Re: [Buildroot] [RFC PATCH v1 2/2] linux: Add host-pahole as linux dependencies if selected by user.

[Francis Laniel <flaniel@linux.microsoft.com>]

Le mardi 21 décembre 2021, 22:58:29 CET Arnout Vandecappelle a écrit :
> On 21/12/2021 15:54, Francis Laniel wrote:
> > If user set BR2_PACKAGE_HOST_PAHOLE, we add host-pahole to linux
> > dependencies in case the user also wants to compile the kernel with
> > CONFIG_DEBUG_BTF_INFO which relies on pahole to generate BTF information
> > used by CO-RE BPF tools.
> > 
> > Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
> > ---
> > 
> >   linux/linux.mk                | 6 ++++++
> >   package/pahole/Config.in.host | 2 ++
> >   2 files changed, 8 insertions(+)
> > 
> > diff --git a/linux/linux.mk b/linux/linux.mk
> > index 61fdc0c76c..057d898c86 100644
> > --- a/linux/linux.mk
> > +++ b/linux/linux.mk
> > @@ -120,6 +120,12 @@ ifeq ($(BR2_PACKAGE_HOST_UBOOT_TOOLS),y)
> > 
> >   LINUX_DEPENDENCIES += host-uboot-tools
> >   endif
> > 
> > +# If host-pahole is selected by the user, assume it is needed to create a
> > custom +# kernel with CONFIG_DEBUG_INFO_BTF.
> > +ifeq ($(BR2_PACKAGE_HOST_PAHOLE),y)
> > +LINUX_DEPENDENCIES += host-pahole
> 
>   This is not a super user-friendly way to do it, but it's hard to do
> better.
> 
>   One way would be to make an explicit Config.in option for it (similar to
> openssl). Or an option that also sets CONFIG_DEBUG_INFO_BTF. But I think
> that adds too much complexity to Buildroot for relatively little gain.
> 
>   Perhaps a better improvement would be to add a check if the config option
> is set and print a warning if not.
> 
> else
> define LINUX_FIXUP_CONFIG_PAHOLE_CHECK
> 	if grep -q "^CONFIG_DEBUG_INFO_BTF=y" $(KCONFIG_DOT_CONFIG); then \
> 		echo "To use CONFIG_DEBUG_INFO_BTF, enable host-pahole
> (BR2_PACKAGE_HOST_PAHOLE)" 1>&2; \
> 		return 1; \
> 	fi
> endef
> 
> (and add LINUX_FIXUP_CONFIG_PAHOLE_CHECK to the end of
> LINUX_KCONFIG_FIXUP_CMDS).
> 
>   It's still pretty clunky though, so maybe not that much of an
> improvement...
> 
>   Anyway, I'd merge this patch without that change (but no time today).

When I first wrote this patch, I was looking for a solution to add dependencies 
conditionally to Linux kernel CONFIG_ but I did not find it.
Your solution is cool, so I added as well as an option (like one used for 
OpenSSL and libelf).
I will send v2 within 10 minutes.

>   Regards,
>   Arnout
> 
> > +endif
> > +
> > 
> >   ifneq ($(ARCH_XTENSA_OVERLAY_FILE),)
> >   define LINUX_XTENSA_OVERLAY_EXTRACT
> >   
> >   	$(call arch-xtensa-overlay-extract,$(@D),linux)
> > 
> > diff --git a/package/pahole/Config.in.host b/package/pahole/Config.in.host
> > index e427629632..521874961b 100644
> > --- a/package/pahole/Config.in.host
> > +++ b/package/pahole/Config.in.host
> > @@ -3,4 +3,6 @@ config BR2_PACKAGE_HOST_PAHOLE
> > 
> >   	help
> >   	
> >   	  Pahole and other DWARF utils.
> > 
> > +	  Select this if you want to build a kernel with CONFIG_DEBUG_INFO_BTF
> > set. +
> > 
> >   	  https://git.kernel.org/pub/scm/devel/pahole/pahole.git
> 
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