[systemd-devel] Antw: Re: rdrand generated with march=winchip-c6 in systemd-241

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Mon May 13 07:10:02 UTC 2019

>>> tedheadster <tedheadster at gmail.com> schrieb am 11.05.2019 um 19:19 in Nachricht
<CAP8WD_Y69T_2gk4+gUan4vKozAYtv_djF7cJ=UuiO8j54D6APw at mail.gmail.com>:
> On Sat, May 11, 2019 at 12:30 PM Florian Weimer <fw at deneb.enyo.de> wrote:
>> Can you capture register contents at the point of the crash?
>> Does this reproduce in a chroot?  Maybe you can trace the whole thing
>> with a debugger.  Does the crash reproduce if you single-step through
>> the whole function?
> Florian,
>   I figured out the problem, I just haven't written code to fix it.
> The documentation I can find is silent about what is returned in %ecx
> and %ebx when calling cpuid function 0x00000001 on IDT Winchip-C6 and
> Winchip2.
> I think %ecx  should properly contain 0x00000000, but it instead puts
> the 'auls' characters from cpuid function 0x00000000 (vendor string
> 'CentaurHauls') in %ecx:
> %ebx = 0x746e6543 = "Cent"
> %edx = 0x48727561 = "aurH"
> %ecx = 0x736c7561 = "auls"
> This sets bit 30 (0x736c7561) 'on', the 'supports rdrand' bit.
> So we have to code around the vendor and chip model in this case.
> Jeffrey Walton gave some coding examples I might consider
> (https://github.com/weidai11/cryptopp/blob/master/cpu.cpp#L380).

I didn't see the start of this thread, but is it another attempt to re-implement /proc/cpuinfo's flags?

> - Matthew
> _______________________________________________
> systemd-devel mailing list
> systemd-devel at lists.freedesktop.org 
> https://lists.freedesktop.org/mailman/listinfo/systemd-devel 

More information about the systemd-devel mailing list