efivarfs: add helper to convert from UC16 name and GUID to utf8 name

These will be used by a later patch to check for uniqueness on initial
EFI variable iteration.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: James Bottomley

fs/efivarfs/internal.h

@@ -55,6 +55,7 @@ bool efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
 		     unsigned long data_size);
 bool efivar_variable_is_removable(efi_guid_t vendor, const char *name,
 				  size_t len);
+char *efivar_get_utf8name(const efi_char16_t *name16, efi_guid_t *vendor);
 
 extern const struct file_operations efivarfs_file_operations;
 extern const struct inode_operations efivarfs_dir_inode_operations;

fs/efivarfs/super.c

@@ -205,27 +205,16 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 	memcpy(entry->var.VariableName, name16, name_size);
 	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
 
-	len = ucs2_utf8size(entry->var.VariableName);
-
-	/* name, plus '-', plus GUID, plus NUL*/
-	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
+	name = efivar_get_utf8name(name16, &vendor);
 	if (!name)
 		goto fail;
 
-	ucs2_as_utf8(name, entry->var.VariableName, len);
+	/* length of the variable name itself: remove GUID and separator */
+	len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1;
 
 	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
 		is_removable = true;
 
-	name[len] = '-';
-
-	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
-
-	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
-
-	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
-	strreplace(name, '/', '!');
-
 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
 				   is_removable);
 	if (!inode)

fs/efivarfs/vars.c

@@ -225,6 +225,31 @@ variable_matches(const char *var_name, size_t len, const char *match_name,
 	}
 }
 
+char *
+efivar_get_utf8name(const efi_char16_t *name16, efi_guid_t *vendor)
+{
+	int len = ucs2_utf8size(name16);
+	char *name;
+
+	/* name, plus '-', plus GUID, plus NUL*/
+	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
+	if (!name)
+		return NULL;
+
+	ucs2_as_utf8(name, name16, len);
+
+	name[len] = '-';
+
+	efi_guid_to_str(vendor, name + len + 1);
+
+	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
+
+	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
+	strreplace(name, '/', '!');
+
+	return name;
+}
+
 bool
 efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
 		unsigned long data_size)