1// SPDX-License-Identifier: GPL-2.0
2
3#include "vmlinux.h"
4#include <bpf/bpf_helpers.h>
5#include "bpf_misc.h"
6
7#ifndef __clang__
8#pragma GCC diagnostic ignored "-Warray-bounds"
9#endif
10
11char _license[] SEC("license") = "GPL";
12
13struct {
14	__uint(type, BPF_MAP_TYPE_HASH);
15	__uint(max_entries, 1);
16	__type(key, u64);
17	__type(value, u64);
18} m_hash SEC(".maps");
19
20SEC("?raw_tp")
21__failure __msg("R8 invalid mem access 'map_value_or_null")
22int jeq_infer_not_null_ptr_to_btfid(void *ctx)
23{
24	struct bpf_map *map = (struct bpf_map *)&m_hash;
25	struct bpf_map *inner_map = map->inner_map_meta;
26	u64 key = 0, ret = 0, *val;
27
28	val = bpf_map_lookup_elem(map, &key);
29	/* Do not mark ptr as non-null if one of them is
30	 * PTR_TO_BTF_ID (R9), reject because of invalid
31	 * access to map value (R8).
32	 *
33	 * Here, we need to inline those insns to access
34	 * R8 directly, since compiler may use other reg
35	 * once it figures out val==inner_map.
36	 */
37	asm volatile("r8 = %[val];\n"
38		     "r9 = %[inner_map];\n"
39		     "if r8 != r9 goto +1;\n"
40		     "%[ret] = *(u64 *)(r8 +0);\n"
41		     : [ret] "+r"(ret)
42		     : [inner_map] "r"(inner_map), [val] "r"(val)
43		     : "r8", "r9");
44
45	return ret;
46}
47