lib/smp_processor_id: Move it into noinstr section (126f21f0) · Commits · 戴 / test

That code is already not traceable. Move it into the noinstr section so the objtool section validation does not trigger. Annotate the warning code as "safe". While it might be not under all circumstances, getting the information out is important enough. Should this ever trigger from the sensitive code which is shielded against instrumentation, e.g. low level entry, then the printk is the least of the worries. Addresses the objtool warnings: vmlinux.o: warning: objtool: context_tracking_recursion_enter()+0x7: call to __this_cpu_preempt_check() leaves .noinstr.text section vmlinux.o: warning: objtool: __context_tracking_exit()+0x17: call to __this_cpu_preempt_check() leaves .noinstr.text section vmlinux.o: warning: objtool: __context_tracking_enter()+0x2a: call to __this_cpu_preempt_check() leaves .noinstr.text section Signed-off-by:

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

Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by:

Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134340.902709267@linutronix.de

lib/smp_processor_id.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -8,7 +8,7 @@
		#include <linux/kprobes.h>
		#include <linux/sched.h>

		notrace static nokprobe_inline
		noinstr static
		unsigned int check_preemption_disabled(const char what1, const char what2)
		{
		int this_cpu = raw_smp_processor_id();
		@@ -37,6 +37,7 @@ unsigned int check_preemption_disabled(const char what1, const char what2)
		*/
		preempt_disable_notrace();

		instrumentation_begin();
		if (!printk_ratelimit())
		goto out_enable;

		@@ -45,6 +46,7 @@ unsigned int check_preemption_disabled(const char what1, const char what2)

		printk("caller is %pS\n", __builtin_return_address(0));
		dump_stack();
		instrumentation_end();

		out_enable:
		preempt_enable_no_resched_notrace();
		@@ -52,16 +54,14 @@ out:
		return this_cpu;
		}

		notrace unsigned int debug_smp_processor_id(void)
		noinstr unsigned int debug_smp_processor_id(void)
		{
		return check_preemption_disabled("smp_processor_id", "");
		}
		EXPORT_SYMBOL(debug_smp_processor_id);
		NOKPROBE_SYMBOL(debug_smp_processor_id);

		notrace void __this_cpu_preempt_check(const char *op)
		noinstr void __this_cpu_preempt_check(const char *op)
		{
		check_preemption_disabled("__this_cpu_", op);
		}
		EXPORT_SYMBOL(__this_cpu_preempt_check);
		NOKPROBE_SYMBOL(__this_cpu_preempt_check);

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