5.15-stable review patch. If anyone has any objections, please let me know.
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From: Donglin Peng dolinux.peng@gmail.com
[ Upstream commit cc5083d1f3881624ad2de1f3cbb3a07e152cb254 ]
I encountered an issue when building the test_progs from the repository [1]:
$ pwd /work/Qemu/x86_64/linux-6.10-rc2/tools/testing/selftests/bpf/
$ make test_progs V=1 [...] ./tools/sbin/bpftool gen object ./ip_check_defrag.bpf.linked2.o ./ip_check_defrag.bpf.linked1.o libbpf: failed to find symbol for variable 'bpf_dynptr_slice' in section '.ksyms' Error: failed to link './ip_check_defrag.bpf.linked1.o': No such file or directory (2) [...]
Upon investigation, I discovered that the btf_types referenced in the '.ksyms' section had a kind of BTF_KIND_FUNC instead of BTF_KIND_VAR:
$ bpftool btf dump file ./ip_check_defrag.bpf.linked1.o [...] [2] DATASEC '.ksyms' size=0 vlen=2 type_id=16 offset=0 size=0 (FUNC 'bpf_dynptr_from_skb') type_id=17 offset=0 size=0 (FUNC 'bpf_dynptr_slice') [...] [16] FUNC 'bpf_dynptr_from_skb' type_id=82 linkage=extern [17] FUNC 'bpf_dynptr_slice' type_id=85 linkage=extern [...]
For a detailed analysis, please refer to [2]. We can add a kind checking to fix the issue.
[1] https://github.com/eddyz87/bpf/tree/binsort-btf-dedup [2] https://lore.kernel.org/all/0c0ef20c-c05e-4db9-bad7-2cbc0d6dfae7@oracle.com/
Fixes: 8fd27bf69b86 ("libbpf: Add BPF static linker BTF and BTF.ext support") Signed-off-by: Donglin Peng dolinux.peng@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Alan Maguire alan.maguire@oracle.com Acked-by: Eduard Zingerman eddyz87@gmail.com Link: https://lore.kernel.org/bpf/20240619122355.426405-1-dolinux.peng@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/linker.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 6b2f59ddb6918..bfe0c30841b9b 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -2193,10 +2193,17 @@ static int linker_fixup_btf(struct src_obj *obj) vi = btf_var_secinfos(t); for (j = 0, m = btf_vlen(t); j < m; j++, vi++) { const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type); - const char *var_name = btf__str_by_offset(obj->btf, vt->name_off); - int var_linkage = btf_var(vt)->linkage; + const char *var_name; + int var_linkage; Elf64_Sym *sym;
+ /* could be a variable or function */ + if (!btf_is_var(vt)) + continue; + + var_name = btf__str_by_offset(obj->btf, vt->name_off); + var_linkage = btf_var(vt)->linkage; + /* no need to patch up static or extern vars */ if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED) continue;