Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754892Ab2KZO06 (ORCPT ); Mon, 26 Nov 2012 09:26:58 -0500 Received: from miso.sublimeip.com ([203.12.5.51]:33359 "EHLO miso.sublimeip.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754674Ab2KZO05 (ORCPT ); Mon, 26 Nov 2012 09:26:57 -0500 Subject: Re: vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range To: gorcunov@openvz.org (Cyrill Gorcunov) Date: Tue, 27 Nov 2012 01:26:55 +1100 (EST) Cc: avagin@gmail.com (Andrey Wagin), oleg@redhat.com (Oleg Nesterov), xemul@parallels.com (Pavel Emelyanov), rostedt@goodmis.org (Steven Rostedt), fweisbec@gmail.com (Frederic Weisbecker), mingo@redhat.com (Ingo Molnar), a.p.zijlstra@chello.nl (Peter Zijlstra), linux-kernel@vger.kernel.org (LKML) Reply-To: u3557@dialix.com.au In-Reply-To: <20121126141843.GE10312@moon> X-Mailer: ELM [version 2.5 PL8] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20121126142655.9AD28592064@miso.sublimeip.com> From: u3557@miso.sublimeip.com (Amnon Shiloh) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1181 Lines: 32 Hi Cyrill, Programmers don't (and the manual-page says they shouldn't even try) call "sigreturn" directly. If an interrupt happens, by bad luck, to occur while the process is running vdso code, then eventually, once signal-processing is complete, "sigreturn" (issued by glibc) will take the process back to where it was before the interrupt happend, inside the vdso page. Best Regards, Amnon. > On Mon, Nov 26, 2012 at 11:55:01PM +1100, Amnon Shiloh wrote: > > > > You could of course keep that old code and modify only the very > > first instruction of each routine into a jump instruction, but then > > the code to which the process returns may not be compatible with > > the new kernel and/or hardware configuration. > > For sure there will be some limitations but I fear we can't do > that much with it. I don't expect the regular program to use > sigreturn for jumping into vdso code, but I could be wrong. > > Cyrill > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/