include/linux/hid_bpf.h

   1 /* SPDX-License-Identifier: GPL-2.0+ */
   2
   3 #ifndef __HID_BPF_H
   4 #define __HID_BPF_H
   5
   6 #include <linux/bpf.h>
   7 #include <linux/mutex.h>
   8 #include <linux/srcu.h>
   9 #include <uapi/linux/hid.h>
  10
  11 struct hid_device;
  12
  13 /*
  14  * The following is the user facing HID BPF API.
  15  *
  16  * Extra care should be taken when editing this part, as
  17  * it might break existing out of the tree bpf programs.
  18  */
  19
  20 /**
  21  * struct hid_bpf_ctx - User accessible data for all HID programs
  22  *
  23  * ``data`` is not directly accessible from the context. We need to issue
  24  * a call to hid_bpf_get_data() in order to get a pointer to that field.
  25  *
  26  * @hid: the &struct hid_device representing the device itself
  27  * @allocated_size: Allocated size of data.
  28  *
  29  *                  This is how much memory is available and can be requested
  30  *                  by the HID program.
  31  *                  Note that for ``HID_BPF_RDESC_FIXUP``, that memory is set to
  32  *                  ``4096`` (4 KB)
  33  * @size: Valid data in the data field.
  34  *
  35  *        Programs can get the available valid size in data by fetching this field.
  36  *        Programs can also change this value by returning a positive number in the
  37  *        program.
  38  *        To discard the event, return a negative error code.
  39  *
  40  *        ``size`` must always be less or equal than ``allocated_size`` (it is enforced
  41  *        once all BPF programs have been run).
  42  * @retval: Return value of the previous program.
  43  *
  44  * ``hid`` and ``allocated_size`` are read-only, ``size`` and ``retval`` are read-write.
  45  */
  46 struct hid_bpf_ctx {
  47         struct hid_device *hid;
  48         __u32 allocated_size;
  49         union {
  50                 __s32 retval;
  51                 __s32 size;
  52         };
  53 };
  54
  55 /*
  56  * Below is HID internal
  57  */
  58
  59 #define HID_BPF_MAX_PROGS_PER_DEV 64
  60 #define HID_BPF_FLAG_MASK (((HID_BPF_FLAG_MAX - 1) << 1) - 1)
  61
  62
  63 struct hid_report_enum;
  64
  65 struct hid_ops {
  66         struct hid_report *(*hid_get_report)(struct hid_report_enum *report_enum, const u8 *data);
  67         int (*hid_hw_raw_request)(struct hid_device *hdev,
  68                                   unsigned char reportnum, __u8 *buf,
  69                                   size_t len, enum hid_report_type rtype,
  70                                   enum hid_class_request reqtype,
  71                                   u64 source, bool from_bpf);
  72         int (*hid_hw_output_report)(struct hid_device *hdev, __u8 *buf, size_t len,
  73                                     u64 source, bool from_bpf);
  74         int (*hid_input_report)(struct hid_device *hid, enum hid_report_type type,
  75                                 u8 *data, u32 size, int interrupt, u64 source, bool from_bpf,
  76                                 bool lock_already_taken);
  77         struct module *owner;
  78         const struct bus_type *bus_type;
  79 };
  80
  81 extern struct hid_ops *hid_ops;
  82
  83 /**
  84  * struct hid_bpf_ops - A BPF struct_ops of callbacks allowing to attach HID-BPF
  85  *                      programs to a HID device
  86  * @hid_id: the HID uniq ID to attach to. This is writeable before ``load()``, and
  87  *          cannot be changed after
  88  * @flags: flags used while attaching the struct_ops to the device. Currently only
  89  *         available value is %0 or ``BPF_F_BEFORE``.
  90  *         Writeable only before ``load()``
  91  */
  92 struct hid_bpf_ops {
  93         /* hid_id needs to stay first so we can easily change it
  94          * from userspace.
  95          */
  96         int                     hid_id;
  97         u32                     flags;
  98
  99         /* private: do not show up in the docs */
 100         struct list_head        list;
 101
 102         /* public: rest should show up in the docs */
 103
 104         /**
 105          * @hid_device_event: called whenever an event is coming in from the device
 106          *
 107          * It has the following arguments:
 108          *
 109          * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx
 110          *
 111          * Return: %0 on success and keep processing; a positive
 112          * value to change the incoming size buffer; a negative
 113          * error code to interrupt the processing of this event
 114          *
 115          * Context: Interrupt context.
