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(0);
40}
41
42static void usage(const char *prog)
43{
44	fprintf(stderr,
45		"%s: %s /sys/bus/hid/devices/0BUS:0VID:0PID:00ID\n\n",
46		__func__, prog);
47	fprintf(stderr,
48		"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(uevent, 0, sizeof(uevent));
62	snprintf(uevent, sizeof(uevent) - 1, "%s/uevent", path);
63
64	fd = open(uevent, O_RDONLY | O_NONBLOCK);
65	if (fd < 0)
66		return -ENOENT;
67
68	close(fd);
69
70	dir = basename((char *)path);
71
72	str_id = dir + sizeof("0003:0001:0A37.");
73	return (int)strtol(str_id, NULL, 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, argv, optstr)) != -1) {
93		switch (opt) {
94		default:
95			usage(basename(argv[0]));
96			return 1;
97		}
98	}
99
100	if (optind == argc) {
101		usage(basename(argv[0]));
102		return 1;
103	}
104
105	sysfs_path = argv[optind];
106	if (!sysfs_path) {
107		perror("sysfs");
108		return 1;
109	}
110
111	skel = hid_mouse__open_and_load();
112	if (!skel) {
113		fprintf(stderr, "%s  %s:%d", __func__, __FILE__, __LINE__);
114		return -1;
115	}
116
117	hid_id = get_hid_id(sysfs_path);
118
119	if (hid_id < 0) {
120		fprintf(stderr, "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, "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, "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, int_exit);
147	signal(SIGTERM, int_exit);
148
149	while (running)
150		sleep(1);
151
152	hid_mouse__destroy(skel);
153
154	return 0;
155}
156