Commit 3ec85602 authored by Andrii Nakryiko's avatar Andrii Nakryiko
Browse files

Merge branch 'libbpf-fix-reuse-of-devmap' 

Yureka Lilian says:

====================
libbpf: fix reuse of DEVMAP

changes in v3:

- instead of setting BPF_F_RDONLY_PROG on both sides, just
  clear BPF_F_RDONLY_PROG in map_info.map_flags as suggested
  by Andrii Nakryiko

- in the test, use ASSERT_* instead of CHECK
- shorten the test by using open_and_load from the skel
- in the test, drop NULL check before unloading/destroying bpf objs

- start the commit messages with "libbpf" and "selftests/bpf"
  respectively instead of just "bpf"

changes in v2:

- preserve compatibility with older kernels
- add a basic selftest covering the re-use of DEVMAP maps
====================

Link: https://patch.msgid.link/20250814180113.1245565-2-yuka@yuka.dev


Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
parents abdaf49b 7f8fa9d3

tools/lib/bpf/libbpf.c

+10 −0
Original line number Diff line number Diff line
@@ -5093,6 +5093,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd) 
		return false;

	}



	/*

	 * bpf_get_map_info_by_fd() for DEVMAP will always return flags with

	 * BPF_F_RDONLY_PROG set, but it generally is not set at map creation time.

	 * Thus, ignore the BPF_F_RDONLY_PROG flag in the flags returned from

	 * bpf_get_map_info_by_fd() when checking for compatibility with an

	 * existing DEVMAP.

	 */

	if (map->def.type == BPF_MAP_TYPE_DEVMAP || map->def.type == BPF_MAP_TYPE_DEVMAP_HASH)

		map_info.map_flags &= ~BPF_F_RDONLY_PROG;



	return (map_info.type == map->def.type &&

		map_info.key_size == map->def.key_size &&

		map_info.value_size == map->def.value_size &&

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

0 → 100644
+50 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <sys/types.h>

#include <sys/stat.h>

#include <unistd.h>

#include <test_progs.h>





#include "test_pinning_devmap.skel.h"



void test_pinning_devmap_reuse(void)

{

	const char *pinpath1 = "/sys/fs/bpf/pinmap1";

	const char *pinpath2 = "/sys/fs/bpf/pinmap2";

	struct test_pinning_devmap *skel1 = NULL, *skel2 = NULL;

	int err;

	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);



	/* load the object a first time */

	skel1 = test_pinning_devmap__open_and_load();

	if (!ASSERT_OK_PTR(skel1, "skel_load1"))

		goto out;



	/* load the object a second time, re-using the pinned map */

	skel2 = test_pinning_devmap__open_and_load();

	if (!ASSERT_OK_PTR(skel2, "skel_load2"))

		goto out;



	/* we can close the reference safely without

	 * the map's refcount falling to 0

	 */

	test_pinning_devmap__destroy(skel1);

	skel1 = NULL;



	/* now, swap the pins */

	err = renameat2(0, pinpath1, 0, pinpath2, RENAME_EXCHANGE);

	if (!ASSERT_OK(err, "swap pins"))

		goto out;



	/* load the object again, this time the re-use should fail */

	skel1 = test_pinning_devmap__open_and_load();

	if (!ASSERT_ERR_PTR(skel1, "skel_load3"))

		goto out;



out:

	unlink(pinpath1);

	unlink(pinpath2);

	test_pinning_devmap__destroy(skel1);

	test_pinning_devmap__destroy(skel2);

}

tools/testing/selftests/bpf/progs/test_pinning_devmap.c

0 → 100644
+20 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>



struct {

	__uint(type, BPF_MAP_TYPE_DEVMAP);

	__uint(max_entries, 1);

	__type(key, __u32);

	__type(value, __u32);

	__uint(pinning, LIBBPF_PIN_BY_NAME);

} pinmap1 SEC(".maps");



struct {

	__uint(type, BPF_MAP_TYPE_DEVMAP);

	__uint(max_entries, 2);

	__type(key, __u32);

	__type(value, __u32);

	__uint(pinning, LIBBPF_PIN_BY_NAME);

} pinmap2 SEC(".maps");