From: Miles Chen <miles.chen@mediatek.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: wsd_upstream@mediatek.com,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
linux-mediatek@lists.infradead.org,
Suren Baghdasaryan <surenb@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type
Date: Tue, 27 Oct 2020 15:41:57 +0800 [thread overview]
Message-ID: <1603784517.12492.2.camel@mtkswgap22> (raw)
In-Reply-To: <20201023101257.GZ1551@shell.armlinux.org.uk>
On Fri, 2020-10-23 at 11:12 +0100, Russell King - ARM Linux admin wrote:
> On Fri, Oct 23, 2020 at 05:14:37PM +0800, Miles Chen wrote:
> > Since kernel no longer writes to the vector, try to replace
> > the vector mem type with read-only type and remove L_PTE_MT_VECTORS.
> >
> > from Catalin in [1]:
> > "
> > > I don't think this matters since the kernel no longer writes to the
> > > vectors page at run-time but it needs cleaning up a bit (and testing in
> > > case I missed something). IOW, do we still need a dedicated mapping type
> > > for the vectors or we can simply use the read-only user page attributes?
> > "
>
> Catalin is incorrect. If CONFIG_KUSER_HELPERS is enabled, then the
> vectors page is definitely written to - it's a user interface, so
> it's not going to change:
>
> #ifdef CONFIG_KUSER_HELPERS
> /*
> * User space must never try to access this
> * directly. Expect your app to break
> * eventually if you do so. The user helper
> * at 0xffff0fe0 must be used instead. (see
> * entry-armv.S for details)
> */
> *((unsigned int *)0xffff0ff0) = val;
> #endif
>
Thanks for the comment.
We have to keep L_PTE_MT_VECTORS for KUSER_HELPERS.
Miles
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prev parent reply other threads:[~2020-10-27 7:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 9:14 [PATCH v2 0/4] arm: support get_user_pages_fast Miles Chen
2020-10-23 9:14 ` [PATCH v2 1/4] arm: mm: use strict p[gum]d types Miles Chen
2020-10-23 9:14 ` [PATCH v2 2/4] arm: mm: reordering memory type table Miles Chen
2020-10-23 10:16 ` Russell King - ARM Linux admin
2020-10-27 8:03 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 3/4] arm: mm: introduce L_PTE_SPECIAL Miles Chen
2020-10-23 10:08 ` Russell King - ARM Linux admin
2020-10-27 7:45 ` Miles Chen
2020-10-27 9:11 ` Russell King - ARM Linux admin
2020-11-01 12:48 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 4/4] arm: replace vector mem type with read-only type Miles Chen
2020-10-23 10:12 ` Russell King - ARM Linux admin
2020-10-27 7:41 ` Miles Chen [this message]
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