Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)

[Andy Lutomirski]

On Mon, Mar 7, 2016 at 10:04 AM, Khalid Aziz <khalid.aziz@xxxxxxxxxx> wrote:
> On 03/07/2016 09:56 AM, David Miller wrote:
>>
>> From: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
>> Date: Mon, 7 Mar 2016 08:07:53 -0700
>>
>>> PR_GET_SPARC_ADICAPS
>>
>>
>> Put this into a new ELF auxiliary vector entry via ARCH_DLINFO.
>>
>> So now all that's left is supposedly the TAG stuff, please explain
>> that to me so I can direct you to the correct existing interface to
>> provide that as well.
>>
>> Really, try to avoid prtctl, it's poorly typed and almost worse than
>> ioctl().
>>
>
> The two remaining operations I am looking at are:
>
> 1. Is PSTATE.mcde bit set for the process? PR_SET_SPARC_ADI provides this in
> its return value in the patch I sent.
>
> 2. Is TTE.mcd set for a given virtual address? PR_GET_SPARC_ADI_STATUS
> provides this function in the patch I sent.
>
> Setting and clearing version tags can be done entirely from userspace:
>
>         while (addr < end) {
>                 asm volatile(
>                         "stxa %1, [%0]ASI_MCD_PRIMARY\n\t"
>                         :
>                         : "r" (addr), "r" (version));
>                 addr += adicap.blksz;
>         }
> so I do not have to add any kernel code for tags.

Is the effect of that to change the tag associated with a page to
which the caller has write access?

I sense DoS issues in your future.