On Thu, 26 Dec 2024 19:35:18 -0800
Linus Torvalds [off-list ref] wrote:

On Thu, 26 Dec 2024 at 13:49, Steven Rostedt [off-list ref] wrote:

quoted

But then, when the linker removes these functions because they were
overridden, the code does not disappear, leaving the pointers in the
__mcount_loc locations.  

Btw, does this actually happen when the compiler does the mcount thing for us?

Yes.

I believe the issue is that the mcount_loc is created during the
compile phase, and it just points to the call to fentry/mcount. The
linker phase doesn't remove the code, just the symbols that are
overridden. That means the pointer to the fentry/mcount calls still
point to the same locations, as the code is still there.

I even sent an email about this to the gcc folks, and Peter responded
basically explaining the above.

  https://lore.kernel.org/all/20241014210841.5a4764de@gandalf.local.home/ (local)

-- Steve