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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