Re: [PATCH dwarves v2 4/4] btf_encoder: add global_var feature to encode globals

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Oct 02, 2024 at 04:11:23PM +0100, Alan Maguire wrote:

SNIP

> >> diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
> >> index 0a9d8ac..4bc2d03 100644
> >> --- a/man-pages/pahole.1
> >> +++ b/man-pages/pahole.1
> >> @@ -230,7 +230,10 @@ the debugging information.
> >>  
> >>  .TP
> >>  .B \-\-skip_encoding_btf_vars
> >> -Do not encode VARs in BTF.
> >> +.TQ
> >> +.B \-\-encode_btf_global_vars
> >> +By default, VARs are encoded only for percpu variables. These options allow
> >> +to skip encoding them, or alternatively to encode all global variables too.
> >>  
> >>  .TP
> >>  .B \-\-skip_encoding_btf_decl_tag
> >> @@ -296,7 +299,8 @@ Encode BTF using the specified feature list, or specify 'default' for all standa
> >>  	encode_force       Ignore invalid symbols when encoding BTF; for example
> >>  	                   if a symbol has an invalid name, it will be ignored
> >>  	                   and BTF encoding will continue.
> >> -	var                Encode variables using BTF_KIND_VAR in BTF.
> >> +	var                Encode percpu variables using BTF_KIND_VAR in BTF.
> >> +	global_var         Encode all global variables in the same way.
> > 
> > hi,
> > I tried to test this but I'm not getting DATASEC sections in the BTF,
> > is the change below enough to enable this in kernel build?
> >
> 
> Yep, that looks right to me and it's what I did to test with kernel
> builds. For me that was enough to get datasecs and all global variables,
> but if it doesn't work at your end we can take a look. Thanks!

I managed to get all that by running pahole directly,
will check it closely with the new version of that patchset

thanks,
jirka

> 
> Stephen, maybe for the respun patches we could add a note to the cover
> letter on how to test with kernel builds? Thanks!
> 
> Alan
> 
> > thanks,
> > jirka
> > 
> > 
> > ---
> > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
> > index b75f09f3f424..c88d9e526426 100644
> > --- a/scripts/Makefile.btf
> > +++ b/scripts/Makefile.btf
> > @@ -19,7 +19,7 @@ pahole-flags-$(call test-ge, $(pahole-ver), 125)	+= --skip_encoding_btf_inconsis
> >  else
> >  
> >  # Switch to using --btf_features for v1.26 and later.
> > -pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func,decl_tag_kfuncs
> > +pahole-flags-$(call test-ge, $(pahole-ver), 126)  = -j --btf_features=encode_force,var,float,enum64,decl_tag,type_tag,optimized_func,consistent_func,decl_tag_kfuncs,global_var
> >  
> >  ifneq ($(KBUILD_EXTMOD),)
> >  module-pahole-flags-$(call test-ge, $(pahole-ver), 126) += --btf_features=distilled_base
>