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tracing/kprobes: Add argument name support

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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 <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Frank Ch. Eigler <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: K.Prasad <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Tom Zanussi <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
This commit is contained in:
Masami Hiramatsu 2009-09-10 19:53:38 -04:00 • committed by Frederic Weisbecker
commit eca0d916f6
2 changed files with 84 additions and 90 deletions
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46
Documentation/trace/kprobetrace.txt
View file

@ -42,7 +42,8 @@ Synopsis of kprobe_events
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 @@ enabled:
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 @@ Usage examples
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 @@ recording return value and return address as "myretprobe" event.
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 @@ format:
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 @@ corresponding to it.
#
# 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