On 10/26/2010 03:08 PM, Mirko Parthey wrote: > Hello all, > > while reading through grub-core/boot/i386/pc/boot.S in the Bazaar version > of Grub 2, I noticed that the floppy probing code calls > int $0x13, %ah===$0x02 /* disk read sector */ > without initializing the %es register, and with %bx holding a value > that was likely meant to go into %es. (boot.S:465) > > You're right patch applied > My proposed change is included below. The two additional instructions have > been > copied from further above in boot.S, where the same BIOS function is > used correctly. The resulting machine code is enlarged by 4 bytes, but > apparently still fits within the 512-byte limit. > > Please note that I found this by inspection, not by observing undesired > behaviour. The patch passes "make" and "make check", but I'm not sure if the > code will actually be exercised by "make check". > I hope you find it useful. > > Mirko > > === modified file 'grub-core/boot/i386/pc/boot.S' > --- grub-core/boot/i386/pc/boot.S 2010-09-19 22:06:45 +0000 > +++ grub-core/boot/i386/pc/boot.S 2010-10-26 09:51:29 +0000 > @@ -459,6 +459,8 @@ > 1: > /* perform read */ > movw $GRUB_BOOT_MACHINE_BUFFER_SEG, %bx > + movw %bx, %es > + xorw %bx, %bx > movw $0x201, %ax > movb $0, %ch > movb $0, %dh > > > _______________________________________________ > Bug-grub mailing list > Bug-grub@gnu.org > http://lists.gnu.org/mailman/listinfo/bug-grub > >
-- Regards Vladimir 'φ-coder/phcoder' Serbinenko
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