s390/uvdevice: Add info IOCTL

Add an IOCTL that allows userspace to find out which IOCTLs the uvdevice
supports without trial and error.

Explicitly expose the IOCTL nr for the request types.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20230615100533.3996107-3-seiden@linux.ibm.com
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-Id: <20230615100533.3996107-3-seiden@linux.ibm.com>

2 files changed, 71 insertions, 8 deletions

diff --git a/drivers/s390/char/Kconfig b/drivers/s390/char/Kconfig
index 80c4e5101c97..8a03af5ee5b3 100644
--- a/drivers/s390/char/Kconfig
+++ b/drivers/s390/char/Kconfig
@@ -96,7 +96,7 @@ config SCLP_OFB
 config S390_UV_UAPI
 	def_tristate m
 	prompt "Ultravisor userspace API"
-	depends on S390
+	depends on S390 && (KVM || PROTECTED_VIRTUALIZATION_GUEST)
 	help
 	  Selecting exposes parts of the UV interface to userspace
 	  by providing a misc character device at /dev/uv.
diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index 1d40457c7b10..7d7866be389b 100644
--- a/drivers/s390/char/uvdevice.c
+++ b/drivers/s390/char/uvdevice.c
@@ -32,6 +32,52 @@
 #include <asm/uvdevice.h>
 #include <asm/uv.h>
 
+#define BIT_UVIO_INTERNAL U32_MAX
+/* Mapping from IOCTL-nr to UVC-bit */
+static const u32 ioctl_nr_to_uvc_bit[] __initconst = {
+	[UVIO_IOCTL_UVDEV_INFO_NR] = BIT_UVIO_INTERNAL,
+	[UVIO_IOCTL_ATT_NR] = BIT_UVC_CMD_RETR_ATTEST,
+};
+
+static_assert(ARRAY_SIZE(ioctl_nr_to_uvc_bit) == UVIO_IOCTL_NUM_IOCTLS);
+
+static struct uvio_uvdev_info uvdev_info = {
+	.supp_uvio_cmds = GENMASK_ULL(UVIO_IOCTL_NUM_IOCTLS - 1, 0),
+};
+
+static void __init set_supp_uv_cmds(unsigned long *supp_uv_cmds)
+{
+	int i;
+
+	for (i = 0; i < UVIO_IOCTL_NUM_IOCTLS; i++) {
+		if (ioctl_nr_to_uvc_bit[i] == BIT_UVIO_INTERNAL)
+			continue;
+		if (!test_bit_inv(ioctl_nr_to_uvc_bit[i], uv_info.inst_calls_list))
+			continue;
+		__set_bit(i, supp_uv_cmds);
+	}
+}
+
+/**
+ * uvio_uvdev_info() - get information about the uvdevice
+ *
+ * @uv_ioctl: ioctl control block
+ *
+ * Lists all IOCTLs that are supported by this uvdevice
+ */
+static int uvio_uvdev_info(struct uvio_ioctl_cb *uv_ioctl)
+{
+	void __user *user_buf_arg = (void __user *)uv_ioctl->argument_addr;
+
+	if (uv_ioctl->argument_len < sizeof(uvdev_info))
+		return -EINVAL;
+	if (copy_to_user(user_buf_arg, &uvdev_info, sizeof(uvdev_info)))
+		return -EFAULT;
+
+	uv_ioctl->uv_rc = UVC_RC_EXECUTED;
+	return 0;
+}
+
 static int uvio_build_uvcb_attest(struct uv_cb_attest *uvcb_attest, u8 *arcb,
 				  u8 *meas, u8 *add_data, struct uvio_attest *uvio_attest)
 {
@@ -185,8 +231,19 @@ out:
 	return ret;
 }
 
-static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp)
+static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp,
+				     unsigned long cmd)
 {
+	u8 nr = _IOC_NR(cmd);
+
+	if (_IOC_DIR(cmd) != (_IOC_READ | _IOC_WRITE))
+		return -ENOIOCTLCMD;
+	if (_IOC_TYPE(cmd) != UVIO_TYPE_UVC)
+		return -ENOIOCTLCMD;
+	if (nr >= UVIO_IOCTL_NUM_IOCTLS)
+		return -ENOIOCTLCMD;
+	if (_IOC_SIZE(cmd) != sizeof(*ioctl))
+		return -ENOIOCTLCMD;
 	if (copy_from_user(ioctl, argp, sizeof(*ioctl)))
 		return -EFAULT;
 	if (ioctl->flags != 0)
@@ -194,7 +251,7 @@ static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *a
 	if (memchr_inv(ioctl->reserved14, 0, sizeof(ioctl->reserved14)))
 		return -EINVAL;
 
-	return 0;
+	return nr;
 }
 
 /*
@@ -205,12 +262,17 @@ static long uvio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	void __user *argp = (void __user *)arg;
 	struct uvio_ioctl_cb uv_ioctl = { };
 	long ret;
+	int nr;
+
+	nr = uvio_copy_and_check_ioctl(&uv_ioctl, argp, cmd);
+	if (nr < 0)
+		return nr;
 
-	switch (cmd) {
-	case UVIO_IOCTL_ATT:
-		ret = uvio_copy_and_check_ioctl(&uv_ioctl, argp);
-		if (ret)
-			return ret;
+	switch (nr) {
+	case UVIO_IOCTL_UVDEV_INFO_NR:
+		ret = uvio_uvdev_info(&uv_ioctl);
+		break;
+	case UVIO_IOCTL_ATT_NR:
 		ret = uvio_attestation(&uv_ioctl);
 		break;
 	default:
@@ -245,6 +307,7 @@ static void __exit uvio_dev_exit(void)
 
 static int __init uvio_dev_init(void)
 {
+	set_supp_uv_cmds((unsigned long *)&uvdev_info.supp_uv_cmds);
 	return misc_register(&uvio_dev_miscdev);
 }