linux-stable.git/tools/lib/bpf/btf.c, branch linux-rolling-stable

libbpf: Fix deduplication of typedef with base definitions

2026-07-24T14:19:03+00:00

[ Upstream commit 0831b110eb4591e4ad8c5fd0d8f0f3f9979a5ff5 ]

When deduplicating definitions for a module, typedef defined in the base
are not removed. This is because the hash used for base types differs
from the one used in the deduplication logic in btf_dedup_struct_type.

This was introduced by the referenced commit when moving the typedef
deduplication logic handling from btf_dedup_ref_type to
btf_dedup_struct_type, as this also changed the hash logic
(btf_hash_common to btf_hash_typedef).

This also impacts other types referencing those typedef (e.g. const). In
my test, the BTF section size of the openvswitch module went from 31KB
to 45KB.

Fixes: 3781413465df ("libbpf: Fix BTF dedup to support recursive typedef definitions").
Signed-off-by: Antoine Tenart 
Signed-off-by: Andrii Nakryiko 
Tested-by: Alan Maguire 
Reviewed-by: Alan Maguire 
Link: https://lore.kernel.org/bpf/20260417083319.32716-1-atenart@kernel.org
Signed-off-by: Sasha Levin

libbpf: BTF validation can use layout for unknown kinds

2026-03-26T20:53:56+00:00

BTF parsing can use layout to navigate unknown kinds, so
btf_validate_type() should take layout information into
account to avoid failure when an unrecognized kind is met.

Signed-off-by: Alan Maguire 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260326145444.2076244-6-alan.maguire@oracle.com

libbpf: Add layout encoding support

2026-03-26T20:53:56+00:00

Support encoding of BTF layout data via btf__new_empty_opts().

Current supported opts are base_btf and add_layout.

Layout information is maintained in btf.c in the layouts[] array;
when BTF is created with the add_layout option it represents the
current view of supported BTF kinds.

Signed-off-by: Alan Maguire 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260326145444.2076244-5-alan.maguire@oracle.com

libbpf: Use layout to compute an unknown kind size

2026-03-26T20:53:56+00:00

This allows BTF parsing to proceed even if we do not know the
kind.  Fall back to base BTF layout if layout information is
not in split BTF.

Signed-off-by: Alan Maguire 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260326145444.2076244-4-alan.maguire@oracle.com

libbpf: Support layout section handling in BTF

2026-03-26T20:53:56+00:00

Support reading in layout fixing endian issues on reading;
also support writing layout section to raw BTF object.
There is not yet an API to populate the layout with meaningful
information.

As part of this, we need to consider multiple valid BTF header
sizes; the original or the layout-extended headers.
So to support this, the "struct btf" representation is modified
to contain a "struct btf_header" and we copy the valid
portion from the raw data to it; this means we can always safely
check fields like btf->hdr.layout_len .

Note if parsed-in BTF has extra header information beyond
sizeof(struct btf_header) - if so we make that BTF ineligible
for modification by setting btf->has_hdr_extra .

Ensure that we handle endianness issues for BTF layout section,
though currently only field that needs this (flags) is unused.

Signed-off-by: Alan Maguire 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260326145444.2076244-3-alan.maguire@oracle.com

libbpf: Support appending split BTF in btf__add_btf()

2026-03-05T22:57:58+00:00

btf__add_btf() currently rejects split BTF sources with -ENOTSUP.
This prevents merging types from multiple kernel module BTFs that
are all split against the same vmlinux base.

Extend btf__add_btf() to handle split BTF sources by:

- Replacing the blanket -ENOTSUP with a validation that src and dst
  share the same base BTF pointer when both are split, returning
  -EOPNOTSUPP on mismatch.

- Computing src_start_id from the source's base to distinguish base
  type ID references (which must remain unchanged) from split type
  IDs (which must be remapped to new positions in the destination).

- Using src_btf->nr_types instead of btf__type_cnt()-1 for the type
  count, which is correct for both split and non-split sources.

- Skipping base string offsets (< start_str_off) during the string
  rewrite loop, mirroring the type ID skip pattern.  Since src and
  dst share the same base BTF, base string offsets are already valid
  and need no remapping.

For non-split sources the behavior is identical: src_start_id is 1,
the type_id < 1 guard is never true (VOID is already skipped), and
the remapping formula reduces to the original.  start_str_off is 0
so no string offsets are skipped.

Assisted-by: Claude:claude-opus-4-6

Signed-off-by: Josef Bacik 
Signed-off-by: Andrii Nakryiko 
Reviewed-by: Alan Maguire 
Link: https://lore.kernel.org/bpf/c00216ed48cf7897078d9645679059d5ebf42738.1772657690.git.josef@toxicpanda.com

btf: Refactor the code by calling str_is_empty

2026-01-14T00:21:56+00:00

Calling the str_is_empty function to clarify the code and
no functional changes are introduced.

Signed-off-by: Donglin Peng 
Signed-off-by: Andrii Nakryiko 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20260109130003.3313716-12-dolinux.peng@gmail.com

libbpf: Verify BTF sorting

2026-01-14T00:16:59+00:00

This patch checks whether the BTF is sorted by name in ascending
order. If sorted, binary search will be used when looking up types.

Signed-off-by: Donglin Peng 
Signed-off-by: Andrii Nakryiko 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20260109130003.3313716-6-dolinux.peng@gmail.com

libbpf: Optimize type lookup with binary search for sorted BTF

2026-01-14T00:16:58+00:00

This patch introduces binary search optimization for BTF type lookups
when the BTF instance contains sorted types.

The optimization significantly improves performance when searching for
types in large BTF instances with sorted types. For unsorted BTF, the
implementation falls back to the original linear search.

Signed-off-by: Donglin Peng 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260109130003.3313716-5-dolinux.peng@gmail.com

libbpf: Add BTF permutation support for type reordering

2026-01-14T00:10:39+00:00

Introduce btf__permute() API to allow in-place rearrangement of BTF types.
This function reorganizes BTF type order according to a provided array of
type IDs, updating all type references to maintain consistency.

Signed-off-by: Donglin Peng 
Signed-off-by: Andrii Nakryiko 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20260109130003.3313716-2-dolinux.peng@gmail.com