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
 10char _license[] SEC("license") = "GPL";
 11
 12struct 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
 30static 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
 60SEC("syscall")
 61int 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}