From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754201Ab3KEDPM (ORCPT ); Mon, 4 Nov 2013 22:15:12 -0500 Received: from mail7.hitachi.co.jp ([133.145.228.42]:58331 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753412Ab3KEDPK (ORCPT ); Mon, 4 Nov 2013 22:15:10 -0500 Message-ID: <527862B9.2060300@hitachi.com> Date: Tue, 05 Nov 2013 12:15:05 +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: Steven Rostedt Cc: Ingo Molnar , 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> In-Reply-To: <20131104210053.76c37210@gandalf.local.home> 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 11:00), 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. > > Now these may be a slow path where we really don't care, but if the > nokprobe expands this can cause issues. > > The "nokprobe" works differently than "notrace" as "notrace" is just an > attribute that tells gcc not to add mcount to it. The "nokprobe" > actually moves the function into a different section. Well, in that case, I can put it in the opt-out type blacklist(kprobe_blacklist). :) Hmm, I think if I can list nokprobe functions up at build time, we can almost remove the .kprobes.text (Note that some of entry functions in asm still require it.) Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com