Commit 23509e92 authored by Martin KaFai Lau's avatar Martin KaFai Lau
Browse files

Merge branch 'Fix elem_size not being set for inner maps' 

Rhys Rustad-Elliott says:

====================

Commit d937bc34 ("bpf: make uniform use of array->elem_size
everywhere in arraymap.c") changed array_map_gen_lookup to use
array->elem_size instead of round_up(map->value_size, 8) as the element
size when generating code to access a value in an array map.

array->elem_size, however, is not set by bpf_map_meta_alloc when
initializing an BPF_MAP_TYPE_ARRAY_OF_MAPS or BPF_MAP_TYPE_HASH_OF_MAPS.
This results in array_map_gen_lookup incorrectly outputting code that
always accesses index 0 in the array (as the index will be calculated
via a multiplication with the element size, which is incorrectly set to
0).

This patchset sets elem_size on the bpf_array object when allocating an
array or hash of maps to fix this and adds a selftest that accesses an
array map nested within a hash of maps at a nonzero index to prevent
regressions.

v1: https://lore.kernel.org/bpf/95b5da7c-ee52-3ecb-0a4e-f6a7a114f269@linux.dev/



Changelog:

v1 -> v2:

Address comments by Martin KaFai Lau:
- Directly use inner_array->elem_size instead of using round_up
- Move selftests to a new patch
- Use ASSERT_* macros instead of CHECK and remove duration
- Remove unnecessary usleep
- Shorten selftest name
====================

Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parents b0fd1852 1022b67b

kernel/bpf/map_in_map.c

+6 −2
Original line number Diff line number Diff line
@@ -69,9 +69,13 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd) 
	/* Misc members not needed in bpf_map_meta_equal() check. */

	inner_map_meta->ops = inner_map->ops;

	if (inner_map->ops == &array_map_ops) {

		struct bpf_array *inner_array_meta =

			container_of(inner_map_meta, struct bpf_array, map);

		struct bpf_array *inner_array = container_of(inner_map, struct bpf_array, map);



		inner_array_meta->index_mask = inner_array->index_mask;

		inner_array_meta->elem_size = inner_array->elem_size;

		inner_map_meta->bypass_spec_v1 = inner_map->bypass_spec_v1;

		container_of(inner_map_meta, struct bpf_array, map)->index_mask =

		     container_of(inner_map, struct bpf_array, map)->index_mask;

	}



	fdput(f);

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

0 → 100644
+31 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only



#include <test_progs.h>



#include "inner_array_lookup.skel.h"



void test_inner_array_lookup(void)

{

	int map1_fd, err;

	int key = 3;

	int val = 1;

	struct inner_array_lookup *skel;



	skel = inner_array_lookup__open_and_load();

	if (!ASSERT_OK_PTR(skel, "open_load_skeleton"))

		return;



	err = inner_array_lookup__attach(skel);

	if (!ASSERT_OK(err, "skeleton_attach"))

		goto cleanup;



	map1_fd = bpf_map__fd(skel->maps.inner_map1);

	bpf_map_update_elem(map1_fd, &key, &val, 0);



	/* Probe should have set the element at index 3 to 2 */

	bpf_map_lookup_elem(map1_fd, &key, &val);

	ASSERT_EQ(val, 2, "value_is_2");



cleanup:

	inner_array_lookup__destroy(skel);

}

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

0 → 100644
+45 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only



#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>



struct inner_map {

	__uint(type, BPF_MAP_TYPE_ARRAY);

	__uint(max_entries, 5);

	__type(key, int);

	__type(value, int);

} inner_map1 SEC(".maps");



struct outer_map {

	__uint(type, BPF_MAP_TYPE_HASH_OF_MAPS);

	__uint(max_entries, 3);

	__type(key, int);

	__array(values, struct inner_map);

} outer_map1 SEC(".maps") = {

	.values = {

		[2] = &inner_map1,

	},

};



SEC("raw_tp/sys_enter")

int handle__sys_enter(void *ctx)

{

	int outer_key = 2, inner_key = 3;

	int *val;

	void *map;



	map = bpf_map_lookup_elem(&outer_map1, &outer_key);

	if (!map)

		return 1;



	val = bpf_map_lookup_elem(map, &inner_key);

	if (!val)

		return 1;



	if (*val == 1)

		*val = 2;



	return 0;

}



char _license[] SEC("license") = "GPL";