On Tue, 05 May 2020 15:41:15 +0200 Thomas Gleixner <[email protected]> wrote:
> Both the callers in the low level ASM code and __context_tracking_exit() > which is invoked from enter_from_user_mode() via user_exit_irqoff() are > marked NOKPROBE. Allowing enter_from_user_mode() to be probed is > inconsistent at best. > > Aside of that while function tracing per se is safe the function trace > entry/exit points can be used via BPF as well which is not safe to use > before context tracking has reached CONTEXT_KERNEL and adjusted RCU. > > Mark it noinstr which moves it into the instrumentation protected text > section and includes notrace. > > Note, this needs further fixups in context tracking to ensure that the > full call chain is protected. Will be addressed in follow up changes. > > Signed-off-by: Thomas Gleixner <[email protected]> Looks good to me. Reviewed-by: Masami Hiramatsu <[email protected]> Thank you, > --- > arch/x86/entry/common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/arch/x86/entry/common.c > +++ b/arch/x86/entry/common.c > @@ -41,7 +41,7 @@ > > #ifdef CONFIG_CONTEXT_TRACKING > /* Called on entry from user mode with IRQs off. */ > -__visible inline void enter_from_user_mode(void) > +__visible inline noinstr void enter_from_user_mode(void) > { > CT_WARN_ON(ct_state() != CONTEXT_USER); > user_exit_irqoff(); > -- Masami Hiramatsu <[email protected]>
