[RFC PATCH 10/10] arm64: mm: restrict __pa() translations to linear virtual addresses

[Ard Biesheuvel]

On 23 February 2016 at 13:26, Will Deacon <will.deacon at arm.com> wrote:
> On Mon, Feb 22, 2016 at 09:54:32PM +0100, Ard Biesheuvel wrote:
>> Now that we have replaced all occurrences of __pa() translations
>> involving virtual addresses that are covered by the kernel text,
>> we can redefine __virt_to_phys and __pa() etc to only take virtual
>> address that are covered by the linear mapping. This means we can
>> remove the comparison with PAGE_OFFSET in the definition of
>> __virt_to_phys().
>>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> ---
>>  arch/arm64/include/asm/memory.h | 12 +++++++-----
>>  1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
>> index 56d6739430f3..3b5dc5b243ac 100644
>> --- a/arch/arm64/include/asm/memory.h
>> +++ b/arch/arm64/include/asm/memory.h
>> @@ -86,11 +86,14 @@
>>   * private definitions which should NOT be used outside memory.h
>>   * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
>>   */
>> -#define __virt_to_phys(x) ({                                         \
>> +#ifndef CONFIG_DEBUG_VM
>> +#define __virt_to_phys(x)    (((phys_addr_t)(x) & ~PAGE_OFFSET) + PHYS_OFFSET)
>> +#else
>> +#define __virt_to_phys(x)    ({                                      \
>>       phys_addr_t __x = (phys_addr_t)(x);                             \
>> -     __x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET :   \
>> -                              (__x - kimage_voffset); })
>> -
>> +     BUG_ON(__x < PAGE_OFFSET);                                      \
>> +     (((phys_addr_t)__x & ~PAGE_OFFSET) + PHYS_OFFSET); })
>
> What's the #include-hell like if you try to use VM_BUG_ON instead?
>

The #include hell would not change I think, since

include/linux/mmdebug.h:18:#define VM_BUG_ON(cond) BUG_ON(cond)

but it would certainly make this code look a lot cleaner.