Commit e00aca65 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
Browse files

libbpf: Make DECLARE_LIBBPF_OPTS macro strictly a variable declaration 



LIBBPF_OPTS is implemented as a mix of field declaration and memset
+ assignment. This makes it neither variable declaration nor purely
statements, which is a problem, because you can't mix it with either
other variable declarations nor other function statements, because C90
compiler mode emits warning on mixing all that together.

This patch changes LIBBPF_OPTS into a strictly declaration of variable
and solves this problem, as can be seen in case of bpftool, which
previously would emit compiler warning, if done this way (LIBBPF_OPTS as
part of function variables declaration block).

This patch also renames LIBBPF_OPTS into DECLARE_LIBBPF_OPTS to follow
kernel convention for similar macros more closely.

v1->v2:
- rename LIBBPF_OPTS into DECLARE_LIBBPF_OPTS (Jakub Sitnicki).

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20191022172100.3281465-1-andriin@fb.com
parent e13a2fe6

tools/bpf/bpftool/prog.c

+4 −4
Original line number Diff line number Diff line
@@ -1091,8 +1091,11 @@ free_data_in: 


static int load_with_options(int argc, char **argv, bool first_prog_only)

{

	struct bpf_object_load_attr load_attr = { 0 };

	enum bpf_prog_type common_prog_type = BPF_PROG_TYPE_UNSPEC;

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts,

		.relaxed_maps = relaxed_maps,

	);

	struct bpf_object_load_attr load_attr = { 0 };

	enum bpf_attach_type expected_attach_type;

	struct map_replace *map_replace = NULL;

	struct bpf_program *prog = NULL, *pos;
@@ -1106,9 +1109,6 @@ static int load_with_options(int argc, char **argv, bool first_prog_only) 
	const char *file;

	int idx, err;



	LIBBPF_OPTS(bpf_object_open_opts, open_opts,

		.relaxed_maps = relaxed_maps,

	);



	if (!REQ_ARGS(2))

		return -1;

tools/lib/bpf/libbpf.c

+2 −2
Original line number Diff line number Diff line
@@ -3678,7 +3678,7 @@ out: 
static struct bpf_object *

__bpf_object__open_xattr(struct bpf_object_open_attr *attr, int flags)

{

	LIBBPF_OPTS(bpf_object_open_opts, opts,

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,

		.relaxed_maps = flags & MAPS_RELAX_COMPAT,

	);
@@ -3730,7 +3730,7 @@ struct bpf_object * 
bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,

			const char *name)

{

	LIBBPF_OPTS(bpf_object_open_opts, opts,

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,

		.object_name = name,

		/* wrong default, but backwards-compatible */

		.relaxed_maps = true,

tools/lib/bpf/libbpf.h

+12 −7
Original line number Diff line number Diff line
@@ -75,14 +75,19 @@ struct bpf_object_open_attr { 
 * 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.

 *

 * Macro declares opts struct of given type and name, zero-initializes,

 * including any extra padding, it with memset() and then assigns initial

 * values provided by users in struct initializer-syntax as varargs.

 */

#define LIBBPF_OPTS(TYPE, NAME, ...)					    \

	struct TYPE NAME;						    \

#define DECLARE_LIBBPF_OPTS(TYPE, NAME, ...)				    \

	struct TYPE NAME = ({ 						    \

		memset(&NAME, 0, sizeof(struct TYPE));			    \

	NAME = (struct TYPE) {						    \

		(struct TYPE) {						    \

			.sz = sizeof(struct TYPE),			    \

			__VA_ARGS__					    \

	}

		};							    \

	})



struct bpf_object_open_opts {

	/* size of this struct, for forward/backward compatiblity */

tools/testing/selftests/bpf/prog_tests/attach_probe.c

+1 −1
Original line number Diff line number Diff line
@@ -50,7 +50,7 @@ void test_attach_probe(void) 
	const int kprobe_idx = 0, kretprobe_idx = 1;

	const int uprobe_idx = 2, uretprobe_idx = 3;

	const char *obj_name = "attach_probe";

	LIBBPF_OPTS(bpf_object_open_opts, open_opts,

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts,

		.object_name = obj_name,

		.relaxed_maps = true,

	);

tools/testing/selftests/bpf/prog_tests/core_reloc.c

+1 −1
Original line number Diff line number Diff line
@@ -377,7 +377,7 @@ void test_core_reloc(void) 
		if (!test__start_subtest(test_case->case_name))

			continue;



		LIBBPF_OPTS(bpf_object_open_opts, opts,

		DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,

			.relaxed_core_relocs = test_case->relaxed_core_relocs,

		);

CRA Git | Maintained and supported by SUSTech CRA and CCSE