Merge branch 'for-6.3/hid-bpf' into for-linus

Initial support of HID-BPF (Benjamin Tissoires)

The history is a little long for this series, as it was intended to be
sent for v6.2. However some last minute issues forced us to postpone it
to v6.3.

Conflicts:
* drivers/hid/i2c-hid/Kconfig:
  commit bf7660dab30d ("HID: stop drivers from selecting CONFIG_HID")
  conflicts with commit 2afac81dd165 ("HID: fix I2C_HID not selected
  when I2C_HID_OF_ELAN is")
  the resolution is simple enough: just drop the "default" and "select"
  lines as the new commit from Arnd is doing

2 files changed, 175 insertions, 0 deletions

diff --git a/include/linux/hid.h b/include/linux/hid.h
index 899d840ffb24..eaf8ab177303 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -26,6 +26,7 @@
 #include <linux/mutex.h>
 #include <linux/power_supply.h>
 #include <uapi/linux/hid.h>
+#include <linux/hid_bpf.h>
 
 /*
  * We parse each description item into this structure. Short items data
@@ -654,6 +655,10 @@ struct hid_device {							/* device report descriptor */
 	wait_queue_head_t debug_wait;
 
 	unsigned int id;						/* system unique id */
+
+#ifdef CONFIG_BPF
+	struct hid_bpf bpf;						/* hid-bpf data */
+#endif /* CONFIG_BPF */
 };
 
