• Liming Wang's avatar
    function tracing: fix wrong position computing of stack_trace · 522a110b
    Liming Wang authored
    Impact: make output of stack_trace complete if buffer overruns
    When read buffer overruns, the output of stack_trace isn't complete.
    When printing records with seq_printf in t_show, if the read buffer
    has overruned by the current record, then this record won't be
    printed to user space through read buffer, it will just be dropped in
    this printing.
    When next printing, t_start should return the "*pos"th record, which
    is the one dropped by previous printing, but it just returns
    (m->private + *pos)th record.
    Here we use a more sane method to implement seq_operations which can
    be found in kernel code. Thus we needn't initialize m->private.
    About testing, it's not easy to overrun read buffer, but we can use
    seq_printf to print more padding bytes in t_show, then it's easy to
    check whether or not records are lost.
    This commit has been tested on both condition of overrun and non
    Signed-off-by: default avatarLiming Wang <liming.wang@windriver.com>
    Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
trace_stack.c 6.52 KB