printk: Disallow instrumenting print_nmi_enter() (b0f51883) · Commits · 戴 / test

It happens early in nmi_enter(), no tracing, probing or other funnies allowed. Specifically as nmi_enter() will be used in do_debug(), which would cause recursive exceptions when kprobed. Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Reviewed-by:

Alexandre Chartre <alexandre.chartre@oracle.com> Link: https://lkml.kernel.org/r/20200505134101.139720912@linutronix.de

kernel/printk/printk_safe.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -10,6 +10,7 @@
		#include <linux/cpumask.h>
		#include <linux/irq_work.h>
		#include <linux/printk.h>
		#include <linux/kprobes.h>

		#include "internal.h"

		@@ -293,12 +294,12 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
		return printk_safe_log_store(s, fmt, args);
		}

		void notrace printk_nmi_enter(void)
		void noinstr printk_nmi_enter(void)
		{
		this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
		}

		void notrace printk_nmi_exit(void)
		void noinstr printk_nmi_exit(void)
		{
		this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
		}

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