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Subject[tip:perf/probes] tracing/kprobes: Make special variable names more self-explainable
Commit-ID:  2e06ff6389aedafc4a3a374344ac70672252f9b5
Gitweb: http://git.kernel.org/tip/2e06ff6389aedafc4a3a374344ac70672252f9b5
Author: Masami Hiramatsu <mhiramat@redhat.com>
AuthorDate: Wed, 7 Oct 2009 18:27:59 -0400
Committer: Frederic Weisbecker <fweisbec@gmail.com>
CommitDate: Mon, 12 Oct 2009 23:30:29 +0200

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: 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>
---
Documentation/trace/kprobetrace.txt | 22 +++++++-------
kernel/trace/trace_kprobe.c | 52 ++++++++++++++++-------------------
2 files changed, 35 insertions(+), 39 deletions(-)
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 4208253..1541524 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -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.

@@ -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
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ba6d3bd..3313fa7 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -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;
}
+ } 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;
}

@@ -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

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