Re: [PATCH v2 bpf-next 13/18] kbuild: Add support for BTF inline information

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

On 14/09/2026 08:50, Nicolas Schier wrote:
> On Tue, Sep 01, 2026 at 05:57:52PM +0100, Alan Maguire wrote:
>> Add CONFIG_DEBUG_INFO_BTF_INLINE to generate BTF inline-location
>> information with pahole v1.31 and later.
>> 
>> Enable pahole's inline feature and pass --inline to resolve_btfids.
>> This extracts LOC_PARAM, LOC_PROTO, and LOCSEC types into a split BTF
>> blob named <output>.BTF.inline while the ordinary BTF remains in .BTF.
>> 
>> Embed the resulting blob in a .BTF.inline ELF section for vmlinux and
>> modules.  Add the vmlinux linker-script output section to avoid it
>> being treated as an orphan.
>> 
>> Use the inline pahole feature unconditionally for both in-tree and
>> external modules; the generated split BTF has the same format in both
>> cases.
>> 
>> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
>> ---
>>  include/asm-generic/vmlinux.lds.h | 11 +++++++++++
>>  lib/Kconfig.debug                 | 17 +++++++++++++++++
>>  scripts/Makefile.btf              |  7 +++++++
>>  scripts/gen-btf.sh                | 17 +++++++++++++++--
>>  4 files changed, 50 insertions(+), 2 deletions(-)
>> 
> 
> [...]
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 1244dcac2294..dd1b2d9ebe99 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -425,6 +425,12 @@ config PAHOLE_HAS_LANG_EXCLUDE
>>  	  otherwise it would emit malformed kernel and module binaries when
>>  	  using DEBUG_INFO_BTF_MODULES.
>>  
>> +config PAHOLE_HAS_INLINE
>> +	def_bool PAHOLE_VERSION >= 131
> [...]
>> +config DEBUG_INFO_BTF_INLINE
>> +	bool "Provide information about inline sites in BTF"
>> +	default n
>> +	depends on DEBUG_INFO_BTF && PAHOLE_HAS_INLINE && SYSFS
> 
> [...]
>> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
>> index a1812985a61a..d42dbc8d7199 100644
>> --- a/scripts/Makefile.btf
>> +++ b/scripts/Makefile.btf
>> @@ -22,7 +22,14 @@ endif
>>  
>>  pahole-flags-$(CONFIG_PAHOLE_HAS_LANG_EXCLUDE)		+= --lang_exclude=rust
>>  
>> +btf-inline := $(CONFIG_DEBUG_INFO_BTF_INLINE)
>> +ifneq ($(btf-inline),)
>> +btf-inline-feat := inline
>> +pahole-flags-$(call test-ge, $(pahole-ver), 131) += --btf_features=$(btf-inline-feat)
>> +endif
>> +
>>  export PAHOLE_FLAGS := $(pahole-flags-y)
>> +export BTF_INLINE := $(btf-inline)
> 
> 
> As btf-inline and btf-inline-feat are not used anywhere else, and 
> CONFIG_DEBUG_INFO_BTF_INLINE can only be set for PAHOLE_VERSION >= 131, 
> this looks a bit noisy to me.  I think it would be good to keep that 
> change in scripts/Makefile.btf as short as possible, e.g.:
> 
>     pahole-flags-$(CONFIG_DEBUG_INFO_BTF_INLINE) += --btf_features=inline
> 
> and for scripts/gen-btf.sh something like:
> 
>     if is_enabled CONFIG_DEBUG_INFO_BTF_INLINE; then
>     	BTF_INLINE=inline
>     fi
> 
>

looks good, I'll make that change for the next revision (splitting this into multiple
series so the kbuild aspects will follow a bit later). Thanks again for taking a look!

Alan