linux-kernel - Re: [RFC PATCH 0/2] mm: update mips to use do_mmap(), make mmap

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Message-ID: <r2gwcapbifzvycf4iqpdfozggqkjckwd3lgthovyuwq6xprz2a@ofcgu6eigkf3>
Date: Tue, 17 Dec 2024 09:11:36 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] mm: update mips to use do_mmap(), make
 mmap_region() internal

* Thomas Bogendoerfer <tsbogend@...ha.franken.de> [241217 03:25]:
> On Thu, Dec 12, 2024 at 03:36:45PM +0000, Lorenzo Stoakes wrote:
> > Currently the only user of mmap_region() outside of the memory management
> > code is the MIPS VDSO implementation.
> > 
> > This uses mmap_region() to map a 'delay slot emulation page' at the top of
> > the stack which is read-only and executable.
> > 
> > This mapping requires that an already-acquired mmap write lock is utilised
> > and that uffd and populate logic is ignored. This rules out vm_mmap(),
> > however do_mmap() fits the bill.
> > 
> > Adapt this code to use do_mmap() and then once done, make mmap_region()
> > internal and userland testable, and avoid any other uses of mmap_region(),
> > which is absolutely and strictly an internal mm function which bypasses a
> > great number of checks and logic.
> > 
> > REVIEWERS NOTES:
> > 
> > Thomas - I lack the hardware or set up to test this beyond a simple
> > cross-compilation test, so I need some input from you MIPS guys as to
> > whether this is workable.
> > 
> > I've therefore sent this as an RFC so we can be sure this is suitable!
> > Please could you check to make sure this change is OK and I haven't missed
> > anything?
> 
> conversation looks correct, but this patch doesn't apply to upstream v6.13-rc1.
> Which tree are you using ?

He's out right now, but generally he works on mm-unstable.  It doesn't
apply cleanly there either, so my guess is mm-unstable has been rebased.

We should do this, but there's no rush.

Thanks,
Liam