From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752552Ab2KTScZ (ORCPT ); Tue, 20 Nov 2012 13:32:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:20171 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859Ab2KTScX (ORCPT ); Tue, 20 Nov 2012 13:32:23 -0500 Date: Tue, 20 Nov 2012 19:32:43 +0100 From: Oleg Nesterov To: Steven Rostedt Cc: Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , Amnon Shiloh , linux-kernel@vger.kernel.org Subject: Re: [PATCH] arch_check_bp_in_kernelspace: fix the range check Message-ID: <20121120183243.GA31290@redhat.com> References: <20121109182943.GA2789@redhat.com> <20121109183026.GA2719@redhat.com> <20121119174728.GA11365@redhat.com> <1353349500.6276.9.camel@gandalf.local.home> <20121120154824.GA17534@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121120154824.GA17534@redhat.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 On 11/20, Oleg Nesterov wrote: > > On 11/19, Steven Rostedt wrote: > > > > Is this really what we want? > > I am not sure, that is why I am asking. Yes. And, > Well yes, with the new implementation __vsyscall_page simply does > syscall, so I guess (say) strace will "just work". But, afaics, only > if vsyscall_mode == NATIVE. > > So perhaps bp in vsyscall_page still makes sense... Or. Perhaps we can define TRAP_VSYSCALL and change emulate_vsyscall() to do if (current->ptrace && test_thread_flag(TIF_SYSCALL_TRACE)) send_sigtrap(TRAP_VSYSCALL, ...); if it returns true? This way the debugger doesn't need to play with the debug registers, it can use ptrace(PTRACE_SYSCALL). The tracee will report SIGTRAP after vsyscall, debugger can detect this case looking at info->si_code. Yes, the tracee won't report _before_ it calls the function, but perhaps this is enough? Amnon? Oleg.