Messages in this thread Patch in this message | | | From | He Kuang <> | Subject | [RFC PATCH v5 1/3] tracing/events: Fix wrong sample output by storing array length instead of size | Date | Tue, 14 Jul 2015 01:59:29 +0000 |
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The output result of trace_foo_bar event in traceevent samples is wrong. This problem can be reproduced as following:
(Build kernel with SAMPLE_TRACE_EVENTS=m)
$ insmod trace-events-sample.ko
$ echo 1 > /sys/kernel/debug/tracing/events/sample-trace/foo_bar/enable
$ cat /sys/kernel/debug/tracing/trace
event-sample-980 [000] .... 43.649559: foo_bar: foo hello 21 0x15 BIT1|BIT3|0x10 {0x1,0x6f6f6e53,0xff007970,0xffffffff} Snoopy ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The array length is not right, should be {0x1}. (ffffffff,ffffffff)
event-sample-980 [000] .... 44.653827: foo_bar: foo hello 22 0x16 BIT2|BIT3|0x10 {0x1,0x2,0x646e6147,0x666c61,0xffffffff,0xffffffff,0x750aeffe,0x7} ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The array length is not right, should be {0x1,0x2}. Gandalf (ffffffff,ffffffff)
The event defined in samples/trace_events/trace-events-sample.h uses this helper function to output dynamic list:
__print_array(__get_dynamic_array(list), __get_dynamic_array_len(list), sizeof(int))
Currently, __get_dynamic_array_len() returns the total size of the array instead of the number of items by referencing the high 16 bits of entry->data_loc_##item. The element size for calculating the number of items can not be fetched by referencing fields from __entry, so macro __get_dynamic_array_len can not return the expected value.
This patch stores array item number instead of the total size in entry->__data_loc_##item, and makes __get_dynamic_array_len get the right value directly. Because the function __get_bitmask() is affected by this change, __bitmask_size is assigned to the array len by multiplied bitmask type size.
After this patch:
event-sample-993 [000] .... 692.348562: foo_bar: foo hello 201 0xc9 BIT1|BIT4|0xc0 {0x1} Snoopy (ffffffff,ffffffff) ^^^^^ Array length fixed.
event-sample-993 [000] .... 693.349276: foo_bar: foo hello 202 0xca BIT2|BIT4|0xc0 {0x1,0x2} Gandalf (ffffffff,ffffffff) ^^^^^^^^^ Array length fixed.
Signed-off-by: He Kuang <hekuang@huawei.com> --- include/trace/trace_events.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h index 43be3b0..5abe027 100644 --- a/include/trace/trace_events.h +++ b/include/trace/trace_events.h @@ -257,7 +257,8 @@ TRACE_MAKE_SYSTEM_STR(); ({ \ void *__bitmask = __get_dynamic_array(field); \ unsigned int __bitmask_size; \ - __bitmask_size = __get_dynamic_array_len(field); \ + __bitmask_size = (__get_dynamic_array_len(field) * \ + sizeof(unsigned long)); \ trace_print_bitmask_seq(p, __bitmask, __bitmask_size); \ }) @@ -453,7 +454,7 @@ trace_event_define_fields_##call(struct trace_event_call *event_call) \ __item_length = (len) * sizeof(type); \ __data_offsets->item = __data_size + \ offsetof(typeof(*entry), __data); \ - __data_offsets->item |= __item_length << 16; \ + __data_offsets->item |= (len) << 16; \ __data_size += __item_length; #undef __string -- 1.8.5.2
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