From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761620AbZBEBtU (ORCPT ); Wed, 4 Feb 2009 20:49:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755611AbZBEBtJ (ORCPT ); Wed, 4 Feb 2009 20:49:09 -0500 Received: from TYO201.gate.nec.co.jp ([202.32.8.193]:38024 "EHLO tyo201.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755056AbZBEBtI (ORCPT ); Wed, 4 Feb 2009 20:49:08 -0500 Message-ID: <498A317A.8030707@mxs.nes.nec.co.jp> Date: Thu, 05 Feb 2009 09:23:22 +0900 From: "Ken'ichi Ohmichi" User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Neil Horman CC: Eric Biederman , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, hbabu@us.ibm.com, Simon Horman , Andrew Morton , Vivek Goyal Subject: Re: [PATCH]: add dmesg log symbols to /proc/vmcoreinfo lists References: <20090119212127.GA13157@hmsreliant.think-freely.org> <20090120141551.GA5125@redhat.com> <20090120150958.GB18207@hmsreliant.think-freely.org> <20090120152255.GB5125@redhat.com> <20090127001211.f847ea5a.akpm@linux-foundation.org> <20090128041109.GA4943@verge.net.au> <20090204120549.GA2182@hmsreliant.think-freely.org> In-Reply-To: <20090204120549.GA2182@hmsreliant.think-freely.org> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Neil, Thank you for a kernel patch and a makedumpfile patch. Neil Horman wrote: >> That aside we aren't currently exporting log_buf_len, so I don't >> think this code works actually works. >> >> Neil can you add a comment in kernel/printk.c of the algorithm >> necessary for external tools to decode the ring buffer? >> >> We need the comment because people working on kernel/printk.c >> need to know what is happening and without having to review lots >> of user space code, and we need the comment to verify that we >> are exporting the right things. >> > > Ok, as per Erics comment, I've written this. It applies on top of whats already > in your tree Andrew. It adds some comments on the function in question so that > anyone working on printk.c will know why we're exporting their symbols. It also > modifies slightly the symbols we are exporting so that we can handle dmesg > buffers that are longer than the standard PAGE_SIZE configuration, and lets us > detect and handle buffer wraps. > > Thanks! > > printk.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > Signed-off-by: Neil Horman > > diff --git a/kernel/printk.c b/kernel/printk.c > index dd5cc7b..6a1163b 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -138,10 +138,20 @@ static int log_buf_len = __LOG_BUF_LEN; > static unsigned logged_chars; /* Number of chars produced since last read+clear operation */ > > #ifdef CONFIG_KEXEC > +/* > + * This appends the listed symbols to /proc/vmcoreinfo > + * /proc/vmcoreinfo is used by various utiilties, like > + * crash and makedumpfile to obtain access to symbols that > + * are otherwise very difficult to locate. These symbols > + * are specifically used so that utilities > + * can access and extract the dmesg log from a vmcore file > + * after a crash > + */ > void log_buf_kexec_setup(void) > { > VMCOREINFO_SYMBOL(log_buf); > - VMCOREINFO_SYMBOL(log_end); > + VMCOREINFO_SYMBOL(log_buf_len); > + VMCOREINFO_SYMBOL(logged_chars) > } > #endif Please do not remove VMCOREINFO_SYMBOL(log_end), because makedumpfile needs it for knowing the latest log offset in ring buffer of dmesg. I updated a makedumpfile patch for handling ring buffer, and it is possible to download the latest patch from the following site: https://sourceforge.net/tracker2/download.php?group_id=178938&atid=887142&file_id=312113&aid=2521075 Thanks Ken'ichi Ohmichi