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 #include "bpf_util.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  */
  22 static 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)ARRAY_SIZE(filter),
  29                 .filter = filter,
  30         };
  31         if (prctl(PR_SET_SECCOMP, 2, &prog))
  32                 perror("prctl");
  33 }
  34
  35 int main(int ac, char **argv)
  36 {
  37         struct bpf_link *link = NULL;
  38         struct bpf_program *prog;
  39         struct bpf_object *obj;
  40         int key, fd, progs_fd;
  41         const char *section;
  42         char filename[256];
  43         FILE *f;
  44
  45         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
  46         obj = bpf_object__open_file(filename, NULL);
  47         if (libbpf_get_error(obj)) {
  48                 fprintf(stderr, "ERROR: opening BPF object file failed\n");
  49                 return 0;
  50         }
  51
  52         prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
  53         if (!prog) {
  54                 printf("finding a prog in obj file failed\n");
  55                 goto cleanup;
  56         }
  57
  58         /* load BPF program */
  59         if (bpf_object__load(obj)) {
  60                 fprintf(stderr, "ERROR: loading BPF object file failed\n");
  61                 goto cleanup;
  62         }
  63
  64         link = bpf_program__attach(prog);
  65         if (libbpf_get_error(link)) {
  66                 fprintf(stderr, "ERROR: bpf_program__attach failed\n");
  67                 link = NULL;
  68                 goto cleanup;
  69         }
  70
  71         progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
  72         if (progs_fd < 0) {
  73                 fprintf(stderr, "ERROR: finding a map in obj file failed\n");
  74                 goto cleanup;
  75         }
  76
  77         bpf_object__for_each_program(prog, obj) {
  78                 section = bpf_program__section_name(prog);
  79                 /* register only syscalls to PROG_ARRAY */
  80                 if (sscanf(section, "kprobe/%d", &key) != 1)
  81                         continue;
  82
  83                 fd = bpf_program__fd(prog);
  84                 bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
  85         }
  86
  87         install_accept_all_seccomp();
  88
  89         f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
  90         (void) f;
  91
  92         read_trace_pipe();
  93
  94 cleanup:
  95         bpf_link__destroy(link);
  96         bpf_object__close(obj);
  97         return 0;
  98 }