Commit 72500589 authored Feb 25, 2020 by Thomas Gleixner

x86/entry/64: Avoid pointless code when CONTEXT_TRACKING=n



GAS cannot optimize out the test and conditional jump when context tracking
is disabled and CALL_enter_from_user_mode is an empty macro.

Wrap it in #ifdeffery. Will go away once all this is moved to C.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134058.955968069@linutronix.de

parent e9660391

arch/x86/entry/entry_64.S

+2 −0

Original line number	Diff line number	Diff line
		@@ -889,12 +889,14 @@ apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt
		TRACE_IRQS_OFF
		.endif

		#ifdef CONFIG_CONTEXT_TRACKING
		.if \paranoid == 0
		testb $3, CS(%rsp)
		jz .Lfrom_kernel_no_context_tracking_\@
		CALL_enter_from_user_mode
		.Lfrom_kernel_no_context_tracking_\@:
		.endif
		#endif

		movq %rsp, %rdi /* pt_regs pointer */

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