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    SubjectRe: [PATCH 09/16] dma-debug: add checking for map/unmap_page/single
    Date
    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)));

    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

    Arnd <><


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