Messages in this thread | | | Date | Tue, 15 Jul 2003 11:17:46 +0200 | From | Koala GNU <> | Subject | Re: Linux boot code |
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Hi, Riley,
thanks for your reply.
I noticed the native boot code for floppy is not supported any more. In fact in the current code display a message and reboot the machine after the press of a key.
But I am interested on how the old native boot code worked.
Do you know if there is a particular reason why the boot sector is moved to 0x9000:0 (excuse me if I repeat the question, but I need help on this)?
I hope someone else can point me a site where is reported the format of the floppy parameter table at address 0x0:0x78.
Thanks in advance and excuse me for this other post.
Riley Williams wrote:
>Hi. > > > I am looking at the boot code in bootsect.S and I have some doubt. > > I tried to search the answers to my questions on > > marc.theaimsgroup.com and on Google but I haven't found them. > >I know nothing about the former site, so can't comment thereon. > > > Probably these are newbie question but I'll appreciate if someone > > of you help me. > >I'll do what I can. > > > 1) In the bootsect code the first thing that is done is to copy > > the boot sector to 0x90000 and move the program count to > > 0x9000, go. Why it is necessary move the code there? Is it not > > possible continue the process from 0x7C00? > >Following moving the boot code there, the next step is to load the >kernel image, either from 0x10000 (64k) or from 1M upwards, this >being dependent on various factors. However, the boot sector holds >several flags whose values are important AFTER the kernel image has >been loaded, so is moved out the way first. > > > 2) Another step is to move the parameters table from 0x78:0 to > > 0x9000:0x4000-12. What are the info contained in this table? > > Can you send me a link to a site that specify these info? > > Without these info I am not able to understand these three > > line of code > > > > movb $36, 0x4(%di) # patch sector count > > movw %di, %fs:(%bx) > > movw %es, %fs:2(%bx) > >That area of memory contains parameters configured by the BIOS of >the machine in question. I would suspect it's the parameters for >the floppy drives, and the code that follows is presumably that >used to determine how many sectors per track the floppy in /dev/fd0 >actually has. > > > Thanks in advance for your help > >No problem. > >Best wishes from Riley. >--- > * Nothing as pretty as a smile, nothing as ugly as a frown. > >--- >Outgoing mail is certified Virus Free. >Checked by AVG anti-virus system (http://www.grisoft.com). >Version: 6.0.500 / Virus Database: 298 - Release Date: 10-Jul-2003 > >- >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/ > > >
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