lkml.org 
[lkml]   [2005]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: How to debug kernel before there is no printk mechanism?
Date
Video memory is at b800:0000, for humans 0x0000b800, not at 0x000b8000


On Wednesday 30 March 2005 04:47 pm, linux-os wrote:
> On Wed, 30 Mar 2005, krishna wrote:
> > Hi all,
> >
> > How can one debug kernel before there is no printk mechanism in kernel.
> >
> > Regards,
> > Krishna Chaitanya
>
> Write directly to screen memory at 0x000b8000, or write to the
> RS-232C UART while polling the TX buf empty bit, or just write
> bits that mean something to you out the printer port.
>
> Screen - memory is 16-bit words with the high-word being
> an attibute byte. FYI 0x07 is a good B&W byte. You can
> initialize a pointer to it as:
>
> unsigned short *screen = 0xc00b8000; Since low memory
> is always mapped, the above cheat will work. The 0xc0000000
> is PAGE_OFFSET.
>
> An early '486 was brought up into a 32-bit protected-mode
> (non linux) operating system using these debugging methods.
> The first time I got to see some symbol written to the
> screen in protected-mode marked the start of a week-end-
> long party. Have fun!
>
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
> Notice : All mail here is now cached for review by Dictator Bush.
> 98.36% of all statistics are fiction.
> -
> 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/
-
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/

\
 
 \ /
  Last update: 2005-04-06 13:31    [W:0.035 / U:0.348 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site