Merge branch 'libbpf-api'

Andrii Nakryiko says:

====================
Add bpf_object__open_file() and bpf_object__open_mem() APIs that use a new
approach to providing future-proof non-ABI-breaking API changes. It relies on
APIs accepting optional self-describing "opts" struct, containing its own
size, filled out and provided by potentially outdated (as well as
newer-than-libbpf) user application. A set of internal helper macros
(OPTS_VALID, OPTS_HAS, and OPTS_GET) streamline and simplify a graceful
handling forward and backward compatibility for user applications dynamically
linked against different versions of libbpf shared library.

Users of libbpf are provided with convenience macro LIBBPF_OPTS that takes
care of populating correct structure size and zero-initializes options struct,
which helps avoid obscure issues of unitialized padding. Uninitialized padding
in a struct might turn into garbage-populated new fields understood by future
versions of libbpf.

Patch #1 removes enforcement of kern_version in libbpf and always populates
correct one on behalf of users.
Patch #2 defines necessary infrastructure for options and two new open APIs
relying on it.
Patch #3 fixes bug in bpf_object__name().
Patch #4 switches two of test_progs' tests to use new APIs as a validation
that they work as expected.

v2->v3:
- fix LIBBPF_OPTS() to ensure zero-initialization of padded bytes;
- pass through name override and relaxed maps flag for open_file() (Toke);
- fix bpf_object__name() to actually return object name;
- don't bother parsing and verifying version section (John);

v1->v2:
- use better approach for tracking last field in opts struct;
- convert few tests to new APIs for validation;
- fix bug with using offsetof(last_field) instead of offsetofend(last_field).
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 43 insertions, 5 deletions

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index e8f70977d137..667e6853e51f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -67,14 +67,52 @@ struct bpf_object_open_attr {
 	enum bpf_prog_type prog_type;
 };
 
+/* Helper macro to declare and initialize libbpf options struct
+ *
+ * This dance with uninitialized declaration, followed by memset to zero,
+ * followed by assignment using compound literal syntax is done to preserve
+ * ability to use a nice struct field initialization syntax and **hopefully**
+ * have all the padding bytes initialized to zero. It's not guaranteed though,
+ * when copying literal, that compiler won't copy garbage in literal's padding
+ * bytes, but that's the best way I've found and it seems to work in practice.
+ */
+#define LIBBPF_OPTS(TYPE, NAME, ...)					    \
+	struct TYPE NAME;						    \
+	memset(&NAME, 0, sizeof(struct TYPE));				    \
+	NAME = (struct TYPE) {						    \
+		.sz = sizeof(struct TYPE),				    \
+		__VA_ARGS__						    \
+	}
+
+struct bpf_object_open_opts {
+	/* size of this struct, for forward/backward compatiblity */
+	size_t sz;
+	/* object name override, if provided:
+	 * - for object open from file, this will override setting object
+	 *   name from file path's base name;
+	 * - for object open from memory buffer, this will specify an object
+	 *   name and will override default "<addr>-<buf-size>" name;
+	 */
+	const char *object_name;
+	/* parse map definitions non-strictly, allowing extra attributes/data */
+	bool relaxed_maps;
+};
+#define bpf_object_open_opts__last_field relaxed_maps
+
 LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
 LIBBPF_API struct bpf_object *
+bpf_object__open_file(const char *path, struct bpf_object_open_opts *opts);
+LIBBPF_API struct bpf_object *
+bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
+		     struct bpf_object_open_opts *opts);
+
+/* deprecated bpf_object__open variants */
+LIBBPF_API struct bpf_object *
+bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,
+			const char *name);
+LIBBPF_API struct bpf_object *
 bpf_object__open_xattr(struct bpf_object_open_attr *attr);
-struct bpf_object *__bpf_object__open_xattr(struct bpf_object_open_attr *attr,
-					    int flags);
-LIBBPF_API struct bpf_object *bpf_object__open_buffer(void *obj_buf,
-						      size_t obj_buf_sz,
-						      const char *name);
+
 int bpf_object__section_size(const struct bpf_object *obj, const char *name,
 			     __u32 *size);
 int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,