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Message-Id: <20200308222609.125574449@linutronix.de>
User-Agent: quilt/0.65
Date:   Sun, 08 Mar 2020 23:24:01 +0100
From:   Thomas Gleixner <tglx@linutronix.de>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Brian Gerst <brgerst@gmail.com>,
        Juergen Gross <jgross@suse.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Alexandre Chartre <alexandre.chartre@oracle.com>
Subject: [patch part-II V2 02/13] x86/entry: Mark enter_from_user_mode() notrace and NOKPROBE
References: <20200308222359.370649591@linutronix.de>
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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 notrace and NOKROBE.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/entry/common.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -40,11 +40,12 @@
 
 #ifdef CONFIG_CONTEXT_TRACKING
 /* Called on entry from user mode with IRQs off. */
-__visible inline void enter_from_user_mode(void)
+__visible inline notrace void enter_from_user_mode(void)
 {
 	CT_WARN_ON(ct_state() != CONTEXT_USER);
 	user_exit_irqoff();
 }
+NOKPROBE_SYMBOL(enter_from_user_mode);
 #else
 static inline void enter_from_user_mode(void) {}
 #endif