Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755825Ab2KWQdI (ORCPT ); Fri, 23 Nov 2012 11:33:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40045 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755631Ab2KWQdG (ORCPT ); Fri, 23 Nov 2012 11:33:06 -0500 Date: Fri, 23 Nov 2012 17:33:20 +0100 From: Oleg Nesterov To: Amnon Shiloh Cc: Cyrill Gorcunov , Pavel Emelyanov , Steven Rostedt , Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: arch_check_bp_in_kernelspace: fix the range check Message-ID: <20121123163320.GA32716@redhat.com> References: <20121122161238.GA27078@redhat.com> <20121123091453.016B0592076@miso.sublimeip.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121123091453.016B0592076@miso.sublimeip.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1275 Lines: 35 Hello Amnon, I am a bit confused, On 11/23, Amnon Shiloh wrote: > > What I discovered now, is that PTRACE_SYSCALL (also PTRACE_SINGLESTEP) > does not work within the vsyscall page, so I cannot trap the kernel-calls > there (this is very simple to verify using "gdb" or "strace"). Sure, but we alredy discussed this? Once again, PTRACE_SYSCALL should work in the NATIVE mode. Obviously it won't work in EMULATE mode but we can change emulate_vsyscall() to report TRAP_VSYSCALL or even introduce PTRACE_EVENT_VSYSCALL. > The necessary patch was already discussed and is very simple. Do you mean TRAP_VSYSCALL/PTRACE_EVENT_VSYSCALL above or additional in_gate_area_no_mm() check to allow the hw bp? > Or, there is an alternative: if only I (the ptracer or the traced process) > was allowed to munmap the vsyscall page, It is not possible to unmap it. The kernel (swapper_pg_dir) has this mapping, not the process. Unlike vdso. IOW, you can only "unmap" it globally and obviously you can't do this from the userspace. Oleg. -- 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/