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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>
This commit is contained in:
Catalin Marinas 2015-03-23 15:06:50 +00:00
parent bc465aa9d0
commit e53f21bce4
1 changed files with 9 additions and 0 deletions
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9
arch/arm64/include/asm/mmu_context.h
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@ -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);
}