• Steven Rostedt's avatar
    tracing/events/ring-buffer: expose format of ring buffer headers to users · d1b182a8
    Steven Rostedt authored
    Currently, every thing needed to read the binary output from the
    ring buffers is available, with the exception of the way the ring
    buffers handles itself internally.
    
    This patch creates two special files in the debugfs/tracing/events
    directory:
    
     # cat /debug/tracing/events/header_page
            field: u64 timestamp;   offset:0;       size:8;
            field: local_t commit;  offset:8;       size:8;
            field: char data;       offset:16;      size:4080;
    
     # cat /debug/tracing/events/header_event
            type        :    2 bits
            len         :    3 bits
            time_delta  :   27 bits
            array       :   32 bits
    
            padding     : type == 0
            time_extend : type == 1
            data        : type == 3
    
    This is to allow a userspace app to see if the ring buffer format changes
    or not.
    
    [ Impact: allow userspace apps to know of ringbuffer format changes ]
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    d1b182a8
ring_buffer.c 74.3 KB