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

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Message-ID: <20251218003314.260269-1-ihor.solodrai@linux.dev>
Date: Wed, 17 Dec 2025 16:33:06 -0800
From: Ihor Solodrai <ihor.solodrai@...ux.dev>
To: Alan Maguire <alan.maguire@...cle.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrea Righi <arighi@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Bill Wendling <morbo@...gle.com>,
	Changwoo Min <changwoo@...lia.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	David Vernet <void@...ifault.com>,
	Donglin Peng <dolinux.peng@...il.com>,
	Eduard Zingerman <eddyz87@...il.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Jonathan Corbet <corbet@....net>,
	Justin Stitt <justinstitt@...gle.com>,
	KP Singh <kpsingh@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Nicolas Schier <nsc@...nel.org>,
	Shuah Khan <shuah@...nel.org>,
	Song Liu <song@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Tejun Heo <tj@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>
Cc: bpf@...r.kernel.org,
	dwarves@...r.kernel.org,
	linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev
Subject: [PATCH bpf-next v4 0/8] resolve_btfids: Support for BTF modifications

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

-- 
2.52.0