[Bug runtime/30777] Systemtap modules unable to run on systemtap supporting Intel CET IBT

[wcohen at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30777

--- Comment #2 from William Cohen <wcohen at redhat dot com> ---
Created attachment 15077
  --> https://sourceware.org/bugzilla/attachment.cgi?id=15077&action=edit
A sample module demonstrating a workaround approach

The flippy_ibt is a really basic module that has surrounds the indirect call
with a ibt_save and ibt_restore operation.  To test out on a machine that
support IBT:

tar xvf flippy_ibt.tar.gz
cd flippy_ibt
make -C /usr/src/kernels/$(uname -r) M=$PWD V=2 
sudo insmod flippy_ibt.ko
sudo rmmod flippy_ibt

You should see success (no trap for the missing ENDBR) in output of:

dmesg 

One can check that the kernel IBT support is actually active with the same
module by installing with:

sudo insmod flippy_ibt.ko ibt_disable=0

You will see a message on the terminal about a segmentation fault and there
will be a trap  for the missing ENDBR in the output of dmesg.

That

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