diff options
author | Andy Polyakov <appro@openssl.org> | 2011-05-16 20:35:11 +0000 |
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committer | Andy Polyakov <appro@openssl.org> | 2011-05-16 20:35:11 +0000 |
commit | b9064221499d6091dbdac4acacd23247faf318ba (patch) | |
tree | 38bffe3edbb4f27444dd46e8b53ea24b6b509bae /doc | |
parent | a3e07010b4682e757c3b1c9e17d21248d33772d6 (diff) |
x86[_64]cpuid.pl: handle new extensions.
Diffstat (limited to 'doc')
-rw-r--r-- | doc/crypto/OPENSSL_ia32cap.pod | 69 |
1 files changed, 45 insertions, 24 deletions
diff --git a/doc/crypto/OPENSSL_ia32cap.pod b/doc/crypto/OPENSSL_ia32cap.pod index dca2e20ace..af6b4f3a4d 100644 --- a/doc/crypto/OPENSSL_ia32cap.pod +++ b/doc/crypto/OPENSSL_ia32cap.pod @@ -2,7 +2,7 @@ =head1 NAME -OPENSSL_ia32cap - finding the IA-32 processor capabilities +OPENSSL_ia32cap - the IA-32 processor capabilities vector =head1 SYNOPSIS @@ -18,30 +18,52 @@ input value (see Intel Application Note #241618). Naturally it's meaningful on x86 and x86_64 platforms only. The variable is normally set up automatically upon toolkit initialization, but can be manipulated afterwards to modify crypto library behaviour. For the -moment of this writing seven bits are significant, namely: - -1. bit #4 denoting presence of Time-Stamp Counter. -2. bit #20, reserved by Intel, is used to choose among RC4 code - paths; -3. bit #23 denoting MMX support; -4. bit #25 denoting SSE support; -5. bit #26 denoting SSE2 support; -6. bit #28 denoting Hyperthreading, which is used to distiguish - cores with shared cache; -7. bit #30, reserved by Intel, is used to choose among RC4 code - paths; -8. bit #57 denoting Intel AES instruction set extension; +moment of this writing following bits are significant: + +=item bit #4 denoting presence of Time-Stamp Counter. + +=item bit #19 denoting availability of CLFLUSH instruction; + +=item bit #20, reserved by Intel, is used to choose among RC4 code paths; + +=item bit #23 denoting MMX support; + +=item bit #24, FXSR bit, denoting availability of XMM registers; + +=item bit #25 denoting SSE support; + +=item bit #26 denoting SSE2 support; + +=item bit #28 denoting Hyperthreading, which is used to distiguish + cores with shared cache; + +=item bit #30, reserved by Intel, is used to choose among RC4 code + paths; + +=item bit #33 denoting availability of PCLMULQDQ instruction; + +=item bit #41 denoting SSSE3, Supplemental SSE3, support; + +=item bit #43 denoting AMD XOP support (forced to zero on Intel); + +=item bit #57 denoting AES-NI instruction set extension; + +=item bit #59, OSXSAVE bit, denoting availability of YMM registers; + +=item bit #60 denoting AVX extension; For example, clearing bit #26 at run-time disables high-performance -SSE2 code present in the crypto library. You might have to do this if -target OpenSSL application is executed on SSE2 capable CPU, but under -control of OS which does not support SSE2 extentions. Even though you -can manipulate the value programmatically, you most likely will find it -more appropriate to set up an environment variable with the same name -prior starting target application, e.g. on Intel P4 processor 'env -OPENSSL_ia32cap=0x12900010 apps/openssl', to achieve same effect -without modifying the application source code. Alternatively you can -reconfigure the toolkit with no-sse2 option and recompile. +SSE2 code present in the crypto library, while clearing bit #24 +disables SSE2 code operating on 128-bit XMM register bank. You might +have to do the latter if target OpenSSL application is executed on SSE2 +capable CPU, but under control of OS that does not enable XMM +registers. Even though you can manipulate the value programmatically, +you most likely will find it more appropriate to set up an environment +variable with the same name prior starting target application, e.g. on +Intel P4 processor 'env OPENSSL_ia32cap=0x16980010 apps/openssl', to +achieve same 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 from CPUID output verbatim, but is adjusted to reflect whether or not @@ -49,4 +71,3 @@ 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. -=cut |