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Date:      Fri, 21 Nov 2025 21:54:18 +0200
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        Michal Meloun <mmel@freebsd.org>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>
Subject:   Re: mmap( MAP_ANON) is broken on current. (was Still seeing Failed assertion: "p[i] == 0" on armv7 buildworld)
Message-ID:  <aSDDatRqKWZ3tUmt@kib.kiev.ua>
In-Reply-To: <ab87cb06-0b54-431c-9529-1fa993e614ef@freebsd.org>
References:  <8657a2f4-cb32-49a5-bbf6-cd5a4394c7be@FreeBSD.org> <aSAklF9D8haCAaNU@kib.kiev.ua> <aSAq8Ds6nCA24YEI@kib.kiev.ua> <ab87cb06-0b54-431c-9529-1fa993e614ef@freebsd.org>

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On Fri, Nov 21, 2025 at 08:08:47PM +0100, Michal Meloun wrote:
> First, many thanks for your efforts, but this check doesn't trigger when the
> problem occurs
> 
Hm, ok.  This is a data point, in fact.

> 
> To be more precise, testing case
> on fresh kernel(d8bfcacd12aba73188c44a157c707908e275825d)
> with PMAP_DEBUG defined in pmap-v6.c and with
> trivial zero check for first page at this place ->
> https://cgit.freebsd.org/src/tree/contrib/jemalloc/src/pages.c#n281
> 
> causes this failure:
> 
> __je_pages_map: addr: 0x0, ret: 0x3087b000, size: 4096, alignment: 4096,
> prot: 0x00000003, flags: 0x0C001002
> __je_pages_map: i: 0, p[i]: 0xFFFFFFFF, p: 0x3087b000
> __je_pages_map: i: 23, p[i]: 0x308E5F94, p: 0x3087b000

Could you, please, when the failure is detected, spawn 'procstat -v <pid>'
and dump the memory map of the process?  To be clear, I want to see all
of this:
- the address of the mapping returned by mmap
- its size
- the location of the first non-zero byte
- memory map



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