1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2022 Benjamin Tissoires
3 *
4 * This is a pure HID-BPF example, and should be considered as such:
5 * on the Etekcity Scroll 6E, the X and Y axes will be swapped and
6 * inverted. On any other device... Not sure what this will do.
7 *
8 * This C main file is generic though. To adapt the code and test, users
9 * must amend only the .bpf.c file, which this program will load any
10 * eBPF program it finds.
11 */
12
13#include <assert.h>
14#include <errno.h>
15#include <fcntl.h>
16#include <libgen.h>
17#include <signal.h>
18#include <stdbool.h>
19#include <stdio.h>
20#include <stdlib.h>
21#include <string.h>
22#include <sys/resource.h>
23#include <unistd.h>
24
25#include <linux/bpf.h>
26#include <linux/errno.h>
27
28#include <bpf/bpf.h>
29#include <bpf/libbpf.h>
30
31#include "hid_mouse.skel.h"
32#include "hid_bpf_attach.h"
33
34static bool running = true;
35
36static void int_exit(int sig)
37{
38 running = false;
39 exit(status: 0);
40}
41
42static void usage(const char *prog)
43{
44 fprintf(stderr,
45 format: "%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
46 __func__, prog);
47 fprintf(stderr,
48 format: "This program will upload and attach a HID-BPF program to the given device.\n"
49 "On the Etekcity Scroll 6E, the X and Y axis will be inverted, but on any other\n"
50 "device, chances are high that the device will not be working anymore\n\n"
51 "consider this as a demo and adapt the eBPF program to your needs\n"
52 "Hit Ctrl-C to unbind the program and reset the device\n");
53}
54
55static int get_hid_id(const char *path)
56{
57 const char *str_id, *dir;
58 char uevent[1024];
59 int fd;
60
61 memset(s: uevent, c: 0, n: sizeof(uevent));
62 snprintf(s: uevent, maxlen: sizeof(uevent) - 1, format: "%s/uevent", path);
63
64 fd = open(file: uevent, O_RDONLY | O_NONBLOCK);
65 if (fd < 0)
66 return -ENOENT;
67
68 close(fd: fd);
69
70 dir = basename(path: (char *)path);
71
72 str_id = dir + sizeof("0003:0001:0A37.");
73 return (int)strtol(nptr: str_id, NULL, base: 16);
74}
75
76int main(int argc, char **argv)
77{
78 struct hid_mouse *skel;
79 struct bpf_program *prog;
80 int err;
81 const char *optstr = "";
82 const char *sysfs_path;
83 int opt, hid_id, attach_fd;
84 struct attach_prog_args args = {
85 .retval = -1,
86 };
87 DECLARE_LIBBPF_OPTS(bpf_test_run_opts, tattr,
88 .ctx_in = &args,
89 .ctx_size_in = sizeof(args),
90 );
91
92 while ((opt = getopt(argc: argc, argv: argv, shortopts: optstr)) != -1) {
93 switch (opt) {
94 default:
95 usage(basename(path: argv[0]));
96 return 1;
97 }
98 }
99
100 if (optind == argc) {
101 usage(basename(path: argv[0]));
102 return 1;
103 }
104
105 sysfs_path = argv[optind];
106 if (!sysfs_path) {
107 perror(s: "sysfs");
108 return 1;
109 }
110
111 skel = hid_mouse__open_and_load();
112 if (!skel) {
113 fprintf(stderr, format: "%s %s:%d", __func__, __FILE__, __LINE__);
114 return -1;
115 }
116
117 hid_id = get_hid_id(path: sysfs_path);
118
119 if (hid_id < 0) {
120 fprintf(stderr, format: "can not open HID device: %m\n");
121 return 1;
122 }
123 args.hid = hid_id;
124
125 attach_fd = bpf_program__fd(skel->progs.attach_prog);
126 if (attach_fd < 0) {
127 fprintf(stderr, format: "can't locate attach prog: %m\n");
128 return 1;
129 }
130
131 bpf_object__for_each_program(prog, *skel->skeleton->obj) {
132 /* ignore syscalls */
133 if (bpf_program__get_type(prog) != BPF_PROG_TYPE_TRACING)
134 continue;
135
136 args.retval = -1;
137 args.prog_fd = bpf_program__fd(prog);
138 err = bpf_prog_test_run_opts(attach_fd, &tattr);
139 if (err) {
140 fprintf(stderr, format: "can't attach prog to hid device %d: %m (err: %d)\n",
141 hid_id, err);
142 return 1;
143 }
144 }
145
146 signal(SIGINT, handler: int_exit);
147 signal(SIGTERM, handler: int_exit);
148
149 while (running)
150 sleep(seconds: 1);
151
152 hid_mouse__destroy(skel);
153
154 return 0;
155}
156

source code of linux/samples/hid/hid_mouse.c