From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yu-cheng Yu Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function Date: Mon, 10 Jun 2019 09:05:13 -0700 Message-ID: <5dc357f5858f8036cad5847cfe214401bb9138bf.camel@intel.com> References: <20190606200926.4029-1-yu-cheng.yu@intel.com> <20190606200926.4029-4-yu-cheng.yu@intel.com> <20190607080832.GT3419@hirez.programming.kicks-ass.net> <20190607174336.GM3436@hirez.programming.kicks-ass.net> <34E0D316-552A-401C-ABAA-5584B5BC98C5@amacapital.net> <7e0b97bf1fbe6ff20653a8e4e147c6285cc5552d.camel@intel.com> <4b448cde-ee4e-1c95-0f7f-4fe694be7db6@intel.com> <0e505563f7dae3849b57fb327f578f41b760b6f7.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Dave Hansen , Andy Lutomirski Cc: Peter Zijlstra , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit List-Id: linux-arch.vger.kernel.org On Fri, 2019-06-07 at 14:09 -0700, Dave Hansen wrote: > On 6/7/19 1:06 PM, Yu-cheng Yu wrote: > > > Huh, how does glibc know about all possible past and future legacy code > > > in the application? > > > > When dlopen() gets a legacy binary and the policy allows that, it will > > manage > > the bitmap: > > > > If a bitmap has not been created, create one. > > Set bits for the legacy code being loaded. > > I was thinking about code that doesn't go through GLIBC like JITs. If JIT manages the bitmap, it knows where it is. It can always read the bitmap again, right? Yu-cheng From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga09.intel.com ([134.134.136.24]:55102 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388850AbfFJQNV (ORCPT ); Mon, 10 Jun 2019 12:13:21 -0400 Message-ID: <5dc357f5858f8036cad5847cfe214401bb9138bf.camel@intel.com> Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function From: Yu-cheng Yu Date: Mon, 10 Jun 2019 09:05:13 -0700 In-Reply-To: References: <20190606200926.4029-1-yu-cheng.yu@intel.com> <20190606200926.4029-4-yu-cheng.yu@intel.com> <20190607080832.GT3419@hirez.programming.kicks-ass.net> <20190607174336.GM3436@hirez.programming.kicks-ass.net> <34E0D316-552A-401C-ABAA-5584B5BC98C5@amacapital.net> <7e0b97bf1fbe6ff20653a8e4e147c6285cc5552d.camel@intel.com> <4b448cde-ee4e-1c95-0f7f-4fe694be7db6@intel.com> <0e505563f7dae3849b57fb327f578f41b760b6f7.camel@intel.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Dave Hansen , Andy Lutomirski Cc: Peter Zijlstra , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Message-ID: <20190610160513.hjTBxfSA0mY3GgLzASRE-NNARS5GgzQwmiW4oeK4JEU@z> On Fri, 2019-06-07 at 14:09 -0700, Dave Hansen wrote: > On 6/7/19 1:06 PM, Yu-cheng Yu wrote: > > > Huh, how does glibc know about all possible past and future legacy code > > > in the application? > > > > When dlopen() gets a legacy binary and the policy allows that, it will > > manage > > the bitmap: > > > > If a bitmap has not been created, create one. > > Set bits for the legacy code being loaded. > > I was thinking about code that doesn't go through GLIBC like JITs. If JIT manages the bitmap, it knows where it is. It can always read the bitmap again, right? Yu-cheng