diff options
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/coresight-cpu-debug.txt | 2 | ||||
| -rw-r--r-- | Documentation/trace/coresight.txt | 82 | ||||
| -rw-r--r-- | Documentation/trace/histogram.rst | 10 | ||||
| -rw-r--r-- | Documentation/trace/kprobetrace.rst | 49 | ||||
| -rw-r--r-- | Documentation/trace/uprobetracer.rst | 17 |
5 files changed, 131 insertions, 29 deletions
diff --git a/Documentation/trace/coresight-cpu-debug.txt b/Documentation/trace/coresight-cpu-debug.txt index f07e38094b40..1a660a39e3c0 100644 --- a/Documentation/trace/coresight-cpu-debug.txt +++ b/Documentation/trace/coresight-cpu-debug.txt @@ -151,7 +151,7 @@ At the runtime you can disable idle states with below methods: It is possible to disable CPU idle states by way of the PM QoS subsystem, more specifically by using the "/dev/cpu_dma_latency" -interface (see Documentation/power/pm_qos_interface.txt for more +interface (see Documentation/power/pm_qos_interface.rst for more details). As specified in the PM QoS documentation the requested parameter will stay in effect until the file descriptor is released. For example: diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt index efbc832146e7..b027d61b27a6 100644 --- a/Documentation/trace/coresight.txt +++ b/Documentation/trace/coresight.txt @@ -188,6 +188,49 @@ specific to that component only. "Implementation defined" customisations are expected to be accessed and controlled using those entries. +Device Naming scheme +------------------------ +The devices that appear on the "coresight" bus were named the same as their +parent devices, i.e, the real devices that appears on AMBA bus or the platform bus. +Thus the names were based on the Linux Open Firmware layer naming convention, +which follows the base physical address of the device followed by the device +type. e.g: + +root:~# ls /sys/bus/coresight/devices/ + 20010000.etf 20040000.funnel 20100000.stm 22040000.etm + 22140000.etm 230c0000.funnel 23240000.etm 20030000.tpiu + 20070000.etr 20120000.replicator 220c0000.funnel + 23040000.etm 23140000.etm 23340000.etm + +However, with the introduction of ACPI support, the names of the real +devices are a bit cryptic and non-obvious. Thus, a new naming scheme was +introduced to use more generic names based on the type of the device. The +following rules apply: + + 1) Devices that are bound to CPUs, are named based on the CPU logical + number. + + e.g, ETM bound to CPU0 is named "etm0" + + 2) All other devices follow a pattern, "<device_type_prefix>N", where : + + <device_type_prefix> - A prefix specific to the type of the device + N - a sequential number assigned based on the order + of probing. + + e.g, tmc_etf0, tmc_etr0, funnel0, funnel1 + +Thus, with the new scheme the devices could appear as : + +root:~# ls /sys/bus/coresight/devices/ + etm0 etm1 etm2 etm3 etm4 etm5 funnel0 + funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0 + +Some of the examples below might refer to old naming scheme and some +to the newer scheme, to give a confirmation that what you see on your +system is not unexpected. One must use the "names" as they appear on +the system under specified locations. + How to use the tracer modules ----------------------------- @@ -326,16 +369,25 @@ amount of processor cores), the "cs_etm" PMU will be listed only once. A Coresight PMU works the same way as any other PMU, i.e the name of the PMU is listed along with configuration options within forward slashes '/'. Since a Coresight system will typically have more than one sink, the name of the sink to -work with needs to be specified as an event option. Names for sink to choose -from are listed in sysFS under ($SYSFS)/bus/coresight/devices: +work with needs to be specified as an event option. +On newer kernels the available sinks are listed in sysFS under: +($SYSFS)/bus/event_source/devices/cs_etm/sinks/ + + root@localhost:/sys/bus/event_source/devices/cs_etm/sinks# ls + tmc_etf0 tmc_etr0 tpiu0 + +On older kernels, this may need to be found from the list of coresight devices, +available under ($SYSFS)/bus/coresight/devices/: + + root:~# ls /sys/bus/coresight/devices/ + etm0 etm1 etm2 etm3 etm4 etm5 funnel0 + funnel1 funnel2 replicator0 stm0 tmc_etf0 tmc_etr0 tpiu0 - root@linaro-nano:~# ls /sys/bus/coresight/devices/ - 20010000.etf 20040000.funnel 20100000.stm 22040000.etm - 22140000.etm 230c0000.funnel 23240000.etm 20030000.tpiu - 20070000.etr 20120000.replicator 220c0000.funnel - 23040000.etm 23140000.etm 23340000.etm + root@linaro-nano:~# perf record -e cs_etm/@tmc_etr0/u --per-thread program - root@linaro-nano:~# perf record -e cs_etm/@20070000.etr/u --per-thread program +As mentioned above in section "Device Naming scheme", the names of the devices could +look different from what is used in the example above. One must use the device names +as it appears under the sysFS. The syntax within the forward slashes '/' is important. The '@' character tells the parser that a sink is about to be specified and that this is the sink @@ -352,7 +404,7 @@ perf can be used to record and analyze trace of programs. Execution can be recorded using 'perf record' with the cs_etm event, specifying the name of the sink to record to, e.g: - perf record -e cs_etm/@20070000.etr/u --per-thread + perf record -e cs_etm/@tmc_etr0/u --per-thread The 'perf report' and 'perf script' commands can be used to analyze execution, synthesizing instruction and branch events from the instruction trace. @@ -381,7 +433,7 @@ sort example is from the AutoFDO tutorial (https://gcc.gnu.org/wiki/AutoFDO/Tuto Bubble sorting array of 30000 elements 5910 ms - $ perf record -e cs_etm/@20070000.etr/u --per-thread taskset -c 2 ./sort + $ perf record -e cs_etm/@tmc_etr0/u --per-thread taskset -c 2 ./sort Bubble sorting array of 30000 elements 12543 ms [ perf record: Woken up 35 times to write data ] @@ -405,7 +457,7 @@ than the program flow through the code. As with any other CoreSight component, specifics about the STM tracer can be found in sysfs with more information on each entry being found in [1]: -root@genericarmv8:~# ls /sys/bus/coresight/devices/20100000.stm +root@genericarmv8:~# ls /sys/bus/coresight/devices/stm0 enable_source hwevent_select port_enable subsystem uevent hwevent_enable mgmt port_select traceid root@genericarmv8:~# @@ -413,14 +465,14 @@ root@genericarmv8:~# Like any other source a sink needs to be identified and the STM enabled before being used: -root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20010000.etf/enable_sink -root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/20100000.stm/enable_source +root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/tmc_etf0/enable_sink +root@genericarmv8:~# echo 1 > /sys/bus/coresight/devices/stm0/enable_source From there user space applications can request and use channels using the devfs interface provided for that purpose by the generic STM API: -root@genericarmv8:~# ls -l /dev/20100000.stm -crw------- 1 root root 10, 61 Jan 3 18:11 /dev/20100000.stm +root@genericarmv8:~# ls -l /dev/stm0 +crw------- 1 root root 10, 61 Jan 3 18:11 /dev/stm0 root@genericarmv8:~# Details on how to use the generic STM API can be found here [2]. diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index fb621a1c2638..8408670d0328 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -1010,7 +1010,7 @@ Extended error information For example, suppose we wanted to take a look at the relative weights in terms of skb length for each callpath that leads to a - netif_receieve_skb event when downloading a decent-sized file using + netif_receive_skb event when downloading a decent-sized file using wget. First we set up an initially paused stacktrace trigger on the @@ -1843,7 +1843,7 @@ practice, not every handler.action combination is currently supported; if a given handler.action combination isn't supported, the hist trigger will fail with -EINVAL; -The default 'handler.action' if none is explicity specified is as it +The default 'handler.action' if none is explicitly specified is as it always has been, to simply update the set of values associated with an entry. Some applications, however, may want to perform additional actions at that point, such as generate another event, or compare and @@ -2088,7 +2088,7 @@ The following commonly-used handler.action pairs are available: and the saved values corresponding to the max are displayed following the rest of the fields. - If a snaphot was taken, there is also a message indicating that, + If a snapshot was taken, there is also a message indicating that, along with the value and event that triggered the global maximum: # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist @@ -2176,7 +2176,7 @@ The following commonly-used handler.action pairs are available: hist trigger entry. Note that in this case the changed value is a global variable - associated withe current trace instance. The key of the specific + associated with current trace instance. The key of the specific trace event that caused the value to change and the global value itself are displayed, along with a message stating that a snapshot has been taken and where to find it. The user can use the key @@ -2203,7 +2203,7 @@ The following commonly-used handler.action pairs are available: and the saved values corresponding to that value are displayed following the rest of the fields. - If a snaphot was taken, there is also a message indicating that, + If a snapshot was taken, there is also a message indicating that, along with the value and event that triggered the snapshot:: # cat /sys/kernel/debug/tracing/events/tcp/tcp_probe/hist diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index 235ce2ab131a..fbb314bfa112 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -51,15 +51,17 @@ Synopsis of kprobe_events $argN : Fetch the Nth function argument. (N >= 1) (\*1) $retval : Fetch return value.