Messages in this thread | | | Subject | Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type | From | Miles Chen <> | Date | Tue, 27 Oct 2020 15:41:57 +0800 |
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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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