cxl/mbox: Move cxl_mem_command construction to helper funcs

Sanitizing and constructing a cxl_mem_command from a userspace
command is part of the validation process prior to submitting
the command to a CXL device. Move this work to helper functions:
cxl_to_mem_cmd(), cxl_to_mem_cmd_raw().

This declutters cxl_validate_cmd_from_user() in preparation for
adding new validation steps.
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/7d9b826f29262e3a484cb4bb7b63872134d60bd7.1648687552.git.alison.schofield@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -207,76 +207,42 @@ static bool cxl_mem_raw_command_allowed(u16 opcode)
 	return true;
 }
 
-/**
- * cxl_validate_cmd_from_user() - Check fields for CXL_MEM_SEND_COMMAND.
- * @cxlds: The device data for the operation
- * @send_cmd: &struct cxl_send_command copied in from userspace.
- * @out_cmd: Sanitized and populated &struct cxl_mem_command.
- *
- * Return:
- *  * %0	- @out_cmd is ready to send.
- *  * %-ENOTTY	- Invalid command specified.
- *  * %-EINVAL	- Reserved fields or invalid values were used.
- *  * %-ENOMEM	- Input or output buffer wasn't sized properly.
- *  * %-EPERM	- Attempted to use a protected command.
- *  * %-EBUSY	- Kernel has claimed exclusive access to this opcode
- *
- * The result of this command is a fully validated command in @out_cmd that is
- * safe to send to the hardware.
- *
- * See handle_mailbox_cmd_from_user()
- */
-static int cxl_validate_cmd_from_user(struct cxl_dev_state *cxlds,
-				      const struct cxl_send_command *send_cmd,
-				      struct cxl_mem_command *out_cmd)
+static int cxl_to_mem_cmd_raw(struct cxl_mem_command *mem_cmd,
+			      const struct cxl_send_command *send_cmd,
+			      struct cxl_dev_state *cxlds)
 {
-	const struct cxl_command_info *info;
-	struct cxl_mem_command *c;
-
-	if (send_cmd->id == 0 || send_cmd->id >= CXL_MEM_COMMAND_ID_MAX)
-		return -ENOTTY;
-
-	/*
-	 * The user can never specify an input payload larger than what hardware
-	 * supports, but output can be arbitrarily large (simply write out as
-	 * much data as the hardware provides).
-	 */
-	if (send_cmd->in.size > cxlds->payload_size)
+	if (send_cmd->raw.rsvd)
 		return -EINVAL;
 
 	/*
-	 * Checks are bypassed for raw commands but a WARN/taint will occur
-	 * later in the callchain
+	 * Unlike supported commands, the output size of RAW commands
+	 * gets passed along without further checking, so it must be
+	 * validated here.
 	 */
-	if (send_cmd->id == CXL_MEM_COMMAND_ID_RAW) {
-		const struct cxl_mem_command temp = {
-			.info = {
-				.id = CXL_MEM_COMMAND_ID_RAW,
-				.flags = 0,
-				.size_in = send_cmd->in.size,
-				.size_out = send_cmd->out.size,
-			},
-			.opcode = send_cmd->raw.opcode
-		};
-
-		if (send_cmd->raw.rsvd)
-			return -EINVAL;
+	if (send_cmd->out.size > cxlds->payload_size)
+		return -EINVAL;
 
-		/*
-		 * Unlike supported commands, the output size of RAW commands
-		 * gets passed along without further checking, so it must be
-		 * validated here.
-		 */
-		if (send_cmd->out.size > cxlds->payload_size)
-			return -EINVAL;
+	if (!cxl_mem_raw_command_allowed(send_cmd->raw.opcode))
+		return -EPERM;
 
-		if (!cxl_mem_raw_command_allowed(send_cmd->raw.opcode))
-			return -EPERM;
+	*mem_cmd = (struct cxl_mem_command) {
+		.info = {
+			.id = CXL_MEM_COMMAND_ID_RAW,
+			.size_in = send_cmd->in.size,
+			.size_out = send_cmd->out.size,
+		},
+		.opcode = send_cmd->raw.opcode
+	};
 
