1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3 #include <linux/stddef.h>
4 #include <linux/bpf.h>
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include <../../../tools/include/linux/filter.h>
8 #include <linux/btf.h>
9
10 char _license[] SEC("license") = "GPL";
11
12 struct args {
13 __u64 log_buf;
14 __u32 log_size;
15 int max_entries;
16 int map_fd;
17 int prog_fd;
18 int btf_fd;
19 };
20
21 #define BTF_INFO_ENC(kind, kind_flag, vlen) \
22 ((!!(kind_flag) << 31) | ((kind) << 24) | ((vlen) & BTF_MAX_VLEN))
23 #define BTF_TYPE_ENC(name, info, size_or_type) (name), (info), (size_or_type)
24 #define BTF_INT_ENC(encoding, bits_offset, nr_bits) \
25 ((encoding) << 24 | (bits_offset) << 16 | (nr_bits))
26 #define BTF_TYPE_INT_ENC(name, encoding, bits_offset, bits, sz) \
27 BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_INT, 0, 0), sz), \
28 BTF_INT_ENC(encoding, bits_offset, bits)
29
btf_load(void)30 static int btf_load(void)
31 {
32 struct btf_blob {
33 struct btf_header btf_hdr;
34 __u32 types[8];
35 __u32 str;
36 } raw_btf = {
37 .btf_hdr = {
38 .magic = BTF_MAGIC,
39 .version = BTF_VERSION,
40 .hdr_len = sizeof(struct btf_header),
41 .type_len = sizeof(__u32) * 8,
42 .str_off = sizeof(__u32) * 8,
43 .str_len = sizeof(__u32),
44 },
45 .types = {
46 /* long */
47 BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8), /* [1] */
48 /* unsigned long */
49 BTF_TYPE_INT_ENC(0, 0, 0, 64, 8), /* [2] */
50 },
51 };
52 static union bpf_attr btf_load_attr = {
53 .btf_size = sizeof(raw_btf),
54 };
55
56 btf_load_attr.btf = (long)&raw_btf;
57 return bpf_sys_bpf(BPF_BTF_LOAD, &btf_load_attr, sizeof(btf_load_attr));
58 }
59
60 SEC("syscall")
bpf_prog(struct args * ctx)61 int bpf_prog(struct args *ctx)
62 {
63 static char license[] = "GPL";
64 static struct bpf_insn insns[] = {
65 BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
66 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
67 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
68 BPF_LD_MAP_FD(BPF_REG_1, 0),
69 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
70 BPF_MOV64_IMM(BPF_REG_0, 0),
71 BPF_EXIT_INSN(),
72 };
73 static union bpf_attr map_create_attr = {
74 .map_type = BPF_MAP_TYPE_HASH,
75 .key_size = 8,
76 .value_size = 8,
77 .btf_key_type_id = 1,
78 .btf_value_type_id = 2,
79 };
80 static union bpf_attr map_update_attr = { .map_fd = 1, };
81 static __u64 key = 12;
82 static __u64 value = 34;
83 static union bpf_attr prog_load_attr = {
84 .prog_type = BPF_PROG_TYPE_XDP,
85 .insn_cnt = sizeof(insns) / sizeof(insns[0]),
86 };
87 int ret;
88
89 ret = btf_load();
90 if (ret <= 0)
91 return ret;
92
93 ctx->btf_fd = ret;
94 map_create_attr.max_entries = ctx->max_entries;
95 map_create_attr.btf_fd = ret;
96
97 prog_load_attr.license = (long) license;
98 prog_load_attr.insns = (long) insns;
99 prog_load_attr.log_buf = ctx->log_buf;
100 prog_load_attr.log_size = ctx->log_size;
101 prog_load_attr.log_level = 1;
102
103 ret = bpf_sys_bpf(BPF_MAP_CREATE, &map_create_attr, sizeof(map_create_attr));
104 if (ret <= 0)
105 return ret;
106 ctx->map_fd = ret;
107 insns[3].imm = ret;
108
109 map_update_attr.map_fd = ret;
110 map_update_attr.key = (long) &key;
111 map_update_attr.value = (long) &value;
112 ret = bpf_sys_bpf(BPF_MAP_UPDATE_ELEM, &map_update_attr, sizeof(map_update_attr));
113 if (ret < 0)
114 return ret;
115
116 ret = bpf_sys_bpf(BPF_PROG_LOAD, &prog_load_attr, sizeof(prog_load_attr));
117 if (ret <= 0)
118 return ret;
119 ctx->prog_fd = ret;
120 return 1;
121 }
122