Re: [RFC PATCH v9 01/27] Documentation/x86: Add CET description

Dave Hansen
2020-03-09T23:21:01Z

On 3/9/20 4:11 PM, H.J. Lu wrote:
> A threaded application is loaded from disk. The object file on disk is
> either CET enabled or not CET enabled.

Huh. Are you saying that all instructions executed on userspace on
Linux come off of object files on the disk? That's an interesting
assertion. You might want to go take a look at the processes on your
systems. Here's my browser for example:

# for p in $(ps aux | grep chromium | awk '{print $2}' ); do cat
/proc/$p/maps; done | grep ' r-xp 00000000 00:00 0'
...
202f00082000-202f000bf000 r-xp 00000000 00:00 0
202f000c2000-202f000c3000 r-xp 00000000 00:00 0
202f00102000-202f00103000 r-xp 00000000 00:00 0
202f00142000-202f00143000 r-xp 00000000 00:00 0
202f00182000-202f001bf000 r-xp 00000000 00:00 0

Lots of funny looking memory areas which are anonymous and executable!
Those didn't come off the disk. Same thing in firefox. Weird. Any
idea what those are?

One guess: https://en.wikipedia.org/wiki/Just-in-time_compilation