Re: [PATCH v3 18/26] arm64: Introduce asm/vdso/processor.h

Vincenzo Frascino
2020-03-16T16:04:55Z

On 3/16/20 3:49 PM, Catalin Marinas wrote:
> On Mon, Mar 16, 2020 at 03:33:30PM +0000, Vincenzo Frascino wrote:
>> On 3/16/20 2:43 PM, Catalin Marinas wrote[...]
[...]
>
>> To make it more explicit we could make COMPAT_VDSO on arm64 depend on
>> ARM64_4K_PAGES. What do you think?
>
> No, I don't see why we should add this limitation.
>

Fine by me.

>>>> Please find below the list of errors for clock_gettime (similar for the other):
>>>>
>>>> passing UINTPTR_MAX to clock_gettime (VDSO): terminated by unexpected signal 7
>>>> clock-gettime-monotonic/abi: 1 failures/inconsistencies encountered
>>>
>>> Ah, so it uses UINTPTR_MAX in the test. Fair enough but I don't think
>>> the arm64 check is entirely useful. On arm32, the check was meant to
>>> return -EFAULT for addresses beyond TASK_SIZE that may enter into the
>>> kernel or module space. On arm64 compat, the kernel space is well above
>>> the reach of the 32-bit code.
>>>
>>> If you want to preserve some compatibility for this specific test, what
>>> about checking for wrapping around 0, I think it would make more sense.
>>> Something like:
>>>
>>> if ((u32)ts > UINTPTR_MAX - sizeof(*ts) + 1)
>>
>> Ok, sounds good to me. But it is something that this patch series inherited,
>> hence I would prefer to send a separate patch that introduces what you are
>> proposing and removes TASK_SIZE_32 from the headers. How does it sound?
>
> I'd rather avoid moving TASK_SIZE_32 unnecessarily. Just add a
> preparatory patch to your series for arm64 compat vdso and follow with
> the rest without moving TASK_SIZE_32 around.
>

Ok, sounds good. I will test it and repost.

--
Regards,
Vincenzo