POWER8 has hardware transactional memory, which glibc uses to implement
locks. In some cases, taking a lock begins a transaction, wrapping
arbitrary user code (!) until the lock is released. If the transaction
is aborted, everything rewinds and glibc tries again with some other
implementation.
The kernel will abort the transaction in a variety of cases. Notably, on
a syscall, the transaction aborts and the syscall *does not happen*.
https://www.kernel.org/doc/Documentation/powerpc/transactional_memory.txt
Yet, for some reason, although the relevant change does appear to be in
the kernel, the transaction is being rewound with getrandom happening
anyway. This does not work very well.
Instead, only guard the DRBG access with the lock, not CRYPTO_sysrand.
This lock is only used to protect the DRBG from the destructor that
zeros everything.
Change-Id: Ied8350f1e808a09300651de4200c7b0d07b3a158
Reviewed-on: https://boringssl-review.googlesource.com/16985
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
17ce286e07
