libbpf/btf: Fix string handling to support multi-split BTF

libbpf handling of split BTF has been written largely with the
assumption that multiple splits are possible, i.e. split BTF on top of
split BTF on top of base BTF.  One area where this does not quite work
is string handling in split BTF; the start string offset should be the
base BTF string section length + the base BTF string offset.  This
worked in the past because for a single split BTF with base the start
string offset was always 0.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250519165935.261614-2-alan.maguire@oracle.com
This commit is contained in:
Alan Maguire
2025-05-19 17:59:34 +01:00
committed by Andrii Nakryiko
parent 31bb8f7936
commit 8df8d67f63

View File

@@ -996,7 +996,7 @@ static struct btf *btf_new_empty(struct btf *base_btf)
if (base_btf) {
btf->base_btf = base_btf;
btf->start_id = btf__type_cnt(base_btf);
btf->start_str_off = base_btf->hdr->str_len;
btf->start_str_off = base_btf->hdr->str_len + base_btf->start_str_off;
btf->swapped_endian = base_btf->swapped_endian;
}