[PATCH] arm: mm: fix lowmem virtual address range check
wangnan0 at huawei.com
Wed May 14 03:24:12 PDT 2014
On 2014/5/14 18:11, Will Deacon wrote:
> On Wed, May 14, 2014 at 07:03:59AM +0100, Wang Nan wrote:
>> This patch makes sure the argument of __phys_to_virt is a valid physical
>> address when clear lowmem memory maps.
>> The last few lines prepare_page_table() clear page mapping in the gap
>> between largest low physical memory and the upper bound of lowmem. It
>> uses __phys_to_virt(end) to calculate virtual address from where the
>> clearing start.
>> However, if the platform uses private nonliner __phys_to_virt(), 'end'
>> may goes into another mapping region.
>> This patch uses __phys_to_virt(end - 1) + 1 for insurance purposes.
>> Signed-off-by: Wang Nan <wangnan0 at huawei.com>
>> Cc: Geng Hui <hui.geng at huawei.com>
>> Cc: Will Deacon <will.deacon at arm.com>
>> arch/arm/mm/mmu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
>> index b68c6b2..87340ee 100644
>> --- a/arch/arm/mm/mmu.c
>> +++ b/arch/arm/mm/mmu.c
>> @@ -1217,7 +1217,7 @@ static inline void prepare_page_table(void)
>> * Clear out all the kernel space mappings, except for the first
>> * memory bank, up to the vmalloc region.
>> - for (addr = __phys_to_virt(end);
>> + for (addr = __phys_to_virt(end - 1) + 1;
>> addr < VMALLOC_START; addr += PMD_SIZE)
> This looks correct to me, but I'd be interested to know which platform this
> is falling over on. Only realview seems to override __phys_to_virt and I
> don't think we want to add more of that if we can help it.
I'm working on realview code now, trying to make it support CONFIG_ARM_PATCH_PHYS_VIRT,
and found this problem when working on its private __phys_to_virt. Realview is the only
in-kernel arm board which uses sparse memory. I think it is a good example when testing
sparse memory support of tools such as kexec-tools, kdump and crash.
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