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USB: usbmon: end ugly tricks with DMA peeking

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This patch fixes crashes when usbmon attempts to access GART aperture.
The old code attempted to take a bus address and convert it into a
virtual address, which clearly was impossible on systems with actual
IOMMUs. Let us not persist in this foolishness, and use transfer_buffer
in all cases instead.

I think downsides are negligible. The ones I see are:
 - A driver may pass an address of one buffer down as transfer_buffer,
   and entirely different entity mapped for DMA, resulting in misleading
   output of usbmon. Note, however, that PIO based controllers would
   do transfer the same data that usbmon sees here.
 - Out of tree drivers may crash usbmon if they store garbage in
   transfer_buffer. I inspected the in-tree drivers, and clarified
   the documentation in comments.
 - Drivers that use get_user_pages will not be possible to monitor.
   I only found one driver with this problem (drivers/staging/rspiusb).
 - Same happens with with usb_storage transferring from highmem, but
   it works fine on 64-bit systems, so I think it's not a concern.
   At least we don't crash anymore.

Why didn't we do this in 2.6.10? That's because back in those days
it was popular not to fill in transfer_buffer, so almost all
traffic would be invisible (e.g. all of HID was like that).
But now, the tree is almost 100% PIO friendly, so we can do the
right thing at last.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Pete Zaitcev
2009-06-11 08:53:20 -06:00
committed by Greg Kroah-Hartman
parent f4e2332cfc
commit 4e9e920035
7 changed files with 15 additions and 142 deletions
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14
drivers/usb/mon/usb_mon.h
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@@ -64,20 +64,6 @@ void mon_text_exit(void);
int __init mon_bin_init(void);
void mon_bin_exit(void);
/*
* DMA interface.
*
* XXX The vectored side needs a serious re-thinking. Abstracting vectors,
* like in Paolo's original patch, produces a double pkmap. We need an idea.
*/
extern char mon_dmapeek(unsigned char *dst, dma_addr_t dma_addr, int len);
struct mon_reader_bin;
extern void mon_dmapeek_vec(const struct mon_reader_bin *rp,
unsigned int offset, dma_addr_t dma_addr, unsigned int len);
extern unsigned int mon_copy_to_buff(const struct mon_reader_bin *rp,
unsigned int offset, const unsigned char *from, unsigned int len);
/*
*/
extern struct mutex mon_lock;