Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755282Ab1BUOZo (ORCPT ); Mon, 21 Feb 2011 09:25:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56827 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755182Ab1BUOZn (ORCPT ); Mon, 21 Feb 2011 09:25:43 -0500 From: Jiri Olsa To: mingo@elte.hu Cc: masami.hiramatsu.pt@hitachi.com, acme@redhat.com, fweisbec@gmail.com, hpa@zytor.com, ananth@in.ibm.com, davem@davemloft.net, linux-kernel@vger.kernel.org, tglx@linutronix.de, a.p.zijlstra@chello.nl, eric.dumazet@gmail.com, 2nddept-manager@sdl.hitachi.co.jp, Jiri Olsa Subject: [PATCH 2/2] kprobes: disabling optimized kprobes for entry text section Date: Mon, 21 Feb 2011 15:25:13 +0100 Message-Id: <1298298313-5980-3-git-send-email-jolsa@redhat.com> In-Reply-To: <1298298313-5980-1-git-send-email-jolsa@redhat.com> References: <20110220125948.GC25700@elte.hu> <1298298313-5980-1-git-send-email-jolsa@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1676 Lines: 51 You can crash the kernel using kprobe tracer by running: echo "p system_call_after_swapgs" > ./kprobe_events echo 1 > ./events/kprobes/enable The reason is that at the system_call_after_swapgs label, the kernel stack is not set up. If optimized kprobes are enabled, the user space stack is being used in this case (see optimized kprobe template) and this might result in a crash. There are several places like this over the entry code (entry_$BIT). As it seems there's no any reasonable/maintainable way to disable only those places where the stack is not ready, I switched off the whole entry code from kprobe optimizing. wbr, jirka Signed-off-by: Jiri Olsa --- arch/x86/kernel/kprobes.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index d91c477..d03bc1e 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -1276,6 +1276,14 @@ static int __kprobes can_optimize(unsigned long paddr) if (!kallsyms_lookup_size_offset(paddr, &size, &offset)) return 0; + /* + * Do not optimize in the entry code due to the unstable + * stack handling. + */ + if ((paddr >= (unsigned long ) __entry_text_start) && + (paddr < (unsigned long ) __entry_text_end)) + return 0; + /* Check there is enough space for a relative jump. */ if (size - offset < RELATIVEJUMP_SIZE) return 0; -- 1.7.1 -- 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/