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Yafang ShaoandNathan Chancellor
e5a259d988
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>