提交 00b27da3 编写于 作者: C Changbin Du 提交者: Jonathan Corbet

trace doc: convert trace/uprobetracer.txt to rst format

This converts the plain text documentation to reStructuredText format and
add it into Sphinx TOC tree. No essential content change.

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NChangbin Du <changbin.du@intel.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>
上级 263ee775
...@@ -10,3 +10,4 @@ Linux Tracing Technologies ...@@ -10,3 +10,4 @@ Linux Tracing Technologies
ftrace ftrace
ftrace-uses ftrace-uses
kprobetrace kprobetrace
uprobetracer
Uprobe-tracer: Uprobe-based Event Tracing =========================================
========================================= Uprobe-tracer: Uprobe-based Event Tracing
=========================================
Documentation written by Srikar Dronamraju :Author: Srikar Dronamraju
Overview Overview
...@@ -19,6 +20,8 @@ user to calculate the offset of the probepoint in the object. ...@@ -19,6 +20,8 @@ user to calculate the offset of the probepoint in the object.
Synopsis of uprobe_tracer Synopsis of uprobe_tracer
------------------------- -------------------------
::
p[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a uprobe p[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a uprobe
r[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a return uprobe (uretprobe) r[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS] : Set a return uprobe (uretprobe)
-:[GRP/]EVENT : Clear uprobe or uretprobe event -:[GRP/]EVENT : Clear uprobe or uretprobe event
...@@ -57,7 +60,7 @@ x86-64 uses x64). ...@@ -57,7 +60,7 @@ x86-64 uses x64).
String type is a special type, which fetches a "null-terminated" string from String type is a special type, which fetches a "null-terminated" string from
user space. user space.
Bitfield is another special type, which takes 3 parameters, bit-width, bit- Bitfield is another special type, which takes 3 parameters, bit-width, bit-
offset, and container-size (usually 32). The syntax is; offset, and container-size (usually 32). The syntax is::
b<bit-width>@<bit-offset>/<container-size> b<bit-width>@<bit-offset>/<container-size>
...@@ -74,28 +77,28 @@ the third is the number of probe miss-hits. ...@@ -74,28 +77,28 @@ the third is the number of probe miss-hits.
Usage examples Usage examples
-------------- --------------
* Add a probe as a new uprobe event, write a new definition to uprobe_events * Add a probe as a new uprobe event, write a new definition to uprobe_events
as below: (sets a uprobe at an offset of 0x4245c0 in the executable /bin/bash) as below (sets a uprobe at an offset of 0x4245c0 in the executable /bin/bash)::
echo 'p /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events echo 'p /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events
* Add a probe as a new uretprobe event: * Add a probe as a new uretprobe event::
echo 'r /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events echo 'r /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events
* Unset registered event: * Unset registered event::
echo '-:p_bash_0x4245c0' >> /sys/kernel/debug/tracing/uprobe_events echo '-:p_bash_0x4245c0' >> /sys/kernel/debug/tracing/uprobe_events
* Print out the events that are registered: * Print out the events that are registered::
cat /sys/kernel/debug/tracing/uprobe_events cat /sys/kernel/debug/tracing/uprobe_events
* Clear all events: * Clear all events::
echo > /sys/kernel/debug/tracing/uprobe_events echo > /sys/kernel/debug/tracing/uprobe_events
Following example shows how to dump the instruction pointer and %ax register Following example shows how to dump the instruction pointer and %ax register
at the probed text address. Probe zfree function in /bin/zsh: at the probed text address. Probe zfree function in /bin/zsh::
# cd /sys/kernel/debug/tracing/ # cd /sys/kernel/debug/tracing/
# cat /proc/`pgrep zsh`/maps | grep /bin/zsh | grep r-xp # cat /proc/`pgrep zsh`/maps | grep /bin/zsh | grep r-xp
...@@ -103,24 +106,27 @@ at the probed text address. Probe zfree function in /bin/zsh: ...@@ -103,24 +106,27 @@ at the probed text address. Probe zfree function in /bin/zsh:
# objdump -T /bin/zsh | grep -w zfree # objdump -T /bin/zsh | grep -w zfree
0000000000446420 g DF .text 0000000000000012 Base zfree 0000000000446420 g DF .text 0000000000000012 Base zfree
0x46420 is the offset of zfree in object /bin/zsh that is loaded at 0x46420 is the offset of zfree in object /bin/zsh that is loaded at
0x00400000. Hence the command to uprobe would be: 0x00400000. Hence the command to uprobe would be::
# echo 'p:zfree_entry /bin/zsh:0x46420 %ip %ax' > uprobe_events # echo 'p:zfree_entry /bin/zsh:0x46420 %ip %ax' > uprobe_events
And the same for the uretprobe would be: And the same for the uretprobe would be::
# echo 'r:zfree_exit /bin/zsh:0x46420 %ip %ax' >> uprobe_events # echo 'r:zfree_exit /bin/zsh:0x46420 %ip %ax' >> uprobe_events
Please note: User has to explicitly calculate the offset of the probe-point .. note:: User has to explicitly calculate the offset of the probe-point
in the object. We can see the events that are registered by looking at the in the object.
uprobe_events file.
We can see the events that are registered by looking at the uprobe_events file.
::
# cat uprobe_events # cat uprobe_events
p:uprobes/zfree_entry /bin/zsh:0x00046420 arg1=%ip arg2=%ax p:uprobes/zfree_entry /bin/zsh:0x00046420 arg1=%ip arg2=%ax
r:uprobes/zfree_exit /bin/zsh:0x00046420 arg1=%ip arg2=%ax r:uprobes/zfree_exit /bin/zsh:0x00046420 arg1=%ip arg2=%ax
Format of events can be seen by viewing the file events/uprobes/zfree_entry/format Format of events can be seen by viewing the file events/uprobes/zfree_entry/format.
::
# cat events/uprobes/zfree_entry/format # cat events/uprobes/zfree_entry/format
name: zfree_entry name: zfree_entry
...@@ -139,16 +145,18 @@ Format of events can be seen by viewing the file events/uprobes/zfree_entry/form ...@@ -139,16 +145,18 @@ Format of events can be seen by viewing the file events/uprobes/zfree_entry/form
print fmt: "(%lx) arg1=%lx arg2=%lx", REC->__probe_ip, REC->arg1, REC->arg2 print fmt: "(%lx) arg1=%lx arg2=%lx", REC->__probe_ip, REC->arg1, REC->arg2
Right after definition, each event is disabled by default. For tracing these Right after definition, each event is disabled by default. For tracing these
events, you need to enable it by: events, you need to enable it by::
# echo 1 > events/uprobes/enable # echo 1 > events/uprobes/enable
Lets disable the event after sleeping for some time. Lets disable the event after sleeping for some time.
::
# sleep 20 # sleep 20
# echo 0 > events/uprobes/enable # echo 0 > events/uprobes/enable
And you can see the traced information via /sys/kernel/debug/tracing/trace. And you can see the traced information via /sys/kernel/debug/tracing/trace.
::
# cat trace # cat trace
# tracer: nop # tracer: nop
......
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