Re: [PATCH 09/16] dma-debug: add checking for map/unmap_page/single

[Arnd Bergmann <arnd@arndb.de>]

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 <><