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Re: use of RDRAND in $random_library

Henrique de Moraes Holschuh wrote:
> Now, the kernel can soft-blacklist RDRAND (and RDSEED) usage[2].  In that
> case, the kernel won't use it and it disappears from /proc/cpuinfo, and we
> could do that also to avoid processor errata, not just due to user request.
> However, AFAIK kernel blacklisting would not cause the instructions to trap
> or fail on bare-metal, so userspace could still just use them anyway.

Not sure what you mean by bare metal here.

> Joey, what does that Haskell lib uses to detect availability of RDRAND?

int cpu_has_rdrand()
    uint32_t ax,bx,cx,dx,func=1;
    __asm__ volatile ("cpuid":\
            "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));
    return (cx & 0x40000000);

see shy jo

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