Re: [PATCH dwarves v9 2/3] pahole: Add --btf_feature=decl_tag_kfuncs feature

[Alan Maguire <alan.maguire@oracle.com>]

On 01/05/2024 00:00, Daniel Xu wrote:
> Hi Arnaldo,
> 
> On Tue, Apr 30, 2024 at 03:48:06PM GMT, Arnaldo Carvalho de Melo wrote:
>> On Mon, Apr 29, 2024 at 04:45:59PM -0600, Daniel Xu wrote:
>>> Add a feature flag to guard tagging of kfuncs. The next commit will
>>> implement the actual tagging.
>>>
>>> Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
>>> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
>>
>> Also 'decl_tag_kfuncs' is not enabled when using --btf_features=default,
>> right? as:
>>
>>         BTF_DEFAULT_FEATURE(decl_tag_kfuncs, btf_decl_tag_kfuncs, false),
>>
>> And that false is .default_enabled=false.
> 
> I think that `false` is for `initial_value`, isn't it? The macro sets
> the `default_enabled` field.
> 

yep it's the initial unset value. Specifying an option in --btf_features
flips that value, so for initial-off values they are switched on, while
initial-on values are switched off. I _think_ the intent here is to tag
kfuncs by default, so we can add tag_kfuncs to the set of options
specified in pahole-flags for v1.26. We won't be using "default" there
as we want to call out the flags explicitly.

Alan

> Building with this seems to tag the kfuncs for me:
> 
> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf                                                                                                                                                                 
> index 82377e470aed..7128dc25ba29 100644                                                                                                                                                                                  
> --- a/scripts/Makefile.btf                                                                                                                                                                                               
> +++ b/scripts/Makefile.btf                                                                                                                                                                                               
> @@ -16,4 +16,6 @@ pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE)                += --lang_exclude=rust                                                                                                                   
>                                                                                                                                                                                                                          
>  pahole-flags-$(call test-ge, $(pahole-ver), 125)       += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized                                                                                                    
>                                                                                                                                                                                                                          
> +pahole-flags-$(call test-ge, $(pahole-ver), 126)       = -j --lang_exclude=rust --btf_features=default                                                                                                                  
> +                                                                                                                                                                                                                        
>  export PAHOLE_FLAGS := $(pahole-flags-y)
> 
> Thanks,
> Daniel