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, Michalhelp
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