Re: [PATCH] x86/boot: Fix build with LLVM toolchain

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

On Wed, Nov 6, 2024 at 11:45 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 06.11.2024 12:34, Frediano Ziglio wrote:
> > On Wed, Nov 6, 2024 at 10:59 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >>
> >> On 06.11.2024 07:56, Frediano Ziglio wrote:
> >>> On Tue, Nov 5, 2024 at 5:06 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >>>>
> >>>> On 05.11.2024 17:35, Frediano Ziglio wrote:
> >>>>> On Tue, Nov 5, 2024 at 3:32 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
> >>>>>>
> >>>>>> On 05.11.2024 15:55, Frediano Ziglio wrote:
> >>>>>>> This toolchain generates different object and map files.
> >>>>>>> Account for these changes.
> >>>>>>
> >>>>>> At least briefly mentioning what exactly the differences are would be
> >>>>>> quite nice, imo.
> >>>>>>
> >>>>>
> >>>>> What about.
> >>>>>
> >>>>> Object have 3 additional sections which must be handled by the linker 
> >>>>> script.
> >>>>
> >>>> I expect these sections are there in both cases. The difference, I 
> >>>> assume,
> >>>> is that for the GNU linker they don't need mentioning in the linker 
> >>>> script.
> >>>> Maybe that's what you mean to say, but to me at least the sentence can 
> >>>> also
> >>>> be interpreted differently.
> >>>
> >>> Why do you expect such sections? They are used for dynamic symbols in
> >>> shared objects, we don't use shared objects here. Normal object
> >>> symbols are not handled by these sections. GNU compiler+linker (we
> >>> link multiple objects together) do not generate these sections. So the
> >>> comment looks correct to me.
> >>
> >> About every ELF object will have .symtab and .strtab, and many also a
> >> separate .shstrtab. There's nothing "dynamic" about them. IOW - I'm
> >> confused by your reply.
> >
> > I checked the object files and there are no such sections using GNU 
> > toolchain.
>
> I think I checked every *.o that's under boot/, and they all have these three
> sections. Can you clarify which one(s) specifically you checked?
>
> Jan

$ gcc --version
gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ ld --version
GNU ld (GNU Binutils for Ubuntu) 2.38
Copyright (C) 2022 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public Licence version 3 or (at your option) a later version.
This program has absolutely no warranty.

$ find xen/normal/ xen/pvh/ -name \*.o | xargs -ifilename sh -c
'objdump -x filename' | grep -e \\.
shstrtab -e \\.strtab -e \\.symtab

(xen/normal and xen/pvh are the build directory, with different configurations)

I'm saying that's possibly why the linker scripts didn't need to
specify these sections.

Frediano