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7bdcedd5c8
BPF kfuncs are often not directly referenced and may be inadvertently
removed by optimization steps during kernel builds, thus the __bpf_kfunc
tag mitigates against this removal by including the __used macro. However,
this macro alone does not prevent removal during linking, and may still
yield build warnings (e.g. on mips64el):
[...]
LD vmlinux
BTFIDS vmlinux
WARN: resolve_btfids: unresolved symbol bpf_verify_pkcs7_signature
WARN: resolve_btfids: unresolved symbol bpf_lookup_user_key
WARN: resolve_btfids: unresolved symbol bpf_lookup_system_key
WARN: resolve_btfids: unresolved symbol bpf_key_put
WARN: resolve_btfids: unresolved symbol bpf_iter_task_next
WARN: resolve_btfids: unresolved symbol bpf_iter_css_task_new
WARN: resolve_btfids: unresolved symbol bpf_get_file_xattr
WARN: resolve_btfids: unresolved symbol bpf_ct_insert_entry
WARN: resolve_btfids: unresolved symbol bpf_cgroup_release
WARN: resolve_btfids: unresolved symbol bpf_cgroup_from_id
WARN: resolve_btfids: unresolved symbol bpf_cgroup_acquire
WARN: resolve_btfids: unresolved symbol bpf_arena_free_pages
NM System.map
SORTTAB vmlinux
OBJCOPY vmlinux.32
[...]
Update the __bpf_kfunc tag to better guard against linker optimization by
including the new __retain compiler macro, which fixes the warnings above.
Verify the __retain macro with readelf by checking object flags for 'R':
$ readelf -Wa kernel/trace/bpf_trace.o
Section Headers:
[Nr] Name Type Address Off Size ES Flg Lk Inf Al
[...]
[178] .text.bpf_key_put PROGBITS 00000000 6420 0050 00 AXR 0 0 8
[...]
Key to Flags:
[...]
R (retain), D (mbind), p (processor specific)
Fixes:
|
||
|---|---|---|
| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kunit | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rv | ||
| scsi | ||
| soc | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| ufs | ||
| vdso | ||
| video | ||
| xen | ||