Re: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage

Peter Zijlstra
2021-11-10T11:10:11Z

On Wed, Nov 10, 2021 at 10:46:42AM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 09 November 2021 21:08
> ...
> >
> > GCC does the same, but I wanted to have the exception stuff be in
> > .text.cold, but alas it doesn't do that. I left the attribute because of
> > it's descriptive value.
> >
> > > Unless the cold attribute is helping move
> > > ("shrink-wrap"?) the basic block to a whole other section
> > > (.text.cold.)?
> >
> > I was hoping it would do that, but it doesn't on gcc-11.
>
> Wouldn't moving part of a function to .text.cold (or .text.unlikely)
> generate the same problems with the stack backtrace code as the
> .text.fixup section you are removing had??

GCC can already split a function into func and func.cold today (or
worse: func, func.isra.N, func.cold, func.isra.N.cold etc..).

I'm assuming reliable unwind and livepatch know how to deal with this.