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Expand on importance of not using fpu for crypto if there's no fpu.

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This commit is contained in:
riastradh 2020-07-19 15:33:08 +00:00
parent e8d07af35a
commit 52c1c2aa09
1 changed files with 5 additions and 2 deletions
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7
crypto/external/bsd/openssl/dist/crypto/ppccap.c vendored
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@ -374,8 +374,11 @@ void OPENSSL_cpuid_setup(void)
size_t len = sizeof(val);
/*
* If machdep.fpu_present == 0, FPU is absent and emulated by software.
* Avoid using it for better performance.
* If machdep.fpu_present == 0, FPU is absent and emulated by
* software. In that case, using FPU instructions hurts rather
* than helps performance, and the software is unlikely to run in
* constant time so it would expose us to timing side channel
* attacks. So don't do it!
*/
error = sysctlbyname("machdep.fpu_present", &val, &len, NULL, 0);
if (error != 0 || (error == 0 && val != 0))