Currently, pahole does not generate kfunc declaration tags when
generating BTF for ELF files with an endianness different from the
host system. For example, this issue occurs when processing a vmlinux
built for s390 on an x86 host.
To reproduce the bug:
- follow the instructions in [0] to build an s390 vmlinux;
- generate BTF requesting declaration tags for kfuncs:
$ pahole --btf_features_strict=decl_tag_kfuncs,decl_tag \
--btf_encode_detached=test.btf vmlinux
- observe that no kfuncs are generated:
$ bpftool btf dump file test.btf format c | grep __ksym
This patch resolves the issue by adding the necessary byte-swapping
operations.
Changelog:
- v1 [1] -> v2:
- avoid modifying the 'idlist' Elf_Data object directly.
Instead, use struct local_elf_data (suggested by Jiri);
- update the description of the .BTF_ids section (suggested by Jiri).
- v2 [2] -> v3:
- use elf_getdata_rawchunk() instead of direct conversion loop
(suggested by Andrii);
- removed Jiri's acked-by and Vadim's reviewed-by,
as patch had changed significantly.
[0] https://docs.kernel.org/bpf/s390.html
[1] https://lore.kernel.org/dwarves/20241122070218.3832680-1-eddyz87@xxxxxxxxx/
[2] https://lore.kernel.org/dwarves/20241122214431.292196-1-eddyz87@xxxxxxxxx/
Cc: Alan Maguire <alan.maguire@xxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Daniel Xu <dxu@xxxxxxxxx>
Cc: Jiri Olsa <olsajiri@xxxxxxxxx>
Cc: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Cc: Vadim Fedorenko <vadfed@xxxxxxxx>
Eduard Zingerman (1):
btf_encoder: handle .BTF_ids section endianness
btf_encoder.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
--
2.47.0
