samples/bpf/tracex5_user.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <stdio.h>
0003 #include <stdlib.h>
0004 #include <unistd.h>
0005 #include <linux/filter.h>
0006 #include <linux/seccomp.h>
0007 #include <sys/prctl.h>
0008 #include <bpf/bpf.h>
0009 #include <bpf/libbpf.h>
0010 #include "trace_helpers.h"
0011 #include "bpf_util.h"
0012
0013 #ifdef __mips__
0014 #define MAX_ENTRIES  6000 /* MIPS n64 syscalls start at 5000 */
0015 #else
0016 #define MAX_ENTRIES  1024
0017 #endif
0018
0019 /* install fake seccomp program to enable seccomp code path inside the kernel,
0020  * so that our kprobe attached to seccomp_phase1() can be triggered
0021  */
0022 static void install_accept_all_seccomp(void)
0023 {
0024     struct sock_filter filter[] = {
0025         BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
0026     };
0027     struct sock_fprog prog = {
0028         .len = (unsigned short)ARRAY_SIZE(filter),
0029         .filter = filter,
0030     };
0031     if (prctl(PR_SET_SECCOMP, 2, &prog))
0032         perror("prctl");
0033 }
0034
0035 int main(int ac, char **argv)
0036 {
0037     struct bpf_link *link = NULL;
0038     struct bpf_program *prog;
0039     struct bpf_object *obj;
0040     int key, fd, progs_fd;
0041     const char *section;
0042     char filename[256];
0043     FILE *f;
0044
0045     snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
0046     obj = bpf_object__open_file(filename, NULL);
0047     if (libbpf_get_error(obj)) {
0048         fprintf(stderr, "ERROR: opening BPF object file failed\n");
0049         return 0;
0050     }
0051
0052     prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
0053     if (!prog) {
0054         printf("finding a prog in obj file failed\n");
0055         goto cleanup;
0056     }
0057
0058     /* load BPF program */
0059     if (bpf_object__load(obj)) {
0060         fprintf(stderr, "ERROR: loading BPF object file failed\n");
0061         goto cleanup;
0062     }
0063
0064     link = bpf_program__attach(prog);
0065     if (libbpf_get_error(link)) {
0066         fprintf(stderr, "ERROR: bpf_program__attach failed\n");
0067         link = NULL;
0068         goto cleanup;
0069     }
0070
0071     progs_fd = bpf_object__find_map_fd_by_name(obj, "progs");
0072     if (progs_fd < 0) {
0073         fprintf(stderr, "ERROR: finding a map in obj file failed\n");
0074         goto cleanup;
0075     }
0076
0077     bpf_object__for_each_program(prog, obj) {
0078         section = bpf_program__section_name(prog);
0079         /* register only syscalls to PROG_ARRAY */
0080         if (sscanf(section, "kprobe/%d", &key) != 1)
0081             continue;
0082
0083         fd = bpf_program__fd(prog);
0084         bpf_map_update_elem(progs_fd, &key, &fd, BPF_ANY);
0085     }
0086
0087     install_accept_all_seccomp();
0088
0089     f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
0090     (void) f;
0091
0092     read_trace_pipe();
0093
0094 cleanup:
0095     bpf_link__destroy(link);
0096     bpf_object__close(obj);
0097     return 0;
0098 }