Patch "tracing: Do not have 'comm' filter override event 'comm' field" has been added to the 4.4-stable tree

Patch "tracing: Do not have 'comm' filter override event 'comm' field" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tracing-do-not-have-comm-filter-override-event-comm-field.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e57cbaf0eb006eaa207395f3bfd7ce52c1b5539c Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Thu, 3 Mar 2016 17:18:20 -0500
Subject: tracing: Do not have 'comm' filter override event 'comm' field

From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>

commit e57cbaf0eb006eaa207395f3bfd7ce52c1b5539c upstream.

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".

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 429fdfc3baf5..925730bc9fc1 100644
--- 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 ab09829d3b97..05ddc0820771 100644
--- 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 f93a219b18da..6816302542b2 100644
--- 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,


Patches currently in stable-queue which might be from rostedt@goodmis.org are

queue-4.4/tracing-do-not-have-comm-filter-override-event-comm-field.patch