tracing: Allow triggers to filter for CPU ids and process names

By extending the filter rules by more generic fields
we can write triggers filters like

  echo 'stacktrace if cpu == 1' > \
	/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger

or

  echo 'stacktrace if comm == sshd'  > \
	/sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger

CPU and COMM are not part of struct trace_entry. We could add the two
new fields to ftrace_common_field list and fix up all depending
sides. But that looks pretty ugly. Another thing I would like to
avoid that the 'format' file contents changes.

All this can be avoided by introducing another list which contains
non field members of struct trace_entry.

Link: http://lkml.kernel.org/r/1439210146-24707-1-git-send-email-daniel.wagner@bmw-carit.de

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 404a372ad85a..7ca09cdc20c2 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -30,6 +30,7 @@
 DEFINE_MUTEX(event_mutex);
 
 LIST_HEAD(ftrace_events);
+static LIST_HEAD(ftrace_generic_fields);
 static LIST_HEAD(ftrace_common_fields);
 
 #define GFP_TRACE (GFP_KERNEL | __GFP_ZERO)
@@ -94,6 +95,10 @@ 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);
+	if (field)
+		return field;
+
 	field = __find_event_field(&ftrace_common_fields, name);
 	if (field)
 		return field;
@@ -144,6 +149,13 @@ int trace_define_field(struct trace_event_call *call, const char *type,
 }
 EXPORT_SYMBOL_GPL(trace_define_field);
 
+#define __generic_field(type, item, filter_type)			\
+	ret = __trace_define_field(&ftrace_generic_fields, #type,	\
+				   #item, 0, 0, is_signed_type(type),	\
+				   filter_type);			\
+	if (ret)							\
+		return ret;
+
 #define __common_field(type, item)					\
 	ret = __trace_define_field(&ftrace_common_fields, #type,	\
 				   "common_" #item,			\
@@ -153,6 +165,16 @@ EXPORT_SYMBOL_GPL(trace_define_field);
 	if (ret)							\
 		return ret;
 
+static int trace_define_generic_fields(void)
+{
+	int ret;
+
+	__generic_field(int, cpu, FILTER_OTHER);
+	__generic_field(char *, comm, FILTER_PTR_STRING);
+
+	return ret;
+}
+
 static int trace_define_common_fields(void)
 {
 	int ret;
@@ -2671,6 +2693,9 @@ static __init int event_trace_init(void)
 	if (!entry)
 		pr_warn("Could not create tracefs 'available_events' entry\n");
 
+	if (trace_define_generic_fields())
+		pr_warn("tracing: Failed to allocated generic fields");
+
 	if (trace_define_common_fields())
 		pr_warn("tracing: Failed to allocate common fields");