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Commit 2e06ff63 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Frederic Weisbecker
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tracing/kprobes: Make special variable names more self-explainable 



Rename special variables to more self-explainable names as below:
- $rv to $retval
- $sa to $stack
- $aN to $argN
- $sN to $stackN

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: <20091007222759.1684.3319.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 99329c44

Documentation/trace/kprobetrace.txt

+11 −11
Original line number Diff line number Diff line
@@ -38,10 +38,10 @@ Synopsis of kprobe_events 
  %REG		: Fetch register REG

  @ADDR		: Fetch memory at ADDR (ADDR should be in kernel)

  @SYM[+|-offs]	: Fetch memory at SYM +|- offs (SYM should be a data symbol)

  $sN	: Fetch Nth entry of stack (N >= 0)

  $sa	: Fetch stack address.

  $aN	: Fetch function argument. (N >= 0)(*)

  $rv	: Fetch return value.(**)

  $stackN	: Fetch Nth entry of stack (N >= 0)

  $stack	: Fetch stack address.

  $argN		: Fetch function argument. (N >= 0)(*)

  $retval	: Fetch return value.(**)

  +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)

  NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
@@ -84,13 +84,13 @@ 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=$arg0 filename=$arg1 flags=$arg2 mode=$arg3 > /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 >> /sys/kernel/debug/tracing/kprobe_events

  echo r:myretprobe do_sys_open $retval >> /sys/kernel/debug/tracing/kprobe_events



 This sets a kretprobe on the return point of do_sys_open() function with

recording return value as "myretprobe" event.
@@ -137,11 +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

           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=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

           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=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

           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3





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

kernel/trace/trace_kprobe.c

+24 −28
Original line number Diff line number Diff line
@@ -215,22 +215,22 @@ static int probe_arg_string(char *buf, size_t n, struct fetch_func *ff) 
	int ret = -EINVAL;



	if (ff->func == fetch_argument)

		ret = snprintf(buf, n, "$a%lu", (unsigned long)ff->data);

		ret = snprintf(buf, n, "$arg%lu", (unsigned long)ff->data);

	else if (ff->func == fetch_register) {

		const char *name;

		name = regs_query_register_name((unsigned int)((long)ff->data));

		ret = snprintf(buf, n, "%%%s", name);

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

		ret = snprintf(buf, n, "$s%lu", (unsigned long)ff->data);

		ret = snprintf(buf, n, "$stack%lu", (unsigned long)ff->data);

	else if (ff->func == fetch_memory)

		ret = snprintf(buf, n, "@0x%p", ff->data);

	else if (ff->func == fetch_symbol) {

		struct symbol_cache *sc = ff->data;

		ret = snprintf(buf, n, "@%s%+ld", sc->symbol, sc->offset);

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

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

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

	else if (ff->func == fetch_stack_address)

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

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

	else if (ff->func == fetch_indirect) {

		struct indirect_fetch_data *id = ff->data;

		size_t l = 0;
@@ -427,40 +427,36 @@ static int parse_probe_vars(char *arg, struct fetch_func *ff, int is_return) 
	int ret = 0;

	unsigned long param;



	switch (arg[0]) {

	case 'a':	/* argument */

		ret = strict_strtoul(arg + 1, 10, &param);

		if (ret || param > PARAM_MAX_ARGS)

			ret = -EINVAL;

		else {

			ff->func = fetch_argument;

			ff->data = (void *)param;

		}

		break;

	case 'r':	/* retval or retaddr */

		if (is_return && arg[1] == 'v') {

	if (strcmp(arg, "retval") == 0) {

		if (is_return) {

			ff->func = fetch_retvalue;

			ff->data = NULL;

		} else

			ret = -EINVAL;

		break;

	case 's':	/* stack */

		if (arg[1] == 'a') {

	} else if (strncmp(arg, "stack", 5) == 0) {

		if (arg[5] == '\0') {

			ff->func = fetch_stack_address;

			ff->data = NULL;

		} else {

			ret = strict_strtoul(arg + 1, 10, &param);

		} else if (isdigit(arg[5])) {

			ret = strict_strtoul(arg + 5, 10, &param);

			if (ret || param > PARAM_MAX_STACK)

				ret = -EINVAL;

			else {

				ff->func = fetch_stack;

				ff->data = (void *)param;

			}

		}

		break;

	default:

		} else

			ret = -EINVAL;

	} else if (strncmp(arg, "arg", 3) == 0 && isdigit(arg[3])) {

		ret = strict_strtoul(arg + 3, 10, &param);

		if (ret || param > PARAM_MAX_ARGS)

			ret = -EINVAL;

		else {

			ff->func = fetch_argument;

			ff->data = (void *)param;

		}

	} else

		ret = -EINVAL;

	return ret;

}
@@ -548,10 +544,10 @@ static int create_trace_probe(int argc, char **argv) 
	 *  - Add kprobe: p[:[GRP/]EVENT] KSYM[+OFFS]|KADDR [FETCHARGS]

	 *  - Add kretprobe: r[:[GRP/]EVENT] KSYM[+0] [FETCHARGS]

	 * Fetch args:

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

	 *  $rv	: fetch return value

	 *  $sa	: fetch stack address

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

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

	 *  $retval	: fetch return value

	 *  $stack	: fetch stack address

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

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

	 *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)

	 *  %REG	: fetch register REG