LXR linux/samples/bpf/tracex5

   1// SPDX-License-Identifier: GPL-2.0
   2#include <stdio.h>
   3#include <stdlib.h>
   4#include <unistd.h>
   5#include <linux/filter.h>
   6#include <linux/seccomp.h>
   7#include <sys/prctl.h>
   8#include <bpf/bpf.h>
   9#include <bpf/libbpf.h>
  10#include <sys/resource.h>
  11#include "trace_helpers.h"
  12
  13#ifdef __mips__
  14#define MAX_ENTRIES  6000 /* MIPS n64 syscalls start at 5000 */
  15#else
  16#define MAX_ENTRIES  1024
  17#endif
  18
  19/* install fake seccomp program to enable seccomp code path inside the kernel,
  20 * so that our kprobe attached to seccomp_phase1() can be triggered
  21 */
  22static void install_accept_all_seccomp(void)
  23{
  24        struct sock_filter filter[] = {
  25                BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
  26        };
  27        struct sock_fprog prog = {
  28                .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
  29                .filter = filter,
  30        };
  31        if (prctl(PR_SET_SECCOMP, 2, &prog))
  32                perror("prctl");
  33}
  34
  35int main(int ac, char **argv)
  36{
  37        struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
  38        struct bpf_link *link = NULL;
  39        struct bpf_program *prog;
  40        struct bpf_object *obj;
  41        int key, fd, progs_fd;
  42        char filename[256];
  43        const char *title;
  44        FILE *f;
  45
  46        setrlimit(RLIMIT_MEMLOCK, &r);
  47
  48        snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  49        obj = bpf_object__open_file(filename, NULL);
  50        if (libbpf_get_error(obj)) {
  51                fprintf(stderr, "ERROR: opening BPF object file failed\n");
  52                return 0;
  53        }
  54
  55        prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
  56        if (!prog) {
  57                printf("finding a prog in obj file failed\n");
  58                goto cleanup;
  59        }
  60
  61        /* load BPF program */
  62        if (bpf_object__load(obj)) {
  63                fprintf(stderr, "ERROR: loading BPF object file failed\n");
  64                goto cleanup;
  65        }
  66
  67        link = bpf_program__attach(prog);
  68        if (libbpf_get_error(link)) {
  69                fprintf(stderr, "ERROR: bpf_program__attach failed\n");
  70                link = NULL;
  71                goto cleanup;
  72        }
  73
  74        progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
  75        if (progs_fd < 0) {
  76                fprintf(stderr, "ERROR: finding a map in obj file failed\n");
  77                goto cleanup;
  78        }
  79
  80        bpf_object__for_each_program(prog, obj) {
  81                title = bpf_program__title(prog, false);
  82                /* register only syscalls to PROG_ARRAY */
  83                if (sscanf(title, "kprobe/%d", &key) != 1)
  84                        continue;
  85
  86                fd = bpf_program__fd(prog);
  87                bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
  88        }
  89
  90        install_accept_all_seccomp();
  91
  92        f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
  93        (void) f;
  94
  95        read_trace_pipe();
  96
  97cleanup:
  98        bpf_link__destroy(link);
  99        bpf_object__close(obj);
 100        return 0;
 101}
 102