tracing: increase size of number of possible events

With the new event tracing registration, we must increase the number
of events that can be registered. Currently the type field is only
one byte, which leaves us only 256 possible events.

Since we do not save the CPU number in the tracer anymore (it is determined
by the per cpu ring buffer that is used) we have an extra byte to use.

This patch increases the size of type from 1 byte (256 events) to
2 bytes (65,536 events).

It also adds a WARN_ON_ONCE if we exceed that limit.

[ Impact: allow more than 255 events ]

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

3 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 2a4a40749911..07e0a6d64a24 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -16,13 +16,16 @@ struct dentry;
  *     bash-15816 [01]   235.197585: idle_cpu <- irq_enter
  */
 struct trace_entry {
-        int                     type;
+        unsigned short          type;
         unsigned char           flags;
         unsigned char           preempt_count;
         int                     pid;
         int                     tgid;
 };
 
+#define FTRACE_MAX_EVENT                                                \
+        ((1 << (sizeof(((struct trace_entry *)0)->type) * 8)) - 1)
+
 /*
  * Trace iterator - used by printout routines who present trace
  * results to users and which routines might sleep, etc:
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 5d6e879cf875..9887131afa03 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -398,7 +398,7 @@ static int trace_write_header(struct trace_seq *s)
                                 "\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
                                 "\tfield:%s %s;\toffset:%zu;\tsize:%zu;\n"
                                 "\n",
-                                FIELD(int, type),
+                                FIELD(unsigned short, type),
                                 FIELD(unsigned char, flags),
                                 FIELD(unsigned char, preempt_count),
                                 FIELD(int, pid),
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 83a8abb9640f..06997e75114b 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -537,6 +537,8 @@ int register_ftrace_event(struct trace_event *event)
  out:
         mutex_unlock(&trace_event_mutex);
 
+        WARN_ON_ONCE(next_event_type > FTRACE_MAX_EVENT);
+
         return ret;
 }
 EXPORT_SYMBOL_GPL(register_ftrace_event);