[Bug 279901] glibc-2.39-2 and above on the host segfault

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=279901

Mark Peek <mp@FreeBSD.org> changed:

           What    |Removed                     |Added
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                 CC|                            |mp@FreeBSD.org

--- Comment #29 from Mark Peek <mp@FreeBSD.org> ---
(In reply to Darren Henderson from comment #28)

The glibc changes indicated in this bug were specific to amd. I have tried
numerous times to reproduce this issue on intel systems but have not seen it
occur. Sadly I don't have an applicable AMD systems to test on.

Here's my arch install as a bhyve guest:
$ uname -a
Linux archlinux 6.12.4-arch1-1 #1 SMP PREEMPT_DYNAMIC Mon, 09 Dec 2024 14:31:57
+0000 x86_64 GNU/Linux
$ ld.so --list-diagnostics | grep -e version.version
version.version="2.40"

Given some of the ld.so output in previous updates to this bug, I did a diff to
try to find the x86 tunable changes between them.
43c40
< version.version="2.36"
---
> version.version="2.40"
189,191c196,199
< x86.cpu_features.rep_movsb_threshold=0x2000
< x86.cpu_features.rep_movsb_stop_threshold=0x80000
< x86.cpu_features.rep_stosb_threshold=0x800
---
> x86.cpu_features.memset_non_temporal_threshold=0xc000000000
> x86.cpu_features.rep_movsb_threshold=0x0
> x86.cpu_features.rep_movsb_stop_threshold=0xc000000000
> x86.cpu_features.rep_stosb_threshold=0xffffffffffffffff

Running binaries with this environment set, so the intel system would run the
same code path in glibc as amd would, did not cause the issue on my intel
system.

GLIBC_TUNABLES="glibc.cpu.x86_memset_non_temporal_threshold=0xc000000000:glibc.cpu.x86_rep_movsb_threshold=0x0:glibc.cpu.x86_rep_movsb_stop_threshold=0xc000000000:glibc.cpu.x86_rep_stosb_threshold=0xffffffffffffffff"

If anyone has seen it on intel, it would be great to have the repro steps added
to this bug.

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