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Thu, 07 May 2020 18:42:01 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 047IavNE026231; Thu, 7 May 2020 18:42:00 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 30sjdyq2v8-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 07 May 2020 18:42:00 +0000 Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 047IfuCW023296; Thu, 7 May 2020 18:41:56 GMT Received: from [10.154.153.82] (/10.154.153.82) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 07 May 2020 11:41:55 -0700 Subject: Re: [RFC 21/43] x86/KASLR: PKRAM: support physical kaslr To: Kees Cook Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, rppt@linux.ibm.com, akpm@linux-foundation.org, hughd@google.com, ebiederm@xmission.com, masahiroy@kernel.org, ardb@kernel.org, ndesaulniers@google.com, dima@golovin.in, daniel.kiper@oracle.com, nivedita@alum.mit.edu, rafael.j.wysocki@intel.com, dan.j.williams@intel.com, zhenzhong.duan@oracle.com, jroedel@suse.de, bhe@redhat.com, guro@fb.com, Thomas.Lendacky@amd.com, andriy.shevchenko@linux.intel.com, hannes@cmpxchg.org, minchan@kernel.org, mhocko@kernel.org, ying.huang@intel.com, yang.shi@linux.alibaba.com, gustavo@embeddedor.com, ziqian.lzq@antfin.com, vdavydov.dev@gmail.com, jason.zeng@intel.com, kevin.tian@intel.com, zhiyuan.lv@intel.com, lei.l.li@intel.com, paul.c.lai@intel.com, ashok.raj@intel.com, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org References: <1588812129-8596-1-git-send-email-anthony.yznaga@oracle.com> <1588812129-8596-22-git-send-email-anthony.yznaga@oracle.com> <202005071049.2D0939137D@keescook> From: Anthony Yznaga Organization: Oracle Corporation Message-ID: <62a1c002-ad7b-a364-5797-6d7f5545d5cf@oracle.com> Date: Thu, 7 May 2020 11:41:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <202005071049.2D0939137D@keescook> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9614 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=0 mlxscore=0 bulkscore=0 adultscore=0 phishscore=0 mlxlogscore=999 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005070151 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9614 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 mlxlogscore=999 spamscore=0 phishscore=0 impostorscore=0 bulkscore=0 priorityscore=1501 malwarescore=0 mlxscore=0 adultscore=0 suspectscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005070151 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/7/20 10:51 AM, Kees Cook wrote: > On Wed, May 06, 2020 at 05:41:47PM -0700, Anthony Yznaga wrote: >> Avoid regions of memory that contain preserved pages when computing >> slots used to select where to put the decompressed kernel. > This is changing the slot-walking code instead of updating > mem_avoid_overlap() -- that's where the check for a "reserved" memory > area should live. > > For example, this is how both mem_avoid_memmap() and the setup_data > memory areas are handled. > > Is there a reason mem_avoid_overlap() can't be used here? > I was thinking it would be more efficient to process just the regions that did not contain preserved pages rather than checking for preserved pages in mem_avoid_overlap(), but I see that may just be adding unnecessary complexity. I'll investigate modifying mem_avoid_overlap(). Thank you for the comments! Anthony