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[134.134.136.100]) by mx.google.com with ESMTPS id g7si2903786pgd.32.2019.06.14.08.33.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2019 08:33:21 -0700 (PDT) Received-SPF: pass (google.com: domain of yu-cheng.yu@intel.com designates 134.134.136.100 as permitted sender) client-ip=134.134.136.100; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yu-cheng.yu@intel.com designates 134.134.136.100 as permitted sender) smtp.mailfrom=yu-cheng.yu@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jun 2019 08:33:20 -0700 X-ExtLoop1: 1 Received: from yyu32-desk1.sc.intel.com ([10.144.153.205]) by fmsmga001.fm.intel.com with ESMTP; 14 Jun 2019 08:33:20 -0700 Message-ID: Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function From: Yu-cheng Yu 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 Date: Fri, 14 Jun 2019 08:25:16 -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> <25281DB3-FCE4-40C2-BADB-B3B05C5F8DD3@amacapital.net> <3f19582d-78b1-5849-ffd0-53e8ca747c0d@intel.com> <5aa98999b1343f34828414b74261201886ec4591.camel@intel.com> <0665416d-9999-b394-df17-f2a5e1408130@intel.com> <5c8727dde9653402eea97bfdd030c479d1e8dd99.camel@intel.com> <328275c9b43c06809c9937c83d25126a6e3efcbd.camel@intel.com> <92e56b28-0cd4-e3f4-867b-639d9b98b86c@intel.com> <1b961c71d30e31ecb22da2c5401b1a81cb802d86.camel@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 2019-06-10 at 15:59 -0700, Dave Hansen wrote: > On 6/10/19 3:40 PM, Yu-cheng Yu wrote: > > Ok, we will go back to do_mmap() with MAP_PRIVATE, MAP_NORESERVE and > > VM_DONTDUMP. The bitmap will cover only 48-bit address space. > > Could you make sure to discuss the downsides of only doing a 48-bit > address space? The downside is that we cannot load legacy lib's above 48-bit address space, but currently ld-linux does not do that. Should ld-linux do that in the future, dlopen() fails. Considering CRIU migration, we probably need to do this anyway? > What are the reasons behind and implications of VM_DONTDUMP? The bitmap is very big. In GDB, it should be easy to tell why a control-protection fault occurred without the bitmap. Yu-cheng