From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753211AbcBWOqZ (ORCPT ); Tue, 23 Feb 2016 09:46:25 -0500 Received: from mail.eperm.de ([89.247.134.16]:60080 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751666AbcBWOqX (ORCPT ); Tue, 23 Feb 2016 09:46:23 -0500 From: Stephan Mueller To: Mathieu Desnoyers Cc: "Paul E. McKenney" , Peter Zijlstra , Will Deacon , Linus Torvalds , LKML , Daniel Borkmann , "Theodore Ts'o" , Hannes Frederic Sowa , mancha security , Mark Charlebois , Behan Webster , Herbert Xu Subject: Re: interesting commit about llvm introducing barrier_data() Date: Tue, 23 Feb 2016 15:46:19 +0100 Message-ID: <1605703.GSn7kbzMda@tauon.atsec.com> User-Agent: KMail/4.14.10 (Linux/4.3.5-300.fc23.x86_64; KDE/4.14.17; x86_64; ; ) In-Reply-To: <675593567.5328.1456237963352.JavaMail.zimbra@efficios.com> References: <1168693945.5302.1456236146207.JavaMail.zimbra@efficios.com> <20160223142336.GK3522@linux.vnet.ibm.com> <675593567.5328.1456237963352.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="nextPart2850483.aJ8ylgFYZo" Content-Transfer-Encoding: 7Bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --nextPart2850483.aJ8ylgFYZo Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Am Dienstag, 23. Februar 2016, 14:32:43 schrieb Mathieu Desnoyers: Hi Mathieu, > ----- On Feb 23, 2016, at 9:23 AM, Paul E. McKenney paulmck@linux.vnet.ibm.com wrote: > > On Tue, Feb 23, 2016 at 02:02:26PM +0000, Mathieu Desnoyers wrote: > >> commit 7829fb09a2b4268b30dd9bc782fa5ebee278b137 > >> Author: Daniel Borkmann > >> Date: Thu Apr 30 04:13:52 2015 +0200 > >> > >> lib: make memzero_explicit more robust against dead store elimination > >> > >> ^ interesting commit. Any idea on the impact of this on kernel RCU > >> implementation and liburcu cmm_barrier() ? > > > > First I knew of it! But I bet that more like this are needed. ;-) > > I recommend you check my IRC discussion with peterz on the matter of > this new "barrier_data()". > The key idea of the memzero_explicit is about forcing the compiler to do a memset. See the trivial test attached. Ciao Stephan --nextPart2850483.aJ8ylgFYZo Content-Disposition: attachment; filename="memset_secure.c.xz" Content-Transfer-Encoding: base64 Content-Type: application/x-xz; name="memset_secure.c.xz" /Td6WFoAAATm1rRGAgAhARYAAAB0L+Wj4A+1BmtdABeKfUvNK1Mdbn6oUrLiHt53Ch4k/05AqKTx