From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Miles Chen <miles.chen@mediatek.com>
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: Fri, 23 Oct 2020 11:12:58 +0100 [thread overview]
Message-ID: <20201023101257.GZ1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20201023091437.8225-5-miles.chen@mediatek.com>
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
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2020-10-23 10:13 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 [this message]
2020-10-27 7:41 ` Miles Chen
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