Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#include <stdio.h>
2#include <sys/types.h>
3#include <sys/stat.h>
4#include <fcntl.h>
5#include <libelf.h>
6#include <gelf.h>
7#include <errno.h>
8#include <unistd.h>
9#include <string.h>
10#include <stdbool.h>
11#include <linux/bpf.h>
12#include <linux/filter.h>
13#include "libbpf.h"
14#include "bpf_helpers.h"
15#include "bpf_load.h"
16
17static char license[128];
18static bool processed_sec[128];
19int map_fd[MAX_MAPS];
20int prog_fd[MAX_PROGS];
21int prog_cnt;
22
23static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
24{
25 int fd;
26 bool is_socket = strncmp(event, "socket", 6) == 0;
27
28 if (!is_socket)
29 /* tracing events tbd */
30 return -1;
31
32 fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
33 prog, size, license);
34
35 if (fd < 0) {
36 printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
37 return -1;
38 }
39
40 prog_fd[prog_cnt++] = fd;
41
42 return 0;
43}
44
45static int load_maps(struct bpf_map_def *maps, int len)
46{
47 int i;
48
49 for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {
50
51 map_fd[i] = bpf_create_map(maps[i].type,
52 maps[i].key_size,
53 maps[i].value_size,
54 maps[i].max_entries);
55 if (map_fd[i] < 0)
56 return 1;
57 }
58 return 0;
59}
60
61static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
62 GElf_Shdr *shdr, Elf_Data **data)
63{
64 Elf_Scn *scn;
65
66 scn = elf_getscn(elf, i);
67 if (!scn)
68 return 1;
69
70 if (gelf_getshdr(scn, shdr) != shdr)
71 return 2;
72
73 *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
74 if (!*shname || !shdr->sh_size)
75 return 3;
76
77 *data = elf_getdata(scn, 0);
78 if (!*data || elf_getdata(scn, *data) != NULL)
79 return 4;
80
81 return 0;
82}
83
84static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
85 GElf_Shdr *shdr, struct bpf_insn *insn)
86{
87 int i, nrels;
88
89 nrels = shdr->sh_size / shdr->sh_entsize;
90
91 for (i = 0; i < nrels; i++) {
92 GElf_Sym sym;
93 GElf_Rel rel;
94 unsigned int insn_idx;
95
96 gelf_getrel(data, i, &rel);
97
98 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
99
100 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
101
102 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
103 printf("invalid relo for insn[%d].code 0x%x\n",
104 insn_idx, insn[insn_idx].code);
105 return 1;
106 }
107 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
108 insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
109 }
110
111 return 0;
112}
113
114int load_bpf_file(char *path)
115{
116 int fd, i;
117 Elf *elf;
118 GElf_Ehdr ehdr;
119 GElf_Shdr shdr, shdr_prog;
120 Elf_Data *data, *data_prog, *symbols = NULL;
121 char *shname, *shname_prog;
122
123 if (elf_version(EV_CURRENT) == EV_NONE)
124 return 1;
125
126 fd = open(path, O_RDONLY, 0);
127 if (fd < 0)
128 return 1;
129
130 elf = elf_begin(fd, ELF_C_READ, NULL);
131
132 if (!elf)
133 return 1;
134
135 if (gelf_getehdr(elf, &ehdr) != &ehdr)
136 return 1;
137
138 /* scan over all elf sections to get license and map info */
139 for (i = 1; i < ehdr.e_shnum; i++) {
140
141 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
142 continue;
143
144 if (0) /* helpful for llvm debugging */
145 printf("section %d:%s data %p size %zd link %d flags %d\n",
146 i, shname, data->d_buf, data->d_size,
147 shdr.sh_link, (int) shdr.sh_flags);
148
149 if (strcmp(shname, "license") == 0) {
150 processed_sec[i] = true;
151 memcpy(license, data->d_buf, data->d_size);
152 } else if (strcmp(shname, "maps") == 0) {
153 processed_sec[i] = true;
154 if (load_maps(data->d_buf, data->d_size))
155 return 1;
156 } else if (shdr.sh_type == SHT_SYMTAB) {
157 symbols = data;
158 }
159 }
160
161 /* load programs that need map fixup (relocations) */
162 for (i = 1; i < ehdr.e_shnum; i++) {
163
164 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
165 continue;
166 if (shdr.sh_type == SHT_REL) {
167 struct bpf_insn *insns;
168
169 if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
170 &shdr_prog, &data_prog))
171 continue;
172
173 insns = (struct bpf_insn *) data_prog->d_buf;
174
175 processed_sec[shdr.sh_info] = true;
176 processed_sec[i] = true;
177
178 if (parse_relo_and_apply(data, symbols, &shdr, insns))
179 continue;
180
181 if (memcmp(shname_prog, "events/", 7) == 0 ||
182 memcmp(shname_prog, "socket", 6) == 0)
183 load_and_attach(shname_prog, insns, data_prog->d_size);
184 }
185 }
186
187 /* load programs that don't use maps */
188 for (i = 1; i < ehdr.e_shnum; i++) {
189
190 if (processed_sec[i])
191 continue;
192
193 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
194 continue;
195
196 if (memcmp(shname, "events/", 7) == 0 ||
197 memcmp(shname, "socket", 6) == 0)
198 load_and_attach(shname, data->d_buf, data->d_size);
199 }
200
201 close(fd);
202 return 0;
203}