Commit e53f21bc authored Mar 23, 2015 by Catalin Marinas

arm64: Use the reserved TTBR0 if context switching to the init_mm



The idle_task_exit() function may call switch_mm() with next ==
&init_mm. On arm64, init_mm.pgd cannot be used for user mappings, so
this patch simply sets the reserved TTBR0.

Cc: <stable@vger.kernel.org>
Reported-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Tested-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent bc465aa9

arch/arm64/include/asm/mmu_context.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -151,6 +151,15 @@ switch_mm(struct mm_struct prev, struct mm_struct next,
		{
		unsigned int cpu = smp_processor_id();

		/*
		* init_mm.pgd does not contain any user mappings and it is always
		* active for kernel addresses in TTBR1. Just set the reserved TTBR0.
		*/
		if (next == &init_mm) {
		cpu_set_reserved_ttbr0();
		return;
		}

		if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) \|\| prev != next)
		check_and_switch_context(next, tsk);
		}