From a5ddde4a558b3bd1e3dc50e274a0db2ea7a8fd06 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Tue, 16 Dec 2008 12:17:29 -0800 Subject: swiotlb: add comment where we handle the overflow of a dma mask on 32 bit Impact: cleanup Signed-off-by: Ian Campbell Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Ingo Molnar --- lib/swiotlb.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/lib/swiotlb.c b/lib/swiotlb.c index db724ba7ebf..1272b23e476 100644 --- a/lib/swiotlb.c +++ b/lib/swiotlb.c @@ -301,6 +301,10 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) start_dma_addr = virt_to_bus(io_tlb_start) & mask; offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT; + + /* + * Carefully handle integer overflow which can occur when mask == ~0UL. + */ max_slots = mask + 1 ? ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT); -- cgit v1.2.3-70-g09d2