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

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Commit 9f61668073 "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: 9f61668073 "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>
This commit is contained in:
Steven Rostedt (Red Hat) 2016-03-03 17:18:20 -05:00 committed by Steven Rostedt
parent d045437a16
commit e57cbaf0eb
3 changed files with 19 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
include/linux/trace_events.h
View file

@ -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);

18
kernel/trace/trace_events.c
View file

@ -97,16 +97,16 @@ trace_find_event_field(struct trace_event_call *call, char *name)
struct ftrace_event_field *field;
struct list_head *head;
head = trace_get_fields(call);
field = __find_event_field(head, name);
if (field)
return field;
field = __find_event_field(&ftrace_generic_fields, name);
if (field)
return field;
field = __find_event_field(&ftrace_common_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;
}

11
kernel/trace/trace_events_filter.c
View file

@ -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);
if (!strcmp(field->name, "comm")) {
fn = filter_pred_comm;
pred->regex.field_len = TASK_COMM_LEN;
} else if (field->filter_type == FILTER_STATIC_STRING) {
} else if (is_string_field(field)) {
filter_build_regex(pred);
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,