From: Christoph Hellwig <hch@infradead.org>
To: Maxwell Bland <mbland@motorola.com>
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Subject: Re: [PATCH 1/4] mm/vmalloc: allow arch-specific vmalloc_node overrides
Date: Tue, 20 Feb 2024 21:43:06 -0800 [thread overview]
Message-ID: <ZdWNalbmABYDuFHE@infradead.org> (raw)
In-Reply-To: <20240220203256.31153-2-mbland@motorola.com>
On Tue, Feb 20, 2024 at 02:32:53PM -0600, Maxwell Bland wrote:
> Present non-uniform use of __vmalloc_node and __vmalloc_node_range makes
> enforcing appropriate code and data seperation untenable on certain
> microarchitectures, as VMALLOC_START and VMALLOC_END are monolithic
> while the use of the vmalloc interface is non-monolithic: in particular,
> appropriate randomness in ASLR makes it such that code regions must fall
> in some region between VMALLOC_START and VMALLOC_end, but this
> necessitates that code pages are intermingled with data pages, meaning
> code-specific protections, such as arm64's PXNTable, cannot be
> performantly runtime enforced.
That's not actually true. We have MODULE_START/END to separate them,
which is used by mips only for now.
>
> The solution to this problem allows architectures to override the
> vmalloc wrapper functions by enforcing that the rest of the kernel does
> not reimplement __vmalloc_node by using __vmalloc_node_range with the
> same parameters as __vmalloc_node or provides a __weak tag to those
> functions using __vmalloc_node_range with parameters repeating those of
> __vmalloc_node.
I'm really not too happy about overriding the functions. Especially
as the separation is a generally good idea and it would be good to
move everyone (or at least all modern architectures) over to a scheme
like this.
next prev parent reply other threads:[~2024-02-21 5:58 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 [this message]
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
2024-02-21 14:50 ` Conor Dooley
2024-02-21 15:42 ` [External] " Maxwell Bland
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