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linux/samples/bpf/bpf_load.c

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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 <stdlib.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/perf_event.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <poll.h>
#include <ctype.h>
#include "libbpf.h"
#include "bpf_load.h"
#include "perf-sys.h"
#define DEBUGFS "/sys/kernel/debug/tracing/"
static char license[128];
static int kern_version;
static bool processed_sec[128];
char bpf_log_buf[BPF_LOG_BUF_SIZE];
int map_fd[MAX_MAPS];
int prog_fd[MAX_PROGS];
int event_fd[MAX_PROGS];
int prog_cnt;
int prog_array_fd = -1;
struct bpf_map_def {
unsigned int type;
unsigned int key_size;
unsigned int value_size;
unsigned int max_entries;
unsigned int map_flags;
};
static int populate_prog_array(const char *event, int prog_fd)
{
int ind = atoi(event), err;
err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
if (err < 0) {
printf("failed to store prog_fd in prog_array\n");
return -1;
}
return 0;
}
static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
bool is_socket = strncmp(event, "socket", 6) == 0;
bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
bool is_xdp = strncmp(event, "xdp", 3) == 0;
bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0;
bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
size_t insns_cnt = size / sizeof(struct bpf_insn);
enum bpf_prog_type prog_type;
char buf[256];
int fd, efd, err, id;
struct perf_event_attr attr = {};
attr.type = PERF_TYPE_TRACEPOINT;
attr.sample_type = PERF_SAMPLE_RAW;
attr.sample_period = 1;
attr.wakeup_events = 1;
if (is_socket) {
prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
} else if (is_kprobe || is_kretprobe) {
prog_type = BPF_PROG_TYPE_KPROBE;
} else if (is_tracepoint) {
prog_type = BPF_PROG_TYPE_TRACEPOINT;
} else if (is_xdp) {
prog_type = BPF_PROG_TYPE_XDP;
} else if (is_perf_event) {
prog_type = BPF_PROG_TYPE_PERF_EVENT;
} else if (is_cgroup_skb) {
prog_type = BPF_PROG_TYPE_CGROUP_SKB;
} else if (is_cgroup_sk) {
prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
} else {
printf("Unknown event '%s'\n", event);
return -1;
}
fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version,
bpf_log_buf, BPF_LOG_BUF_SIZE);
if (fd < 0) {
printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf);
return -1;
}
prog_fd[prog_cnt++] = fd;
if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
return 0;
if (is_socket) {
event += 6;
if (*event != '/')
return 0;
event++;
if (!isdigit(*event)) {
printf("invalid prog number\n");
return -1;
}
return populate_prog_array(event, fd);
}
if (is_kprobe || is_kretprobe) {
if (is_kprobe)
event += 7;
else
event += 10;
if (*event == 0) {
printf("event name cannot be empty\n");
return -1;
}
if (isdigit(*event))
return populate_prog_array(event, fd);
snprintf(buf, sizeof(buf),
"echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
is_kprobe ? 'p' : 'r', event, event);
err = system(buf);
if (err < 0) {
printf("failed to create kprobe '%s' error '%s'\n",
event, strerror(errno));
return -1;
}
strcpy(buf, DEBUGFS);
strcat(buf, "events/kprobes/");
strcat(buf, event);
strcat(buf, "/id");
} else if (is_tracepoint) {
event += 11;
if (*event == 0) {
printf("event name cannot be empty\n");
return -1;
}
strcpy(buf, DEBUGFS);
strcat(buf, "events/");
strcat(buf, event);
strcat(buf, "/id");
}
efd = open(buf, O_RDONLY, 0);
if (efd < 0) {
printf("failed to open event %s\n", event);
return -1;
}
err = read(efd, buf, sizeof(buf));
if (err < 0 || err >= sizeof(buf)) {
printf("read from '%s' failed '%s'\n", event, strerror(errno));
return -1;
}
close(efd);
buf[err] = 0;
id = atoi(buf);
attr.config = id;
efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
if (efd < 0) {
printf("event %d fd %d err %s\n", id, efd, strerror(errno));
return -1;
}
event_fd[prog_cnt - 1] = efd;
ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
ioctl(efd, PERF_EVENT_IOC_SET_BPF, 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,
maps[i].map_flags);
if (map_fd[i] < 0) {
printf("failed to create a map: %d %s\n",
errno, strerror(errno));
return 1;
}
if (maps[i].type == BPF_MAP_TYPE_PROG_ARRAY)
prog_array_fd = map_fd[i];
}
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;
/* clear all kprobes */
i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
