[PATCH perf/core 02/10] perf probe: Accept %sdt and %cached event name

Masami Hiramatsu
2016-07-12T10:04:53Z

From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

To improbe usability, support %[PROVIDER:]SDTEVENT format to
add new probes on SDT and cached events.

e.g.
----
# perf probe -x /lib/libc-2.17.so %lll_lock_wait_private
Added new event:
sdt_libc:lll_lock_wait_private (on %lll_lock_wait_private in
/usr/lib/libc-2.17.so)

You can now use it in all perf tools, such as:

perf record -e sdt_libc:lll_lock_wait_private -aR sleep 1

# perf probe -l | more
sdt_libc:lll_lock_wait_private (on __lll_lock_wait_private+21
in /usr/lib/libc-2.17.so)
----

Note that this is not only for SDT events, but also normal
events with event-name.

e.g. define "myevent" on cache (-n doesn't add the real probe)
----
# perf probe -x ./perf --cache -n --add 'myevent=dso__load $params'
----
Reuse the "myevent" from cache as below.
----
# perf probe -x ./perf %myevent
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v10:
- Update Documentation/perf-probe.txt to add a link about SDT.
Changes in v7:
- Fix a bug to return an error if no SDT/cached events found in cache.
---
tools/perf/Documentation/perf-probe.txt | 9 +++
tools/perf/util/probe-event.c | 82 ++++++++++++++++++++++---------
tools/perf/util/probe-event.h | 1
tools/perf/util/probe-file.c | 9 +++
4 files changed, 76 insertions(+), 25 deletions(-)

diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt
index 7a258e9..39e3870 100644
--- a/tools/perf/Documentation/perf-probe.txt
+++ b/tools/perf/Documentation/perf-probe.txt
@@ -151,6 +151,8 @@ Probe points are defined by following syntax.
3) Define event based on source file with lazy pattern
[[GROUP:]EVENT=]SRC;PTN [ARG ...]

+ 4) Pre-defined SDT events or cached event with name
+ %[PROVIDER:]SDTEVENT

'EVENT' specifies the name of new event, if omitted, it will be set the name of the probed function. You can also specify a group name by 'GROUP', if omitted, set 'probe' is used for kprobe and 'probe_<bin>' is used for uprobe.
Note that using existing group name can conflict with other events. Especially, using the group name reserved for kernel modules can hide embedded events in the
@@ -158,6 +160,11 @@ modules.
'FUNC' specifies a probed function name, and it may have one of the following options; '+OFFS' is the offset from function entry address in bytes, ':RLN' is the relative-line number from function entry line, and '%return' means that it probes function return. And ';PTN' means lazy matching pattern (see LAZY MATCHING). Note that ';PTN' must be the end of the probe point definition. In addition, '@SRC' specifies a source file which has that function.
It is also possible to specify a probe point by the source line number or lazy matching by using 'SRC:ALN' or 'SRC;PTN' syntax, where 'SRC' is the source file path, ':ALN' is the line number and ';PTN' is the lazy matching pattern.
'ARG' specifies the arguments of this probe point, (see PROBE ARGUMENT).
+'SDTEVENT' and 'PROVIDER' is the pre-defined event name which is defined by user SDT (Statically Defined Tracing) or the pre-cached probes with event name.
+Note that before using the SDT event, the target binary (on which SDT events are defined) must be scanned by linkperf:perf-buildid-cache[1] to make SDT events as cached events.
+
+For details of the SDT, see below.
+https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html

PROBE ARGUMENT
--------------
@@ -237,4 +244,4 @@ Add probes at malloc() function on libc

SEE ALSO
--------
-linkperf:perf-trace[1], linkperf:perf-record[1]
+linkperf:perf-trace[1], linkperf:perf-record[1], linkperf:perf-buildid-cache[1]
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index dff9a54..3642cca 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1197,6 +1197,34 @@ err:
return err;
}

