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    SubjectRe: [PATCH 09/16] dma-debug: add checking for map/unmap_page/single
    On Sun, Jan 25, 2009 at 10:17:19PM +0900, FUJITA Tomonori wrote:
    > On Fri, 23 Jan 2009 11:28:27 +0100
    > Joerg Roedel <joro@8bytes.org> wrote:
    >
    > > On Wed, Jan 21, 2009 at 01:17:32AM +0100, Arnd Bergmann wrote:
    > > > On Monday 19 January 2009, Joerg Roedel wrote:
    > > > > Impact: add debug callbacks for dma_{un}map_[page|single]
    > > >
    > > > In the discussion about "[PATCH] usb/mcs7830: Don't use buffers from
    > > > stack for USB transfers", I have raised the question of whether we can
    > > > add a check for the DMA address being on the stack, I guess this would
    > > > be the right place for it.
    > > >
    > > > Maybe you can add another check like:
    > > >
    > > > WARN_ON(is_kernel_stack(page_to_virt(page)));
    > >
    > > Good idea. This would be the right place for such a check.
    > >
    > > > Unfortunately, I can't think of a way to define a generic is_kernel_stack
    > > > function. On most architectures (all that put thread_info at the top of the
    > > > stack), something like this should work:
    > > >
    > > > #ifndef is_kernel_stack
    > > > static inline int is_kernel_stack(void *p)
    > > > {
    > > > return (unsigned long)p & ~(THREAD_SIZE - 1) == current_thread_info();
    > > > }
    > > > #endif
    > >
    > > Hmm, this function is indeed required on all architectures. If you send
    > > a patchset which adds it I will add the check for stack addresses to
    > > this debugging code :)
    >
    > object_is_on_stack()

    Oh cool. This function exists already. Thanks for the hint :)

    Joerg


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