src/shared/bpf-compat.h

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 #pragma once
   3
   4 /* libbpf has been moving quickly.
   5  * They added new symbols in the 0.x versions and shortly after removed
   6  * deprecated symbols in 1.0.
   7  * We only need bpf_map_create and libbpf_probe_bpf_prog_type so we work
   8  * around the incompatibility here by:
   9  *  - declaring both symbols, and looking for either depending on the libbpf
  10  *    so version we found
  11  *  - having helpers that automatically use the appropriate version behind the
  12  *    new API for easy cleanup later
  13  *
  14  * The advantage of doing this instead of only looking for the symbols declared at
  15  * compile time is that we can then load either the old or the new symbols at runtime
  16  * regardless of the version we were compiled with */
  17
  18
  19 /* declare the struct for libbpf <= 0.6.0 -- it causes no harm on newer versions */
  20 struct bpf_map_create_opts;
  21
  22 /* new symbols available from 0.7.0.
  23  * We need the symbols here:
  24  *  - after bpf_map_create_opts struct has been defined for older libbpf
  25  *  - before the compat static inline helpers that use them.
  26  * When removing this file move these back to bpf-dlopen.h */
  27 extern int (*sym_bpf_map_create)(enum bpf_map_type,  const char *, __u32, __u32, __u32, const struct bpf_map_create_opts *);
  28 extern int (*sym_libbpf_probe_bpf_prog_type)(enum bpf_prog_type, const void *);
  29 extern struct bpf_map* (*sym_bpf_object__next_map)(const struct bpf_object *obj, const struct bpf_map *map);
  30
  31 /* compat symbols removed in libbpf 1.0 */
  32 extern int (*sym_bpf_create_map)(enum bpf_map_type, int key_size, int value_size, int max_entries, __u32 map_flags);
  33 extern bool (*sym_bpf_probe_prog_type)(enum bpf_prog_type, __u32);
  34
  35 /* helpers to use the available variant behind new API */
  36 static inline int compat_bpf_map_create(enum bpf_map_type map_type,
  37                 const char *map_name,
  38                 __u32 key_size,
  39                 __u32 value_size,
  40                 __u32 max_entries,
  41                 const struct bpf_map_create_opts *opts) {
  42         if (sym_bpf_map_create)
  43                 return sym_bpf_map_create(map_type, map_name, key_size,
  44                                           value_size, max_entries, opts);
  45
  46         return sym_bpf_create_map(map_type, key_size, value_size, max_entries,
  47                                   0 /* opts->map_flags, but opts is always NULL for us so skip build dependency on the type */);
  48 }
  49
  50 static inline int compat_libbpf_probe_bpf_prog_type(enum bpf_prog_type prog_type, const void *opts) {
  51         if (sym_libbpf_probe_bpf_prog_type)
  52                 return sym_libbpf_probe_bpf_prog_type(prog_type, opts);
  53
  54         return sym_bpf_probe_prog_type(prog_type, 0);
  55 }