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#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libelf.h>
#include <gelf.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include "libbpf.h"
#include "bpf_helpers.h"
#include "bpf_load.h"
static char license[128];
static bool processed_sec[128];
int map_fd[MAX_MAPS];
int prog_fd[MAX_PROGS];
int prog_cnt;
static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
int fd;
bool is_socket = strncmp(event, "socket", 6) == 0;
if (!is_socket)
/* tracing events tbd */
return -1;
fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
prog, size, license);
if (fd < 0) {
printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
return -1;
}
prog_fd[prog_cnt++] = fd;
return 0;
}
static int load_maps(struct bpf_map_def *maps, int len)
{
int i;
for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {
map_fd[i] = bpf_create_map(maps[i].type,
maps[i].key_size,
maps[i].value_size,
maps[i].max_entries);
if (map_fd[i] < 0)
return 1;
}
return 0;
}
static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
GElf_Shdr *shdr, Elf_Data **data)
{
Elf_Scn *scn;
scn = elf_getscn(elf, i);
if (!scn)
return 1;
if (gelf_getshdr(scn, shdr) != shdr)
return 2;
*shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
if (!*shname || !shdr->sh_size)
return 3;
*data = elf_getdata(scn, 0);
if (!*data || elf_getdata(scn, *data) != NULL)
return 4;
return 0;
}
static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
GElf_Shdr *shdr, struct bpf_insn *insn)
{
int i, nrels;
nrels = shdr->sh_size / shdr->sh_entsize;
for (i = 0; i < nrels; i++) {
GElf_Sym sym;
GElf_Rel rel;
unsigned int insn_idx;
gelf_getrel(data, i, &rel);
insn_idx = rel.r_offset / sizeof(struct bpf_insn);
gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
printf("invalid relo for insn[%d].code 0x%x\n",
insn_idx, insn[insn_idx].code);
return 1;
}
insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
}
return 0;
}
int load_bpf_file(char *path)
{
int fd, i;
Elf *elf;
GElf_Ehdr ehdr;
GElf_Shdr shdr, shdr_prog;
Elf_Data *data, *data_prog, *symbols = NULL;
char *shname, *shname_prog;
if (elf_version(EV_CURRENT) == EV_NONE)
return 1;
fd = open(path, O_RDONLY, 0);
if (fd < 0)
return 1;
elf = elf_begin(fd, ELF_C_READ, NULL);
if (!elf)
return 1;
if (gelf_getehdr(elf, &ehdr) != &ehdr)
return 1;
/* scan over all elf sections to get license and map info */
for (i = 1; i < ehdr.e_shnum; i++) {
if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
continue;
if (0) /* helpful for llvm debugging */
printf("section %d:%s data %p size %zd link %d flags %d\n",
i, shname, data->d_buf, data->d_size,
shdr.sh_link, (int) shdr.sh_flags);
if (strcmp(shname, "license") == 0) {
processed_sec[i] = true;
memcpy(license, data->d_buf, data->d_size);
} else if (strcmp(shname, "maps") == 0) {
processed_sec[i] = true;
if (load_maps(data->d_buf, data->d_size))
return 1;
} else if (shdr.sh_type == SHT_SYMTAB) {
symbols = data;
}
}
/* load programs that need map fixup (relocations) */
for (i = 1; i < ehdr.e_shnum; i++) {
if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
continue;
if (shdr.sh_type == SHT_REL) {
struct bpf_insn *insns;
if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
&shdr_prog, &data_prog))
continue;
insns = (struct bpf_insn *) data_prog->d_buf;
processed_sec[shdr.sh_info] = true;
processed_sec[i] = true;
if (parse_relo_and_apply(data, symbols, &shdr, insns))
continue;
if (memcmp(shname_prog, "events/", 7) == 0 ||
memcmp(shname_prog, "socket", 6) == 0)
load_and_attach(shname_prog, insns, data_prog->d_size);
}
}
/* load programs that don't use maps */
for (i = 1; i < ehdr.e_shnum; i++) {
if (processed_sec[i])
continue;
if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
continue;
if (memcmp(shname, "events/", 7) == 0 ||
memcmp(shname, "socket", 6) == 0)
load_and_attach(shname, data->d_buf, data->d_size);
}
close(fd);
return 0;
}
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