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SubjectRe: [Bug report] __arch_hweight32/64 x86
On 6/27/23 06:25, Borislav Petkov wrote:
> On Mon, Jun 26, 2023 at 03:41:27PM -0700, Dave Hansen wrote:
>> I'm not even sure that UML needs GENERIC_HWEIGHT. From a quick glance,
>> it looks like x86 used to use GENERIC_HWEIGHT, but got arch-specific
>> versions later. UML just never moved over to the arch-specific versions.
>
> Thanks - that could very well be the explanation.
>
> That bug report made me blink a couple of times since I did take extra
> precaution to not clobber regs in arch/x86/lib/hweight.S as this was
> part of the whole pain back then with calling a function from asm where
> gcc doesn't even know we're calling a function, see:
>
> f5967101e9de ("x86/hweight: Get rid of the special calling convention")
>
>> I _think_ the attached patch might just fix the problems with the C
>> version and bring the x86/UML implementation back in line with the rest
>> of x86.
>>
>> Thoughts?
>
>> diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
>> index 186f13268401..76d507860be4 100644
>> --- a/arch/x86/um/Kconfig
>> +++ b/arch/x86/um/Kconfig
>> @@ -44,6 +44,3 @@ config ARCH_HAS_SC_SIGNALS
>>
>> config ARCH_REUSE_HOST_VSYSCALL_AREA
>> def_bool !64BIT
>> -
>> -config GENERIC_HWEIGHT
>> - def_bool y
>
> Yeah, we should do it. UML should not do anything different wrt calling
> conventions so it should be able to handle the arch/x86/lib/hweight.S
> versions just fine.

Thank you for the quick resolution! It fixes the problem for me and sorry for
not explaining well enough.

> Richi?
>

--
Sebastian Sumpf
Genode Labs

http://www.genode-labs.com · http://genode.org

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth




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