Messages in this thread | | | Date | Thu, 14 Oct 2021 14:44:33 +0300 | From | Ville Syrjälä <> | Subject | [regression] commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits") |
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Hi,
I have a 32bit installation here that stopped working. Bisected it to commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits").
dhcpcd was the first thing I notice being affected on account of network not coming up, and after trying to look at it with gdb also gdb turned out to be broken.
strace of dhcpcd shows a SIGFPE getting delivered, after which it gets stuck (seem to be sitting in poll but not responding to even ^C). And gdb seems to be stuck in a perpetual SIGFPE loop and won't even get to the prompt.
The crucial bit here seems to be that most of the software is built with -mfpmath=sse. After rebuilding dhcpcd without that it started to work on the broken kernel. Rebuilding gdb didn't help so I whatever SSE usage is causing the issue is presumably happening in a library. Had to do the rebuilds on a working kernel as well because otherwise the build itself would die to a SIGFPE somewhere.
Tested the same disk on on both a 64bit capable Pentium D and a 32bit only Pentium 4 just to rule out the specific CPU. Busted on both.
-- Ville Syrjälä Intel
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