tree 3b296986c80eb539d74b9a934aaf49afbcdb872b
parent 30742686c6958159ab392129a51d57e1ba1f67a2
author David Benjamin <davidben@google.com> 1705010156 -0500
committer Boringssl LUCI CQ <boringssl-scoped@luci-project-accounts.iam.gserviceaccount.com> 1705012669 +0000

Do not condition CRYPTO_is_RDRAND_capable on __RDRND__

On some AMD processors, we will act as if the hardware is
RDRAND-incapable, even it actually supports it, to workaround some bugs
where their RDRAND would return all ones. However, this works by
clearing the RDRAND bit, and the static capability check bypasses this.

That means, when compiling binaries for an RDRAND-capable baseline CPU,
we might end up disabling the workaround. Thanks to Brian Smith for
noticing this.

Fortunately, we believe this had no real impact and the workaround was
actually redundant with other parts of our PRNG logic. See
https://crbug.com/boringssl/675#c2 for a more detailed analysis.

Fixed: 675
Change-Id: I91d844cfaafb22eb29254f81fb6719588937a4a8
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/65267
Commit-Queue: David Benjamin <davidben@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Bob Beck <bbe@google.com>