On Wed, May 8, 2019 at 4:53 AM wuzhouhui <wuzhouhui14@xxxxxxxxxxxxxxxx> wrote:
> Hi,
> Suppose I have two kernels, one is A.B.C build by people Tom. And
> the other is A.B.C build by Jerry. The source code have been deleted
> after kernel is build and installed. Now I want to know whether the
> source code of these two kernel is the same (even if they have the same
> name). All I have is binaries (e.g. vmlinux, config, *.ko, System.map).
> Is it possible?
Within sane defaults yes it is possible. Think of it this way, if the source code is the 'same' we can safely assume that the kernel built by Tom will function and behave
'exactly' the same as the kernel built by Jerry. Behavior can be traced and analyzed.
diff, dmesg, lsmod, tree and objdump are your friends :-)
Run diff vmlinuz-Tom vmlinuz-Jerry and see if they differ. Then just to make
sure follow below steps:
1 - Boot kernel-Tom and redirect dmesg output to file(s)
2 - dmesg -k > kernel-Tom.txt
3 - dmesg -u > userspace-Tom.txt
4 - lsmod > modules-Tom.txt
5 - tree / > fs-Tom.txt
Now we have what the kernel prints while booting in kernel-Tom.txt and what userspace prints
in userspace-Tom.txt and loaded modules in modules-Tom.txt and the folder structure under root
in fs-Tom.txt.
Now repeat the same process with kernel-Jerry
1 - Boot kernel-Jerry
2 - dmesg -k > kernel-Jerry.txt
3 - dmesg -u > userspace-Jerry.txt
4 - lsmod > modules-Jerry.txt
5 - tree / > fs-Jerry.txt
Then run diff on those files..
1 - diff kernel-Tom.txt kernel-Jerry.txt
2 - diff userspace-Tom userspace-Jerry
3 - diff modules-Tom modules-Jerry
4 - diff fs-Tom fs-Jerry
if you want to dig deeper use objdump -d vmlinuz-Tom then objdump -d vmlinuz-Jerry
which is really overkill unless there is output from diff that says the file(s) differ.
If you really really need the source there are decompilers :
Keep in mind what Valdis pointed out that though the source may be exactly the same,
depending on what compiler flags were used the binaries may differ.
You had asked..
> Is it possible?
Simple answer: In the Linux world the impossible becomes very possible :)
Good luck - Aruna
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