/* 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, "version") == 0) {
processed_sec[i] = true;
if (data->d_size != sizeof(int)) {
printf("invalid size of version section %zd\n",
data->d_size);
return 1;
}
memcpy(&kern_version, data->d_buf, sizeof(int));
} 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;
if (shdr_prog.sh_type != SHT_PROGBITS ||
!(shdr_prog.sh_flags & SHF_EXECINSTR))
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, "kprobe/", 7) == 0 ||
memcmp(shname_prog, "kretprobe/", 10) == 0 ||
memcmp(shname_prog, "tracepoint/", 11) == 0 ||
memcmp(shname_prog, "xdp", 3) == 0 ||
memcmp(shname_prog, "perf_event", 10) == 0 ||
memcmp(shname_prog, "socket", 6) == 0 ||
memcmp(shname_prog, "cgroup/", 7) == 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, "kprobe/", 7) == 0 ||
memcmp(shname, "kretprobe/", 10) == 0 ||
memcmp(shname, "tracepoint/", 11) == 0 ||
memcmp(shname, "xdp", 3) == 0 ||
memcmp(shname, "perf_event", 10) == 0 ||
memcmp(shname, "socket", 6) == 0 ||
memcmp(shname, "cgroup/", 7) == 0)
load_and_attach(shname, data->d_buf, data->d_size);
}
close(fd);
return 0;
}
void read_trace_pipe(void)
{
int trace_fd;
trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
if (trace_fd < 0)
return;
while (1) {
static char buf[4096];
ssize_t sz;
sz = read(trace_fd, buf, sizeof(buf));
if (sz > 0) {
buf[sz] = 0;
puts(buf);
}
}
}
#define MAX_SYMS 300000
static struct ksym syms[MAX_SYMS];
static int sym_cnt;
static int ksym_cmp(const void *p1, const void *p2)
{
return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
}
int load_kallsyms(void)
{
FILE *f = fopen("/proc/kallsyms", "r");
char func[256], buf[256];
char symbol;
void *addr;
int i = 0;
if (!f)
return -ENOENT;
while (!feof(f)) {
if (!fgets(buf, sizeof(buf), f))
break;
if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
break;
if (!addr)
continue;
syms[i].addr = (long) addr;
syms[i].name = strdup(func);
i++;
}
sym_cnt = i;
qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
return 0;
}
struct ksym *ksym_search(long key)
{
int start = 0, end = sym_cnt;
int result;
while (start < end) {
size_t mid = start + (end - start) / 2;
result = key - syms[mid].addr;
if (result < 0)
end = mid;
else if (result > 0)
start = mid + 1;
else
return &syms[mid];
}
if (start >= 1 && syms[start - 1].addr < key &&
key < syms[start].addr)
/* valid ksym */
return &syms[start - 1];
/* out of range. return _stext */
return &syms[0];
}
int set_link_xdp_fd(int ifindex, int fd)
{
struct sockaddr_nl sa;
int sock, seq = 0, len, ret = -1;
char buf[4096];
struct nlattr *nla, *nla_xdp;
struct {
struct nlmsghdr nh;
struct ifinfomsg ifinfo;
char attrbuf[64];
} req;
struct nlmsghdr *nh;
struct nlmsgerr *err;
memset(&sa, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
if (sock < 0) {
printf("open netlink socket: %s\n", strerror(errno));
return -1;
}
if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
printf("bind to netlink: %s\n", strerror(errno));
goto cleanup;
}
memset(&req, 0, sizeof(req));
req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
req.nh.nlmsg_type = RTM_SETLINK;
req.nh.nlmsg_pid = 0;
req.nh.nlmsg_seq = ++seq;
req.ifinfo.ifi_family = AF_UNSPEC;
req.ifinfo.ifi_index = ifindex;
nla = (struct nlattr *)(((char *)&req)
+ NLMSG_ALIGN(req.nh.nlmsg_len));
nla->nla_type = NLA_F_NESTED | 43/*IFLA_XDP*/;
nla_xdp = (struct nlattr *)((char *)nla + NLA_HDRLEN);
nla_xdp->nla_type = 1/*IFLA_XDP_FD*/;
nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
nla->nla_len = NLA_HDRLEN + nla_xdp->nla_len;
req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
printf("send to netlink: %s\n", strerror(errno));
goto cleanup;
}
len = recv(sock, buf, sizeof(buf), 0);
if (len < 0) {
printf("recv from netlink: %s\n", strerror(errno));
goto cleanup;
}
for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
nh = NLMSG_NEXT(nh, len)) {
if (nh->nlmsg_pid != getpid()) {
printf("Wrong pid %d, expected %d\n",
nh->nlmsg_pid, getpid());
goto cleanup;
}
if (nh->nlmsg_seq != seq) {
printf("Wrong seq %d, expected %d\n",
nh->nlmsg_seq, seq);
goto cleanup;
}
switch (nh->nlmsg_type) {
case NLMSG_ERROR:
err = (struct nlmsgerr *)NLMSG_DATA(nh);
if (!err->error)
continue;
printf("nlmsg error %s\n", strerror(-err->error));
goto cleanup;
case NLMSG_DONE:
break;
}
}
ret = 0;
cleanup:
close(sock);
return ret;
}
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