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}