[RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool
Sami Tolvanen
samitolvanen at google.com
Wed Jul 22 16:03:12 EDT 2020
On Wed, Jul 22, 2020 at 12:09 PM Steven Rostedt <rostedt at goodmis.org> wrote:
>
> On Wed, 22 Jul 2020 20:41:37 +0200
> Peter Zijlstra <peterz at infradead.org> wrote:
>
> > > That said, Andi Kleen added an option to gcc called -mnop-mcount which
> > > will have gcc do both create the mcount section and convert the calls
> > > into nops. When doing so, it defines CC_USING_NOP_MCOUNT which will
> > > tell ftrace to expect the calls to already be converted.
> >
> > That seems like the much easier solution, then we can forget about
> > recordmcount / objtool entirely for this.
>
> Of course that was only for some gcc compilers, and I'm not sure if
> clang can do this.
>
> Or do you just see all compilers doing this in the future, and not
> worrying about record-mcount at all, and bothering with objtool?
Clang appears to only support -mrecord-mcount and -mnop-mcount for
s390, so we still need recordmcount / objtool for x86.
Sami
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