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SubjectRe: 2.6.22.6 - Discrepancy between running and on-disk kernels
Can you point me to where in the source that self-patching happens? I
tried grep'ing
through the source for anything relevant, and came out empty handed.

-yan

On Fri, Mar 14, 2008 at 12:00 PM, Arjan van de Ven <arjan@infradead.org> wrote:
> On Fri, 14 Mar 2008 10:51:43 -0400
> Yan <rottled@gmail.com> wrote:
>
> > Hello,
> >
> > I have been trying to compare the code from the on-disk compressed
> > kernel that was booted and the running kernel extracted
> > from /dev/kmem. I extracted the kernel's code from the disk image by
> > stripping the head.S and similar and gunzipping it, and extracted the
> > kernel from /dev/kmem by reading data between _text and _etext symbol
> > offsets.
> >
> > I then ran both through a disassembler and diff'ed the outputs.
> > Predictably, the disassembly was similar, but not identical. Some
> > instructions (e.g. bts) had a 'lock' prefix, where as others had a
> > 'nop' in its place.
> >
> > There were other differences with some instructions like mfence.
> > Everything else matched just fine, the differences were mostly in
> > memory-referencing instructions.
> >
> > My question is, what can be changing the kernel between being on
> > static storage and being loaded?
>
> the kernel code is self-patching, it gets modified to match your system
> during boot time. So you cannot assume that the kernel on disk and the kernel
> in memory are identical.
> (Same goes for modules)
>


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