Em Tue, Jan 18, 2022 at 03:13:27PM +0100, Toke Høiland-Jørgensen escreveu: > 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 The coexistence of enums with the defines (in turn #ifndef guarded) as something I hadn't considered, clever. Should fix lots of build errors in my test containers :-) FWIW: Acked-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> > 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@xxxxxxxxxx> > --- > tools/lib/bpf/btf.h | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h > index 061839f04525..51862fdee850 100644 > --- a/tools/lib/bpf/btf.h > +++ b/tools/lib/bpf/btf.h > @@ -375,8 +375,28 @@ btf_dump__dump_type_data(struct btf_dump *d, __u32 id, > 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); > -- > 2.34.1 -- - Arnaldo
