Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753458AbbBYLtH (ORCPT ); Wed, 25 Feb 2015 06:49:07 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:34903 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753231AbbBYLtE (ORCPT ); Wed, 25 Feb 2015 06:49:04 -0500 Message-ID: <54EDB629.4020908@huawei.com> Date: Wed, 25 Feb 2015 19:46:49 +0800 From: Wang Nan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Masami Hiramatsu CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , "yrl.pp-manager.tt@hitachi.com" Subject: Re: [RFC PATCH v3 00/26] Early kprobe: enable kprobes at very early booting stage. References: <1423805941-61407-1-git-send-email-wangnan0@huawei.com> <54E6B139.20909@hitachi.com> <54EDADD6.5070404@huawei.com> In-Reply-To: <54EDADD6.5070404@huawei.com> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.69.129] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2715 Lines: 66 On 2015/2/25 19:11, Wang Nan wrote: > On 2015/2/20 11:59, Masami Hiramatsu wrote: >> Hi, >> >> Sorry for replying late. >> >> (2015/02/13 14:39), Wang Nan wrote: >>> I fell very sorry for people who reviewed my v2 patch series yesterday >>> at https://lkml.org/lkml/2015/2/12/234 because I didn't provide enough >>> information in commit log. This v3 patch series add those missing >>> commit messages. There are also 2 small fix based on v2: >>> >>> 1. Fixes ftrace_sort_mcount_area. Original patch doesn't work for module. >>> 2. Wraps setting of kprobes_initialized in stop_machine() context. >> >> From the viewpoint of the maintenance, it seems over-engineered and >> not general implementation. Please reconsider just initializing breakpoint >> handler in earlier stage. Since those exceptions may happen anywhere, >> those trap handlers setup very early stage. E.g. on x86, setup_arch() >> setup early_trap_init() at beginning. So we just need to initialize >> kprobes earlier. > > I tried as your suggestion. For x86, int3 handler doesn't work correctly until > trap_init(). I don't have enough time to look into this problem today (and I don't > familiar with x86 architecture). Could you please have a look on it? > > Thank you. > Hi Masami, Sorry for the noise. I have futher information may be useful. I initialize kprobe and probed an instruction with int3 between setup_arch() and trap_init(). It doesn't work at first. By dumping __log_buf[] I fount it reports NULL pointer panic. With some random test I found following patch, which makes it works (looks like) correctly. However I think there must be some reason to set dpl to '3' instead of '0' (set_mni_gate use 0 as dpl). Do you have any suggestion on it? Thank you. ------------- The patch --------------- diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 9d2073e..ac29277 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -925,9 +925,9 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code) /* Set of traps needed for early debugging. */ void __init early_trap_init(void) { - set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK); + set_intr_gate_ist(X86_TRAP_DB, &debug, 0); /* int3 can be called from all */ - set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK); + set_intr_gate_ist(X86_TRAP_BP, &int3, 0); #ifdef CONFIG_X86_32 set_intr_gate(X86_TRAP_PF, page_fault); #endif -- 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/