From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.1 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_EF,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 2111A1F463 for ; Tue, 10 Sep 2019 15:57:46 +0000 (UTC) DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type; q=dns; s=default; b=Z6r9g 0mTzDfQmSYA2VYmWhbYtzUqdyTjesZ6L9gS7KYagtQpiahrt52mrx7fgIBvd1BVO mRgMyMDFJBMZLn0FlHg0qozeKlVc9f8GM28ZcXFAYm/a+l0SeskhZ/Q6S1Pplznh pFtvOZeSqEj20KAOb6XlaniNrtRuoWHAO+gS3E= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:from:to:cc:subject:references:date:in-reply-to :message-id:mime-version:content-type; s=default; bh=pf2hHT7EWI6 BVpRDfjL521/kAZg=; b=M5GkHrsiPuQBBAzOUHDZ7IgQMv3zYG3gBeJQ5hpfG2R ugj3JSNDBAWg4ubQMp3zcujRY0KRU2I0UjAzPMvQIkvyCiErtIyUnjK1mSk8bbQ5 t5AhSamrzWj9Y8xW5ndQj2uigUVrHP7m3PQSLuLeUofigyhjbW6iwSQxBnKXItd0 = Received: (qmail 23274 invoked by alias); 10 Sep 2019 15:57:43 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 23265 invoked by uid 89); 10 Sep 2019 15:57:42 -0000 Authentication-Results: sourceware.org; auth=none X-HELO: mx1.redhat.com From: Florian Weimer To: DJ Delorie Cc: "Richard Earnshaw \(lists\)" , libc-alpha@sourceware.org Subject: Re: RFD - Support for memory tagging in GLIBC References: Date: Tue, 10 Sep 2019 17:57:38 +0200 In-Reply-To: (DJ Delorie's message of "Mon, 09 Sep 2019 15:11:27 -0400") Message-ID: <87tv9kxhxp.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain * DJ Delorie: > I wonder if we could generically abuse these bits on other architectures > as well, but as a no-op? It might require some platform-independent > kernel interface to say "I want my address space to ignore the top four > bits please". You can get hardware support for this using alias mappings, but it's going to be some bits in the middle, not the top bits, and you'll probably waste TLB slots. OpenJDK's ZGC does this even on aarch64 because as mentioned on this thread, the system calls currently expect the canonical bits. Thanks, Florian