From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id 4453A6B025F for ; Tue, 12 Dec 2017 21:14:40 -0500 (EST) Received: by mail-oi0-f71.google.com with SMTP id c85so448405oib.13 for ; Tue, 12 Dec 2017 18:14:40 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 77si190685oik.236.2017.12.12.18.14.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Dec 2017 18:14:39 -0800 (PST) Subject: Re: pkeys: Support setting access rights for signal handlers References: <5fee976a-42d4-d469-7058-b78ad8897219@redhat.com> <5965d682-61b2-d7da-c4d7-c223aa396fab@redhat.com> <20171212231324.GE5460@ram.oc3035372033.ibm.com> From: Florian Weimer Message-ID: <9dc13a32-b1a6-8462-7e19-cfcf9e2c151e@redhat.com> Date: Wed, 13 Dec 2017 03:14:36 +0100 MIME-Version: 1.0 In-Reply-To: <20171212231324.GE5460@ram.oc3035372033.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ram Pai , Dave Hansen Cc: linux-mm , x86@kernel.org, linux-arch , linux-x86_64@vger.kernel.org, Linux API On 12/13/2017 12:13 AM, Ram Pai wrote: > On POWER, the value of the pkey_read() i.e contents the AMR > register(pkru equivalent), is always the same regardless of its > context; signal handler or not. > > In other words, the permission of any allocated key will not > reset in a signal handler context. That's certainly the simpler semantics, but I don't like how they differ from x86. Is the AMR register reset to the original value upon (regular) return from the signal handler? > I was not aware that x86 would reset the key permissions in signal > handler. I think, the proposed behavior for PKEY_ALLOC_SETSIGNAL should > actually be the default behavior. Note that PKEY_ALLOC_SETSIGNAL does something different: It requests that the kernel sets the access rights for the key to the bits specified at pkey_alloc time when the signal handler is invoked. So there is still a reset with PKEY_ALLOC_SETSIGNAL, but to a different value. It did not occur to me that it might be desirable to avoid resetting the value on a per-key basis. Thanks, Florian -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org