samples/bpf/tracex5_user.c

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