Date: Fri, 21 Nov 2025 22:02:57 +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: <aSDFcWRx3vV86KvL@kib.kiev.ua> In-Reply-To: <aSDDatRqKWZ3tUmt@kib.kiev.ua> References: <8657a2f4-cb32-49a5-bbf6-cd5a4394c7be@FreeBSD.org> <aSAklF9D8haCAaNU@kib.kiev.ua> <aSAq8Ds6nCA24YEI@kib.kiev.ua> <ab87cb06-0b54-431c-9529-1fa993e614ef@freebsd.org> <aSDDatRqKWZ3tUmt@kib.kiev.ua>
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On Fri, Nov 21, 2025 at 09:54:23PM +0200, Konstantin Belousov wrote: > 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 Also, regardless of the output above, please try this as a wild guess: diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c index 5b4517d2bf0c..5c6ed51706bf 100644 --- a/sys/vm/vm_object.c +++ b/sys/vm/vm_object.c @@ -2222,7 +2222,7 @@ vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset, * Remove any pages that may still be in the object from a previous * deallocation. */ - if (next_pindex < prev_object->size) { + if (true || next_pindex < prev_object->size) { vm_object_page_remove(prev_object, next_pindex, next_pindex + next_size, 0); #if 0
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