block: sed-opal: Implement IOC_OPAL_DISCOVERY

Add IOC_OPAL_DISCOVERY ioctl to return raw discovery data to a SED Opal
application. This allows the application to display drive capabilities
and state.

Signed-off-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jonathan Derrick <jonathan.derrick@linux.dev>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/20230721211534.3437070-2-gjoyce@linux.vnet.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/sed-opal.c

@@ -463,8 +463,11 @@ static int execute_steps(struct opal_dev *dev,
 	return error;
 }
 
-static int opal_discovery0_end(struct opal_dev *dev)
+static int opal_discovery0_end(struct opal_dev *dev, void *data)
 {
+	struct opal_discovery *discv_out = data; /* may be NULL */
+	u8 __user *buf_out;
+	u64 len_out;
 	bool found_com_id = false, supported = true, single_user = false;
 	const struct d0_header *hdr = (struct d0_header *)dev->resp;
 	const u8 *epos = dev->resp, *cpos = dev->resp;
@@ -480,6 +483,15 @@ static int opal_discovery0_end(struct opal_dev *dev)
 		return -EFAULT;
 	}
 
+	if (discv_out) {
+		buf_out = (u8 __user *)(uintptr_t)discv_out->data;
+		len_out = min_t(u64, discv_out->size, hlen);
+		if (buf_out && copy_to_user(buf_out, dev->resp, len_out))
+			return -EFAULT;
+
+		discv_out->size = hlen; /* actual size of data */
+	}
+
 	epos += hlen; /* end of buffer */
 	cpos += sizeof(*hdr); /* current position on buffer */
 
@@ -565,13 +577,13 @@ static int opal_discovery0(struct opal_dev *dev, void *data)
 	if (ret)
 		return ret;
 
-	return opal_discovery0_end(dev);
+	return opal_discovery0_end(dev, data);
 }
 
 static int opal_discovery0_step(struct opal_dev *dev)
 {
 	const struct opal_step discovery0_step = {
-		opal_discovery0,
+		opal_discovery0, NULL
 	};
 
 	return execute_step(dev, &discovery0_step, 0);
@@ -2435,6 +2447,22 @@ static int opal_secure_erase_locking_range(struct opal_dev *dev,
 	return ret;
 }
 
+static int opal_get_discv(struct opal_dev *dev, struct opal_discovery *discv)
+{
+	const struct opal_step discovery0_step = {
+		opal_discovery0, discv
+	};
+	int ret = 0;
+
+	mutex_lock(&dev->dev_lock);
+	setup_opal_dev(dev);
+	ret = execute_step(dev, &discovery0_step, 0);
+	mutex_unlock(&dev->dev_lock);
+	if (ret)
+		return ret;
+	return discv->size; /* modified to actual length of data */
+}
+
 static int opal_erase_locking_range(struct opal_dev *dev,
 				    struct opal_session_info *opal_session)
 {
@@ -3056,6 +3084,10 @@ int sed_ioctl(struct opal_dev *dev, unsigned int cmd, void __user *arg)
 	case IOC_OPAL_GET_GEOMETRY:
 		ret = opal_get_geometry(dev, arg);
 		break;
+	case IOC_OPAL_DISCOVERY:
+		ret = opal_get_discv(dev, p);
+		break;
+
 	default:
 		break;
 	}

include/linux/sed-opal.h

@@ -47,6 +47,7 @@ static inline bool is_sed_ioctl(unsigned int cmd)
 	case IOC_OPAL_GET_STATUS:
 	case IOC_OPAL_GET_LR_STATUS:
 	case IOC_OPAL_GET_GEOMETRY:
+	case IOC_OPAL_DISCOVERY:
 		return true;
 	}
 	return false;

include/uapi/linux/sed-opal.h

@@ -173,6 +173,11 @@ struct opal_geometry {
 	__u8  __align[3];
 };
 
+struct opal_discovery {
+	__u64 data;
+	__u64 size;
+};
+
 #define IOC_OPAL_SAVE		    _IOW('p', 220, struct opal_lock_unlock)
 #define IOC_OPAL_LOCK_UNLOCK	    _IOW('p', 221, struct opal_lock_unlock)
 #define IOC_OPAL_TAKE_OWNERSHIP	    _IOW('p', 222, struct opal_key)
@@ -192,5 +197,6 @@ struct opal_geometry {
 #define IOC_OPAL_GET_STATUS         _IOR('p', 236, struct opal_status)
 #define IOC_OPAL_GET_LR_STATUS      _IOW('p', 237, struct opal_lr_status)
 #define IOC_OPAL_GET_GEOMETRY       _IOR('p', 238, struct opal_geometry)
+#define IOC_OPAL_DISCOVERY          _IOW('p', 239, struct opal_discovery)
 
 #endif /* _UAPI_SED_OPAL_H */