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libbpf: Sync progs autoload with maps autocreate for struct_ops maps

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Automatically select which struct_ops programs to load depending on
which struct_ops maps are selected for automatic creation.
E.g. for the BPF code below:

    SEC("struct_ops/test_1") int BPF_PROG(foo) { ... }
    SEC("struct_ops/test_2") int BPF_PROG(bar) { ... }

    SEC(".struct_ops.link")
    struct test_ops___v1 A = {
        .foo = (void *)foo
    };

    SEC(".struct_ops.link")
    struct test_ops___v2 B = {
        .foo = (void *)foo,
        .bar = (void *)bar,
    };

And the following libbpf API calls:

    bpf_map__set_autocreate(skel->maps.A, true);
    bpf_map__set_autocreate(skel->maps.B, false);

The autoload would be enabled for program 'foo' and disabled for
program 'bar'.

During load, for each struct_ops program P, referenced from some
struct_ops map M:
- set P.autoload = true if M.autocreate is true for some M;
- set P.autoload = false if M.autocreate is false for all M;
- don't change P.autoload, if P is not referenced from any map.

Do this after bpf_object__init_kern_struct_ops_maps()
to make sure that shadow vars assignment is done.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-9-eddyz87@gmail.com
This commit is contained in:
Eduard Zingerman 2024-03-06 12:45:22 +02:00 committed by Andrii Nakryiko
parent 1863acccdf
commit fe9d049c3d
1 changed files with 43 additions and 0 deletions
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43
tools/lib/bpf/libbpf.c
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@ -1031,6 +1031,48 @@ static bool is_valid_st_ops_program(struct bpf_object *obj,
return false;
}
/* For each struct_ops program P, referenced from some struct_ops map M,
* enable P.autoload if there are Ms for which M.autocreate is true,
* disable P.autoload if for all Ms M.autocreate is false.
* Don't change P.autoload for programs that are not referenced from any maps.
*/
static int bpf_object_adjust_struct_ops_autoload(struct bpf_object *obj)
{
struct bpf_program *prog, *slot_prog;
struct bpf_map *map;
int i, j, k, vlen;
for (i = 0; i < obj->nr_programs; ++i) {
int should_load = false;
int use_cnt = 0;
prog = &obj->programs[i];
if (prog->type != BPF_PROG_TYPE_STRUCT_OPS)
continue;
for (j = 0; j < obj->nr_maps; ++j) {
map = &obj->maps[j];
if (!bpf_map__is_struct_ops(map))
continue;
vlen = btf_vlen(map->st_ops->type);
for (k = 0; k < vlen; ++k) {
slot_prog = map->st_ops->progs[k];
if (prog != slot_prog)
continue;
use_cnt++;
if (map->autocreate)
should_load = true;
}
}
if (use_cnt)
prog->autoload = should_load;
}
return 0;
}
/* Init the map's fields that depend on kern_btf */
static int bpf_map__init_kern_struct_ops(struct bpf_map *map)
{
@ -8175,6 +8217,7 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_maps(obj);
err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
err = err ? : bpf_object_adjust_struct_ops_autoload(obj);
err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : target_btf_path);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__create_maps(obj);