=head1 NAME
-OPENSSL_ia32cap - the IA-32 processor capabilities vector
+OPENSSL_ia32cap, OPENSSL_ia32cap_loc - the IA-32 processor capabilities vector
=head1 SYNOPSIS
manipulated afterwards to modify crypto library behaviour. For the
moment of this writing following bits are significant:
+=over
+
=item bit #4 denoting presence of Time-Stamp Counter.
=item bit #19 denoting availability of CLFLUSH instruction;
=item bit #26 denoting SSE2 support;
-=item bit #28 denoting Hyperthreading, which is used to distiguish
- cores with shared cache;
+=item bit #28 denoting Hyperthreading, which is used to distinguish
+cores with shared cache;
=item bit #30, reserved by Intel, denotes specifically Intel CPUs;
=item bit #62 denoting availability of RDRAND instruction;
+=back
+
For example, clearing bit #26 at run-time disables high-performance
SSE2 code present in the crypto library, while clearing bit #24
disables SSE2 code operating on 128-bit XMM register bank. You might
effect without modifying the application source code. Alternatively you
can reconfigure the toolkit with no-sse2 option and recompile.
-Less intuituve is clearing bit #28. The truth is that it's not copied
+Less intuitive is clearing bit #28. The truth is that it's not copied
from CPUID output verbatim, but is adjusted to reflect whether or not
the data cache is actually shared between logical cores. This in turn
affects the decision on whether or not expensive countermeasures
against cache-timing attacks are applied, most notably in AES assembler
module.
+
+The vector is further extended with EBX value returned by CPUID with
+EAX=7 and ECX=0 as input. Following bits are significant:
+
+=over
+
+=item bit #64+3 denoting availability of BMI1 instructions, e.g. ANDN;
+
+=item bit #64+5 denoting availability of AVX2 instructions;
+
+=item bit #64+8 denoting availability of BMI2 instructions, e.g. MUXL
+and RORX;
+
+=item bit #64+18 denoting availability of RDSEED instruction;
+
+=item bit #64+19 denoting availability of ADCX and ADOX instructions;
+
+=back