[PATCH bpf-next v4 0/8] resolve_btfids: Support for BTF modifications

Ihor Solodrai
2025-12-18T00:34:14Z

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/20321339588

[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/

---

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 | 26 +-
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 | 356 ++++++++++++------
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, 446 insertions(+), 190 deletions(-)
create mode 100755 scripts/gen-btf.sh

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2.52.0