[PATCH v2 3/3] arm64: prevent __va() translations before memstart_addr is assigned

[Ard Biesheuvel]

On 12 February 2016 at 12:49, Will Deacon <will.deacon at arm.com> wrote:
> On Thu, Feb 11, 2016 at 05:48:02PM +0100, Ard Biesheuvel wrote:
>> Just a hack to check whether all early __va() calls are gone.
>> ---
>>  arch/arm64/include/asm/memory.h | 10 +++++++++-
>>  arch/arm64/mm/init.c            |  2 +-
>>  2 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
>> index 083361531a61..0d4d1b3b9695 100644
>> --- a/arch/arm64/include/asm/memory.h
>> +++ b/arch/arm64/include/asm/memory.h
>> @@ -90,7 +90,9 @@
>>       __x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) :        \
>>                            (__x - kimage_voffset); })
>>
>> -#define __phys_to_virt(x)    ((unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET))
>> +#define __phys_to_virt(x) ({                                         \
>> +     assert_memstart_addr_assigned();                                \
>> +     (unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET); })
>>  #define __phys_to_kimg(x)    ((unsigned long)((x) + kimage_voffset))
>>
>>  /*
>> @@ -133,6 +135,12 @@ extern u64                       kimage_vaddr;
>>  /* the offset between the kernel virtual and physical mappings */
>>  extern u64                   kimage_voffset;
>>
>> +static inline void assert_memstart_addr_assigned(void)
>> +{
>> +     if (unlikely(memstart_addr == (phys_addr_t)-1))
>> +             asm("brk #%0" :: "I"(0x800));
>
> Ok, I'll bite! Why isn't this just a BUG_ON?
>

Because circular header dependencies prevent BUG_ON() from being used
here, and I was reluctant to move this function into a .c file.

Note that I am not necessarily suggesting that this patch be merged,
but I included it since it's the code I used to confirm that no other
early instance of __va() remain. I can try and clean it up if we want
to keep it.

-- 
Ard.