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 
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")
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