[PATCH 1/2] arm64: mm: make create_mapping_late() non-allocating

[Ard Biesheuvel]

> On 25 jul. 2016, at 15:46, Mark Rutland <mark.rutland at arm.com> wrote:
> 
> Hi Ard,
> 
>> On Fri, Jul 22, 2016 at 07:32:24PM +0200, Ard Biesheuvel wrote:
>> The only purpose served by create_mapping_late() is to remap the already
>> mapped .text and .rodata kernel segments with read-only permissions. Since
>> we no longer allow block mappings to be split or merged,
>> create_mapping_late() should not pass an allocation function pointer into
>> __create_pgd_mapping(). So pass NULL instead.
>> 
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> ---
>> arch/arm64/mm/mmu.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index a96a2413fa18..33f36cede02d 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -312,7 +312,7 @@ static void create_mapping_late(phys_addr_t phys, unsigned long virt,
>>    }
>> 
>>    __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
>> -                 late_pgtable_alloc, !debug_pagealloc_enabled());
>> +                 NULL, !debug_pagealloc_enabled());
>> }
> 
> How about we drop the __init marker from create_mapping_noalloc(), and
> update the callers in mark_rodata_ro() to use that, so that we can drop
> create_mapping_late() entirely.
> 
> Other than the __init marker and name, create_mapping_late() and
> create_mapping_noalloc() would be identical after this change, and the
> naming of create_mapping_noalloc() does better describe what we're
> trying to achieve in mark_rodata_ro().
> 

Not entirely. The _late() variant should map down to pages if the first mapping was mapped down to pages as well. The _noalloc() variant may end attempting to merge regions