On Wednesday 30 March 2005 06:09 pm, linux-os wrote: > On Wed, 30 Mar 2005, Vicente Feito wrote: > > Video memory is at b800:0000, for humans 0x0000b800, not at 0x000b8000 > > Wrong. "real-mode" can use a segment address of b800, that doesn't > work in protected mode. A segment address of b800:0000 is never > under any conditions 0000b800. I was referring to the basic conditions, haven't played under protected mode with that, only in real mode, I assumed the question was under that mode. What you mean is this: B800:0010 -> B8010H right?
> > FYI, a real-mode segment is a 16-byte entity, therefore there are > many segment:offset combinations that can get you to 0x000b8000. I'm aware of that, it has nothing to do with my statement. > > > 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 [EMAIL PROTECTED] > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >> Please read the FAQ at http://www.tux.org/lkml/ > > 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
