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tracing/kprobes: Make special variable names more self-explainable
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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: Masami 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: Frederic Weisbecker <fweisbec@gmail.com>
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Masami Hiramatsu authored and Frederic Weisbecker committed Oct 12, 2009
1 parent 99329c4 commit 2e06ff6
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Showing 2 changed files with 35 additions and 39 deletions.
22 changes: 11 additions & 11 deletions Documentation/trace/kprobetrace.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,13 +35,13 @@ Synopsis of kprobe_events
MEMADDR : Address where the probe is inserted.

FETCHARGS : Arguments. Each probe can have up to 128 args.
%REG : Fetch register REG
@ADDR : Fetch memory at ADDR (ADDR should be in kernel)
%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.

Expand Down Expand Up @@ -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.
Expand Down Expand Up @@ -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
Expand Down
52 changes: 24 additions & 28 deletions kernel/trace/trace_kprobe.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
} 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;
}
break;
default:
} else
ret = -EINVAL;
}
return ret;
}

Expand Down Expand Up @@ -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
Expand Down

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