Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity
 (ADI)
To: Khalid Aziz <khalid.aziz@oracle.com>, David Miller <davem@davemloft.net>
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From: Rob Gardner <rob.gardner@oracle.com>
Message-ID: <56DDC3EB.8060909@oracle.com>
Date: Mon, 7 Mar 2016 10:09:47 -0800
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On 03/07/2016 10:04 AM, Khalid Aziz wrote:
> On 03/07/2016 09:56 AM, David Miller wrote:
>> From: Khalid Aziz <khalid.aziz@oracle.com>
>> 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.
>

What about clearing the tags when the user is done with the memory? You 
can't count on the user to do that, so doesn't the kernel have to do it 
someplace?

Rob