• Steven Rostedt (Red Hat)'s avatar
    tracing: Fix sample output of dynamic arrays · d6726c81
    Steven Rostedt (Red Hat) authored
    He Kuang noticed that the trace event samples for arrays was broken:
    
    "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)"
    
    This was caused by an update to have __print_array()'s second parameter
    be the count of items in the array and not the size of the array.
    
    As there is already users of __print_array(), it can not change. But
    the sample code can and we can also improve on the documentation about
    __print_array() and __get_dynamic_array_len().
    
    Link: http://lkml.kernel.org/r/1436839171-31527-2-git-send-email-hekuang@huawei.com
    
    Fixes: ac01ce14 ("tracing: Make ftrace_print_array_seq compute buf_len")
    Reported-by: default avatarHe Kuang <hekuang@huawei.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    d6726c81
trace-events-sample.h 17 KB