[PATCH v2 06/12] tracing/kprobe: Add per-probe delete from event

Masami Hiramatsu
2019-06-19T15:08:15Z

Allow user to delete a probe from event. This is done by head
match. For example, if we have 2 probes on an event

$ cat kprobe_events
p:kprobes/testprobe _do_fork r1=%ax r2=%dx
p:kprobes/testprobe idle_fork r1=%ax r2=%cx

Then you can remove one of them by passing the head of definition
which identify the probe.

$ echo "-:kprobes/testprobe idle_fork" >> kprobe_events

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
kernel/trace/trace_kprobe.c | 25 ++++++++++++++++++++++++-
kernel/trace/trace_probe.c | 18 ++++++++++++++++++
kernel/trace/trace_probe.h | 2 ++
3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index f43098bf62dd..18c4175b6585 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -137,13 +137,36 @@ static bool trace_kprobe_is_busy(struct dyn_event *ev)
return trace_probe_is_enabled(&tk->tp);
}

+static bool trace_kprobe_match_command_head(struct trace_kprobe *tk,
+ int argc, const char **argv)
+{
+ char buf[MAX_ARGSTR_LEN + 1];
+
+ if (!argc)
+ return true;
+
+ if (!tk->symbol)
+ snprintf(buf, sizeof(buf), "0x%p", tk->rp.kp.addr);
+ else if (tk->rp.kp.offset)
+ snprintf(buf, sizeof(buf), "%s+%u",
+ trace_kprobe_symbol(tk), tk->rp.kp.offset);
+ else
+ snprintf(buf, sizeof(buf), "%s", trace_kprobe_symbol(tk));
+ if (strcmp(buf, argv[0]))
+ return false;
+ argc--; argv++;
+
+ return trace_probe_match_command_args(&tk->tp, argc, argv);
+}
+
static bool trace_kprobe_match(const char *system, const char *event,
int argc, const char **argv, struct dyn_event *ev)
{
struct trace_kprobe *tk = to_trace_kprobe(ev);

return strcmp(trace_probe_name(&tk->tp), event) == 0 &&
- (!system || strcmp(trace_probe_group_name(&tk->tp), system) == 0);
+ (!system || strcmp(trace_probe_group_name(&tk->tp), system) == 0) &&
+ trace_kprobe_match_command_head(tk, argc, argv);
}

static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk)
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 651a1449acde..f8c3c65c035d 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1047,3 +1047,21 @@ int trace_probe_compare_arg_type(struct trace_probe *a, struct trace_probe *b)

return 0;
}
+
+bool trace_probe_match_command_args(struct trace_probe *tp,
+ int argc, const char **argv)
+{
+ char buf[MAX_ARGSTR_LEN + 1];
+ int i;
+
+ if (tp->nr_args < argc)
+ return false;
+
+ for (i = 0; i < argc; i++) {
+ snprintf(buf, sizeof(buf), "%s=%s",
+ tp->args[i].name, tp->args[i].comm);
+ if (strcmp(buf, argv[i]))
+ return false;
+ }
+ return true;
+}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 39926e8a344b..2dcc4e317787 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -332,6 +332,8 @@ int trace_probe_remove_file(struct trace_probe *tp,
struct event_file_link *trace_probe_get_file_link(struct trace_probe *tp,
struct trace_event_file *file);
int trace_probe_compare_arg_type(struct trace_probe *a, struct trace_probe *b);
+bool trace_probe_match_command_args(struct trace_probe *tp,
+ int argc, const char **argv);

#define trace_probe_for_each_link(pos, tp) \
list_for_each_entry(pos, &(tp)->event->files, list)