Hi Pavel,
Thanks for your review.
On Tue, Jul 28, 2015 at 02:01:12PM +0200, Pavel Machek wrote:
> Hi!
>
> > This patch adds the codes for generating random number array as the
> > HMAC key that will used by later EFI stub codes.
> >
> > The original codes in efi_random copied from aslr and add the codes
> > to accept input entropy and EFI debugging. In later patch will add
> > the codes to get random number by EFI protocol. The separate codes
> > can avoid impacting aslr function.
> >
> > Signed-off-by: Lee, Chun-Yi <jlee@xxxxxxxx>
>
> > +#define X86_FEATURE_EDX_TSC (1 << 4)
> > +#define X86_FEATURE_ECX_RDRAND (1 << 30)
>
> Can you pull it from existing includes somewhere?
>
I didn't see similar definition in header.
> > +static bool rdrand_feature(void)
> > +{
> > + return (cpuid_ecx(0x1) & X86_FEATURE_ECX_RDRAND);
> > +}
> > +
> > +static bool rdtsc_feature(void)
> > +{
> > + return (cpuid_edx(0x1) & X86_FEATURE_EDX_TSC);
> > +}
>
> Are these helpers neccessary?
I will try to simplify it.
>
> > + if (rdrand_feature()) {
> > + efi_printk(sys_table, " RDRAND");
> > + if (rdrand_long(&raw)) {
> > + random ^= raw;
> > + use_i8254 = false;
> > + }
> > + }
> > +
> > + if (rdtsc_feature()) {
> > + efi_printk(sys_table, " RDTSC");
> > + rdtscll(raw);
> > +
> > + random ^= raw;
> > + use_i8254 = false;
> > + }
>
> You'll do two (expensive) cpuids calls here.
>
I will try to avoid call cpuid many times.
Thanks a lot!
Joey Lee
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