tracing/kprobes: Add argument name support
Add argument name assignment support and remove "alias" lines from format.
This allows user to assign unique name to each argument. For example,
$ echo p do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > kprobe_events
This assigns dfd, filename, flags, and mode to 1st - 4th arguments
respectively. Trace buffer shows those names too.
<...>-1439 [000] 1200885.933147: do_sys_open+0x0/0xdf: dfd=ffffff9c filename=bfa898ac flags=8000 mode=0
This helps users to know what each value means.
Users can filter each events by these names too. Note that you can not
filter by argN anymore.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <20090910235337.22412.77383.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 8f882eb..aaa6c10 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -42,7 +42,8 @@
aN : Fetch function argument. (N >= 0)(*)
rv : Fetch return value.(**)
ra : Fetch return address.(**)
- +|-offs(FETCHARG) : fetch memory at FETCHARG +|- offs address.(***)
+ +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
+ NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
(*) aN may not correct on asmlinkaged functions and at the middle of
function body.
@@ -62,12 +63,10 @@
You can enable/disable the probe by writing 1 or 0 on it.
format:
- This shows the format of this probe event. It also shows aliases of arguments
- which you specified to kprobe_events.
+ This shows the format of this probe event.
filter:
- You can write filtering rules of this event. And you can use both of aliase
- names and field names for describing filters.
+ You can write filtering rules of this event.
id:
This shows the id of this probe event.
@@ -85,10 +84,11 @@
To add a probe as a new event, write a new definition to kprobe_events
as below.
- echo p:myprobe do_sys_open a0 a1 a2 a3 > /sys/kernel/debug/tracing/kprobe_events
+ echo p:myprobe do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > /sys/kernel/debug/tracing/kprobe_events
This sets a kprobe on the top of do_sys_open() function with recording
-1st to 4th arguments as "myprobe" event.
+1st to 4th arguments as "myprobe" event. As this example shows, users can
+choose more familiar names for each arguments.
echo r:myretprobe do_sys_open rv ra >> /sys/kernel/debug/tracing/kprobe_events
@@ -99,7 +99,7 @@
cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format
name: myprobe
-ID: 23
+ID: 75
format:
field:unsigned short common_type; offset:0; size:2;
field:unsigned char common_flags; offset:2; size:1;
@@ -109,21 +109,15 @@
field: unsigned long ip; offset:16;tsize:8;
field: int nargs; offset:24;tsize:4;
- field: unsigned long arg0; offset:32;tsize:8;
- field: unsigned long arg1; offset:40;tsize:8;
- field: unsigned long arg2; offset:48;tsize:8;
- field: unsigned long arg3; offset:56;tsize:8;
+ field: unsigned long dfd; offset:32;tsize:8;
+ field: unsigned long filename; offset:40;tsize:8;
+ field: unsigned long flags; offset:48;tsize:8;
+ field: unsigned long mode; offset:56;tsize:8;
- alias: a0; original: arg0;
- alias: a1; original: arg1;
- alias: a2; original: arg2;
- alias: a3; original: arg3;
-
-print fmt: "%lx: 0x%lx 0x%lx 0x%lx 0x%lx", ip, arg0, arg1, arg2, arg3
+print fmt: "%lx: dfd=%lx filename=%lx flags=%lx mode=%lx", ip, REC->dfd, REC->filename, REC->flags, REC->mode
- You can see that the event has 4 arguments and alias expressions
-corresponding to it.
+ You can see that the event has 4 arguments as in the expressions you specified.
echo > /sys/kernel/debug/tracing/kprobe_events
@@ -135,12 +129,12 @@
#
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
- <...>-1447 [001] 1038282.286875: do_sys_open+0x0/0xd6: 0x3 0x7fffd1ec4440 0x8000 0x0
- <...>-1447 [001] 1038282.286878: sys_openat+0xc/0xe <- do_sys_open: 0xfffffffffffffffe 0xffffffff81367a3a
- <...>-1447 [001] 1038282.286885: do_sys_open+0x0/0xd6: 0xffffff9c 0x40413c 0x8000 0x1b6
- <...>-1447 [001] 1038282.286915: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
- <...>-1447 [001] 1038282.286969: do_sys_open+0x0/0xd6: 0xffffff9c 0x4041c6 0x98800 0x10
- <...>-1447 [001] 1038282.286976: sys_open+0x1b/0x1d <- do_sys_open: 0x3 0xffffffff81367a3a
+ <...>-1447 [001] 1038282.286875: do_sys_open+0x0/0xd6: dfd=3 filename=7fffd1ec4440 flags=8000 mode=0
+ <...>-1447 [001] 1038282.286878: sys_openat+0xc/0xe <- do_sys_open: rv=fffffffffffffffe ra=ffffffff81367a3a
+ <...>-1447 [001] 1038282.286885: do_sys_open+0x0/0xd6: dfd=ffffff9c filename=40413c flags=8000 mode=1b6
+ <...>-1447 [001] 1038282.286915: sys_open+0x1b/0x1d <- do_sys_open: rv=3 ra=ffffffff81367a3a
+ <...>-1447 [001] 1038282.286969: do_sys_open+0x0/0xd6: dfd=ffffff9c filename=4041c6 flags=98800 mode=10
+ <...>-1447 [001] 1038282.286976: sys_open+0x1b/0x1d <- do_sys_open: rv=3 ra=ffffffff81367a3a
Each line shows when the kernel hits a probe, and <- SYMBOL means kernel