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Subject[tip:tracing/core] tracing/events: record the size of dynamic arrays
Commit-ID:  7d536cb3fb9993bdcd5a2fbaa6b0670ded4e101c
Gitweb: http://git.kernel.org/tip/7d536cb3fb9993bdcd5a2fbaa6b0670ded4e101c
Author: Li Zefan <lizf@cn.fujitsu.com>
AuthorDate: Thu, 16 Jul 2009 10:54:02 +0800
Committer: Steven Rostedt <rostedt@goodmis.org>
CommitDate: Mon, 20 Jul 2009 11:38:44 -0400

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>


---
include/trace/ftrace.h | 14 ++++++++------
kernel/trace/trace_events_filter.c | 6 ++++--
2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index cc78943..3cbb96e 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 b9aae72..1c80ef7 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;


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