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. Thanks Siva -----Original Message----- From: Clemens Koller [mailto:[EMAIL PROTECTED] Sent: Friday, December 14, 2007 8:16 AM To: David Newall Cc: Siva Prasad; linux-kernel@vger.kernel.org Subject: Re: printf internals David Newall schrieb: > Siva Prasad wrote: >> I am looking at how exactly does the printf in user programs succeeds in >> displaying characters to the serial console. > > Is it a student assignment? This is so not the right mailing list. Come on, are we playing hide and seek here? You can use strace to follow a typical hello world example and see what device it opens to feed the hello out. I.e. it can be to the current /dev/ttyX and not to /dev/console or if you are logged in via SSH to a machine, the device is again different... or if you use screen, ... Work your way from there and then use a Linux Source code Cross Reference (lxr, ask Google for one) and follow the code. Regards, -- Clemens Koller __________________________________ R&D Imaging Devices Anagramm GmbH Rupert-Mayer-Straße 45/1 Linhof Werksgelände D-81379 München Tel.089-741518-50 Fax 089-741518-19 http://www.anagramm-technology.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
