From 1723be30e46fbda0c5971d3a19a37a7c2499bc90 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sat, 29 Feb 2020 15:12:33 +0100 Subject: [PATCH] x86/entry: Mark enter_from_user_mode() noinstr 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 Reviewed-by: Masami Hiramatsu Reviewed-by: Alexandre Chartre Acked-by: Peter Zijlstra Link: https://lkml.kernel.org/r/20200505134340.429059405@linutronix.de --- arch/x86/entry/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 76735ec813e6b..d862add7918b7 100644 --- 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();