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Date: Mon, 1 Aug 2022 11:32:25 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
Ingo Molnar <mingo@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH 2/3] tracing/eprobe: Add eprobe filter support
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Add the filter option to the event probe. This is useful if user wants
to derive a new event based on the condition of the original event.
E.g.
echo 'e:egroup/stat_runtime_4core sched/sched_stat_runtime \
runtime=$runtime:u32 if cpu < 4' >> ../dynamic_events
Then it can filter the events only on first 4 cores.
Note that the fields used for 'if' must be the fields in the original
events, not eprobe events.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
kernel/trace/trace_eprobe.c | 104 ++++++++++++++++++++++++++++++++++++++++---
kernel/trace/trace_probe.h | 3 +
2 files changed, 98 insertions(+), 9 deletions(-)
diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 4a0e9d927443..8b32d1a3b9c7 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -26,6 +26,9 @@ struct trace_eprobe {
/* tracepoint event */
const char *event_name;
+ /* filter string for the tracepoint */
+ char *filter_str;
+
struct trace_event_call *event;
struct dyn_event devent;
@@ -589,14 +592,15 @@ static struct event_trigger_data *
new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file)
{
struct event_trigger_data *trigger;
+ struct event_filter *filter = NULL;
struct eprobe_data *edata;
+ int ret;
edata = kzalloc(sizeof(*edata), GFP_KERNEL);
trigger = kzalloc(sizeof(*trigger), GFP_KERNEL);
if (!trigger || !edata) {
- kfree(edata);
- kfree(trigger);
- return ERR_PTR(-ENOMEM);
+ ret = -ENOMEM;
+ goto error;
}
trigger->flags = EVENT_TRIGGER_FL_PROBE;
@@ -611,13 +615,25 @@ new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file)
trigger->cmd_ops = &event_trigger_cmd;
INIT_LIST_HEAD(&trigger->list);
- RCU_INIT_POINTER(trigger->filter, NULL);
+
+ if (ep->filter_str) {
+ ret = create_event_filter(file->tr, file->event_call,
+ ep->filter_str, false, &filter);
+ if (ret)
+ goto error;
+ }
+ RCU_INIT_POINTER(trigger->filter, filter);
edata->file = file;
edata->ep = ep;
trigger->private_data = edata;
return trigger;
+error:
+ free_event_filter(filter);
+ kfree(edata);
+ kfree(trigger);
+ return ERR_PTR(ret);
}
static int enable_eprobe(struct trace_eprobe *ep,
@@ -651,6 +667,7 @@ static int disable_eprobe(struct trace_eprobe *ep,
{
struct event_trigger_data *trigger = NULL, *iter;
struct trace_event_file *file;
+ struct event_filter *filter;
struct eprobe_data *edata;
file = find_event_file(tr, ep->event_system, ep->event_name);
@@ -677,6 +694,10 @@ static int disable_eprobe(struct trace_eprobe *ep,
/* Make sure nothing is using the edata or trigger */
tracepoint_synchronize_unregister();
+ filter = rcu_access_pointer(trigger->filter);
+
+ if (filter)
+ free_event_filter(filter);
kfree(edata);
kfree(trigger);
@@ -848,12 +869,62 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[
return ret;
}
+static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const char *argv[])
+{
+ struct event_filter *dummy;
+ int i, ret, len = 0;
+ char *p;
+
+ if (argc == 0) {
+ trace_probe_log_err(0, NO_EP_FILTER);
+ return -EINVAL;
+ }
+
+ /* Recover the filter string */
+ for (i = 0; i < argc; i++)
+ len += strlen(argv[i]) + 1;
+
+ ep->filter_str = kzalloc(len, GFP_KERNEL);
+ if (!ep->filter_str)
+ return -ENOMEM;
+
+ p = ep->filter_str;
+ for (i = 0; i < argc; i++) {
+ ret = snprintf(p, len, "%s ", argv[i]);
+ if (ret < 0)
+ goto error;
+ if (ret > len) {
+ ret = -E2BIG;
+ goto error;
+ }
+ p += ret;
+ len -= ret;
+ }
+ p[-1] = '\0';
+
+ /*
+ * Ensure the filter string can be parsed correctly. Note, this
+ * filter string is for the original event, not for the eprobe.
+ */
+ ret = create_event_filter(top_trace_array(), ep->event, ep->filter_str,
+ true, &dummy);
+ free_event_filter(dummy);
+ if (ret)
+ goto error;
+
+ return 0;
+error:
+ kfree(ep->filter_str);
+ ep->filter_str = NULL;
+ return ret;
+}
+
static int __trace_eprobe_create(int argc, const char *argv[])
{
/*
* Argument syntax:
- * e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS]
- * Fetch args:
+ * e[:[GRP/][ENAME]] SYSTEM.EVENT [FETCHARGS] [if FILTER]
+ * Fetch args (no space):
* <name>=$<field>[:TYPE]
*/
const char *event = NULL, *group = EPROBE_EVENT_SYSTEM;
@@ -863,8 +934,8 @@ static int __trace_eprobe_create(int argc, const char *argv[])
char buf1[MAX_EVENT_NAME_LEN];
char buf2[MAX_EVENT_NAME_LEN];
char gbuf[MAX_EVENT_NAME_LEN];
- int ret = 0;
- int i;
+ int ret = 0, filter_idx = 0;
+ int i, filter_cnt;
if (argc < 2 || argv[0][0] != 'e')
return -ECANCELED;
@@ -894,6 +965,15 @@ static int __trace_eprobe_create(int argc, const char *argv[])
event = buf1;
}
+ for (i = 2; i < argc; i++) {
+ if (!strcmp(argv[i], "if")) {
+ filter_idx = i + 1;
+ filter_cnt = argc - filter_idx;
+ argc = i;
+ break;
+ }
+ }
+
mutex_lock(&event_mutex);
event_call = find_and_get_event(sys_name, sys_event);
ep = alloc_event_probe(group, event, event_call, argc - 2);
@@ -909,6 +989,14 @@ static int __trace_eprobe_create(int argc, const char *argv[])
goto error;
}
+ if (filter_idx) {
+ trace_probe_log_set_index(filter_idx);
+ ret = trace_eprobe_parse_filter(ep, filter_cnt, argv + filter_idx);
+ if (ret)
+ goto parse_error;
+ } else
+ ep->filter_str = NULL;
+
argc -= 2; argv += 2;
/* parse arguments */
for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 3b3869ae8cfd..de38f1c03776 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -445,7 +445,8 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
C(SAME_PROBE, "There is already the exact same probe event"),\
C(NO_EVENT_INFO, "This requires both group and event name to attach"),\
C(BAD_ATTACH_EVENT, "Attached event does not exist"),\
- C(BAD_ATTACH_ARG, "Attached event does not have this field"),
+ C(BAD_ATTACH_ARG, "Attached event does not have this field"),\
+ C(NO_EP_FILTER, "No filter rule after 'if'"),
#undef C
#define C(a, b) TP_ERR_##a
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