Re: [PATCH v2 1/2] xen: move CONFIG_DEBUG_INFO out of EXPERT section

[Juergen Gross <jgross@xxxxxxxx>]

On 05.04.23 15:14, Jan Beulich wrote:
> On 03.04.2023 18:28, Juergen Gross wrote:
> > In order to support hypervisor analysis of crash dumps, xen-syms needs
> > to contain debug_info. It should be allowed to configure the hypervisor
> > to be built with CONFIG_DEBUG_INFO in non-debug builds without having
> > to enable EXPERT.
> >
> > Using a rather oldish gcc (7.5) it was verified that code generation
> > doesn't really differ between CONFIG_DEBUG_INFO on or off without
> > CONFIG_DEBUG being set (only observed differences were slightly
> > different symbol addresses, verified via "objdump -d", resulting from
> > the different config.gz in the binary). The old gcc version selection
> > was based on the assumption, that newer gcc won't regress in this
> > regard.
> >
> > So move CONFIG_DEBUG_INFO out of the section guarded by EXPERT.
> >
> > It should be mentioned that there have been reports that the linking
> > of the xen.efi might take considerably longer with CONFIG_DEBUG_INFO
> > selected when using newer binutils.
> Thinking of it: Because of the need to deal with older binutils, we
> already force --strip-debug as a linking option for xen.efi in
> certain cases. Perhaps we could make another (x86-only) Kconfig
> control which allows to force this mode even with recent binutils?
> If so, would you be willing to include this right here, or should I
> take care of this afterwards (or maybe even in parallel)?
I'm planning to do the EFI side in the next days, hoping that I can setup
the test system.

I'd include that additional config option in the probably needed patch(es)
then (crash isn't happy with xen.efi anyway, so I'll need some kind of
xen-syms.efi or whatever you want to call it).

> > --- a/xen/Kconfig.debug
> > +++ b/xen/Kconfig.debug
> > @@ -11,6 +11,13 @@ config DEBUG
> >   
> >   	  You probably want to say 'N' here.
> >   
> > +config DEBUG_INFO
> > +       bool "Compile Xen with debug info"
> > +       default DEBUG
> > +       help
> > +         If you say Y here the resulting Xen will include debugging info
> > +         resulting in a larger binary image.
> > +
> >   if DEBUG || EXPERT
> Just to repeat my v1 comment (to which your response was "Fine with me"):
>
> The new placement isn't very helpful when considering some of the ways
> kconfig data is presented. At least for the non-graphical presentation
> it used to be the case that hierarchies were presented properly only
> when dependencies immediately followed their dependents (i.e. here:
> DEBUG is a dependent of everything inside the "if" above). Therefore I
> think rather than moving the block up you may better move it down past
> the "endif".
Oh, I seem to have missed that last paragraph when going through the thread.

Will correct it.


Juergen

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