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 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
  94cleanup:
  95        bpf_link__destroy(link);
  96        bpf_object__close(obj);
  97        return 0;
  98}
  99