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Date:      Fri, 21 Nov 2025 08:12:55 +0100
From:      Michal Meloun <mmel@FreeBSD.org>
To:        FreeBSD Current <freebsd-current@freebsd.org>, Konstantin Belousov <kib@freebsd.org>
Subject:   mmap( MAP_ANON) is broken on current. (was Still seeing Failed assertion: "p[i] == 0" on armv7 buildworld)
Message-ID:  <8657a2f4-cb32-49a5-bbf6-cd5a4394c7be@FreeBSD.org>
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I have confirmed that jmalloc assertions are caused by mmap() failure. 
It can return non-zeroed page(s) for mmap(MAP_ANON), which is clearly a bug.

I have confirmed this on native ARMv7, and according to Mark, it is also 
reproducible on ARM32 and i386 jails. I think I saw it also on a 
memory-constrained (4 GB) aarch64, but I cannot reproduce it yet.

Have somebody idea how to identify vm faults associated with anon mmap 
to  trigger detection of this failure in kernel? Or any other hint?


Thanks,
Michal
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