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Re: How to debug 'out of disk' error.


From: Lennart Sorensen
Subject: Re: How to debug 'out of disk' error.
Date: Thu, 17 Mar 2011 14:40:14 -0400
User-agent: Mutt/1.5.18 (2008-05-17)

On Thu, Mar 17, 2011 at 05:29:51PM +0100, Vladimir 'φ-coder/phcoder' Serbinenko 
wrote:
> On 17.03.2011 17:09, Lennart Sorensen wrote:
> > On Wed, Mar 16, 2011 at 11:16:05PM +0100, Vladimir 'φ-coder/phcoder' 
> > Serbinenko wrote:
> >   
> >> It's not really a fixup. Correct return on no error is CF=0 AH=0. Some
> >> BIOSes in some other functions returned CF=0, AH!= 0 on no error so it
> >> was a wild guess.
> >>     
> >>> Failed int13_ext call: ah=42, drive=80, dap=   6fe00 returned eax=8000
> >>>   
> >>>       
> >> Error 0x80 according to
> >> http://www.delorie.com/djgpp/doc/rbinter/it/34/2.html means timeout.
> >> Following code would retry on timeout:
> >> === modified file 'grub-core/disk/i386/pc/biosdisk.c'
> >> --- grub-core/disk/i386/pc/biosdisk.c    2011-01-04 14:42:47 +0000
> >> +++ grub-core/disk/i386/pc/biosdisk.c    2011-03-16 22:13:12 +0000
> >> @@ -72,6 +72,8 @@
> >>  grub_biosdisk_rw_int13_extensions (int ah, int drive, void *dap)
> >>  {
> >>    struct grub_bios_int_registers regs;
> >> +  int tries = 4;
> >> + retry:
> >>    regs.eax = ah << 8;
> >>    /* compute the address of disk_address_packet */
> >>    regs.ds = (((grub_addr_t) dap) & 0xffff0000) >> 4;
> >> @@ -80,6 +82,16 @@
> >>    regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
> >>  
> >>    grub_bios_interrupt (0x13, &regs);
> >> +  if (!(regs.flags & GRUB_CPU_INT_FLAGS_CARRY))
> >> +    return 0;
> >> +
> >> +  if (((regs.eax >> 8) & 0xff) == 0x80 && tries)
> >> +    {
> >> +      grub_millisleep (10);
> >> +      tries--;
> >> +      goto retry;
> >> +    }
> >> +
> >>    return (regs.eax >> 8) & 0xff;
> >>  }
> >>     
> > So that didn't make any difference to it.
> >
> > It just keeps returning 0x8000 in eax on every retry.
> >
> >   
> Another wild guess:
> @@ -506,6 +520,8 @@ get_safe_sectors (grub_disk_addr_t secto
>    grub_size_t size;
>    grub_uint32_t offset;
>  
> +  return 1;
> +
>    /* OFFSET = SECTOR % SECTORS */
>    grub_divmod64 (sector, sectors, &offset);

No go either.

Here is what I see with some more debugging:

[snip]
int13_ext call: ah=42, drive=80, dap=   6fe00 (len=16 rsvd=0 blks=1 
buf=1744830464 sec=2078)
int13_ext call: ah=42, drive=80, dap=   6fe00 (len=16 rsvd=0 blks=1 
buf=1744830464 sec=2079)
int13_ext call: ah=42, drive=80, dap=   6fe00 (len=16 rsvd=0 blks=1 
buf=1744830464 sec=72091664)
failed int13_ext call: ah=42, drive=80, dap=   6fe00 returned eax=8000
error: hd0 out of disk.
Entering rescue mode...
grub rescue>

Now it has no excuse for failing a call for sector 72091664 when the
drive has 156000000 or so sectors.

I imagine if I made a small boot partition (less than 8G), the stupid
thing would boot fine, but that's not acceptable on a brand new design.
I am going to try resizing the partition as a test.

-- 
Len Sorensen



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