From owner-freebsd-hackers@FreeBSD.ORG Mon Apr 13 11:34:04 2015 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 0F8B66D6 for ; Mon, 13 Apr 2015 11:34:04 +0000 (UTC) Received: from mail-la0-x231.google.com (mail-la0-x231.google.com [IPv6:2a00:1450:4010:c03::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 9EDBEAB9 for ; Mon, 13 Apr 2015 11:34:03 +0000 (UTC) Received: by layy10 with SMTP id y10so54693029lay.0 for ; Mon, 13 Apr 2015 04:34:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=iQSyRmRJ72eS3XUY6rCpEK6FVLDpw2WjBbsXpUFw13E=; b=BUGaYkkVXA7PhuXoAmI2tAcBMjSihENwemPdn8TaaTWnkJEo8J9tTYCohm2yuJoAAz UlzyHJ10owoMjoKw4wPk3kiapJ6qdFblFf5c+Geb3oU6ZuQA6sz2kN/e5vjNJsr5Pzpn c5Zp5yj4adI2gVwlUGxIYDbAusCoFQOEIwt9JqLbQLNzCW9ANhJn/vKcIkwVbSR2cgy3 Nx9AEaq0pEuSXP4QgWki6zJG69z3wTKFQueVVzGNU0Mwue48n2sJYSl+c/E+uqvhamDu vURtMRyZdmrDO2eX1Dov0cE6ZOGilkdA30hjigPBwfe/xifd7wCWOMWH3CokPcHmocQN B2bQ== MIME-Version: 1.0 X-Received: by 10.112.98.201 with SMTP id ek9mr12900045lbb.68.1428924841734; Mon, 13 Apr 2015 04:34:01 -0700 (PDT) Received: by 10.152.18.226 with HTTP; Mon, 13 Apr 2015 04:34:01 -0700 (PDT) In-Reply-To: References: Date: Mon, 13 Apr 2015 14:34:01 +0300 Message-ID: Subject: Re: another question - VM mappings From: Kimmo Paasiala To: Oliver Pinter Content-Type: text/plain; charset=UTF-8 Cc: "freebsd-hackers@freebsd.org" , Wojciech Puchar X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Apr 2015 11:34:04 -0000 On Mon, Apr 13, 2015 at 2:25 PM, Oliver Pinter wrote: > Under amd64 exists an so called shared-page - similar to linux's vdso > mechanism - https://github.com/freebsd/freebsd/blob/master/sys/kern/kern_exec.c#L1045 > . > > This page is double mapped with user-space and with kernel. From > security reason it's only RO, otherwise, when mapped with RW or RWX, > then you could write kernel memory from user-space. > > On Mon, Apr 13, 2015 at 9:31 AM, Wojciech Puchar wrote: >> below is mapping for very simple process (no libc etc) >> >> [wojtek@laptop ~]$ procstat -v 917 >> PID START END PRT RES PRES REF SHD FL TP >> PATH >> 917 0x400000 0x401000 r-x 1 0 1 0 CN-- vn >> /home/wojtek/test/1 >> 917 0x600000 0x601000 rw- 1 0 1 0 ---- df >> 917 0x7ffffffdf000 0x7ffffffff000 rw- 1 0 1 0 ---D df >> 917 0x7ffffffff000 0x800000000000 r-x 0 0 39 0 ---- ph >> >> >> what is "ph" mapping and why read&executable? > _______________________________________________ What is the function is this page, why is it there for every process? -Kimmo