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 <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  */
  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)(sizeof(filter)/sizeof(filter[0])),
  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 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
  97 cleanup:
  98         bpf_link__destroy(link);
  99         bpf_object__close(obj);
 100         return 0;
 101 }