Re: [PATCH bpf-next v6 0/8] resolve_btfids: Support for BTF modifications

Alan Maguire
2025-12-19T13:01:56Z

On 19/12/2025 01:59, Ihor Solodrai wrote:
> This series changes resolve_btfids and kernel build scripts to enable
> BTF transformations in resolve_btfids. Main motivation for enhancing
> resolve_btfids is to reduce dependency of the kernel build on pahole
> capabilities [1] and enable BTF features and optimizations [2][3]
> particular to the kernel.
>
> Patches #1-#4 in the series are non-functional changes in
> resolve_btfids.
>
> Patch #5 makes kernel build notice pahole version changes between
> builds.
>
> Patch #6 changes minimum version of pahole required for
> CONFIG_DEBUG_INFO_BTF to v1.22
>
> Patch #7 makes a small prep change in selftests/bpf build.
>
> The last patch (#8) makes significant changes in resolve_btfids and
> introduces scripts/gen-btf.sh. See implementation details in the patch
> description.
>
> Successful BPF CI run: https://github.com/kernel-patches/bpf/actions/runs/20353330265
>

Thanks for this; in particular patch 5 is a great help! I verified that
changing pahole version (without running "make oldconfig") results in updates
to the CONFIG_PAHOLE_VERSION etc. Feel free to add for the series

Tested-by: Alan Maguire <alan.maguire@oracle.com>

> [1] https://lore.kernel.org/dwarves/ba1650aa-fafd-49a8-bea4-bdddee7c38c9@linux.dev/
> [2] https://lore.kernel.org/bpf/20251029190113.3323406-1-ihor.solodrai@linux.dev/
> [3] https://lore.kernel.org/bpf/20251119031531.1817099-1-dolinux.peng@gmail.com/
>
> ---
>
> v5->v6:
> - patch #8: fix double free when btf__distill_base fails (reported by AI)
> https://lore.kernel.org/bpf/e269870b8db409800045ee0061fc02d21721e0efadd99ca83960b48f8db7b3f3@mail.kernel.org/
>
> v5: https://lore.kernel.org/bpf/20251219003147.587098-1-ihor.solodrai@linux.dev/
>
> v4->v5:
> - patch #3: fix an off-by-one bug (reported by AI)
> https://lore.kernel.org/bpf/106b6e71bce75b8f12a85f2f99e75129e67af7287f6d81fa912589ece14044f9@mail.kernel.org/
> - patch #8: cleanup GEN_BTF in Makefile.btf
>
> v4: https://lore.kernel.org/bpf/20251218003314.260269-1-ihor.solodrai@linux.dev/
>
> v3->v4:
> - add patch #4: "resolve_btfids: Always build with -Wall -Werror"
> - add patch #5: "kbuild: Sync kconfig when PAHOLE_VERSION changes" (Alan)
> - fix clang cross-compilation (LKP)
> https://lore.kernel.org/bpf/cecb6351-ea9a-4f8a-863a-82c9ef02f012@linux.dev/
> - remove GEN_BTF env variable (Andrii)
> - nits and cleanup in resolve_btfids/main.c (Andrii, Eduard)
> - nits in a patch bumping minimum pahole version (Andrii, AI)
>
> v3: https://lore.kernel.org/bpf/20251205223046.4155870-1-ihor.solodrai@linux.dev/
>
> v2->v3:
> - add patch #4 bumping minimum pahole version (Andrii, Alan)
> - add patch #5 pre-fixing resolve_btfids test (Donglin)
> - add GEN_BTF var and assemble RESOLVE_BTFIDS_FLAGS in Makefile.btf (Alan)
> - implement --distill_base flag in resolve_btfids, set it depending
> on KBUILD_EXTMOD in Makefile.btf (Eduard)
> - various implementation nits, see the v2 thread for details (Andrii, Eduard)
>
> v2: https://lore.kernel.org/bpf/20251127185242.3954132-1-ihor.solodrai@linux.dev/
>
> v1->v2:
> - gen-btf.sh and other shell script fixes (Donglin)
> - update selftests build (Donglin)
> - generate .BTF.base only when KBUILD_EXTMOD is set (Alan)
> - proper endianness handling for cross-compilation
> - change elf_begin mode from ELF_C_RDWR_MMAP to ELF_C_READ_MMAP_PRIVATE
> - remove compressed_section_fix()
> - nit NULL check in patch #3 (suggested by AI)
>
> v1: https://lore.kernel.org/bpf/20251126012656.3546071-1-ihor.solodrai@linux.dev/
>
> Ihor Solodrai (8):
> resolve_btfids: Rename object btf field to btf_path
> resolve_btfids: Factor out load_btf()
> resolve_btfids: Introduce enum btf_id_kind
> resolve_btfids: Always build with -Wall -Werror
> kbuild: Sync kconfig when PAHOLE_VERSION changes
> lib/Kconfig.debug: Set the minimum required pahole version to v1.22
> selftests/bpf: Run resolve_btfids only for relevant .test.o objects
> resolve_btfids: Change in-place update with raw binary output
>
> Documentation/scheduler/sched-ext.rst | 1 -
> MAINTAINERS | 1 +
> Makefile | 9 +-
> init/Kconfig | 2 +-
> lib/Kconfig.debug | 13 +-
> scripts/Makefile.btf | 21 +-
> scripts/Makefile.modfinal | 5 +-
> scripts/Makefile.vmlinux | 2 +-
> scripts/gen-btf.sh | 157 ++++++++
> scripts/link-vmlinux.sh | 42 +-
> tools/bpf/resolve_btfids/Makefile | 3 +-
> tools/bpf/resolve_btfids/main.c | 358 ++++++++++++------
> tools/sched_ext/README.md | 1 -
> tools/testing/selftests/bpf/.gitignore | 3 +
> tools/testing/selftests/bpf/Makefile | 11 +-
> .../selftests/bpf/prog_tests/resolve_btfids.c | 4 +-
> 16 files changed, 443 insertions(+), 190 deletions(-)
> create mode 100755 scripts/gen-btf.sh
>