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 char _license[] SEC("license") = "GPL";
8
9 struct {
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
16 SEC("?raw_tp")
17 __failure __msg("R8 invalid mem access 'map_value_or_null")
jeq_infer_not_null_ptr_to_btfid(void * ctx)18 int 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