From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753098Ab2GRRSX (ORCPT ); Wed, 18 Jul 2012 13:18:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43845 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007Ab2GRRSU (ORCPT ); Wed, 18 Jul 2012 13:18:20 -0400 Date: Wed, 18 Jul 2012 13:18:12 -0400 From: Vivek Goyal To: linux kernel mailing list Cc: Kexec Mailing List , "Eric W. Biederman" , Andrew Morton , Kay Sievers Subject: [PATCH] printk: Export struct log size and member offsets through vmcoreinfo Message-ID: <20120718171812.GC21746@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are tools like makedumpfile and vmcore-dmesg which can extract kernel log buffer from vmcore. Since we introduced structured logging, that functionality is broken. Now user space tools need to know about "struct log" and offsets of various fields to be able to parse struct log data and extract text message or dictonary. This patch exports some of the fields. Currently I am not exporting log "level" info as that is a bitfield and offsetof() bitfields can't be calculated. But if people start asking for log level info in the output then we probably either need to seprate out "level" or use bit shift operations for flags and level. Signed-off-by: Vivek Goyal --- kernel/printk.c | 9 +++++++++ 1 file changed, 9 insertions(+) Index: linux-2.6/kernel/printk.c =================================================================== --- linux-2.6.orig/kernel/printk.c 2012-07-20 14:02:38.213581253 -0400 +++ linux-2.6/kernel/printk.c 2012-07-20 14:02:42.004581438 -0400 @@ -646,6 +646,15 @@ void log_buf_kexec_setup(void) VMCOREINFO_SYMBOL(log_buf_len); VMCOREINFO_SYMBOL(log_first_idx); VMCOREINFO_SYMBOL(log_next_idx); + /* + * Export struct log size and field offsets. User space tools can + * parse it and detect any changes to structure down the line. + */ + VMCOREINFO_STRUCT_SIZE(log); + VMCOREINFO_OFFSET(log, ts_nsec); + VMCOREINFO_OFFSET(log, len); + VMCOREINFO_OFFSET(log, text_len); + VMCOREINFO_OFFSET(log, dict_len); } #endif