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

[Lennart Sorensen]

On Thu, Mar 17, 2011 at 10:06:06AM -0400, Lennart Sorensen wrote:
> On Wed, Mar 16, 2011 at 11:16:05PM +0100, Vladimir 'φ-coder/phcoder' 
> Serbinenko wrote:
> > On 16.03.2011 23:00, Lennart Sorensen wrote:
> > > On Wed, Mar 16, 2011 at 09:19:12PM +0100, Vladimir 'φ-coder/phcoder' 
> > > Serbinenko wrote:
> > >   
> > >> Following may help:
> > >> === 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 20:17:57 +0000
> > >> @@ -80,6 +80,9 @@
> > >>    regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
> > >>  
> > >>    grub_bios_interrupt (0x13, &regs);
> > >> +  if (!(regs.flags & GRUB_CPU_INT_FLAGS_CARRY))
> > >> +    return 0;
> > >> +
> > >>    return (regs.eax >> 8) & 0xff;
> > >>  }
> > >>     
> > > I now got this:
> > >
> > > GRUB loading.
> > > Welcome to GRUB!
> > >
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > > int13_ext fixup due to CARRY flag
> > >   
> > 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;
> >  }
> >  
> > 
> > > error: hd0 out of disk.
> > > Entering rescue mode...
> > > grub rescue>
> > >
> > > I am now using 1.99-rc1.  Here is the biosdisk.c with my changes.
> > >
> > >   
> > >
> > >
> > > _______________________________________________
> > > Grub-devel mailing list
> > > address@hidden
> > > http://lists.gnu.org/mailman/listinfo/grub-devel
> > >   
> 
> I am trying that now.
> 
> By the way I think I spotted a bug:
> 
>       else
>         if (grub_biosdisk_rw_int13_extensions (cmd + 0x42, data->drive, dap))
>           {
>             /* Fall back to the CHS mode.  */
>             data->flags &= ~GRUB_BIOSDISK_FLAG_LBA;
>             disk->total_sectors = data->cylinders * data->heads * 
> data->sectors;
>             return grub_biosdisk_rw (cmd, disk, sector, size, segment);
>           }
> 
> I think that + 0x42 is wrong.  The extended commands are 0x40 above the
> normal ones.  + 0x40 makes more sense to me.
> 
> 0x42 = extended read.
> 0x02 = normal read.
> 
> 0x48 = extended parameter read.
> 0x08 = normal parameter read.

Never mind.  cmd = 0 for read, not 0x2.  Oh well.  I found it adds 0x02
in _standard, so it works the same.

Still testing the other stuff.

-- 
Len Sorensen