[PATCH 3/3] aarch64: Save and restore SVE registers in ld.so

[Carlos O'Donell]

On 08/02/2018 09:32 AM, Szabolcs Nagy wrote:
> On 02/08/18 14:05, Richard Henderson wrote:
>> On 08/02/2018 03:29 AM, Florian Weimer wrote:
>>> On 08/02/2018 12:23 AM, rth@twiddle.net wrote:
>>>> +/*
>>>> + * For functions conforming to the procedure call standard as
>>>> + * amended for SVE support (ARM_100986_0000_00_en (SVEpcs 00bet1)),
>>>> + * we must save the entire contents of Z0-Z7 as well as P0-P3.
>>>> + */
>>>
>>> What's the worst-case additional stack usage due to this change?
>>
>> The current architectural maximum vector size is 256 bytes,
>> so 2176 bytes total.
>>
> 
> that limit can increase in the future and saving 8 z regs is not enough,
> you need to save all 32 if the resolver code may touch the 32 fp regs.
> (so with 256byte regs it's 8k + 128bytes for 4 pregs)

AArch64 has PTHREAD_MIN_STACK of 128KiB so this should be more than enough
to save and restore SVE registers for some simple function calling.

-- 
Cheers,
Carlos.