Re: [PATCH] tracing: Error if a trace event has an array for a __field()

Re: [PATCH] tracing: Error if a trace event has an array for a __field()

[kernel test robot]

Hi Steven,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.3-rc1]
[cannot apply to next-20230310]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Error-if-a-trace-event-has-an-array-for-a-__field/20230310-111456
patch link:    https://lore.kernel.org/r/20230309221302.642e82d9%40gandalf.local.home
patch subject: [PATCH] tracing: Error if a trace event has an array for a __field()
config: x86_64-randconfig-a006 (https://download.01.org/0day-ci/archive/20230310/202303101645.28bnQoH2-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/4828e98216144ead91bbb26298aae865dac9f837
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Steven-Rostedt/tracing-Error-if-a-trace-event-has-an-array-for-a-__field/20230310-111456
        git checkout 4828e98216144ead91bbb26298aae865dac9f837
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/rcu/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303101645.28bnQoH2-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/trace/define_trace.h:102,
                    from include/trace/events/rcu.h:839,
                    from kernel/rcu/rcu.h:13,
                    from kernel/rcu/update.c:49:
   include/trace/events/rcu.h: In function 'trace_event_get_offsets_rcu_torture_read':
>> include/trace/stages/stage5_get_offsets.h:23:53: error: expected ')' before '*' token
      23 |         { (void)sizeof(struct _test_no_array_##item *); }
         |                       ~                             ^
   include/trace/trace_events.h:263:9: note: in definition of macro 'DECLARE_EVENT_CLASS'
     263 |         tstruct;                                                        \
         |         ^~~~~~~
   include/trace/trace_events.h:43:30: note: in expansion of macro 'PARAMS'
      43 |                              PARAMS(tstruct),                  \
         |                              ^~~~~~
   include/trace/events/rcu.h:11:25: note: in expansion of macro 'TRACE_EVENT'
      11 | #define TRACE_EVENT_RCU TRACE_EVENT
         |                         ^~~~~~~~~~~
   include/trace/events/rcu.h:770:9: note: in expansion of macro 'TP_STRUCT__entry'
     770 |         TP_STRUCT__entry(
         |         ^~~~~~~~~~~~~~~~
   include/trace/events/rcu.h:771:17: note: in expansion of macro '__field'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                 ^~~~~~~
>> include/trace/events/rcu.h:771:45: error: array type has incomplete element type 'struct _test_no_array_rcutorturename'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                                             ^
   include/trace/trace_events.h:263:9: note: in definition of macro 'DECLARE_EVENT_CLASS'
     263 |         tstruct;                                                        \
         |         ^~~~~~~
   include/trace/trace_events.h:43:30: note: in expansion of macro 'PARAMS'
      43 |                              PARAMS(tstruct),                  \
         |                              ^~~~~~
   include/trace/events/rcu.h:11:25: note: in expansion of macro 'TRACE_EVENT'
      11 | #define TRACE_EVENT_RCU TRACE_EVENT
         |                         ^~~~~~~~~~~
   include/trace/events/rcu.h:770:9: note: in expansion of macro 'TP_STRUCT__entry'
     770 |         TP_STRUCT__entry(
         |         ^~~~~~~~~~~~~~~~
   include/trace/events/rcu.h:771:17: note: in expansion of macro '__field'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                 ^~~~~~~


vim +23 include/trace/stages/stage5_get_offsets.h

    11	
    12	/*
    13	 * Fields should never declare an array: i.e. __field(int, arr[5])
    14	 * If they do, it will cause issues in parsing and possibly corrupt the
    15	 * events. To prevent that from happening, test the sizeof() a fictitious
    16	 * type called "struct _test_no_array_##item" which will fail if "item"
    17	 * contains array elements (like "arr[5]").
    18	 *
    19	 * If you hit this, use __array(int, arr, 5) instead.
    20	 */
    21	#undef __field
    22	#define __field(type, item)					\
  > 23		{ (void)sizeof(struct _test_no_array_##item *); }
    24	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests

Re: [PATCH] tracing: Error if a trace event has an array for a __field()

[Steven Rostedt]

On Fri, 10 Mar 2023 16:37:09 +0800
kernel test robot <lkp@intel.com> wrote:

>    include/trace/events/rcu.h:771:17: note: in expansion of macro '__field'
>      771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
>          |                 ^~~~~~~

Awesome, it found the bug that this patch is suppose to find! :-)

The above needs to be changed to:

		__array(char, rcutorturename, RCUTORTURENAME_LEN)

And my patch will fail builds that have arrays in __field() macros.

Yes, I'm not going to apply this patch until the current bugs in the kernel
are fixed, because this patch will cause the kernel not to build if it has
this type of bug.

-- Steve