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author | Pete Zaitcev <zaitcev@redhat.com> | 2009-06-11 08:53:20 -0600 |
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committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-09-23 06:46:19 -0700 |
commit | 4e9e92003529e5c7bb11281f7c2c9b3fe8858403 (patch) | |
tree | 07169c9a996a119aebb5865a76ff1177afe90a22 /include | |
parent | f4e2332cfcf900e0a926c4e0fc35f751bcbcaa1b (diff) | |
download | linux-4e9e92003529e5c7bb11281f7c2c9b3fe8858403.tar.gz linux-4e9e92003529e5c7bb11281f7c2c9b3fe8858403.tar.bz2 linux-4e9e92003529e5c7bb11281f7c2c9b3fe8858403.zip |
USB: usbmon: end ugly tricks with DMA peeking
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>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/usb.h | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/include/linux/usb.h b/include/linux/usb.h index 19fabc487beb..3b45a0d27b80 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -1036,9 +1036,10 @@ typedef void (*usb_complete_t)(struct urb *); * @transfer_flags: A variety of flags may be used to affect how URB * submission, unlinking, or operation are handled. Different * kinds of URB can use different flags. - * @transfer_buffer: This identifies the buffer to (or from) which - * the I/O request will be performed (unless URB_NO_TRANSFER_DMA_MAP - * is set). This buffer must be suitable for DMA; allocate it with + * @transfer_buffer: This identifies the buffer to (or from) which the I/O + * request will be performed unless URB_NO_TRANSFER_DMA_MAP is set + * (however, do not leave garbage in transfer_buffer even then). + * This buffer must be suitable for DMA; allocate it with * kmalloc() or equivalent. For transfers to "in" endpoints, contents * of this buffer will be modified. This buffer is used for the data * stage of control transfers. @@ -1104,9 +1105,15 @@ typedef void (*usb_complete_t)(struct urb *); * allocate a DMA buffer with usb_buffer_alloc() or call usb_buffer_map(). * When these transfer flags are provided, host controller drivers will * attempt to use the dma addresses found in the transfer_dma and/or - * setup_dma fields rather than determining a dma address themselves. (Note - * that transfer_buffer and setup_packet must still be set because not all - * host controllers use DMA, nor do virtual root hubs). + * setup_dma fields rather than determining a dma address themselves. + * + * Note that transfer_buffer must still be set if the controller + * does not support DMA (as indicated by bus.uses_dma) and when talking + * to root hub. If you have to trasfer between highmem zone and the device + * on such controller, create a bounce buffer or bail out with an error. + * If transfer_buffer cannot be set (is in highmem) and the controller is DMA + * capable, assign NULL to it, so that usbmon knows not to use the value. + * The setup_packet must always be set, so it cannot be located in highmem. * * Initialization: * |