libbpf: fix error when st-prefix_ops and ops from differ btf #6052
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When a module registers a struct_ops, the struct_ops type and its
corresponding map_value type ("bpf_struct_ops_") may reside in different
btf objects, here are four possible case:
+--------+---------------+-------------+---------------------------------+
| |bpf_struct_ops_| xxx_ops | |
+--------+---------------+-------------+---------------------------------+
| case 0 | btf_vmlinux | bft_vmlinux | be used and reg only in vmlinux |
+--------+---------------+-------------+---------------------------------+
| case 1 | btf_vmlinux | mod_btf | INVALID |
+--------+---------------+-------------+---------------------------------+
| case 2 | mod_btf | btf_vmlinux | reg in mod but be used both in |
| | | | vmlinux and mod. |
+--------+---------------+-------------+---------------------------------+
| case 3 | mod_btf | mod_btf | be used and reg only in mod |
+--------+---------------+-------------+---------------------------------+
Currently we figure out the mod_btf by searching with the struct_ops type,
which makes it impossible to figure out the mod_btf when the struct_ops
type is in btf_vmlinux while it's corresponding map_value type is in
mod_btf (case 2).
The fix is to use the corresponding map_value type ("bpf_struct_ops_")
as the lookup anchor instead of the struct_ops type to figure out the
`btf` and `mod_btf` via find_ksym_btf_id(), and then we can locate
the kern_type_id via btf__find_by_name_kind() with the `btf` we just
obtained from find_ksym_btf_id().
With this change the lookup obtains the correct btf and mod_btf for case 2,
preserves correct behavior for other valid cases, and still fails as
expected for the invalid scenario (case 1).
Fixes: 590a008 ("bpf: libbpf: Add STRUCT_OPS support")
Signed-off-by: D. Wythe <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=1006462 irrelevant now. Closing PR. |
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Pull request for series with
subject: libbpf: fix error when st-prefix_ops and ops from differ btf
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1006462