On Sun, 2015-01-18 at 00:04 +0100, Niels Möller wrote:
> [email protected] (Niels Möller) writes:
> 
> > I think I'm going to add an environment variable to override
> > the cpu detection, so different variants can be checked easily at
> > runtime.
> 
> Say we add a secure_getenv("NETTLE_FAT_OVERRIDE") in the fat
> initialization. What should it look like? Some alternatives:
> 1. Specify substitute values to replace result of the cpuid calls?
> 2. A list of feature keywords?
> 3. A list of function:variant, where each entry specifies an override
>    for the particular function?

For gnutls I have an environment variable which is interpreted as an
alternative CPUID. E.g. you can put a flag with the following in
GNUTLS_CPUID_OVERRIDE:
  0x1: Disable all run-time detected optimizations
  0x2: Enable AES-NI  
  0x4: Enable SSSE3
  0x8: Enable PCLMUL
  0x100000: Enable VIA padlock
  0x200000: Enable VIA PHE
  0x400000: Enable VIA PHE SHA512




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