From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Julien Thierry <julien.thierry@arm.com>,
catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
valentin.schneider@arm.com, mingo@redhat.com,
james.morse@arm.com, hpa@zytor.com,
Ingo Molnar <mingo@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region
Date: Wed, 13 Feb 2019 15:17:12 +0100 [thread overview]
Message-ID: <20190213141712.GV32494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190213140025.GB6346@brain-police>
On Wed, Feb 13, 2019 at 02:00:26PM +0000, Will Deacon wrote:
> > This; how is getting preempted fundamentally different from scheduling
> > ourselves?
>
> 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. Consequently, taking an irq in a
> user_access_{begin,end} section and then scheduling is fine, but calling
> schedule directly within such a section is not.
So how's this then:
if (user_access_begin()) {
preempt_disable();
<IRQ>
set_need_resched();
</IRQ no preempt>
preempt_enable()
__schedule();
user_access_end();
}
That _should_ work just fine but explodes with the proposed nonsense.
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next prev parent reply other threads:[~2019-02-13 14:17 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-15 13:58 [PATCH v3 0/4] uaccess: Add unsafe accessors for arm64 Julien Thierry
2019-01-15 13:58 ` [PATCH v3 1/4] arm64: uaccess: Cleanup get/put_user() Julien Thierry
2019-01-15 13:58 ` [PATCH v3 2/4] arm64: uaccess: Implement unsafe accessors Julien Thierry
2019-01-15 13:58 ` [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region Julien Thierry
2019-01-30 16:58 ` Valentin Schneider
2019-02-04 13:27 ` Julien Thierry
2019-02-11 13:45 ` Ingo Molnar
2019-02-11 13:51 ` Peter Zijlstra
2019-02-12 9:15 ` Julien Thierry
2019-02-13 8:21 ` Ingo Molnar
2019-02-13 10:35 ` Peter Zijlstra
2019-02-13 10:50 ` Julien Thierry
2019-02-13 13:17 ` Peter Zijlstra
2019-02-13 13:20 ` Peter Zijlstra
2019-02-13 14:00 ` Will Deacon
2019-02-13 14:07 ` Julien Thierry
2019-02-13 14:17 ` Peter Zijlstra [this message]
2019-02-13 14:24 ` Julien Thierry
2019-02-13 14:40 ` Peter Zijlstra
2019-02-13 15:08 ` Peter Zijlstra
2019-02-13 14:25 ` Peter Zijlstra
2019-02-13 14:39 ` Julien Thierry
2019-02-13 14:41 ` Peter Zijlstra
2019-02-13 15:45 ` Peter Zijlstra
2019-02-13 18:54 ` Peter Zijlstra
[not found] ` <D61C430D-4321-4114-AB85-671A3C7B8EAE@amacapital.net>
2019-02-13 22:21 ` Peter Zijlstra
2019-02-13 22:49 ` Andy Lutomirski
2019-02-14 10:14 ` [PATCH] sched/x86: Save [ER]FLAGS on context switch Peter Zijlstra
2019-02-14 16:18 ` Brian Gerst
2019-02-14 19:34 ` Peter Zijlstra
2019-02-15 14:34 ` Brian Gerst
2019-02-15 17:18 ` Linus Torvalds
2019-02-15 17:40 ` Peter Zijlstra
2019-02-15 18:28 ` Andy Lutomirski
2019-02-15 23:34 ` Peter Zijlstra
2019-02-16 0:21 ` Linus Torvalds
2019-02-16 10:32 ` Peter Zijlstra
2019-02-16 4:06 ` hpa
2019-02-16 10:30 ` Peter Zijlstra
2019-02-18 22:30 ` H. Peter Anvin
2019-02-19 0:24 ` Linus Torvalds
2019-02-19 2:20 ` Andy Lutomirski
2019-02-19 2:46 ` H. Peter Anvin
2019-02-19 9:07 ` Julien Thierry
2019-02-19 8:53 ` Julien Thierry
2019-02-19 9:15 ` Peter Zijlstra
2019-02-19 9:19 ` Peter Zijlstra
2019-02-19 9:04 ` Peter Zijlstra
2019-02-19 9:21 ` hpa
2019-02-19 9:44 ` Peter Zijlstra
2019-02-19 11:38 ` Thomas Gleixner
2019-02-19 11:58 ` Peter Zijlstra
2019-02-19 12:48 ` Will Deacon
2019-02-20 22:55 ` H. Peter Anvin
2019-02-21 12:06 ` Julien Thierry
2019-02-21 21:35 ` Thomas Gleixner
2019-02-21 22:08 ` Linus Torvalds
2019-02-22 12:58 ` Peter Zijlstra
2019-02-22 18:10 ` Thomas Gleixner
2019-02-22 22:26 ` [RFC][PATCH] objtool: STAC/CLAC validation Peter Zijlstra
2019-02-22 23:34 ` Linus Torvalds
2019-02-23 8:43 ` Peter Zijlstra
2019-02-22 23:39 ` hpa
2019-02-23 8:39 ` Peter Zijlstra
2019-02-25 8:47 ` hpa
2019-02-25 13:21 ` Peter Zijlstra
2019-03-01 15:07 ` Peter Zijlstra
2019-02-25 8:49 ` hpa
2019-02-22 23:55 ` Andy Lutomirski
2019-02-23 8:37 ` Peter Zijlstra
2019-02-23 10:52 ` Peter Zijlstra
2019-02-25 10:51 ` Peter Zijlstra
2019-02-25 11:53 ` Peter Zijlstra
2019-02-25 15:36 ` Andy Lutomirski
2019-02-23 0:34 ` Andy Lutomirski
2019-02-23 1:12 ` Linus Torvalds
2019-02-23 1:16 ` Andy Lutomirski
2019-02-23 1:33 ` Linus Torvalds
2019-02-23 1:40 ` Linus Torvalds
2019-02-25 8:33 ` Julien Thierry
2019-02-25 11:55 ` Peter Zijlstra
2019-02-21 12:46 ` [PATCH] sched/x86: Save [ER]FLAGS on context switch Will Deacon
2019-02-21 22:06 ` Andy Lutomirski
2019-02-18 9:03 ` [PATCH v2] " Peter Zijlstra
2019-02-13 23:19 ` [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region Linus Torvalds
2019-01-15 13:58 ` [PATCH v3 4/4] arm64: uaccess: Implement user_access_region_active Julien Thierry
2019-01-25 14:27 ` [PATCH v3 0/4] uaccess: Add unsafe accessors for arm64 Catalin Marinas
2019-01-30 16:17 ` Julien Thierry
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