On Wed, Aug 28, 2019 at 02:38:23PM +0100, Alexandru Elisei wrote:
> When the MMU is off, all addresses are physical addresses. If the stack
> pointer is not an identity mapped address (the virtual address is not the
> same as the physical address), then we end up trying to access an invalid
> memory region. This can happen if we call mmu_disable from a secondary CPU,
> which has its stack allocated from the vmalloc region.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> ---
> lib/arm/mmu.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index 3d38c8397f5a..161f7a8e607c 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -66,8 +66,12 @@ void mmu_enable(pgd_t *pgtable)
> extern void asm_mmu_disable(void);
> void mmu_disable(void)
> {
> + unsigned long sp = current_stack_pointer;
> int cpu = current_thread_info()->cpu;
>
> + assert_msg(__virt_to_phys(sp) == sp,
> + "Attempting to disable MMU with non-identity mapped stack");
> +
> mmu_mark_disabled(cpu);
>
> asm_mmu_disable();
> --
> 2.7.4
>
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
