From: Maxwell Bland <mbland@motorola.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
"linux-arm-kernel@lists.infradead.org"
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Subject: Re: [PATCH 0/4] arm64: mm: support dynamic vmalloc/pmd configuration
Date: Wed, 21 Feb 2024 17:57:05 +0000 [thread overview]
Message-ID: <SEZPR03MB6786142493B476B96F46081BB4572@SEZPR03MB6786.apcprd03.prod.outlook.com> (raw)
In-Reply-To: <4368e86f-d6aa-4db8-b4cf-42174191dcf9@csgroup.eu>
> On Wednesday, February 21, 2024 at 1:32 AM, Christophe Leroy wrote:
>
> On powerpc (book3s/32) we have more or less the same although it is not
> directly linked to PMDs: the virtual 4G address space is split in
> segments of 256M. On each segment there's a bit called NX to forbit
> execution. Vmalloc space is allocated in a segment with NX bit set while
> Module spare is allocated in a segment with NX bit unset. We never have
> to override vmalloc wrappers. All consumers of exec memory allocate it
> using module_alloc() while vmalloc() provides non-exec memory.
>
> For modules, all you have to do is select
> ARCH_WANTS_MODULES_DATA_IN_VMALLOC and module data will be allocated
> using vmalloc() hence non-exec memory in our case.
This critique has led me to some valuable ideas, and I can definitely find a simpler
approach without overrides.
I do want to mention changes to how VMALLOC_* and MODULE_* constants
are used on arm64 may introduce other issues. See discussion/code on the patch
that motivated this patch at:
https://lore.kernel.org/all/CAP5Mv+ydhk=Ob4b40ZahGMgT-5+-VEHxtmA=-LkJiEOOU+K6hw@mail.gmail.com/
In short, maybe the issue of code/data intermixing requires a rework of arm64
memory infrastructure, but I see a potentially elegant solution here based on the
comments given on this patch.
Thanks,
Maxwell
next prev parent reply other threads:[~2024-02-21 22:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-20 20:32 [PATCH 0/4] arm64: mm: support dynamic vmalloc/pmd configuration Maxwell Bland
2024-02-20 20:32 ` [PATCH 1/4] mm/vmalloc: allow arch-specific vmalloc_node overrides Maxwell Bland
2024-02-21 5:43 ` Christoph Hellwig
2024-02-21 7:38 ` Christophe Leroy
2024-02-21 6:59 ` Christophe Leroy
2024-02-21 17:19 ` Maxwell Bland
2024-02-20 20:32 ` [PATCH 2/4] mm: pgalloc: support address-conditional pmd allocation Maxwell Bland
2024-02-21 7:13 ` Christophe Leroy
2024-02-21 9:27 ` David Hildenbrand
2024-02-21 15:54 ` [External] " Maxwell Bland
2024-02-20 20:32 ` [PATCH 3/4] arm64: separate code and data virtual memory allocation Maxwell Bland
2024-02-21 7:20 ` Christophe Leroy
2024-02-20 20:32 ` [PATCH 4/4] arm64: dynamic enforcement of pmd-level PXNTable Maxwell Bland
2024-02-21 7:32 ` [PATCH 0/4] arm64: mm: support dynamic vmalloc/pmd configuration Christophe Leroy
2024-02-21 17:57 ` Maxwell Bland [this message]
2024-02-21 14:50 ` Conor Dooley
2024-02-21 15:42 ` [External] " Maxwell Bland
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