 116          */
 117         int (*hid_device_event)(struct hid_bpf_ctx *ctx, enum hid_report_type report_type,
 118                                 u64 source);
 119
 120         /**
 121          * @hid_rdesc_fixup: called when the probe function parses the report descriptor
 122          * of the HID device
 123          *
 124          * It has the following arguments:
 125          *
 126          * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx
 127          *
 128          * Return: %0 on success and keep processing; a positive
 129          * value to change the incoming size buffer; a negative
 130          * error code to interrupt the processing of this device
 131          */
 132         int (*hid_rdesc_fixup)(struct hid_bpf_ctx *ctx);
 133
 134         /**
 135          * @hid_hw_request: called whenever a hid_hw_raw_request() call is emitted
 136          * on the HID device
 137          *
 138          * It has the following arguments:
 139          *
 140          * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx
 141          *
 142          * ``reportnum``: the report number, as in hid_hw_raw_request()
 143          *
 144          * ``rtype``: the report type (``HID_INPUT_REPORT``, ``HID_FEATURE_REPORT``,
 145          * ``HID_OUTPUT_REPORT``)
 146          *
 147          * ``reqtype``: the request
 148          *
 149          * ``source``: a u64 referring to a uniq but identifiable source. If %0, the
 150          * kernel itself emitted that call. For hidraw, ``source`` is set
 151          * to the associated ``struct file *``.
 152          *
 153          * Return: %0 to keep processing the request by hid-core; any other value
 154          * stops hid-core from processing that event. A positive value should be
 155          * returned with the number of bytes returned in the incoming buffer; a
 156          * negative error code interrupts the processing of this call.
 157          */
 158         int (*hid_hw_request)(struct hid_bpf_ctx *ctx, unsigned char reportnum,
 159                                enum hid_report_type rtype, enum hid_class_request reqtype,
 160                                u64 source);
 161
 162         /**
 163          * @hid_hw_output_report: called whenever a hid_hw_output_report() call is emitted
 164          * on the HID device
 165          *
 166          * It has the following arguments:
 167          *
 168          * ``ctx``: The HID-BPF context as &struct hid_bpf_ctx
 169          *
 170          * ``source``: a u64 referring to a uniq but identifiable source. If %0, the
 171          * kernel itself emitted that call. For hidraw, ``source`` is set
 172          * to the associated ``struct file *``.
 173          *
 174          * Return: %0 to keep processing the request by hid-core; any other value
 175          * stops hid-core from processing that event. A positive value should be
 176          * returned with the number of bytes written to the device; a negative error
 177          * code interrupts the processing of this call.
 178          */
 179         int (*hid_hw_output_report)(struct hid_bpf_ctx *ctx, u64 source);
 180
 181
 182         /* private: do not show up in the docs */
 183         struct hid_device *hdev;
 184 };
 185
 186 /* stored in each device */
 187 struct hid_bpf {
 188         u8 *device_data;                /* allocated when a bpf program of type
 189                                          * SEC(f.../hid_bpf_device_event) has been attached
 190                                          * to this HID device
 191                                          */
 192         u32 allocated_data;
 193         bool destroyed;                 /* prevents the assignment of any progs */
 194
 195         struct hid_bpf_ops *rdesc_ops;
 196         struct list_head prog_list;
 197         struct mutex prog_list_lock;    /* protects prog_list update */
 198         struct srcu_struct srcu;        /* protects prog_list read-only access */
 199 };
 200
 201 #ifdef CONFIG_HID_BPF
 202 u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
 203                                   u32 *size, int interrupt, u64 source, bool from_bpf);
 204 int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
 205                                   unsigned char reportnum, __u8 *buf,
 206                                   u32 size, enum hid_report_type rtype,
 207                                   enum hid_class_request reqtype,
 208                                   u64 source, bool from_bpf);
 209 int dispatch_hid_bpf_output_report(struct hid_device *hdev, __u8 *buf, u32 size,
 210                                    u64 source, bool from_bpf);
 211 int hid_bpf_connect_device(struct hid_device *hdev);
 212 void hid_bpf_disconnect_device(struct hid_device *hdev);
 213 void hid_bpf_destroy_device(struct hid_device *hid);
 214 int hid_bpf_device_init(struct hid_device *hid);
 215 const u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, const u8 *rdesc, unsigned int *size);
 216 #else /* CONFIG_HID_BPF */
 217 static inline u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type,
 218                                                 u8 *data, u32 *size, int interrupt,
 219                                                 u64 source, bool from_bpf) { return data; }
 220 static inline int dispatch_hid_bpf_raw_requests(struct hid_device *hdev,
 221                                                 unsigned char reportnum, u8 *buf,
 222                                                 u32 size, enum hid_report_type rtype,
 223                                                 enum hid_class_request reqtype,
 224                                                 u64 source, bool from_bpf) { return 0; }
 225 static inline int dispatch_hid_bpf_output_report(struct hid_device *hdev, __u8 *buf, u32 size,
 226                                                  u64 source, bool from_bpf) { return 0; }
 227 static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; }
 228 static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {}
 229 static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
 230 static inline int hid_bpf_device_init(struct hid_device *hid) { return 0; }
 231 static inline const u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, const u8 *rdesc,
 232                                                  unsigned int *size) { return rdesc; }
 233
 234 #endif /* CONFIG_HID_BPF */
 235
 236 #endif /* __HID_BPF_H */