-		memcpy(out_cmd, &temp, sizeof(temp));
+	return 0;
+}
 
-		return 0;
-	}
+static int cxl_to_mem_cmd(struct cxl_mem_command *mem_cmd,
+			  const struct cxl_send_command *send_cmd,
+			  struct cxl_dev_state *cxlds)
+{
+	struct cxl_mem_command *c = &cxl_mem_commands[send_cmd->id];
+	const struct cxl_command_info *info = &c->info;
 
 	if (send_cmd->flags & ~CXL_MEM_COMMAND_FLAG_MASK)
 		return -EINVAL;
@@ -287,10 +253,6 @@ static int cxl_validate_cmd_from_user(struct cxl_dev_state *cxlds,
 	if (send_cmd->in.rsvd || send_cmd->out.rsvd)
 		return -EINVAL;
 
-	/* Convert user's command into the internal representation */
-	c = &cxl_mem_commands[send_cmd->id];
-	info = &c->info;
-
 	/* Check that the command is enabled for hardware */
 	if (!test_bit(info->id, cxlds->enabled_cmds))
 		return -ENOTTY;
@@ -307,15 +269,58 @@ static int cxl_validate_cmd_from_user(struct cxl_dev_state *cxlds,
 	if (info->size_out >= 0 && send_cmd->out.size < info->size_out)
 		return -ENOMEM;
 
-	memcpy(out_cmd, c, sizeof(*c));
-	out_cmd->info.size_in = send_cmd->in.size;
+	*mem_cmd = (struct cxl_mem_command) {
+		.info = {
+			.id = info->id,
+			.flags = info->flags,
+			.size_in = send_cmd->in.size,
+			.size_out = send_cmd->out.size,
+		},
+		.opcode = c->opcode
+	};
+
+	return 0;
+}
+
+/**
+ * cxl_validate_cmd_from_user() - Check fields for CXL_MEM_SEND_COMMAND.
+ * @cxlds: The device data for the operation
+ * @send_cmd: &struct cxl_send_command copied in from userspace.
+ * @out_cmd: Sanitized and populated &struct cxl_mem_command.
+ *
+ * Return:
+ *  * %0	- @out_cmd is ready to send.
+ *  * %-ENOTTY	- Invalid command specified.
+ *  * %-EINVAL	- Reserved fields or invalid values were used.
+ *  * %-ENOMEM	- Input or output buffer wasn't sized properly.
+ *  * %-EPERM	- Attempted to use a protected command.
+ *  * %-EBUSY	- Kernel has claimed exclusive access to this opcode
+ *
+ * The result of this command is a fully validated command in @out_cmd that is
+ * safe to send to the hardware.
+ *
+ * See handle_mailbox_cmd_from_user()
+ */
+static int cxl_validate_cmd_from_user(struct cxl_dev_state *cxlds,
+				      const struct cxl_send_command *send_cmd,
+				      struct cxl_mem_command *out_cmd)
+{
+	if (send_cmd->id == 0 || send_cmd->id >= CXL_MEM_COMMAND_ID_MAX)
+		return -ENOTTY;
+
 	/*
-	 * XXX: out_cmd->info.size_out will be controlled by the driver, and the
-	 * specified number of bytes @send_cmd->out.size will be copied back out
-	 * to userspace.
+	 * The user can never specify an input payload larger than what hardware
+	 * supports, but output can be arbitrarily large (simply write out as
+	 * much data as the hardware provides).
 	 */
+	if (send_cmd->in.size > cxlds->payload_size)
+		return -EINVAL;
 
-	return 0;
+	/* Sanitize and construct a cxl_mem_command */
+	if (send_cmd->id == CXL_MEM_COMMAND_ID_RAW)
+		return cxl_to_mem_cmd_raw(out_cmd, send_cmd, cxlds);
+	else
+		return cxl_to_mem_cmd(out_cmd, send_cmd, cxlds);
 }
 
 int cxl_query_cmd(struct cxl_memdev *cxlmd,