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auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: base64 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org RnJvbTogU3RldmVuIFByaWNlDQo+IFNlbnQ6IDI0IE1heSAyMDIxIDEyOjIxDQouLi4NCj4gU28g YSAiZ2VuZXJpYyIgd2F5IG9mIHJlcXVlc3RlZCB0aGUga2VybmVsIGxpbWl0IHRoZSBhZGRyZXNz IHNwYWNlIGZvcg0KPiBhbGxvY2F0aW9ucyB3b3VsZCBiZSBwb3RlbnRpYWxseSB1c2VmdWwgZm9y IG90aGVyIHB1cnBvc2VzLiBBZGRpbmcgYSBuZXcNCj4gc3lzY2FsbCBmb3IgdGhpcyBwdXJwb3Nl IHdvdWxkIGJlIHNlbnNpYmxlLiBXZSBhbHJlYWR5IGhhdmUgKGF0IGxlYXN0KQ0KPiB0d28gImhh Y2tzIiBpbiBtbWFwIGZvciBjb250cm9sbGluZyB0aGUgYWRkcmVzcyByYW5nZSB0aGF0IGNhbiBi ZSB1c2VkOg0KPiANCj4gICogTUFQXzMyQklUIC0geDg2IG9ubHksIGFuZCByZWFsbHkgIjMxIGJp dCINCj4gDQo+ICAqIFByb3ZpZGluZyBhIG1tYXAoKSBoaW50IHdpdGggdGhlIHRvcCBiaXRzIHNl dCB0byBvcHQtaW4gdG8gNTItYml0IFZBcy4NCj4gDQo+IEEgd2VsbCBkZWZpbmVkIG1lY2hhbmlz bSBmb3IgY29udHJvbGxpbmcgdGhlIHZhbGlkIFZBIHJhbmdlIGZvcg0KPiBhbGxvY2F0aW9ucyB3 b3VsZCBiZSBtdWNoIGJldHRlciB0aGFuIGFkZGluZyBtb3JlIGhhY2tzIC0gYW5kIGJvbnVzDQo+ IHBvaW50cyBpZiBpdCB3b3JrcyBmb3IgYWxsIHRoZSBkaWZmZXJlbnQgdHlwZXMgb2YgYWxsb2Nh dGlvbiB1bmxpa2UgdGhlDQo+IGFib3ZlLg0KDQpJJ2QgaGF2ZSB0aG91Z2h0IGEgJ01BUF9CRUxP VycgZmxhZyAoY2YgTUFQX0ZJWEVEKSB3b3VsZCBzdWZmaWNlLg0KSSdtIHNvcnQgb2Ygc3VycHJp c2VkIE1BUF8zMkJJVCB3YXNuJ3QgaW1wbGVtZW50ZWQgdGhhdCB3YXkuDQonbWFuIG1tYXAnIHNh eXMgTUFQXzMyQklUIHdhcyBhZGRlZCBmb3IgeDY0IHRocmVhZCBzdGFja3MgLSBJIHRob3VnaA0K dGhlIHJlcXVpcmVtZW50IGNhbiBmcm9tIDMyYml0IHdpbmUgKHdpbmRvd3MgaGFzIGEgMkcgdXNl ci9rZXJuZWwgYm91bmRhcnkpLg0KDQoJRGF2aWQNCg0KLQ0KUmVnaXN0ZXJlZCBBZGRyZXNzIExh a2VzaWRlLCBCcmFtbGV5IFJvYWQsIE1vdW50IEZhcm0sIE1pbHRvbiBLZXluZXMsIE1LMSAxUFQs IFVLDQpSZWdpc3RyYXRpb24gTm86IDEzOTczODYgKFdhbGVzKQ0K From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D42EC2B9F7 for ; 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Mon, 24 May 2021 13:38:19 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.015; Mon, 24 May 2021 13:38:19 +0100 From: David Laight To: 'Steven Price' , Amanieu d'Antras CC: Arnd Bergmann , Ryan Houdek , Catalin Marinas , Will Deacon , Mark Rutland , Mark Brown , "Linux ARM" , Linux Kernel Mailing List Subject: RE: [RESEND PATCH v4 8/8] arm64: Allow 64-bit tasks to invoke compat syscalls Thread-Topic: [RESEND PATCH v4 8/8] arm64: Allow 64-bit tasks to invoke compat syscalls Thread-Index: AQHXUI7V2V8LHoAybE2lBVUPxoeiSarykJcA Date: Mon, 24 May 2021 12:38:19 +0000 Message-ID: References: <20210518090658.9519-1-amanieu@gmail.com> <20210518090658.9519-9-amanieu@gmail.com> <14982d7d-bee1-6c25-8b18-123c29959f52@arm.com> <1c2bd27a-1c96-f154-ed18-f33630b109b1@arm.com> <419f410f-21b3-a4c6-3cd8-025007e9c31e@arm.com> In-Reply-To: <419f410f-21b3-a4c6-3cd8-025007e9c31e@arm.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210524_053830_118204_81E999FD X-CRM114-Status: GOOD ( 13.75 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Steven Price > Sent: 24 May 2021 12:21 ... > So a "generic" way of requested the kernel limit the address space for > allocations would be potentially useful for other purposes. Adding a new > syscall for this purpose would be sensible. We already have (at least) > two "hacks" in mmap for controlling the address range that can be used: > > * MAP_32BIT - x86 only, and really "31 bit" > > * Providing a mmap() hint with the top bits set to opt-in to 52-bit VAs. > > A well defined mechanism for controlling the valid VA range for > allocations would be much better than adding more hacks - and bonus > points if it works for all the different types of allocation unlike the > above. I'd have thought a 'MAP_BELOW' flag (cf MAP_FIXED) would suffice. I'm sort of surprised MAP_32BIT wasn't implemented that way. 'man mmap' says MAP_32BIT was added for x64 thread stacks - I though the requirement can from 32bit wine (windows has a 2G user/kernel boundary). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel