Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()

[H. Peter Anvin]

On 10/11/23 15:37, Ingo Molnar wrote:
> * Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > > The only drawback is a larger binary size:
> > >
> > >    text    data     bss     dec     hex filename
> > > 25546594        4387686  808452 30742732        1d518cc vmlinux-new.o
> > > 25515256        4387814  808452 30711522        1d49ee2 vmlinux-old.o
> > >
> > > that increases by 31k (0.123%), probably due to 1578 rdgsbase alternatives.
> >
> > I'm actually surprised that it increases the text size. The 'rdgsbase'
> > instruction should be smaller than a 'mov %gs', so I would have
> > expected the *data* size to increase due to the alternatives tables,
> > but not the text size.
> >
> > [ Looks around ]
> >
> > Oh. It's because we put the altinstructions into the text section.
> > That's kind of silly, but whatever.
>
> Yeah, we should probably move .altinstructions from init-text to .init.data
> or so? Contains a bunch of other sections too that don't get executed
> directly ... and in fact has some non-code data structures too, such as ...
> ".apicdrivers". :-/
>
> I suspect people put all that into .text because it was the easiest place
> to modify in the x86 linker script, and linker scripts are arguably scary.

Well, it's more than that; "size" considers all non-writable sections to 
be "text".

	-hpa