Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751886AbbEGRLx (ORCPT ); Thu, 7 May 2015 13:11:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58434 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbbEGRLt (ORCPT ); Thu, 7 May 2015 13:11:49 -0400 Date: Thu, 7 May 2015 19:11:19 +0200 From: Oleg Nesterov To: Srikar Dronamraju Cc: Ananth N Mavinakayanahalli , Anton Arapov , David Long , Denys Vlasenko , "Frank Ch. Eigler" , Ingo Molnar , Jan Willeke , Jim Keniston , Mark Wielaard , Pratyush Anand , linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/10] uprobes/x86: Introduce arch_uretprobe_is_alive() Message-ID: <20150507171119.GC18652@redhat.com> References: <20150504124835.GA22462@redhat.com> <20150504124914.GA22512@redhat.com> <20150507110852.GF30396@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150507110852.GF30396@linux.vnet.ibm.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: 1874 Lines: 56 On 05/07, Srikar Dronamraju wrote: > > > > > diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h > > index f011fd0..60777f3 100644 > > --- a/arch/x86/include/asm/uprobes.h > > +++ b/arch/x86/include/asm/uprobes.h > > @@ -57,6 +57,7 @@ struct arch_uprobe { > > }; > > > > struct arch_uretprobe { > > + unsigned long sp; > > While this looks good, I was wondering if you did think of having the sp > in the return_instance structure itself. I mean can we use > user_stack_pointer() to populate the ri->sp? Yes, yes, I considered this option. And note that we can cleanup the (a bit ugly) arch_uretprobe_hijack_return_addr() if we export "struct return_instance" and pass it to arch_ helper. > In which case the weak function itself should suffice for most archs. > > Something like this. > prepare_uretprobe() we can have > ri->sp = user_stack_pointer(regs) Yes, and we can do this without changing arch_uretprobe_hijack_return_addr() interface (which imo should be changed anyway, but this is off-topic). > and handle_trampoline() would call something like > > arch_uretprobe_is_alive(next->sp, regs); > > bool __weak arch_uretprobe_is_alive(unsigned long sp, struct pt_regs *regs) > { > return user_stack_pointer(regs) <= sp; > } The problem is, I simply do not know if this is right on !x86. And. I wanted to ensure that if (say) arch/ppc needs something else to save/check in hijack/alive, then this architecture can just add the new members in arch_uretprobe and change the arch_ helpers. > Am I missing something? I do not know. Lets wait for the comments from arch/ maintainers? 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/