From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 0253F6B0082 for ; Mon, 13 Jun 2011 05:07:39 -0400 (EDT) Received: from d03relay05.boulder.ibm.com (d03relay05.boulder.ibm.com [9.17.195.107]) by e39.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p5D8rJMP024475 for ; Mon, 13 Jun 2011 02:53:19 -0600 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay05.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5D97VGb334298 for ; Mon, 13 Jun 2011 03:07:31 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5D37Txi022775 for ; Sun, 12 Jun 2011 21:07:31 -0600 Date: Mon, 13 Jun 2011 14:29:55 +0530 From: Srikar Dronamraju Subject: Re: [PATCH v4 3.0-rc2-tip 2/22] 2: uprobes: Breakground page replacement. Message-ID: <20110613085955.GD27130@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20110607125804.28590.92092.sendpatchset@localhost6.localdomain6> <20110607125835.28590.25476.sendpatchset@localhost6.localdomain6> <1307660609.2497.1773.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1307660609.2497.1773.camel@laptop> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: Ingo Molnar , Steven Rostedt , Linux-mm , Arnaldo Carvalho de Melo , Linus Torvalds , Masami Hiramatsu , Hugh Dickins , Christoph Hellwig , Andi Kleen , Thomas Gleixner , Jonathan Corbet , Oleg Nesterov , Andrew Morton , Jim Keniston , Roland McGrath , Ananth N Mavinakayanahalli , LKML * Peter Zijlstra [2011-06-10 01:03:29]: > On Tue, 2011-06-07 at 18:28 +0530, Srikar Dronamraju wrote: > > + vaddr_old = kmap_atomic(old_page, KM_USER0); > > + vaddr_new = kmap_atomic(new_page, KM_USER1); > > + > > + memcpy(vaddr_new, vaddr_old, PAGE_SIZE); > > + /* poke the new insn in, ASSUMES we don't cross page boundary */ > > + addr = vaddr; > > + vaddr &= ~PAGE_MASK; > > + memcpy(vaddr_new + vaddr, &opcode, uprobe_opcode_sz); > > + > > + kunmap_atomic(vaddr_new); > > + kunmap_atomic(vaddr_old); > > > > + vaddr_new = kmap_atomic(page, KM_USER0); > > + vaddr &= ~PAGE_MASK; > > + memcpy(opcode, vaddr_new + vaddr, uprobe_opcode_sz); > > + kunmap_atomic(vaddr_new); > > > > Both sequences in resp {write,read}_opcode() assume the opcode doesn't > cross page boundaries but don't in fact have any assertions validating > this assumption. > read_opcode and write_opcode reads/writes just one breakpoint instruction I had the below note just above the write_opcode definition. /* * NOTE: * Expect the breakpoint instruction to be the smallest size instruction for * the architecture. If an arch has variable length instruction and the * breakpoint instruction is not of the smallest length instruction * supported by that architecture then we need to modify read_opcode / * write_opcode accordingly. This would never be a problem for archs that * have fixed length instructions. */ Do we have archs which have a breakpoint instruction which isnt of the smallest instruction size for that arch. If we do have can we change the write_opcode/read_opcode while we support that architecture? -- Thanks and Regards Srikar > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org