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kbuild: rpm-pkg: Preserve BTF sections in kernel modules during debuginfo stripping

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After switching to the kernel's default package scripts for our local
kernel RPM builds, we noticed that module BTF entries were missing:

  $ ls /sys/kernel/btf/
  vmlinux    <<<< only vmlinux, no module BTF

Root cause: find-debuginfo.sh (from the debugedit package) prefers
eu-strip over strip when elfutils is installed, which is the common
case on RHEL 9. eu-strip removes non-allocated ELF sections, including
the .BTF section that contains BPF Type Format information for kernel
modules. Without .BTF, BPF tools (bpftool, bcc, bpftrace) cannot resolve
kernel types at runtime, and /sys/kernel/btf/<module> entries are not
created when modules are loaded.

Additionally, since commit 8646db2389 ("libbpf,bpf: Share BTF
relocate-related code with kernel"), modules contain a .BTF.base section
that maps distilled type IDs to vmlinux types. If .BTF.base is stripped,
btf_parse_module() falls back to vmlinux BTF directly, causing type ID
mismatches and rejecting the module's BTF entirely.

Fix by passing --keep-section .BTF and --keep-section .BTF.base via
_find_debuginfo_opts, which adds -K .BTF and -K .BTF.base to the
eu-strip/strip command, preserving both sections while allowing normal
debuginfo extraction to proceed.

After this change, all module BTF files are properly generated:

  $ ls /sys/kernel/btf/
  aesni_intel         drm                 i2c_i801            mfd_core
  ahci                drm_client_lib      i2c_mux             net_failover
  backlight           drm_kms_helper      i2c_smbus           pcspkr
  ccp                 drm_shmem_helper    input_leds          qemu_fw_cfg
  dm_log              failover            intel_rapl_common   sch_fq_codel
  dm_mirror           fat                 intel_rapl_msr      serio_raw
  dm_mod              fuse                irqbypass           sunrpc
  dm_region_hash      gf128mul            iTCO_wdt            vfat
  virtio_balloon      virtio_console      virtio_dma_buf      virtio_gpu
  virtio_net          virtio_rng          virtio_blk          vmlinux
  xfs

Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>
Link: https://patch.msgid.link/20260728024950.44946-1-laoar.shao@gmail.com
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
This commit is contained in:
Yafang Shao 2026-07-28 10:49:50 +08:00 committed by Nathan Chancellor
parent 39d6e68f50
commit e5a259d988
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1 changed files with 11 additions and 0 deletions
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11
scripts/package/kernel.spec
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@ -67,7 +67,18 @@ This package provides debug information for the kernel image and modules from th
%undefine _unique_debug_srcs
%undefine _debugsource_packages
%undefine _debuginfo_subpackages
# Preserve .BTF and .BTF.base sections in kernel modules during debuginfo
# stripping. find-debuginfo.sh uses eu-strip which removes non-allocated ELF
# sections like .BTF by default. .BTF.base is required for BTF distillation
# support; without it, module BTF validation fails.
%global with_keep_section %(%{__find_debuginfo} --help 2>&1 | grep -c keep-section)
%if %{with_keep_section}
%global _find_debuginfo_opts -r --keep-section .BTF --keep-section .BTF.base
%else
%global _find_debuginfo_opts -r
%endif
%global _missing_build_ids_terminate_build 1
%global _no_recompute_build_ids 1
%{debug_package}