diff options
Diffstat (limited to 'Documentation/usb/usbmon.txt')
| -rw-r--r-- | Documentation/usb/usbmon.txt | 100 |
1 files changed, 60 insertions, 40 deletions
diff --git a/Documentation/usb/usbmon.txt b/Documentation/usb/usbmon.txt index 28425f736756..b0bd51080799 100644 --- a/Documentation/usb/usbmon.txt +++ b/Documentation/usb/usbmon.txt @@ -1,4 +1,9 @@ -* Introduction +====== +usbmon +====== + +Introduction +============ The name "usbmon" in lowercase refers to a facility in kernel which is used to collect traces of I/O on the USB bus. This function is analogous @@ -16,7 +21,8 @@ Two APIs are currently implemented: "text" and "binary". The binary API is available through a character device in /dev namespace and is an ABI. The text API is deprecated since 2.6.35, but available for convenience. -* How to use usbmon to collect raw text traces +How to use usbmon to collect raw text traces +============================================ Unlike the packet socket, usbmon has an interface which provides traces in a text format. This is used for two purposes. First, it serves as a @@ -26,38 +32,41 @@ are finalized. Second, humans can read it in case tools are not available. To collect a raw text trace, execute following steps. 1. Prepare +---------- Mount debugfs (it has to be enabled in your kernel configuration), and load the usbmon module (if built as module). The second step is skipped -if usbmon is built into the kernel. +if usbmon is built into the kernel:: -# mount -t debugfs none_debugs /sys/kernel/debug -# modprobe usbmon -# + # mount -t debugfs none_debugs /sys/kernel/debug + # modprobe usbmon + # -Verify that bus sockets are present. +Verify that bus sockets are present: -# ls /sys/kernel/debug/usb/usbmon -0s 0u 1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u -# + # ls /sys/kernel/debug/usb/usbmon + 0s 0u 1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u + # Now you can choose to either use the socket '0u' (to capture packets on all buses), and skip to step #3, or find the bus used by your device with step #2. This allows to filter away annoying devices that talk continuously. 2. Find which bus connects to the desired device +------------------------------------------------ Run "cat /sys/kernel/debug/usb/devices", and find the T-line which corresponds to the device. Usually you do it by looking for the vendor string. If you have many similar devices, unplug one and compare the two /sys/kernel/debug/usb/devices outputs. The T-line will have a bus number. -Example: -T: Bus=03 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 0 -D: Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 -P: Vendor=0557 ProdID=2004 Rev= 1.00 -S: Manufacturer=ATEN -S: Product=UC100KM V2.00 +Example:: + + T: Bus=03 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 2 Spd=12 MxCh= 0 + D: Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 + P: Vendor=0557 ProdID=2004 Rev= 1.00 + S: Manufacturer=ATEN + S: Product=UC100KM V2.00 "Bus=03" means it's bus 3. Alternatively, you can look at the output from "lsusb" and get the bus number from the appropriate line. Example: @@ -65,23 +74,28 @@ S: Product=UC100KM V2.00 Bus 003 Device 002: ID 0557:2004 ATEN UC100KM V2.00 3. Start 'cat' +-------------- + +:: -# cat /sys/kernel/debug/usb/usbmon/3u > /tmp/1.mon.out + # cat /sys/kernel/debug/usb/usbmon/3u > /tmp/1.mon.out -to listen on a single bus, otherwise, to listen on all buses, type: +to listen on a single bus, otherwise, to listen on all buses, type:: -# cat /sys/kernel/debug/usb/usbmon/0u > /tmp/1.mon.out + # cat /sys/kernel/debug/usb/usbmon/0u > /tmp/1.mon.out This process will read until it is killed. Naturally, the output can be redirected to a desirable location. This is preferred, because it is going to be quite long. 4. Perform the desired operation on the USB bus +----------------------------------------------- This is where you do something that creates the traffic: plug in a flash key, copy files, control a webcam, etc. 5. Kill cat +----------- Usually it's done with a keyboard interrupt (Control-C). @@ -89,7 +103,8 @@ At this point the output file (/tmp/1.mon.out in this example) can be saved, sent by e-mail, or inspected with a text editor. In the last case make sure that the file size is not excessive for your favourite editor. -* Raw text data format +Raw text data format +==================== Two formats are supported currently: the original, or '1t' format, and the '1u' format. The '1t' format is deprecated in kernel 2.6.21. The '1u' @@ -122,10 +137,14 @@ Here is the list of words, from left to right: - "Address" word (formerly a "pipe"). It consists of four fields, separated by colons: URB type and direction, Bus number, Device address, Endpoint number. Type and direction are encoded with two bytes in the following manner: + + == == ============================= Ci Co Control input and output Zi Zo Isochronous input and output Ii Io Interrupt input and output Bi Bo Bulk input and output + == == ============================= + Bus number, Device address, and Endpoint are decimal numbers, but they may have leading zeros, for the sake of human readers. @@ -178,24 +197,25 @@ Here is the list of words, from left to right: Examples: -An input control transfer to get a port status. +An input control transfer to get a port status:: -d5ea89a0 3575914555 S Ci:1:001:0 s a3 00 0000 0003 0004 4 < -d5ea89a0 3575914560 C Ci:1:001:0 0 4 = 01050000 + d5ea89a0 3575914555 S Ci:1:001:0 s a3 00 0000 0003 0004 4 < + d5ea89a0 3575914560 C Ci:1:001:0 0 4 = 01050000 An output bulk transfer to send a SCSI command 0x28 (READ_10) in a 31-byte -Bulk wrapper to a storage device at address 5: +Bulk wrapper to a storage device at address 5:: -dd65f0e8 4128379752 S Bo:1:005:2 -115 31 = 55534243 ad000000 00800000 80010a28 20000000 20000040 00000000 000000 -dd65f0e8 4128379808 C Bo:1:005:2 0 31 > + dd65f0e8 4128379752 S Bo:1:005:2 -115 31 = 55534243 ad000000 00800000 80010a28 20000000 20000040 00000000 000000 + dd65f0e8 4128379808 C Bo:1:005:2 0 31 > -* Raw binary format and API +Raw binary format and API +========================= The overall architecture of the API is about the same as the one above, only the events are delivered in binary format. Each event is sent in -the following structure (its name is made up, so that we can refer to it): +the following structure (its name is made up, so that we can refer to it):: -struct usbmon_packet { + struct usbmon_packet { u64 id; /* 0: URB ID - from submission to callback */ unsigned char type; /* 8: Same as text; extensible. */ unsigned char xfer_type; /* ISO (0), Intr, Control, Bulk (3) */ @@ -220,7 +240,7 @@ struct usbmon_packet { int start_frame; /* 52: For ISO */ unsigned int xfer_flags; /* 56: copy of URB's transfer_flags */ unsigned int ndesc; /* 60: Actual number of ISO descriptors */ -}; /* 64 total length */ + }; /* 64 total length */ These events can be received from a character device by reading with read(2), with an ioctl(2), or by accessing the buffer with mmap. However, read(2) @@ -244,12 +264,12 @@ no events are available. MON_IOCG_STATS, defined as _IOR(MON_IOC_MAGIC, 3, struct mon_bin_stats) -The argument is a pointer to the following structure: +The argument is a pointer to the following structure:: -struct mon_bin_stats { + struct mon_bin_stats { u32 queued; u32 dropped; -}; + }; The member "queued" refers to the number of events currently queued in the buffer (and not to the number of events processed since the last reset). @@ -273,13 +293,13 @@ This call returns the current size of the buffer in bytes. These calls wait for events to arrive if none were in the kernel buffer, then return the first event. The argument is a pointer to the following -structure: +structure:: -struct mon_get_arg { + struct mon_get_arg { struct usbmon_packet *hdr; void *data; size_t alloc; /* Length of data (can be zero) */ -}; + }; Before the call, hdr, data, and alloc should be filled. Upon return, the area pointed by hdr contains the next event structure, and the data buffer contains @@ -290,13 +310,13 @@ The MON_IOCX_GET copies 48 bytes to hdr area, MON_IOCX_GETX copies 64 bytes. MON_IOCX_MFETCH, defined as _IOWR(MON_IOC_MAGIC, 7, struct mon_mfetch_arg) This ioctl is primarily used when the application accesses the buffer -with mmap(2). Its argument is a pointer to the following structure: +with mmap(2). Its argument is a pointer to the following structure:: -struct mon_mfetch_arg { + struct mon_mfetch_arg { uint32_t *offvec; /* Vector of events fetched */ uint32_t nfetch; /* Number of events to fetch (out: fetched) */ uint32_t nflush; /* Number of events to flush */ -}; + }; The ioctl operates in 3 stages. @@ -329,7 +349,7 @@ be polled with select(2) and poll(2). But lseek(2) does not work. The basic idea is simple: To prepare, map the buffer by getting the current size, then using mmap(2). -Then, execute a loop similar to the one written in pseudo-code below: +Then, execute a loop similar to the one written in pseudo-code below:: struct mon_mfetch_arg fetch; struct usbmon_packet *hdr; |