From: Toke Høiland-Jørgensen toke@redhat.com
commit eaa266d83a3730a15de2ceebcc89e8f6290e8cf6 upstream.
The btf.h header included with libbpf contains inline helper functions to check for various BTF kinds. These helpers directly reference the BTF_KIND_* constants defined in the kernel header, and because the header file is included in user applications, this happens in the user application compile units.
This presents a problem if a user application is compiled on a system with older kernel headers because the constants are not available. To avoid this, add #defines of the constants directly in btf.h before using them.
Since the kernel header moved to an enum for BTF_KIND_*, the #defines can shadow the enum values without any errors, so we only need #ifndef guards for the constants that predates the conversion to enum. We group these so there's only one guard for groups of values that were added together.
[0] Closes: https://github.com/libbpf/libbpf/issues/436
Fixes: 223f903e9c83 ("bpf: Rename BTF_KIND_TAG to BTF_KIND_DECL_TAG") Fixes: 5b84bd10363e ("libbpf: Add support for BTF_KIND_TAG") Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Arnaldo Carvalho de Melo acme@redhat.com Link: https://lore.kernel.org/bpf/20220118141327.34231-1-toke@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/lib/bpf/btf.h | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)
--- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -313,8 +313,28 @@ btf_dump__dump_type_data(struct btf_dump const struct btf_dump_type_data_opts *opts);
/* - * A set of helpers for easier BTF types handling + * A set of helpers for easier BTF types handling. + * + * The inline functions below rely on constants from the kernel headers which + * may not be available for applications including this header file. To avoid + * compilation errors, we define all the constants here that were added after + * the initial introduction of the BTF_KIND* constants. */ +#ifndef BTF_KIND_FUNC +#define BTF_KIND_FUNC 12 /* Function */ +#define BTF_KIND_FUNC_PROTO 13 /* Function Proto */ +#endif +#ifndef BTF_KIND_VAR +#define BTF_KIND_VAR 14 /* Variable */ +#define BTF_KIND_DATASEC 15 /* Section */ +#endif +#ifndef BTF_KIND_FLOAT +#define BTF_KIND_FLOAT 16 /* Floating point */ +#endif +/* The kernel header switched to enums, so these two were never #defined */ +#define BTF_KIND_DECL_TAG 17 /* Decl Tag */ +#define BTF_KIND_TYPE_TAG 18 /* Type Tag */ + static inline __u16 btf_kind(const struct btf_type *t) { return BTF_INFO_KIND(t->info);