Messages in this thread | | | Date | Fri, 14 Mar 2008 12:08:16 -0400 | From | Yan <> | Subject | Re: 2.6.22.6 - Discrepancy between running and on-disk kernels |
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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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