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


  • To: Juergen Gross <jgross@xxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 5 Apr 2023 15:14:43 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • Delivery-date: Wed, 05 Apr 2023 13:15:07 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

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)?

> --- 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".

Jan



 


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