Re: [PATCH bpf-next v3 4/6] lib/Kconfig.debug: Set the minimum required pahole version to v1.22

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 12/5/25 4:32 PM, Andrii Nakryiko wrote:
> On Fri, Dec 5, 2025 at 2:32 PM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>
>> Subsequent patches in the series change vmlinux linking scripts to
>> unconditionally pass --btf_encode_detached to pahole, which was
>> introduced in v1.22 [1][2].
>>
>> This change allows to remove PAHOLE_HAS_SPLIT_BTF Kconfig option and
>> other checks of older pahole versions.
>>
>> [1] https://github.com/acmel/dwarves/releases/tag/v1.22
>> [2] https://lore.kernel.org/bpf/cbafbf4e-9073-4383-8ee6-1353f9e5869c@oracle.com/
>>
>> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
>> ---
>>  lib/Kconfig.debug         | 13 ++++---------
>>  scripts/Makefile.btf      |  9 +--------
>>  tools/sched_ext/README.md |  1 -
>>  3 files changed, 5 insertions(+), 18 deletions(-)
>>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 742b23ef0d8b..3abf3ae554b6 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -389,18 +389,13 @@ config DEBUG_INFO_BTF
>>         depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
>>         depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
>>         depends on BPF_SYSCALL
>> -       depends on PAHOLE_VERSION >= 116
>> -       depends on DEBUG_INFO_DWARF4 || PAHOLE_VERSION >= 121
>> +       depends on PAHOLE_VERSION >= 122
>>         # pahole uses elfutils, which does not have support for Hexagon relocations
>>         depends on !HEXAGON
>>         help
>>           Generate deduplicated BTF type information from DWARF debug info.
>> -         Turning this on requires pahole v1.16 or later (v1.21 or later to
>> -         support DWARF 5), which will convert DWARF type info into equivalent
>> -         deduplicated BTF type info.
>> -
>> -config PAHOLE_HAS_SPLIT_BTF
>> -       def_bool PAHOLE_VERSION >= 119
>> +         Turning this on requires pahole v1.22 or later, which will convert
>> +         DWARF type info into equivalent deduplicated BTF type info.
>>
>>  config PAHOLE_HAS_BTF_TAG
>>         def_bool PAHOLE_VERSION >= 123
>> @@ -422,7 +417,7 @@ config PAHOLE_HAS_LANG_EXCLUDE
>>  config DEBUG_INFO_BTF_MODULES
>>         bool "Generate BTF type information for kernel modules"
>>         default y
>> -       depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF
>> +       depends on DEBUG_INFO_BTF && MODULES
>>         help
>>           Generate compact split BTF type information for kernel modules.
>>
>> diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf
>> index db76335dd917..7c1cd6c2ff75 100644
>> --- a/scripts/Makefile.btf
>> +++ b/scripts/Makefile.btf
>> @@ -7,14 +7,7 @@ JOBS := $(patsubst -j%,%,$(filter -j%,$(MAKEFLAGS)))
>>
>>  ifeq ($(call test-le, $(pahole-ver), 125),y)
>>
>> -# pahole 1.18 through 1.21 can't handle zero-sized per-CPU vars
>> -ifeq ($(call test-le, $(pahole-ver), 121),y)
>> -pahole-flags-$(call test-ge, $(pahole-ver), 118)       += --skip_encoding_btf_vars
>> -endif
>> -
>> -pahole-flags-$(call test-ge, $(pahole-ver), 121)       += --btf_gen_floats
>> -
>> -pahole-flags-$(call test-ge, $(pahole-ver), 122)       += -j$(JOBS)
>> +pahole-flags-$(call test-ge, $(pahole-ver), 122)       += --btf_gen_floats -j$(JOBS)
> 
> this should be unconditional given we expect at least 1.22, no?

Yes, it can be unconditional, but still under if ver < 125.

> 
>>
>>  pahole-flags-$(call test-ge, $(pahole-ver), 125)       += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized
>>
>> diff --git a/tools/sched_ext/README.md b/tools/sched_ext/README.md
>> index 16a42e4060f6..56a9d1557ac4 100644
>> --- a/tools/sched_ext/README.md
>> +++ b/tools/sched_ext/README.md
>> @@ -65,7 +65,6 @@ It's also recommended that you also include the following Kconfig options:
>>  ```
>>  CONFIG_BPF_JIT_ALWAYS_ON=y
>>  CONFIG_BPF_JIT_DEFAULT_ON=y
>> -CONFIG_PAHOLE_HAS_SPLIT_BTF=y
>>  CONFIG_PAHOLE_HAS_BTF_TAG=y
>>  ```
>>
>> --
>> 2.52.0
>>