• Steven Rostedt's avatar
    function-graph: add stack frame test · 71e308a2
    Steven Rostedt authored
    
    
    In case gcc does something funny with the stack frames, or the return
    from function code, we would like to detect that.
    
    An arch may implement passing of a variable that is unique to the
    function and can be saved on entering a function and can be tested
    when exiting the function. Usually the frame pointer can be used for
    this purpose.
    
    This patch also implements this for x86. Where it passes in the stack
    frame of the parent function, and will test that frame on exit.
    
    There was a case in x86_32 with optimize for size (-Os) where, for a
    few functions, gcc would align the stack frame and place a copy of the
    return address into it. The function graph tracer modified the copy and
    not the actual return address. On return from the funtion, it did not go
    to the tracer hook, but returned to the parent. This broke the function
    graph tracer, because the return of the parent (where gcc did not do
    this funky manipulation) returned to the location that the child function
    was suppose to. This caused strange kernel crashes.
    
    This test detected the problem and pointed out where the issue was.
    
    This modifies the parameters of one of the functions that the arch
    specific code calls, so it includes changes to arch code to accommodate
    the new prototype.
    
    Note, I notice that the parsic arch implements its own push_return_trace.
    This is now a generic function and the ftrace_push_return_trace should be
    used instead. This patch does not touch that code.
    
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Helge Deller <deller@gmx.de>
    Cc: Kyle McMartin <kyle@mcmartin.ca>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    71e308a2
ftrace.h 14 KB