I just noticed this in old mails (not committed), there isn't really any downside to this is there?
In gmane.os.openbsd.misc, Miod wrote: >> On 2014-04-26, Miod Vallat <[email protected]> wrote: >> >> The question I have is can I disable the random number generator?s use of >> >> that instruction? I?d rather be on -current than years old. >> > >> > Apart from the following hammer, I see no easy way to achieve this. >> > >> > Index: i386/machdep.c >> >=================================================================== >> > RCS file: /cvs/src/sys/arch/i386/i386/machdep.c,v >> > retrieving revision 1.536 >> > diff -u -p -r1.536 machdep.c >> > --- i386/machdep.c 29 Mar 2014 18:09:29 -0000 1.536 >> > +++ i386/machdep.c 26 Apr 2014 19:13:14 -0000 >> > @@ -1964,7 +1964,8 @@ identifycpu(struct cpu_info *ci) >> > } >> > >> > if (ci->ci_flags & CPUF_PRIMARY) { >> > - if (cpu_ecxfeature & CPUIDECX_RDRAND) >> > + if (cpu_ecxfeature & CPUIDECX_RDRAND && >> > + vendor != CPUVENDOR_CYRIX) >> > has_rdrand = 1; >> > #ifndef SMALL_KERNEL >> > if (ci->ci_feature_sefflags & SEFF0EBX_SMAP) >> > >> > >> >> Funnily enough it's handled here: http://rt.openssl.org/m/ticket/history?id=3005 > Then this ought to work as well: > > Index: i386/locore.s >=================================================================== > RCS file: /cvs/src/sys/arch/i386/i386/locore.s,v > retrieving revision 1.147 > diff -u -p -r1.147 locore.s > --- i386/locore.s 13 Jun 2013 02:26:53 -0000 1.147 > +++ i386/locore.s 26 Apr 2014 21:21:01 -0000 > @@ -401,6 +401,7 @@ try586: /* Use the `cpuid' instruction. > movl $0, RELOC(_C_LABEL(cpu_vendor))+12 > > movl $1,%eax > + xorl %ecx,%ecx > cpuid > movl %eax,RELOC(_C_LABEL(cpu_id)) # store cpu_id and features > movl %ebx,RELOC(_C_LABEL(cpu_miscinfo)) > >
