1// SPDX-License-Identifier: GPL-2.0
2
3#include "vmlinux.h"
4#include <bpf/bpf_helpers.h>
5#include "bpf_misc.h"
6
7char _license[] SEC("license") = "GPL";
8
9struct {
10	__uint(type, BPF_MAP_TYPE_HASH);
11	__uint(max_entries, 1);
12	__type(key, u64);
13	__type(value, u64);
14} m_hash SEC(".maps");
15
16SEC("?raw_tp")
17__failure __msg("R8 invalid mem access 'map_value_or_null")
18int jeq_infer_not_null_ptr_to_btfid(void *ctx)
19{
20	struct bpf_map *map = (struct bpf_map *)&m_hash;
21	struct bpf_map *inner_map = map->inner_map_meta;
22	u64 key = 0, ret = 0, *val;
23
24	val = bpf_map_lookup_elem(map, &key);
25	/* Do not mark ptr as non-null if one of them is
26	 * PTR_TO_BTF_ID (R9), reject because of invalid
27	 * access to map value (R8).
28	 *
29	 * Here, we need to inline those insns to access
30	 * R8 directly, since compiler may use other reg
31	 * once it figures out val==inner_map.
32	 */
33	asm volatile("r8 = %[val];\n"
34		     "r9 = %[inner_map];\n"
35		     "if r8 != r9 goto +1;\n"
36		     "%[ret] = *(u64 *)(r8 +0);\n"
37		     : [ret] "+r"(ret)
38		     : [inner_map] "r"(inner_map), [val] "r"(val)
39		     : "r8", "r9");
40
41	return ret;
42}
43