck: add hooks for page- and sg-dma-mappings

This is needed for page allocator support to prevent false positives
when accessing pages which are dma-mapped.

[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>

arch/x86/include/asm/dma-mapping.h

@@ -89,8 +89,12 @@ dma_map_sg(struct device *hwdev, struct scatterlist *sg,
 {
 	struct dma_map_ops *ops = get_dma_ops(hwdev);
 	int ents;
+	struct scatterlist *s;
+	int i;
 
 	BUG_ON(!valid_dma_direction(dir));
+	for_each_sg(sg, s, nents, i)
+		kmemcheck_mark_initialized(sg_virt(s), s->length);
 	ents = ops->map_sg(hwdev, sg, nents, dir, NULL);
 	debug_dma_map_sg(hwdev, sg, nents, ents, dir);
 
@@ -202,6 +206,7 @@ static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
+	kmemcheck_mark_initialized(page_address(page) + offset, size);
 	addr = ops->map_page(dev, page, offset, size, dir, NULL);
 	debug_dma_map_page(dev, page, offset, size, dir, addr, false);