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SubjectRe: [PATCH v4 4/4] sparc64: Add support for ADI (Application Data Integrity)
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From: Khalid Aziz <khalid.aziz@oracle.com>
Date: Tue, 17 Jan 2017 12:32:46 -0700

> On 01/16/2017 09:39 PM, David Miller wrote:
>> From: Khalid Aziz <khalid.aziz@oracle.com>
>> Date: Wed, 11 Jan 2017 09:12:54 -0700
>>
>>> + __asm__ __volatile__(
>>> + ".word 0xa1438000\n\t" /* rd %mcdper, %l0 */
>>
>> Just use "rd %%asr14, %0" this way you don't have to play all of these
>> fixed register games which kill the code generated by gcc. If you
>> forcefully clobber a windowed register like %l0 it means the function
>> being emitted can never be a leaf function, tail calls are no longer
>> allowed, etc.
>
> Hi David,
>
> "rd %%asr14, %0" should work but does not due to bugs in assembler -
> <https://sourceware.org/ml/binutils/2016-03/msg00302.html>, and
> <https://sourceware.org/ml/binutils/2016-03/msg00303.html>. These bugs
> were fixed in binutils 2.27 but older assemblers will cause kernel
> build to fail. Using byte coded equivalent is the safest option.

Fair enough.

Then please at least use %g1 or another usable global register to
avoid at least some of the problems I mentioned.

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