QGXf2SH439Jj7zwvwDhrOdu6JDg+yiV6yIC9jhtwtbYyXzMwJsp6SDr1lWilrweCi+rZKfK6ZXgy PG3NGyLI31Vo3GPQHEsCUzo3jMu8ijOAX1u4le/CJueojyUXo5A72hwEGwpH0/1Ff5C4CMEfJ4Ta OHkfFVn0U3FpqyIN34D+phPSQv6T6Q3Fd9diRh6e9+jFPDyMnkGzn0QZPRY5t11fKl5va3LU6/Hp ScHbAVGfqOOJ4L8531d8AU2O7Am+FaK6l+RIXTGFQMuX11zEa3X0e9uYPTun2j3BUb0S3fg1uh7o KuFYoZNK1sNU6oBL69KhzeFEU+SGRNhpPUeTkwCoxYkDrAp/gEc+BfJ2TT9Y/k2LBemALUNZcUd0 sOyOSiMgpzYntcbEhGRDPYTsZCDBX2HuQgY6Uwu3zrJjRx7ADfq0tjCiBNv2Qojc8SU95pVjezxl bzQk9NsJMaUJh1CXtqtkyE+fNLHkUnkbWmzZN0Z6u/1DI99P9OYtwQWNt2Vz9fk+1puY8w9sUGJ9 RULQqxnVDSPfIbs3EO7902dG0ehmUFzONRbF3ytE1dopLHYdJyLuYD9HaDr9bJKUpJEOwHhjWpMX q6cyfqOWqkodAslAFZgvanQSbRLYFvluz4jlvYP7zyzYkbmI+Jz4T9qkfOUbgngSTjKdNbzzQMsE NHoJ5mfBMRJL1nNfUI7nfL5wZqTKctYE1zLn2Il3aksYn6vzjrfkrzSYTATkoM8Pglg0WfKxqf2u TYi6QrrFi/Wx0fZxC+2VxpmrUZwoUoqicp7OEh+vwmdSsj3xJ9/V5Lmu4AhdZ9xBA495VTOMptp3 qdac5/UUdkcEVvEYu5RvsCsvX1j4vnWCrZ7bmcy2/Tf3iBJxsWNbjNLjncmE7QFI9/WimXJ+XpmG FV15XRqtlZjBC74M+smYm33A8tme+Pt3FQUio6UBpZc32s7XWf34C9wpp4HU3WapX0mXRNdjTFo/ N1OS4nwN9898J5+93Ry9VSoN/LszP7Z/OWmNrOFXrf4PoSgBl+LNwDYvqMGetUshJI6byHJuwZgb 9ACCZxICb46FKYk8d8s9iEU74ZAnCpfhkoYSm2TsCsh5WmBTtEwQkdmaGmC/L1+D6QB0g2VjvgPt WcYDvxSBO0Ujd4sxYtYfqjQgc+GYnahv/FKIAJ6KfFgDQJVc0QsNycKH+lAeOyqS6WQaM/TURDGV XOgOCzSLYcdQez/pdGda3lfNKuJULRkqdHPTnQOhMJiq/9ysNHKu0sRmuxCNiyq6hV6cRvYYZAZg jehizj2Pk1coBCWAUGrLNxmTNFAMJJ173bT4ojhY5fbWuvtpS0JVKgPUpOvTKcRAYh7ldz3tOO79 +q2gnmLM5TIsW/Pp8eDU/lXLiwL+6QvsorMbTLsBQyHIpPJSz8f/LaUoienYShyOXqcAfAI8oqEg 5nybTV+2pTCq65WIRvKKONhWMdITUsBbY2hYBM3xxxkOXUM4xbxmfFdbzR5oQn8MV89K2B898UNV 5GvMYMTHH0JB2QyeHftI2yCoaBqlYkIdDHFu2u7Sr2SM9ybD3+yQxNqNVyP2RnSuMylf79mvvd/m ixeqQ96F5mbvf2MYMyGPtO8jh6QfZR9+jomo2pQyEYW6bxzleXbZs27INUGYdVgazWmZcj/RgCJ1 KeEbIqhuZvgzXGDRZtqSNF47b5RblzLxkRG6USuCwJFlEpvt411u7/82KxDbqeKUhKxnk6yWW/Vx XKUvH+H7GwFNH1u9MxWuoQMRUvKgru0zXoRlr1YmRi0sLKQYKehzBGLDJeXyLpR/BTgrMVd8OPME cN5IgXbo/XOzugo6FYAX57ZZlRT4dKfRlZkn9lpnEsVK/lyPx9kFrwXgxsw5NIMQuXlvWIWqPNNw i6vi4HHqTPSXcUUJXFET+b6GSNp5hGhNhUoIAIPBBd0nKFICn55q8tNSG1vhusEmgaV23ae+VnhE YLJOFbL+Oclw1Vm73yyZUcEvNm8xUi1luZX1IGpSFrEzzRtXTkjhYhapK/aE4VCmC4crLKIrXSPq j7yl2uje0+aGkdWBAflwS9twR3DKUwSXJheoizUwsN/AS5JywSQr0fFj8lz216NAmrn3iiRyvN90 pprLdWhLfJ26Z5Xf1woXoJsWjDfQAABCV3k4auKm3gABhw22HwAAB8ETF7HEZ/sCAAAAAARZWg== --nextPart2850483.aJ8ylgFYZo--