| 1 | |
| 2 |
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| 3 | #include "vmlinux.h"
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| 4 | #include <bpf/bpf_helpers.h>
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| 5 | #include <bpf/bpf_tracing.h>
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| 6 | #include "hid_bpf_helpers.h"
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| 7 |
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| 8 | static int hid_y_event(struct hid_bpf_ctx *hctx)
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| 9 | {
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| 10 | s16 y;
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| 11 | __u8 *data = hid_bpf_get_data(hctx, 0 , 9 );
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| 12 |
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| 13 | if (!data)
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| 14 | return 0;
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| 15 |
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| 16 | bpf_printk("event: size: %d", hctx->size);
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| 17 | bpf_printk("incoming event: %02x %02x %02x",
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| 18 | data[0],
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| 19 | data[1],
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| 20 | data[2]);
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| 21 | bpf_printk(" %02x %02x %02x",
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| 22 | data[3],
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| 23 | data[4],
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| 24 | data[5]);
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| 25 | bpf_printk(" %02x %02x %02x",
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| 26 | data[6],
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| 27 | data[7],
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| 28 | data[8]);
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| 29 |
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| 30 | y = data[3] | (data[4] << 8);
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| 31 |
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| 32 | y = -y;
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| 33 |
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| 34 | data[3] = y & 0xFF;
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| 35 | data[4] = (y >> 8) & 0xFF;
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| 36 |
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| 37 | bpf_printk("modified event: %02x %02x %02x",
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| 38 | data[0],
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| 39 | data[1],
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| 40 | data[2]);
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| 41 | bpf_printk(" %02x %02x %02x",
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| 42 | data[3],
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| 43 | data[4],
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| 44 | data[5]);
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| 45 | bpf_printk(" %02x %02x %02x",
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| 46 | data[6],
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| 47 | data[7],
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| 48 | data[8]);
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| 49 |
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| 50 | return 0;
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| 51 | }
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| 52 |
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| 53 | static int hid_x_event(struct hid_bpf_ctx *hctx)
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| 54 | {
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| 55 | s16 x;
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| 56 | __u8 *data = hid_bpf_get_data(hctx, 0 , 9 );
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| 57 |
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| 58 | if (!data)
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| 59 | return 0;
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| 60 |
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| 61 | x = data[1] | (data[2] << 8);
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| 62 |
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| 63 | x = -x;
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| 64 |
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| 65 | data[1] = x & 0xFF;
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| 66 | data[2] = (x >> 8) & 0xFF;
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| 67 | return 0;
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| 68 | }
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| 69 |
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| 70 | SEC("struct_ops/hid_device_event")
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| 71 | int BPF_PROG(hid_event, struct hid_bpf_ctx *hctx, enum hid_report_type type)
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| 72 | {
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| 73 | int ret = hid_y_event(hctx);
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| 74 |
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| 75 | if (ret)
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| 76 | return ret;
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| 77 |
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| 78 | return hid_x_event(hctx);
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| 79 | }
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| 80 |
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| 81 |
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| 82 | SEC("struct_ops/hid_rdesc_fixup")
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| 83 | int BPF_PROG(hid_rdesc_fixup, struct hid_bpf_ctx *hctx)
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| 84 | {
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| 85 | __u8 *data = hid_bpf_get_data(hctx, 0 , 4096 );
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| 86 |
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| 87 | if (!data)
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| 88 | return 0;
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| 89 |
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| 90 | bpf_printk("rdesc: %02x %02x %02x",
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| 91 | data[0],
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| 92 | data[1],
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| 93 | data[2]);
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| 94 | bpf_printk(" %02x %02x %02x",
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| 95 | data[3],
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| 96 | data[4],
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| 97 | data[5]);
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| 98 | bpf_printk(" %02x %02x %02x ...",
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| 99 | data[6],
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| 100 | data[7],
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| 101 | data[8]);
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| 102 |
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| 103 | |
| 104 | * The original report descriptor contains:
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| 105 | *
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| 106 | * 0x05, 0x01, // Usage Page (Generic Desktop) 30
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| 107 | * 0x16, 0x01, 0x80, // Logical Minimum (-32767) 32
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| 108 | * 0x26, 0xff, 0x7f, // Logical Maximum (32767) 35
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| 109 | * 0x09, 0x30, // Usage (X) 38
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| 110 | * 0x09, 0x31, // Usage (Y) 40
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| 111 | *
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| 112 | * So byte 39 contains Usage X and byte 41 Usage Y.
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| 113 | *
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| 114 | * We simply swap the axes here.
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| 115 |
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| 116 | data[39] = 0x31;
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| 117 | data[41] = 0x30;
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| 118 |
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| 119 | return 0;
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| 120 | }
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| 121 |
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| 122 | SEC(".struct_ops.link")
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| 123 | struct hid_bpf_ops mouse_invert = {
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| 124 | .hid_rdesc_fixup = (void *)hid_rdesc_fixup,
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| 125 | .hid_device_event = (void *)hid_event,
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| 126 | };
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| 127 |
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| 128 | char _license[] SEC("license") = "GPL";
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