tracing: Do not have 'comm' filter override event 'comm' field

Commit 9f61668073a8d "tracing: Allow triggers to filter for CPU ids and
process names" added a 'comm' filter that will filter events based on the
current tasks struct 'comm'. But this now hides the ability to filter events
that have a 'comm' field too. For example, sched_migrate_task trace event.
That has a 'comm' field of the task to be migrated.

 echo 'comm == "bash"' > events/sched_migrate_task/filter

will now filter all sched_migrate_task events for tasks named "bash" that
migrates other tasks (in interrupt context), instead of seeing when "bash"
itself gets migrated.

This fix requires a couple of changes.

1) Change the look up order for filter predicates to look at the events
   fields before looking at the generic filters.

2) Instead of basing the filter function off of the "comm" name, have the
   generic "comm" filter have its own filter_type (FILTER_COMM). Test
   against the type instead of the name to assign the filter function.

3) Add a new "COMM" filter that works just like "comm" but will filter based
   on the current task, even if the trace event contains a "comm" field.

Do the same for "cpu" field, adding a FILTER_CPU and a filter "CPU".

Cc: stable@vger.kernel.org # v4.3+
Fixes: 9f61668073a8d "tracing: Allow triggers to filter for CPU ids and process names"
Reported-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 429fdfc3baf59e018d0e198062f894642af8a5bc..925730bc9fc1bb4914410779bdf5ea469ed41c18 100644 (file)
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -568,6 +568,8 @@ enum {
        FILTER_DYN_STRING,
        FILTER_PTR_STRING,
        FILTER_TRACE_FN,
+       FILTER_COMM,
+       FILTER_CPU,
 };
 
 extern int trace_event_raw_init(struct trace_event_call *call);

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ab09829d3b97ac83eb34c5afd25bf487abfdbe68..05ddc0820771eb7bc456aab9e2f0e5167ce7f023 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -97,16 +97,16 @@ trace_find_event_field(struct trace_event_call *call, char *name)
        struct ftrace_event_field *field;
        struct list_head *head;
 
-       field = __find_event_field(&ftrace_generic_fields, name);
+       head = trace_get_fields(call);
+       field = __find_event_field(head, name);
        if (field)
                return field;
 
-       field = __find_event_field(&ftrace_common_fields, name);
+       field = __find_event_field(&ftrace_generic_fields, name);
        if (field)
                return field;
 
-       head = trace_get_fields(call);
-       return __find_event_field(head, name);
+       return __find_event_field(&ftrace_common_fields, name);
 }
 
 static int __trace_define_field(struct list_head *head, const char *type,
@@ -171,8 +171,10 @@ static int trace_define_generic_fields(void)
 {
        int ret;
 
-       __generic_field(int, cpu, FILTER_OTHER);
-       __generic_field(char *, comm, FILTER_PTR_STRING);
+       __generic_field(int, CPU, FILTER_CPU);
+       __generic_field(int, cpu, FILTER_CPU);
+       __generic_field(char *, COMM, FILTER_COMM);
+       __generic_field(char *, comm, FILTER_COMM);
 
        return ret;
 }

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index f93a219b18daaa92ed314ad7ac4ba8e0ed3c4c09..6816302542b28158a4756373f5b3a57ed1a907fa 100644 (file)
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1043,13 +1043,14 @@ static int init_pred(struct filter_parse_state *ps,
                return -EINVAL;
        }
 
-       if (is_string_field(field)) {
+       if (field->filter_type == FILTER_COMM) {
+               filter_build_regex(pred);
+               fn = filter_pred_comm;
+               pred->regex.field_len = TASK_COMM_LEN;
+       } else if (is_string_field(field)) {
                filter_build_regex(pred);
 
-               if (!strcmp(field->name, "comm")) {
-                       fn = filter_pred_comm;
-                       pred->regex.field_len = TASK_COMM_LEN;
-               } else if (field->filter_type == FILTER_STATIC_STRING) {
+               if (field->filter_type == FILTER_STATIC_STRING) {
                        fn = filter_pred_string;
                        pred->regex.field_len = field->size;
                } else if (field->filter_type == FILTER_DYN_STRING)
@@ -1072,7 +1073,7 @@ static int init_pred(struct filter_parse_state *ps,
                }
                pred->val = val;
 
-               if (!strcmp(field->name, "cpu"))
+               if (field->filter_type == FILTER_CPU)
                        fn = filter_pred_cpu;
                else
                        fn = select_comparison_fn(pred->op, field->size,