Minus 0x50 offset in Ubuntu Trusty kernel symbols

[Mathieu Tarral]

Hi !

I'm facing an issue while trying to debug the kernel of
Ubuntu Trusty server (14.04.0)

I installed the distro using old-releases iso, i386 platform,
and used http://ddebs.ubuntu.com to download the kernel symbols.

I copied /usr/lib/debug/boot/vmlinux-3.13.0-24-generic on the host (sha1sum 4d27116f162bcac7f839eabfb18849ae66d4ea32), and loading the symbols in GDB, only to notice that there was a mismatch with what /proc/kallsyms was saying versus what GDB was printing.

Now, I used the same procedure with Ubuntu Xenial server (16.04.0),
and everything worked as expected, the symbols were aligned
with /proc/kallsyms.

Do you have any idea what could be the cause of this -0x50 offset in Trusty?

Here are some pictures from Twitter, if that helps:
https://twitter.com/mtarral/status/1089547885442711553

Apart from KASLR (which is not present in Ubuntu Trusty, and not activated on Xenial), I don't know what else to look into.

If you have an idea, please share.


Best regards,
Mathieu Tarral