[PATCH 1/1] Add support for using DRNG random number generator

[Jussi Kivilinna]

Quoting Dmitry Kasatkin <dmitry.kasatkin at intel.com>:

> This patch provides support for using Digital Random Number Generator (DRNG)
> engine, which is available on the latest Intel's CPUs. DRNG engine is
> accesible via new the RDRAND instruction.
>
> This patch adds the following:
> - support for disabling using of rdrand instruction
> - checking for RDRAND instruction support using cpuid
> - RDRAND usage implementation
>
> Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin at intel.com>
> ---
<snip>
>
> diff --git a/src/hwfeatures.c b/src/hwfeatures.c
> index 82c435b..e55d9b6 100644
> --- a/src/hwfeatures.c
> +++ b/src/hwfeatures.c
> @@ -134,6 +134,20 @@ detect_x86_64_gnuc (void)
>       : "%eax", "%ebx", "%ecx", "%edx", "cc"
>       );
>  #endif /*#ifdef ENABLE_AESNI_SUPPORT*/
> +#ifdef ENABLE_DRNG_SUPPORT
> +   asm volatile
> +     ("movl $1, %%eax\n\t"           /* Get CPU info and feature flags.  */
> +      "cpuid\n"
> +      "testl $0x40000000, %%ecx\n\t" /* Test bit 30.  */
> +      "jz .Lno_rdrand%=\n\t"         /* No RDRAND support.  */
> +      "orl $512, %0\n"               /* Set our HWF_INTEL_RDRAND bit.  */
> +
> +      ".Lno_rdrand%=:\n"
> +      : "+r" (hw_features)
> +      :
> +      : "%eax", "%ecx", "%edx", "cc"

%ebx gets modified by cpuid too.

> +      );
> +#endif /* #ifdef ENABLE_DRNG_SUPPORT */
>
>  }
>  #endif /* __x86_64__ && __GNUC__ */
> @@ -267,6 +281,22 @@ detect_ia32_gnuc (void)
>       : "%eax", "%ecx", "%edx", "cc"
>       );
>  #endif /*ENABLE_AESNI_SUPPORT*/
> +#ifdef ENABLE_DRNG_SUPPORT
> +   asm volatile
> +     ("pushl %%ebx\n\t"	        /* Save GOT register.  */
> +      "movl $1, %%eax\n\t"           /* Get CPU info and feature flags.  */
> +      "cpuid\n"
> +      "popl %%ebx\n\t"	        /* Restore GOT register. */
> +      "testl $0x40000000, %%ecx\n\t" /* Test bit 30.  */
> +      "jz .Lno_rdrand%=\n\t"         /* No RDRAND support.  */
> +      "orl $512, %0\n"               /* Set our HWF_INTEL_RDRAND bit.  */
> +
> +      ".Lno_rdrand%=:\n"
> +      : "+r" (hw_features)
> +      :
> +      : "%eax", "%ecx", "%edx", "cc"
> +      );
> +#endif /*ENABLE_DRNG_SUPPORT*/
>
>  }
>  #endif /* __i386__ && SIZEOF_UNSIGNED_LONG == 4 && __GNUC__ */
> --
> 1.7.10.4
>
>
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