On Mon 2019-10-14 12:59:23, Miroslav Benes wrote: > Livepatch uses ftrace for redirection to new patched functions. It means > that if ftrace is disabled, all live patched functions are disabled as > well. Toggling global 'ftrace_enabled' sysctl thus affect it directly. > It is not a problem per se, because only administrator can set sysctl > values, but it still may be surprising. > > Introduce PERMANENT ftrace_ops flag to amend this. If the > FTRACE_OPS_FL_PERMANENT is set on any ftrace ops, the tracing cannot be > disabled by disabling ftrace_enabled. Equally, a callback with the flag > set cannot be registered if ftrace_enabled is disabled. > > Signed-off-by: Miroslav Benes <mbenes@xxxxxxx> Looks fine to me. I finally understand which ftrace_enabled toggle we are talking about ;-) Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> > --- > - return codes. I chose EBUSY, because it seemed the least > inappropriate. I usually pick the wrong one, so suggestions are > welcome. -EBUSY is perfectly fine in ftrace_enable_sysctl(). It is not ideal in __register_ftrace_function(). But it still looks better than -ENODEV there. Best Regards, Petr
