Re: [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region
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From: Peter Zijlstra <peterz@infradead.org>
Date: 2019-02-13 14:41:53
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On Wed, Feb 13, 2019 at 02:39:22PM +0000, Julien Thierry wrote:
Hi Peter, On 13/02/2019 14:25, Peter Zijlstra wrote:quoted
On Wed, Feb 13, 2019 at 02:00:26PM +0000, Will Deacon wrote:quoted
The difference is because getting preempted in the sequence above is triggered off the back of an interrupt. On arm64, and I think also on x86, the user access state (SMAP or PAN) is saved and restored across exceptions but not across context switch.A quick reading of the SDM seems to suggest the SMAP state is part of EFLAGS, which is context switched just fine AFAIK.I fail to see where this is happening when looking at the switch_to() logic in x86_64.
Yeah, me too.. we obviously preserve EFLAGS for user context, but for kernel-kernel switches we do not seem to preserve it :-( _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel