bpftool: Provide a helper method for accessing skeleton's embedded ELF data

This adds a skeleton method X__elf_bytes() which returns the binary data of
the compiled and embedded BPF object file. It additionally sets the size of
the return data to the provided size_t pointer argument.

The assignment to s->data is cast to void * to ensure no warning is issued if
compiled with a previous version of libbpf where the bpf_object_skeleton field
is void * instead of const void *

Signed-off-by: Matt Smith <alastorze@fb.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210901194439.3853238-3-alastorze@fb.com

diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index d40d92b..e3ec47a 100644 (file)
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -238,8 +238,8 @@ static void codegen(const char *template, ...)
                } else if (c == '\n') {
                        break;
                } else {
-                       p_err("unrecognized character at pos %td in template '%s'",
-                             src - template - 1, template);
+                       p_err("unrecognized character at pos %td in template '%s': '%c'",
+                             src - template - 1, template, c);
                        free(s);
                        exit(-1);
                }
@@ -406,7 +406,7 @@ static void codegen_destroy(struct bpf_object *obj, const char *obj_name)
        }
 
        bpf_object__for_each_map(map, obj) {
-               const char * ident;
+               const char *ident;
 
                ident = get_map_ident(map);
                if (!ident)
@@ -862,6 +862,8 @@ static int do_skeleton(int argc, char **argv)
        codegen("\
                \n\
                                                                            \n\
+               static inline const void *%1$s__elf_bytes(size_t *sz);      \n\
+                                                                           \n\
                static inline int                                           \n\
                %1$s__create_skeleton(struct %1$s *obj)                     \n\
                {                                                           \n\
@@ -943,10 +945,20 @@ static int do_skeleton(int argc, char **argv)
        codegen("\
                \n\
                                                                            \n\
-                       s->data_sz = %d;                                    \n\
-                       s->data = (void *)\"\\                              \n\
-               ",
-               file_sz);
+                       s->data = (void *)%2$s__elf_bytes(&s->data_sz);     \n\
+                                                                           \n\
+                       return 0;                                           \n\
+               err:                                                        \n\
+                       bpf_object__destroy_skeleton(s);                    \n\
+                       return -ENOMEM;                                     \n\
+               }                                                           \n\
+                                                                           \n\
+               static inline const void *%2$s__elf_bytes(size_t *sz)       \n\
+               {                                                           \n\
+                       *sz = %1$d;                                         \n\
+                       return (const void *)\"\\                           \n\
+               "
+               , file_sz, obj_name);
 
        /* embed contents of BPF object file */
        print_hex(obj_data, file_sz);
@@ -954,11 +966,6 @@ static int do_skeleton(int argc, char **argv)
        codegen("\
                \n\
                \";                                                         \n\
-                                                                           \n\
-                       return 0;                                           \n\
-               err:                                                        \n\
-                       bpf_object__destroy_skeleton(s);                    \n\
-                       return -ENOMEM;                                     \n\
                }                                                           \n\
                                                                            \n\
                #endif /* %s */                                             \n\