@AndresFreundTec@mastodon.social
Post #2194762
2024-03-30 22:26 UTC
One more aspect that I think emphasizes the number of coincidences that had to come together to find this:
I run a number "buildfarm" instances for automatic testing of postgres. Among them with valgrind. For some other test instance I had used -fno-omit-frame-pointer for some reason I do not remember. A year or so ago I moved all the test instances to a common base configuration, instead of duplicate configurations. I chose to make all of them use -fno-omit-frame-pointer.
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@AndresFreundTec@mastodon.social 2024-03-30 22:29
Afaict valgrind would not have complained about the payload without -fno-omit-frame-pointer. It was because _get_cpuid() expected the stack frame to look a certain way. Additionally, I chose to use debian unstable to find possible portability problems earlier. Without that valgrind would have had nothing to complain. Without having seen the odd complaints in valgrind, I don't think I would have looked deeply enough when seeing the high cpu in sshd below _get_cpuid().