+static int parse_perf_probe_event_name(char **arg, struct perf_probe_event *pev)
+{
+ char *ptr;
+
+ ptr = strchr(*arg, ':');
+ if (ptr) {
+ *ptr = '\0';
+ if (!is_c_func_name(*arg))
+ goto ng_name;
+ pev->group = strdup(*arg);
+ if (!pev->group)
+ return -ENOMEM;
+ *arg = ptr + 1;
+ } else
+ pev->group = NULL;
+ if (!is_c_func_name(*arg)) {
+ng_name:
+ semantic_error("%s is bad for event name -it must "
+ "follow C symbol-naming rule.\n", *arg);
+ return -EINVAL;
+ }
+ pev->event = strdup(*arg);
+ if (pev->event == NULL)
+ return -ENOMEM;
+
+ return 0;
+}
+
/* Parse probepoint definition. */
static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
{
@@ -1204,38 +1232,43 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
char *ptr, *tmp;
char c, nc = 0;
bool file_spec = false;
+ int ret;
+
/*
* <Syntax>
* perf probe [GRP:][EVENT=]SRC[:LN|;PTN]
* perf probe [GRP:][EVENT=]FUNC[@SRC][+OFFS|%return|:LN|;PAT]
+ * perf probe %[GRP:]SDT_EVENT
*/
if (!arg)
return -EINVAL;

+ if (arg[0] == '%') {
+ pev->sdt = true;
+ arg++;
+ }
+
ptr = strpbrk(arg, ";=@+%");
- if (ptr && *ptr == '=') { /* Event name */
- *ptr = '\0';
- tmp = ptr + 1;
- ptr = strchr(arg, ':');
+ if (pev->sdt) {
if (ptr) {
- *ptr = '\0';
- if (!is_c_func_name(arg))
- goto not_fname;
- pev->group = strdup(arg);
- if (!pev->group)
- return -ENOMEM;
- arg = ptr + 1;
- } else
- pev->group = NULL;
- if (!is_c_func_name(arg)) {
-not_fname:
- semantic_error("%s is bad for event name -it must "
- "follow C symbol-naming rule.\n", arg);
+ semantic_error("%s must contain only an SDT event name.\n", arg);
return -EINVAL;
}
- pev->event = strdup(arg);
- if (pev->event == NULL)
- return -ENOMEM;
+ ret = parse_perf_probe_event_name(&arg, pev);
+ if (ret == 0) {
+ if (asprintf(&pev->point.function, "%%%s", pev->event) < 0)
+ ret = -errno;
+ }
+ return ret;
+ }
+
+ if (ptr && *ptr == '=') { /* Event name */
+ *ptr = '\0';
+ tmp = ptr + 1;
+ ret = parse_perf_probe_event_name(&arg, pev);
+ if (ret < 0)
+ return ret;
+
arg = tmp;
}

@@ -2876,7 +2909,8 @@ static int find_probe_trace_events_from_cache(struct perf_probe_event *pev,

entry = probe_cache__find(cache, pev);
if (!entry) {
- ret = 0;
+ /* SDT must be in the cache */
+ ret = pev->sdt ? -ENOENT : 0;
goto out;
}

@@ -2915,7 +2949,7 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
{
int ret;

- if (!pev->group) {
+ if (!pev->group && !pev->sdt) {
/* Set group name if not given */
if (!pev->uprobes) {
pev->group = strdup(PERFPROBE_GROUP);
@@ -2934,8 +2968,8 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,

/* At first, we need to lookup cache entry */
ret = find_probe_trace_events_from_cache(pev, tevs);
- if (ret > 0)
- return ret; /* Found in probe cache */
+ if (ret > 0 || pev->sdt) /* SDT can be found only in the cache */
+ return ret == 0 ? -ENOENT : ret; /* Found in probe cache */

if (arch__prefers_symtab() && !perf_probe_event_need_dwarf(pev)) {
ret = find_probe_trace_events_from_map(pev, tevs);
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 432b690..e18ea9f 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -85,6 +85,7 @@ struct perf_probe_event {
char *group; /* Group name */
struct perf_probe_point point; /* Probe point */
int nargs; /* Number of arguments */
+ bool sdt; /* SDT/cached event flag */
bool uprobes; /* Uprobe event flag */
char *target; /* Target binary */
struct perf_probe_arg *args; /* Arguments */
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 5b563b2..b642d06 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -547,6 +547,15 @@ probe_cache__find(struct probe_cache *pcache, struct perf_probe_event *pev)
return NULL;

list_for_each_entry(entry, &pcache->entries, node) {
+ if (pev->sdt) {
+ if (entry->pev.event &&
+ streql(entry->pev.event, pev->event) &&
+ (!pev->group ||
+ streql(entry->pev.group, pev->group)))
+ goto found;
+
+ continue;
+ }
/* Hit if same event name or same command-string */
if ((pev->event &&
(streql(entry->pev.group, pev->group) &&