tracing/events: record the size of dynamic arrays

When a dynamic array is defined, we add __data_loc_foo in
trace_entry to record the offset of the array, but the
size of the array is not recorded, which causes 2 problems:

- the event filter just compares the first 2 chars of the strings.

- parsers can't parse dynamic arrays.

So we encode the size of each dynamic array in the higher 16 bits
of __data_loc_foo, while the offset is in lower 16 bits.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A5E964A.9000403@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 12 insertions, 8 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index cc78943e0038..3cbb96ef34f4 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -25,7 +25,7 @@
 #define __array(type, item, len)        type    item[len];
 
 #undef __dynamic_array
-#define __dynamic_array(type, item, len) unsigned short __data_loc_##item;
+#define __dynamic_array(type, item, len) u32 __data_loc_##item;
 
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
@@ -51,13 +51,14 @@
  * Include the following:
  *
  * struct ftrace_data_offsets_<call> {
- *      int                             <item1>;
- *      int                             <item2>;
+ *      u32                             <item1>;
+ *      u32                             <item2>;
  *      [...]
  * };
  *
- * The __dynamic_array() macro will create each int <item>, this is
+ * The __dynamic_array() macro will create each u32 <item>, this is
  * to keep the offset of each array from the beginning of the event.
+ * The size of an array is also encoded, in the higher 16 bits of <item>.
  */
 
 #undef __field
@@ -67,7 +68,7 @@
 #define __array(type, item, len)
 
 #undef __dynamic_array
-#define __dynamic_array(type, item, len)        int item;
+#define __dynamic_array(type, item, len)        u32 item;
 
 #undef __string
 #define __string(item, src) __dynamic_array(char, item, -1)
@@ -207,7 +208,7 @@ ftrace_format_##call(struct trace_seq *s)				\
 
 #undef __get_dynamic_array
 #define __get_dynamic_array(field)      \
-                ((void *)__entry + __entry->__data_loc_##field)
+                ((void *)__entry + (__entry->__data_loc_##field & 0xffff))
 
 #undef __get_str
 #define __get_str(field) (char *)__get_dynamic_array(field)
@@ -325,6 +326,7 @@ ftrace_define_fields_##call(void)					\
 #define __dynamic_array(type, item, len)                                \
         __data_offsets->item = __data_size +                            \
                                offsetof(typeof(*entry), __data);        \
+        __data_offsets->item |= (len * sizeof(type)) << 16;             \
         __data_size += (len) * sizeof(type);
 
 #undef __string
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index b9aae72d13db..1c80ef702b83 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -176,11 +176,13 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
 static int filter_pred_strloc(struct filter_pred *pred, void *event,
                               int val1, int val2)
 {
-        unsigned short str_loc = *(unsigned short *)(event + pred->offset);
+        u32 str_item = *(u32 *)(event + pred->offset);
+        int str_loc = str_item & 0xffff;
+        int str_len = str_item >> 16;
         char *addr = (char *)(event + str_loc);
         int cmp, match;
 
-        cmp = strncmp(addr, pred->str_val, pred->str_len);
+        cmp = strncmp(addr, pred->str_val, str_len);
 
         match = (!cmp) ^ pred->not;