From 1e9d90dbed120ec98517428ffff4dacd9797e39d Mon Sep 17 00:00:00 2001 From: Nicolin Chen Date: Tue, 1 Sep 2020 15:16:45 -0700 Subject: dma-mapping: introduce dma_get_seg_boundary_nr_pages() We found that callers of dma_get_seg_boundary mostly do an ALIGN with page mask and then do a page shift to get number of pages: ALIGN(boundary + 1, 1 << shift) >> shift However, the boundary might be as large as ULONG_MAX, which means that a device has no specific boundary limit. So either "+ 1" or passing it to ALIGN() would potentially overflow. According to kernel defines: #define ALIGN_MASK(x, mask) (((x) + (mask)) & ~(mask)) #define ALIGN(x, a) ALIGN_MASK(x, (typeof(x))(a) - 1) We can simplify the logic here into a helper function doing: ALIGN(boundary + 1, 1 << shift) >> shift = ALIGN_MASK(b + 1, (1 << s) - 1) >> s = {[b + 1 + (1 << s) - 1] & ~[(1 << s) - 1]} >> s = [b + 1 + (1 << s) - 1] >> s = [b + (1 << s)] >> s = (b >> s) + 1 This patch introduces and applies dma_get_seg_boundary_nr_pages() as an overflow-free helper for the dma_get_seg_boundary() callers to get numbers of pages. It also takes care of the NULL dev case for non-DMA API callers. Suggested-by: Christoph Hellwig Signed-off-by: Nicolin Chen Acked-by: Niklas Schnelle Acked-by: Michael Ellerman (powerpc) Signed-off-by: Christoph Hellwig --- drivers/parisc/sba_iommu.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'drivers/parisc/sba_iommu.c') diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c index d4314fba0269..959bda193b96 100644 --- a/drivers/parisc/sba_iommu.c +++ b/drivers/parisc/sba_iommu.c @@ -342,8 +342,7 @@ sba_search_bitmap(struct ioc *ioc, struct device *dev, unsigned long shift; int ret; - boundary_size = ALIGN((unsigned long long)dma_get_seg_boundary(dev) + 1, - 1ULL << IOVP_SHIFT) >> IOVP_SHIFT; + boundary_size = dma_get_seg_boundary_nr_pages(dev, IOVP_SHIFT); #if defined(ZX1_SUPPORT) BUG_ON(ioc->ibase & ~IOVP_MASK); -- cgit