 #define to_hid_device(pdev) \
diff --git a/include/linux/hid_bpf.h b/include/linux/hid_bpf.h
new file mode 100644
index 000000000000..e9afb61e6ee0
--- /dev/null
+++ b/include/linux/hid_bpf.h
@@ -0,0 +1,170 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef __HID_BPF_H
+#define __HID_BPF_H
+
+#include <linux/bpf.h>
+#include <linux/spinlock.h>
+#include <uapi/linux/hid.h>
+
+struct hid_device;
+
+/*
+ * The following is the user facing HID BPF API.
+ *
+ * Extra care should be taken when editing this part, as
+ * it might break existing out of the tree bpf programs.
+ */
+
+/**
+ * struct hid_bpf_ctx - User accessible data for all HID programs
+ *
+ * ``data`` is not directly accessible from the context. We need to issue
+ * a call to ``hid_bpf_get_data()`` in order to get a pointer to that field.
+ *
+ * All of these fields are currently read-only.
+ *
+ * @index: program index in the jump table. No special meaning (a smaller index
+ *         doesn't mean the program will be executed before another program with
+ *         a bigger index).
+ * @hid: the ``struct hid_device`` representing the device itself
+ * @report_type: used for ``hid_bpf_device_event()``
+ * @allocated_size: Allocated size of data.
+ *
+ *                  This is how much memory is available and can be requested
+ *                  by the HID program.
+ *                  Note that for ``HID_BPF_RDESC_FIXUP``, that memory is set to
+ *                  ``4096`` (4 KB)
+ * @size: Valid data in the data field.
+ *
+ *        Programs can get the available valid size in data by fetching this field.
+ *        Programs can also change this value by returning a positive number in the
+ *        program.
+ *        To discard the event, return a negative error code.
+ *
+ *        ``size`` must always be less or equal than ``allocated_size`` (it is enforced
+ *        once all BPF programs have been run).
+ * @retval: Return value of the previous program.
+ */
+struct hid_bpf_ctx {
+	__u32 index;
+	const struct hid_device *hid;
+	__u32 allocated_size;
+	enum hid_report_type report_type;
+	union {
+		__s32 retval;
+		__s32 size;
+	};
+};
+
+/**
+ * enum hid_bpf_attach_flags - flags used when attaching a HIF-BPF program
+ *
+ * @HID_BPF_FLAG_NONE: no specific flag is used, the kernel choses where to
+ *                     insert the program
+ * @HID_BPF_FLAG_INSERT_HEAD: insert the given program before any other program
+ *                            currently attached to the device. This doesn't
+ *                            guarantee that this program will always be first
+ * @HID_BPF_FLAG_MAX: sentinel value, not to be used by the callers
+ */
+enum hid_bpf_attach_flags {
+	HID_BPF_FLAG_NONE = 0,
+	HID_BPF_FLAG_INSERT_HEAD = _BITUL(0),
+	HID_BPF_FLAG_MAX,
+};
+
+/* Following functions are tracepoints that BPF programs can attach to */
+int hid_bpf_device_event(struct hid_bpf_ctx *ctx);
+int hid_bpf_rdesc_fixup(struct hid_bpf_ctx *ctx);
+
+/* Following functions are kfunc that we export to BPF programs */
+/* available everywhere in HID-BPF */
+__u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx, unsigned int offset, const size_t __sz);
+
+/* only available in syscall */
+int hid_bpf_attach_prog(unsigned int hid_id, int prog_fd, __u32 flags);
+int hid_bpf_hw_request(struct hid_bpf_ctx *ctx, __u8 *buf, size_t buf__sz,
+		       enum hid_report_type rtype, enum hid_class_request reqtype);
+struct hid_bpf_ctx *hid_bpf_allocate_context(unsigned int hid_id);
+void hid_bpf_release_context(struct hid_bpf_ctx *ctx);
+
+/*
+ * Below is HID internal
+ */
+
+/* internal function to call eBPF programs, not to be used by anybody */
+int __hid_bpf_tail_call(struct hid_bpf_ctx *ctx);
+
+#define HID_BPF_MAX_PROGS_PER_DEV 64
+#define HID_BPF_FLAG_MASK (((HID_BPF_FLAG_MAX - 1) << 1) - 1)
+
+/* types of HID programs to attach to */
+enum hid_bpf_prog_type {
+	HID_BPF_PROG_TYPE_UNDEF = -1,
+	HID_BPF_PROG_TYPE_DEVICE_EVENT,			/* an event is emitted from the device */
+	HID_BPF_PROG_TYPE_RDESC_FIXUP,
+	HID_BPF_PROG_TYPE_MAX,
+};
+
+struct hid_report_enum;
+
+struct hid_bpf_ops {
+	struct hid_report *(*hid_get_report)(struct hid_report_enum *report_enum, const u8 *data);
+	int (*hid_hw_raw_request)(struct hid_device *hdev,
+				  unsigned char reportnum, __u8 *buf,
+				  size_t len, enum hid_report_type rtype,
+				  enum hid_class_request reqtype);
+	struct module *owner;
+	struct bus_type *bus_type;
+};
+
+extern struct hid_bpf_ops *hid_bpf_ops;
+
+struct hid_bpf_prog_list {
+	u16 prog_idx[HID_BPF_MAX_PROGS_PER_DEV];
+	u8 prog_cnt;
+};
+
+/* stored in each device */
+struct hid_bpf {
+	u8 *device_data;		/* allocated when a bpf program of type
+					 * SEC(f.../hid_bpf_device_event) has been attached
+					 * to this HID device
+					 */
+	u32 allocated_data;
+
+	struct hid_bpf_prog_list __rcu *progs[HID_BPF_PROG_TYPE_MAX];	/* attached BPF progs */
+	bool destroyed;			/* prevents the assignment of any progs */
+
+	spinlock_t progs_lock;		/* protects RCU update of progs */
+};
+
+/* specific HID-BPF link when a program is attached to a device */
+struct hid_bpf_link {
+	struct bpf_link link;
+	int hid_table_index;
+};
+
+#ifdef CONFIG_HID_BPF
+u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type, u8 *data,
+				  u32 *size, int interrupt);
+int hid_bpf_connect_device(struct hid_device *hdev);
+void hid_bpf_disconnect_device(struct hid_device *hdev);
+void hid_bpf_destroy_device(struct hid_device *hid);
+void hid_bpf_device_init(struct hid_device *hid);
+u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size);
+#else /* CONFIG_HID_BPF */
+static inline u8 *dispatch_hid_bpf_device_event(struct hid_device *hid, enum hid_report_type type,
+						u8 *data, u32 *size, int interrupt) { return data; }
+static inline int hid_bpf_connect_device(struct hid_device *hdev) { return 0; }
+static inline void hid_bpf_disconnect_device(struct hid_device *hdev) {}
+static inline void hid_bpf_destroy_device(struct hid_device *hid) {}
+static inline void hid_bpf_device_init(struct hid_device *hid) {}
+static inline u8 *call_hid_bpf_rdesc_fixup(struct hid_device *hdev, u8 *rdesc, unsigned int *size)
+{
+	return kmemdup(rdesc, *size, GFP_KERNEL);
+}
+
+#endif /* CONFIG_HID_BPF */
+
+#endif /* __HID_BPF_H */