Re: [PATCH] dma-mapping: Add BUG_ON for uninitialized dma_ops

[Bjorn Helgaas]

[+cc Marek]

On Mon, Jun 3, 2013 at 6:44 AM, Michal Simek <michal.simek@xxxxxxxxxx> wrote:
> Check that dma_ops are initialized correctly.
>
> Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>
> ---
> Functions dma_mmap_attrs(), dma_get_sgtable_attrs()
> already have this checking.
>
> ---
>  include/asm-generic/dma-mapping-common.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/include/asm-generic/dma-mapping-common.h b/include/asm-generic/dma-mapping-common.h
> index de8bf89..d430cab 100644
> --- a/include/asm-generic/dma-mapping-common.h
> +++ b/include/asm-generic/dma-mapping-common.h
> @@ -16,6 +16,7 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
>         dma_addr_t addr;
>
>         kmemcheck_mark_initialized(ptr, size);
> +       BUG_ON(!ops);

Does this actually help anything?  I expected that if "ops" is NULL,
we would just oops anyway when we attempted to call "ops->map_page()"
because we already trap null pointer dereferences.  At least, when I
tried leaving a pci_bus.ops pointer NULL, I got a nice panic and
backtrace even without adding an explicit BUG_ON().

I cc'd Marek, who added the similar BUG_ON()s in dma_mmap_attrs() and
dma_get_sgtable_attrs() with d2b7428eb0 and 64ccc9c033.

>         BUG_ON(!valid_dma_direction(dir));
>         addr = ops->map_page(dev, virt_to_page(ptr),
>                              (unsigned long)ptr & ~PAGE_MASK, size,
> @@ -33,6 +34,7 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->unmap_page)
>                 ops->unmap_page(dev, addr, size, dir, attrs);
> @@ -49,6 +51,7 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
>
>         for_each_sg(sg, s, nents, i)
>                 kmemcheck_mark_initialized(sg_virt(s), s->length);
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         ents = ops->map_sg(dev, sg, nents, dir, attrs);
>         debug_dma_map_sg(dev, sg, nents, ents, dir);
> @@ -62,6 +65,7 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         debug_dma_unmap_sg(dev, sg, nents, dir);
>         if (ops->unmap_sg)
> @@ -76,6 +80,7 @@ static inline dma_addr_t dma_map_page(struct device *dev, struct page *page,
>         dma_addr_t addr;
>
>         kmemcheck_mark_initialized(page_address(page) + offset, size);
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         addr = ops->map_page(dev, page, offset, size, dir, NULL);
>         debug_dma_map_page(dev, page, offset, size, dir, addr, false);
> @@ -88,6 +93,7 @@ static inline void dma_unmap_page(struct device *dev, dma_addr_t addr,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->unmap_page)
>                 ops->unmap_page(dev, addr, size, dir, NULL);
> @@ -100,6 +106,7 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_single_for_cpu)
>                 ops->sync_single_for_cpu(dev, addr, size, dir);
> @@ -112,6 +119,7 @@ static inline void dma_sync_single_for_device(struct device *dev,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_single_for_device)
>                 ops->sync_single_for_device(dev, addr, size, dir);
> @@ -126,6 +134,7 @@ static inline void dma_sync_single_range_for_cpu(struct device *dev,
>  {
>         const struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_single_for_cpu)
>                 ops->sync_single_for_cpu(dev, addr + offset, size, dir);
> @@ -140,6 +149,7 @@ static inline void dma_sync_single_range_for_device(struct device *dev,
>  {
>         const struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_single_for_device)
>                 ops->sync_single_for_device(dev, addr + offset, size, dir);
> @@ -152,6 +162,7 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_sg_for_cpu)
>                 ops->sync_sg_for_cpu(dev, sg, nelems, dir);
> @@ -164,6 +175,7 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
>  {
>         struct dma_map_ops *ops = get_dma_ops(dev);
>
> +       BUG_ON(!ops);
>         BUG_ON(!valid_dma_direction(dir));
>         if (ops->sync_sg_for_device)
>                 ops->sync_sg_for_device(dev, sg, nelems, dir);
> --
> 1.8.2.3
>
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