(\*2) $comm : Fetch current task comm. - +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(\*3) + +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*3)(\*4) NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types - (x8/x16/x32/x64), "string" and bitfield are supported. + (x8/x16/x32/x64), "string", "ustring" and bitfield + are supported. (\*1) only for the probe on function entry (offs == 0). (\*2) only for return probe. (\*3) this is useful for fetching a field of data structures. + (\*4) "u" means user-space dereference. See :ref:`user_mem_access`. Types ----- @@ -77,7 +79,8 @@ apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is wrong, but '+8($stack):x8[8]' is OK.) String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container -has been paged out. +has been paged out. "ustring" type is an alternative of string for user-space. +See :ref:`user_mem_access` for more info.. The string array type is a bit different from other types. For other base types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same as +0(%di):x32.) But string[1] is not equal to string. The string type itself @@ -92,6 +95,25 @@ Symbol type('symbol') is an alias of u32 or u64 type (depends on BITS_PER_LONG) which shows given pointer in "symbol+offset" style. For $comm, the default type is "string"; any other type is invalid. +.. _user_mem_access: +User Memory Access +------------------ +Kprobe events supports user-space memory access. For that purpose, you can use +either user-space dereference syntax or 'ustring' type. + +The user-space dereference syntax allows you to access a field of a data +structure in user-space. This is done by adding the "u" prefix to the +dereference syntax. For example, +u4(%si) means it will read memory from the +address in the register %si offset by 4, and the memory is expected to be in +user-space. You can use this for strings too, e.g. +u0(%si):string will read +a string from the address in the register %si that is expected to be in user- +space. 'ustring' is a shortcut way of performing the same task. That is, ++0(%si):ustring is equivalent to +u0(%si):string. + +Note that kprobe-event provides the user-memory access syntax but it doesn't +use it transparently. This means if you use normal dereference or string type +for user memory, it might fail, and may always fail on some archs. The user +has to carefully check if the target data is in kernel or user space. Per-Probe Event Filtering ------------------------- @@ -124,6 +146,20 @@ You can check the total number of probe hits and probe miss-hits via The first column is event name, the second is the number of probe hits, the third is the number of probe miss-hits. +Kernel Boot Parameter +--------------------- +You can add and enable new kprobe events when booting up the kernel by +"kprobe_event=" parameter. The parameter accepts a semicolon-delimited +kprobe events, which format is similar to the kprobe_events. +The difference is that the probe definition parameters are comma-delimited +instead of space. For example, adding myprobe event on do_sys_open like below + + p:myprobe do_sys_open dfd=%ax filename=%dx flags=%cx mode=+4($stack) + +should be below for kernel boot parameter (just replace spaces with comma) + + p:myprobe,do_sys_open,dfd=%ax,filename=%dx,flags=%cx,mode=+4($stack) + Usage examples -------------- @@ -189,6 +225,13 @@ events, you need to enable it. echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable +Use the following command to start tracing in an interval. +:: + + # echo 1 > tracing_on + Open something... + # echo 0 > tracing_on + And you can see the traced information via /sys/kernel/debug/tracing/trace. :: diff --git a/Documentation/trace/uprobetracer.rst b/Documentation/trace/uprobetracer.rst index 4346e23e3ae7..6e75a6c5a2c8 100644 --- a/Documentation/trace/uprobetracer.rst +++ b/Documentation/trace/uprobetracer.rst @@ -42,16 +42,18 @@ Synopsis of uprobe_tracer @+OFFSET : Fetch memory at OFFSET (OFFSET from same file as PATH) $stackN : Fetch Nth entry of stack (N >= 0) $stack : Fetch stack address. - $retval : Fetch return value.(*) + $retval : Fetch return value.(\*1) $comm : Fetch current task comm. - +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**) + +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*2)(\*3) NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types (x8/x16/x32/x64), "string" and bitfield are supported. - (*) only for return probe. - (**) this is useful for fetching a field of data structures. + (\*1) only for return probe. + (\*2) this is useful for fetching a field of data structures. + (\*3) Unlike kprobe event, "u" prefix will just be ignored, becuse uprobe + events can access only user-space memory. Types ----- @@ -152,10 +154,15 @@ events, you need to enable it by:: # echo 1 > events/uprobes/enable -Lets disable the event after sleeping for some time. +Lets start tracing, sleep for some time and stop tracing. :: + # echo 1 > tracing_on # sleep 20 + # echo 0 > tracing_on + +Also, you can disable the event by:: + # echo 0 > events/uprobes/enable And you can see the traced information via /sys/kernel/debug/tracing/trace. |