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▲ mattashii 2 hours ago

I remember that PR for similarly interesting reasons:

Someone on the pgsql-hackers@ mailing list noticed that, with a then-recent OpenSSL version on graviton, there were issues validating the "control file" of a PostgreSQL instance [0] (control files contain some basic ground truths about a cluster).

The report included a lot of detailed information about the program state, sufficient for me to figure out that one of the registers was definitely getting clobbered during the pg_strong_random() calls[1], but without access to the environment I couldn't prove whether it was the OpenSSL library, or a compiler bug.

A few days later an Apt developer was debugging the same issue from another direction, eventually figured out that this was caused by a typo in openssl's register restoration code (which was written in ASM introduced in the PR linked by parent post), and then submitted a PR to OpenSSL to fix the issue [2], now (presumably) for good.

[0] https://postgr.es/m/Z4VjonBTm6IG8mGa%40msg.df7cb.de

[1] https://postgr.es/m/CAEze2WiRijBaoeFgi1JvsZeO6qXvpYkh4ax1bUV...

[2] https://github.com/openssl/openssl/pull/26469