From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 8891 invoked by alias); 8 Jun 2017 00:30:20 -0000 Mailing-List: contact gnu-gabi-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Post: List-Help: List-Subscribe: Sender: gnu-gabi-owner@sourceware.org Received: (qmail 8711 invoked by uid 89); 8 Jun 2017 00:30:03 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Checked: by ClamAV 0.99.2 on sourceware.org X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.8 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy= X-Spam-Status: No, score=-1.8 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on sourceware.org X-Spam-Level: X-HELO: mail-wm0-f53.google.com Received: from mail-wm0-f53.google.com (HELO mail-wm0-f53.google.com) (74.125.82.53) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 08 Jun 2017 00:30:02 +0000 Received: by mail-wm0-f53.google.com with SMTP id d73so21022899wma.0 for ; Wed, 07 Jun 2017 17:30:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=dU7hl82ywhoCAYuckemtG8YJDuNg9QoXn6tzdq7L/U0=; b=SG2hdndLOXhq4unPb7HWzn+61wUNLZL/OYcC8bqUMZwcPedRrHwuw9YdgNJ7xX/tTd 2Fu0+bVr9mRMbNHB/EXvYlCEU+xvKllJSvx9s1f9TifuKVvchHvIRL35ZkG4isWuzUKs 9V3iv3SlEBRtkUjOyGALfYdTe61fZ4mz2FHmBm6+foB7X+3jS+5k110RzLvR2CKHYgEU nixvZQVAiJ0YDdhCoovWm/2G6aE85JM6qMet06VNIuPxOrdvIub2QuQCQUeiqbq9x4U6 tF8g4/5atpOzmjm3b3Tr0pjLN7Za2nnUq5NJ72EJNTeydi+i5bXwK/oJWZI4rMoj87CI 4ppQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=dU7hl82ywhoCAYuckemtG8YJDuNg9QoXn6tzdq7L/U0=; b=YUIbKsEpXk1QEMBzht6oPjfQlrVgaVV3aj87SxPw79LnqTcVKqg3KoIzyhe04H79cM 9EcUj+4MQQtFMjAqVYRKiOIfgQqsrHX9PcWRLXOIDCoJ5n+vDnW7zkG2mx0Zxxta9Ahz X6v6zlqmerWVabCSCyIEZnfD35JtzFqqBB4q0ZndRlaxdIA3k30eoMOIbp8uqgVl40+8 ZgWe+tlPX8l4lYSW0/V7/oKVQjZvxydMqI058U10ALREBB1VgvKD0RRPvN1eUEv46Jwf UDpoLx4PBRdWme91glIjfsENgWmkuC5MeOQafSTw3EUw5LDmk2VqgOmufiYnZ4j0a0l6 cWhA== X-Gm-Message-State: AODbwcBS+OAtpH8zLcSNsG8+KScrm3SW1oYNZ7W+s2fRs3y+fU/t5EZ/ rcamE4ImjcHoIAgfwpuckWI/o7v3uA== X-Received: by 10.80.212.156 with SMTP id s28mr18099535edi.28.1496881804169; Wed, 07 Jun 2017 17:30:04 -0700 (PDT) MIME-Version: 1.0 Received: by 10.80.132.100 with HTTP; Wed, 7 Jun 2017 17:30:03 -0700 (PDT) In-Reply-To: References: <5d71c4e4-19d2-3861-e212-5e86d29c53fc@zytor.com> From: Cary Coutant Date: Sun, 01 Jan 2017 00:00:00 -0000 Message-ID: Subject: Re: gABI extension proposal: PT_SHMMAP To: James Y Knight Cc: "H. Peter Anvin" , gnu-gabi@sourceware.org Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2017-q2/txt/msg00023.txt.bz2 > Why is MAP_SHARED even needed for the linux vdso use-case? > > All the mappings created for the vdso are read-only mappings, right? > And on Linux, MAP_PRIVATE mappings already reflect changes made to the > underlying file, so long as the process hasn't written to the page, I > think? > > So, if you're intending to use this to implement the "vvar" mapping, > isn't the default MAP_PRIVATE already sufficient? He mentioned that this was for the kernel-provided *data* page, implying to me that he wants a writable, but still sharable (i.e., not copy-on-write) mapping. It seems generally useful to me. I probably wouldn't object to a new gABI bit, but a little more background would be helpful in deciding. -cary