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Commit 99329c44 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Frederic Weisbecker
Browse files

tracing/kprobes: Remove '$ra' special variable 



Remove '$ra' (return address) because it is already shown at the head of
each entry.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Frank Ch. Eigler <fche@redhat.com>
LKML-Reference: <20091007222748.1684.12711.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 405b2651

Documentation/trace/kprobetrace.txt

+6 −7
Original line number Diff line number Diff line
@@ -42,7 +42,6 @@ Synopsis of kprobe_events 
  $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.
@@ -91,10 +90,10 @@ as below. 
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 >> /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.

recording return value as "myretprobe" event.

 You can see the format of these events via

/sys/kernel/debug/tracing/events/kprobes/<EVENT>/format.
@@ -138,11 +137,11 @@ 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

           <...>-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

           <...>-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





 Each line shows when the kernel hits an event, and <- SYMBOL means kernel

kernel/trace/trace_kprobe.c

+0 −11
Original line number Diff line number Diff line
@@ -85,11 +85,6 @@ static __kprobes unsigned long fetch_retvalue(struct pt_regs *regs, 
	return regs_return_value(regs);

}



static __kprobes unsigned long fetch_ip(struct pt_regs *regs, void *dummy)

{

	return instruction_pointer(regs);

}



static __kprobes unsigned long fetch_stack_address(struct pt_regs *regs,

						   void *dummy)

{
@@ -234,8 +229,6 @@ static int probe_arg_string(char *buf, size_t n, struct fetch_func *ff) 
		ret = snprintf(buf, n, "@%s%+ld", sc->symbol, sc->offset);

	} else if (ff->func == fetch_retvalue)

		ret = snprintf(buf, n, "$rv");

	else if (ff->func == fetch_ip)

		ret = snprintf(buf, n, "$ra");

	else if (ff->func == fetch_stack_address)

		ret = snprintf(buf, n, "$sa");

	else if (ff->func == fetch_indirect) {
@@ -448,9 +441,6 @@ static int parse_probe_vars(char *arg, struct fetch_func *ff, int is_return) 
		if (is_return && arg[1] == 'v') {

			ff->func = fetch_retvalue;

			ff->data = NULL;

		} else if (is_return && arg[1] == 'a') {

			ff->func = fetch_ip;

			ff->data = NULL;

		} else

			ret = -EINVAL;

		break;
@@ -560,7 +550,6 @@ static int create_trace_probe(int argc, char **argv) 
	 * Fetch args:

	 *  $aN	: fetch Nth of function argument. (N:0-)

	 *  $rv	: fetch return value

	 *  $ra	: fetch return address

	 *  $sa	: fetch stack address

	 *  $sN	: fetch Nth of stack (N:0-)

	 *  @ADDR	: fetch memory at ADDR (ADDR should be in kernel)