// SPDX-License-Identifier: GPL-2.0

#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"

#ifndef __clang__
#pragma GCC diagnostic ignored "-Warray-bounds"
#endif

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

struct {
        __uint(type, BPF_MAP_TYPE_HASH);
        __uint(max_entries, 1);
        __type(key, u64);
        __type(value, u64);
} m_hash SEC(".maps");

SEC("?raw_tp")
__failure __msg("R8 invalid mem access 'map_value_or_null")
int jeq_infer_not_null_ptr_to_btfid(void *ctx)
{
        struct bpf_map *map = (struct bpf_map *)&m_hash;
        struct bpf_map *inner_map = map->inner_map_meta;
        u64 key = 0, ret = 0, *val;

        val = bpf_map_lookup_elem(map, &key);
        /* Do not mark ptr as non-null if one of them is
         * PTR_TO_BTF_ID (R9), reject because of invalid
         * access to map value (R8).
         *
         * Here, we need to inline those insns to access
         * R8 directly, since compiler may use other reg
         * once it figures out val==inner_map.
         */
        asm volatile("r8 = %[val];\n"
                     "r9 = %[inner_map];\n"
                     "if r8 != r9 goto +1;\n"
                     "%[ret] = *(u64 *)(r8 +0);\n"
                     : [ret] "+r"(ret)
                     : [inner_map] "r"(inner_map), [val] "r"(val)
                     : "r8", "r9");

        return ret;
}