linux setup

[Nicolas Pitre]

On Tue, 23 Jul 2013, Catalin Marinas wrote:

> On Mon, Jul 22, 2013 at 02:28:50PM +0100, zhaobin xv wrote:
> > I recently read lernel source .
> > I have a question:In
> > folder:linux/arch/arm/boot/compressed/head.S(linux2.6.22.6):
> > 
> > 
> > start:
> >         .type    start,#function
> >         .rept    8
> >         mov    r0, r0
> >         .endr
> > 
> >         b    1f
> >         .word    0x016f2818        @ Magic numbers to help the loader
> >         .word    start            @ absolute load/run zImage address
> >         .word    _edata            @ zImage end address
> > 1:        mov    r7, r1            @ save architecture ID
> >         mov    r8, r2            @ save atags pointer
> > 
> > 
> > I don't kown why the “mov r0 r0 ” repeated  emergence 8 times.
> 
> I think some people used that in the past to be able to modify the
> zImage binary directly and work around wrong register values passed by
> the boot loader. I've never used it myself but I saw it mentioned once.

The whole reason for this is because in a distant past the kernel image 
was an a.out binary containing a 32-bytes header.  Those nops are simply 
padding so to be compatible with those bootloaders expecting the kernel 
code to start at an offset of 32.


Nicolas