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tracing/kprobes: Add $ prefix to special variables

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Add $ prefix to the special variables(e.g. sa, rv) of kprobe-tracer.
This resolves consistency issues between kprobe_events and perf-kprobe.

The main goal is to avoid conflicts between local variable names of
probed functions, used by perf probe, and special variables used
in the kprobe event creation interface (stack values, etc...) and
also available from perf probe.

ie: we don't want rv (return value) to conflict with a local variable
named rv in a probed function.

Signed-off-by: Masami Hiramatsu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Ananth N Mavinakayanahalli <[email protected]>
Cc: Jim Keniston <[email protected]>
Cc: Frank Ch. Eigler <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
This commit is contained in:
Masami Hiramatsu 2009-10-07 18:27:40 -04:00 • committed by Frederic Weisbecker
commit 405b2651e4
2 changed files with 47 additions and 33 deletions
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20
Documentation/trace/kprobetrace.txt
View file

@ -36,13 +36,13 @@ Synopsis of kprobe_events
FETCHARGS : Arguments. Each probe can have up to 128 args.
%REG : Fetch register REG
sN : Fetch Nth entry of stack (N >= 0)
sa : Fetch stack address.
@ADDR : Fetch memory at ADDR (ADDR should be in kernel)
@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
aN : Fetch function argument. (N >= 0)(*)
rv : Fetch return value.(**)
ra : Fetch return address.(**)
$sN : Fetch Nth entry of stack (N >= 0)
$sa : Fetch stack address.
$aN : Fetch function argument. (N >= 0)(*)
$rv : Fetch return value.(**)
$ra : Fetch return address.(**)
+|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
@ -85,13 +85,13 @@ Usage examples
To add a probe as a new event, write a new definition to kprobe_events
as below.
echo p:myprobe do_sys_open dfd=a0 filename=a1 flags=a2 mode=a3 > /sys/kernel/debug/tracing/kprobe_events
echo p:myprobe do_sys_open dfd=$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. 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
echo r:myretprobe do_sys_open $rv $ra >> /sys/kernel/debug/tracing/kprobe_events
This sets a kretprobe on the return point of do_sys_open() function with
recording return value and return address as "myretprobe" event.
@ -138,11 +138,11 @@ events, you need to enable it.
# TASK-PID CPU# TIMESTAMP FUNCTION
# | | | | |
<...>-1447 [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0
<...>-1447 [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) rv=fffffffffffffffe ra=ffffffff81367a3a
<...>-1447 [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $rv=fffffffffffffffe $ra=ffffffff81367a3a
<...>-1447 [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6
<...>-1447 [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) rv=3 ra=ffffffff81367a3a
<...>-1447 [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3 $ra=ffffffff81367a3a
<...>-1447 [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10
<...>-1447 [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) rv=3 ra=ffffffff81367a3a
<...>-1447 [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3 $ra=ffffffff81367a3a
Each line shows when the kernel hits an event, and <- SYMBOL means kernel