Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757925AbXLSXfW (ORCPT ); Wed, 19 Dec 2007 18:35:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756487AbXLSXfE (ORCPT ); Wed, 19 Dec 2007 18:35:04 -0500 Received: from nofear-snat.bivio.net ([216.142.75.231]:33254 "EHLO corpexc01.corp.networkrobots.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757516AbXLSXe7 convert rfc822-to-8bit (ORCPT ); Wed, 19 Dec 2007 18:34:59 -0500 X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: printf internals Date: Wed, 19 Dec 2007 15:31:15 -0800 Message-ID: In-Reply-To: <1198107085.7740.0.camel@oasis.donpoo.home> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: printf internals Thread-Index: AchClsMdyDxsjMeDSYSFTMXDdvaWMQAAD4BA References: <4761E289.9070007@davidnewall.com> <4762AC35.3010706@anagramm.de> <1198107085.7740.0.camel@oasis.donpoo.home> From: "Siva Prasad" To: "Scott Russell" Cc: "Clemens Koller" , "David Newall" , Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1913 Lines: 52 Yes!... this is a embedded system, and will not have monitor. So, serial is the default console. I pass cmdline as "root=/dev/ram rw console=ttyS0,115200" Thanks Siva -----Original Message----- From: Scott Russell [mailto:catfather@donpoo.net] Sent: Wednesday, December 19, 2007 3:31 PM To: Siva Prasad Cc: Clemens Koller; David Newall; linux-kernel@vger.kernel.org Subject: RE: printf internals On Wed, 2007-12-19 at 14:33 -0800, Siva Prasad wrote: > Thank you very much for your response Clemens. > > I tried strace on a regular system. It does not show which tty, etc., as it uses the stdout (fd = 1) and write(1, ...) to it. > > This is not a student project. I am trying to build my own kernel and ramdisk. Kernel boots fine to a point where it starts accessing ramdisk and executes init scripts. From there on nothing gets printed. I did some debugging and found that prints of user land programs are not coming to the serial console, while kernel prints are working fine. I found all the programs getting executed, by placing a printk in execve routine and printing the arguments. > > So, I wanted to trace down the path from user program to the kernel and see why it is not printing messages from user program. I placed a printk in drivers/char/tty_io.c:tty_write() and it is not getting called from my file system. I tried the same thing on my good system (say regular PC) and it works as expected. > > Any clues that can help debug this issue is highly appreciated. > How can I get access to the same printf string inside kernel. This sounds like you're printing out the serial console instead. -- Scott AIM: BlueCame1 -- 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/