• Steven Rostedt's avatar
    ftrace/recordmcount: Make ignored mcount calls into nops at compile time · ffd618fa
    Steven Rostedt authored
    There are sections that are ignored by ftrace for the function tracing because
    the text is in a section that can be removed without notice. The mcount calls
    in these sections are ignored and ftrace never sees them. The downside of this
    is that the functions in these sections still call mcount. Although the mcount
    function is defined in assembly simply as a return, this added overhead is
    unnecessary.
    
    The solution is to convert these callers into nops at compile time.
    A better solution is to add 'notrace' to the section markers, but as new sections
    come up all the time, it would be nice that they are delt with when they
    are created.
    
    Later patches will deal with finding these sections and doing the proper solution.
    
    Thanks to H. Peter Anvin for giving me the right nops to use for x86.
    
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: John Reiser <jreiser@bitwagon.com>
    Link: http://lkml.kernel.org/r/20110421023738.237101176@goodmis.orgSigned-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    ffd618fa
recordmcount.c 11.5 KB