• Steven Rostedt's avatar
    ftrace/x86: Add separate function to save regs · 08f6fba5
    Steven Rostedt authored
    Add a way to have different functions calling different trampolines.
    If a ftrace_ops wants regs saved on the return, then have only the
    functions with ops registered to save regs. Functions registered by
    other ops would not be affected, unless the functions overlap.
    
    If one ftrace_ops registered functions A, B and C and another ops
    registered fucntions to save regs on A, and D, then only functions
    A and D would be saving regs. Function B and C would work as normal.
    Although A is registered by both ops: normal and saves regs; this is fine
    as saving the regs is needed to satisfy one of the ops that calls it
    but the regs are ignored by the other ops function.
    
    x86_64 implements the full regs saving, and i386 just passes a NULL
    for regs to satisfy the ftrace_ops passing. Where an arch must supply
    both regs and ftrace_ops parameters, even if regs is just NULL.
    
    It is OK for an arch to pass NULL regs. All function trace users that
    require regs passing must add the flag FTRACE_OPS_FL_SAVE_REGS when
    registering the ftrace_ops. If the arch does not support saving regs
    then the ftrace_ops will fail to register. The flag
    FTRACE_OPS_FL_SAVE_REGS_IF_SUPPORTED may be set that will prevent the
    ftrace_ops from failing to register. In this case, the handler may
    either check if regs is not NULL or check if ARCH_SUPPORTS_FTRACE_SAVE_REGS.
    If the arch supports passing regs it will set this macro and pass regs
    for ops that request them. All other archs will just pass NULL.
    
    Link: Link: http://lkml.kernel.org/r/20120711195745.107705970@goodmis.org
    
    
    
    Cc: Alexander van Heukelum <heukelum@fastmail.fm>
    Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    08f6fba5
ftrace.h 24.7 KB