From 4e9e92003529e5c7bb11281f7c2c9b3fe8858403 Mon Sep 17 00:00:00 2001 From: Pete Zaitcev Date: Thu, 11 Jun 2009 08:53:20 -0600 Subject: 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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/mon/mon_main.c | 1 - 1 file changed, 1 deletion(-) (limited to 'drivers/usb/mon/mon_main.c') diff --git a/drivers/usb/mon/mon_main.c b/drivers/usb/mon/mon_main.c index 5e0ab4201c0..e0c2db3b767 100644 --- a/drivers/usb/mon/mon_main.c +++ b/drivers/usb/mon/mon_main.c @@ -361,7 +361,6 @@ static int __init mon_init(void) } // MOD_INC_USE_COUNT(which_module?); - mutex_lock(&usb_bus_list_lock); list_for_each_entry (ubus, &usb_bus_list, bus_list) { mon_bus_init(ubus); -- cgit v1.2.3-70-g09d2