On Wed, 2012-09-05 at 07:57 -0400, Konrad Rzeszutek Wilk wrote: > On Tue, Sep 04, 2012 at 04:57:56PM -0600, Shuah Khan wrote: > > On Tue, 2012-09-04 at 17:05 -0400, Konrad Rzeszutek Wilk wrote: > > > On Sun, Sep 02, 2012 at 08:14:17AM -0600, Shuah Khan wrote: > > > > A recent dma mapping error analysis effort showed that a large precentage > > > > of dma_map_single() and dma_map_page() returns are not checked for mapping > > > > errors. Reference: https://lkml.org/lkml/2012/8/10/326 > > > > > > > > > > So were you able to catch some naughty drivers with this? > > > > I did compile a complete list of drivers that don't check dma mapping > > errors from my analysis. Are you interested in seeing the full analysis? > > Yes, plus the authors of the drivers are probably interested in it as > well. > ..snip.. I compiled very detailed information on the nature of problems with dma mapping error checking, ranging from not checking mapping errors to not unmapping etc. I would like to share this information in such a way that others can leverage the research I already did. One good way to communicate this information would be on one of the kernel wikis. Ideas, suggestions? > > > I was initially thinking that this patch would contain a state for the driver > > > of whether after map it has called dma_mapping_error. So this function would > > > increment some internal state, and if dma_mapping_error on that specific dma_addr > > > it would decrement it. If it never occured, then we would print on the unmap > > > that the device never had called dma_mapping_error on said dma_addr? > > > > That is a good idea. Let me see if I understand what you are saying > > correctly. Add a new field to dma_debug_entry structure and keep state > > and clear it if dma_mapping_error() is called. This will require adding > > a debug interface for dma_mapping_error() which is not hard to do. Is > > this close to what you are thinking? > > Right. It is more complex than this patch but it should provide a nicer > "trap" mechanism to alert driver writers that they are not checking DMA > addresses properly. I will go back and work on improving this patch. I will have to think about how to track overflow buffer triggers as well without impacting the production kernel. That is a separate effort. -- Shuah -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
