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// SPDX-License-Identifier: GPL-2.0
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include "hid_bpf_helpers.h"
SEC("fmod_ret/hid_bpf_device_event")
int BPF_PROG(hid_y_event, struct hid_bpf_ctx *hctx)
{
s16 y;
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);
if (!data)
return 0; /* EPERM check */
bpf_printk("event: size: %d", hctx->size);
bpf_printk("incoming event: %02x %02x %02x",
data[0],
data[1],
data[2]);
bpf_printk(" %02x %02x %02x",
data[3],
data[4],
data[5]);
bpf_printk(" %02x %02x %02x",
data[6],
data[7],
data[8]);
y = data[3] | (data[4] << 8);
y = -y;
data[3] = y & 0xFF;
data[4] = (y >> 8) & 0xFF;
bpf_printk("modified event: %02x %02x %02x",
data[0],
data[1],
data[2]);
bpf_printk(" %02x %02x %02x",
data[3],
data[4],
data[5]);
bpf_printk(" %02x %02x %02x",
data[6],
data[7],
data[8]);
return 0;
}
SEC("fmod_ret/hid_bpf_device_event")
int BPF_PROG(hid_x_event, struct hid_bpf_ctx *hctx)
{
s16 x;
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 9 /* size */);
if (!data)
return 0; /* EPERM check */
x = data[1] | (data[2] << 8);
x = -x;
data[1] = x & 0xFF;
data[2] = (x >> 8) & 0xFF;
return 0;
}
SEC("fmod_ret/hid_bpf_rdesc_fixup")
int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)
{
__u8 *data = hid_bpf_get_data(hctx, 0 /* offset */, 4096 /* size */);
if (!data)
return 0; /* EPERM check */
bpf_printk("rdesc: %02x %02x %02x",
data[0],
data[1],
data[2]);
bpf_printk(" %02x %02x %02x",
data[3],
data[4],
data[5]);
bpf_printk(" %02x %02x %02x ...",
data[6],
data[7],
data[8]);
/*
* The original report descriptor contains:
*
* 0x05, 0x01, // Usage Page (Generic Desktop) 30
* 0x16, 0x01, 0x80, // Logical Minimum (-32767) 32
* 0x26, 0xff, 0x7f, // Logical Maximum (32767) 35
* 0x09, 0x30, // Usage (X) 38
* 0x09, 0x31, // Usage (Y) 40
*
* So byte 39 contains Usage X and byte 41 Usage Y.
*
* We simply swap the axes here.
*/
data[39] = 0x31;
data[41] = 0x30;
return 0;
}
char _license[] SEC("license") = "GPL";
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