HID: bpf: add bpf_hid_set_data() helper

So we can set a value of a given size (in bits) from a variable index
to the data field.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

drivers/hid/hid-bpf.c

@@ -303,6 +303,28 @@ static const struct bpf_func_proto bpf_hid_raw_request_proto = {
 	.arg5_type = ARG_ANYTHING,
 };
 
+BPF_CALL_4(bpf_hid_set_data, void*, ctx, u64, offset, u8, n, u32, data)
+{
+	struct hid_bpf_ctx *bpf_ctx = ctx;
+
+	if (n > 32 ||
+	    ((offset + n) >> 3) >= HID_BPF_MAX_BUFFER_SIZE)
+		return -EINVAL;
+
+	implement(bpf_ctx->hdev, bpf_ctx->event.data, offset, n, data);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_hid_set_data_proto = {
+	.func      = bpf_hid_set_data,
+	.gpl_only  = true,
+	.ret_type  = RET_INTEGER,
+	.arg1_type = ARG_PTR_TO_CTX,
+	.arg2_type = ARG_ANYTHING,
+	.arg3_type = ARG_ANYTHING,
+	.arg4_type = ARG_ANYTHING,
+};
+
 static const struct bpf_func_proto *
 hid_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
@@ -313,6 +335,8 @@ hid_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_hid_hw_close_proto;
 	case BPF_FUNC_hid_raw_request:
 		return &bpf_hid_raw_request_proto;
+	case BPF_FUNC_hid_set_data:
+		return &bpf_hid_set_data_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}

drivers/hid/hid-core.c

@@ -1416,8 +1416,8 @@ static void __implement(u8 *report, unsigned offset, int n, u32 value)
 	}
 }
 
-static void implement(const struct hid_device *hid, u8 *report,
-		      unsigned offset, unsigned n, u32 value)
+void implement(const struct hid_device *hid, u8 *report,
+	       unsigned offset, unsigned n, u32 value)
 {
 	if (unlikely(n > 32)) {
 		hid_warn(hid, "%s() called with n (%d) > 32! (%s)\n",

include/linux/hid.h

@@ -676,6 +676,8 @@ bool hid_compare_device_paths(struct hid_device *hdev_a,
 s32 hid_snto32(__u32 value, unsigned n);
 __u32 hid_field_extract(const struct hid_device *hid, __u8 *report,
 		     unsigned offset, unsigned n);
+void implement(const struct hid_device *hid, u8 *report,
+	       unsigned offset, unsigned n, u32 value);
 
 #ifdef CONFIG_PM
 int hid_driver_suspend(struct hid_device *hdev, pm_message_t state);

include/uapi/linux/bpf.h

@@ -4960,6 +4960,13 @@ union bpf_attr {
  *		signal underlaying HW to stop delivering events
  *	Return
  *		Nothing
+ *
+ * int bpf_hid_set_data(void *ctx, u64 offset, u8 n, u32 data)
+ *	Description
+ *		Set the data of size size at offset offset in the
+ *		ctx->event.data field
+ *	Return
+ *		0 on success, a negative error on failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5145,6 +5152,7 @@ union bpf_attr {
 	FN(hid_raw_request),		\
 	FN(hid_hw_open),		\
 	FN(hid_hw_close),		\
+	FN(hid_set_data),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper

tools/include/uapi/linux/bpf.h

@@ -4960,6 +4960,13 @@ union bpf_attr {
  *		signal underlaying HW to stop delivering events
  *	Return
  *		Nothing
+ *
+ * int bpf_hid_set_data(void *ctx, u64 offset, u8 n, u32 data)
+ *	Description
+ *		Set the data of size size at offset offset in the
+ *		ctx->event.data field
+ *	Return
+ *		0 on success, a negative error on failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5145,6 +5152,7 @@ union bpf_attr {
 	FN(hid_raw_request),		\
 	FN(hid_hw_open),		\
 	FN(hid_hw_close),		\
+	FN(hid_set_data),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper