This patchset teaches pahole to parse symbols in .BTF_ids section in
vmlinux and discover exported kfuncs. Pahole then takes the list of
kfuncs and injects a BTF_KIND_DECL_TAG for each kfunc.
Example of encoding:
$ bpftool btf dump file .tmp_vmlinux.btf | rg "DECL_TAG 'bpf_kfunc'" | wc -l
121
$ bpftool btf dump file .tmp_vmlinux.btf | rg 56337
[56337] FUNC 'bpf_ct_change_timeout' type_id=56336 linkage=static
[127861] DECL_TAG 'bpf_kfunc' type_id=56337 component_idx=-1
This enables downstream users and tools to dynamically discover which
kfuncs are available on a system by parsing vmlinux or module BTF, both
available in /sys/kernel/btf.
This feature is enabled with --btf_features=decl_tag,decl_tag_kfuncs.
Tested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
=== Changelog ===
Changes from v8:
* Fix another get_func_name() edge case
Changes from v7:
* Fix/support detached BTF encoding
Changes from v6:
* Rebase and add decl_tag_kfuncs as default feature
Changes from v5:
* Add gobuffer__sort() helper
* Use strstarts() instead of strncmp()
* Use uint64_t instead of size_t
* Add clarifying comments for get_func_name()
Changes from v4:
* Update man page with decl_tag_kfuncs feature
* Fix release mode build warnings
* Add elf_getshrstrndx() error checking
* Disable tagging if decl_tag feature is off
* Fix malformed func name handling
Changes from v3:
* Guard kfunc tagging behind feature flag
* Use struct btf_id_set8 definition
* Remove unnecessary member from btf_encoder
* Fix code styling
Changes from v2:
* More reliably detect kfunc membership in set8 by tracking set addr ranges
* Rename some variables/functions to be more clear about kfunc vs func
Changes from v1:
* Fix resource leaks
* Fix callee -> caller typo
* Rename btf_decl_tag from kfunc -> bpf_kfunc
* Only grab btf_id_set funcs tagged kfunc
* Presort btf func list
Daniel Xu (3):
pahole: Save input filename separate from output
pahole: Add --btf_feature=decl_tag_kfuncs feature
pahole: Inject kfunc decl tags into BTF
btf_encoder.c | 377 +++++++++++++++++++++++++++++++++++++++++++++
dwarves.h | 1 +
man-pages/pahole.1 | 1 +
pahole.c | 1 +
4 files changed, 380 insertions(+)
--
2.44.0
