Re: [RFC PATCH kernel] trace: Make FTRACE_MCOUNT_USE_RECORDMCOUNT configurable

[Sami Tolvanen]

On Fri, Feb 11, 2022 at 4:11 PM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> + Sami, Kees
>
> Do you guys remember why we don't support
> FTRACE_MCOUNT_USE_RECORDMCOUNT with LTO?

It's because recordmcount cannot distinguish between calls and other
references to mcount/fentry, which is a problem with LTO where we have
to process the entire vmlinux.o and cannot ignore individual
translation units. Instead of resorting to workarounds, Peter was kind
enough to implement a smarter mcount pass in objtool, which we now use
on x86_64 with LTO.

Alexey, which architecture are you trying to fix here?

Sami