From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754011Ab3KEG7L (ORCPT ); Tue, 5 Nov 2013 01:59:11 -0500 Received: from mail9.hitachi.co.jp ([133.145.228.44]:34321 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753575Ab3KEG7I (ORCPT ); Tue, 5 Nov 2013 01:59:08 -0500 Message-ID: <5278973A.1010705@hitachi.com> Date: Tue, 05 Nov 2013 15:59:06 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Ingo Molnar Cc: Steven Rostedt , Ananth N Mavinakayanahalli , x86@kernel.org, lkml , =?UTF-8?B?VXdlIEtsZQ==?= =?UTF-8?B?aW5lLUvDtm5pZw==?= , Andrew Morton , Borislav Petkov Subject: Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on func_ptr_is_kernel_text References: <20131101112530.14657.87835.stgit@kbuild-fedora.novalocal> <20131101112537.14657.88496.stgit@kbuild-fedora.novalocal> <20131104210053.76c37210@gandalf.local.home> <20131105060901.GA29936@gmail.com> In-Reply-To: <20131105060901.GA29936@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2013/11/05 15:09), Ingo Molnar wrote: > > * Steven Rostedt wrote: > >> On Fri, 01 Nov 2013 11:25:37 +0000 >> Masami Hiramatsu wrote: >> >>> Prohibit probing on func_ptr_is_kernel_text(). >>> Since the func_ptr_is_kernel_text() is called from >>> notifier_call_chain() which is called from int3 handler, >>> probing it may cause double int3 fault and kernel will >>> reboot. >>> >>> This happenes when the kernel built with CONFIG_DEBUG_NOTIFIERS=y. >>> >>> Signed-off-by: Masami Hiramatsu >>> Cc: Andrew Morton >>> Cc: "Uwe Kleine-König" >>> Cc: Borislav Petkov >>> Cc: Ingo Molnar >>> --- >>> kernel/extable.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/kernel/extable.c b/kernel/extable.c >>> index 832cb28..022fb25 100644 >>> --- a/kernel/extable.c >>> +++ b/kernel/extable.c >>> @@ -129,7 +129,7 @@ int kernel_text_address(unsigned long addr) >>> * pointer is part of the kernel text, we need to do some >>> * special dereferencing first. >>> */ >>> -int func_ptr_is_kernel_text(void *ptr) >>> +int nokprobe func_ptr_is_kernel_text(void *ptr) >>> { >>> unsigned long addr; >>> addr = (unsigned long) dereference_function_descriptor(ptr); >>> >> >> One thing I worry about the "nokprobe" annotation, is that it moves the >> location of the function out of local. This function no exists in the >> section with its users. Same with the debug functions in the other >> patch. > > Well, it's a bit like noinline, that changes the position of the function > as well. So it's not true that 'noxyz' attributes don't affect function > placement - they often don't, but some do. > > The more important aspect is that 'noprobe' makes it really, really > apparent what the tag is about, at first sight. > > _How_ the 'non probing' is achived is an implementational detail when > kprobes are enabled: right now it puts a function into a separate section, > but we could just a much build a list of function names and check against > it at probe insertion time. Actually, kprobes already has it -- kprobes_blacklist. Currently the list is manually maintained in kprobes.c separated from the function definition. I hope to build the list when the kernel build time if possible... Would you have any idea to classify some annotated(but no side-effect) functions? Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com