linux-kernel - [PATCH] efi/efivars: create efivars mount point when get variable services are available

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Date:   Wed, 19 Aug 2020 17:28:38 +0800
From:   "Lee, Chun-Yi" <joeyli.kernel@...il.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Lee, Chun-Yi" <jlee@...e.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH] efi/efivars: create efivars mount point when get variable services are available

The efivars filesystem depends on GetVariable or GetNextVariable EFI
runtime services. So the /sys/firmware/efi/efivars does not need to be
created when GetVariable and GetNextVariable are not available.

It is useful for userland to determine the availability of efivars
filesystem.

Cc: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Cc: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: "Lee, Chun-Yi" <jlee@...e.com>
---
 drivers/firmware/efi/efi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index fdd1db025dbf..929fbf4dfd5d 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -404,11 +404,14 @@ static int __init efisubsys_init(void)
 	if (error)
 		goto err_remove_group;
 
-	/* and the standard mountpoint for efivarfs */
-	error = sysfs_create_mount_point(efi_kobj, "efivars");
-	if (error) {
-		pr_err("efivars: Subsystem registration failed.\n");
-		goto err_remove_group;
+	if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
+				      EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
+		/* and the standard mountpoint for efivarfs */
+		error = sysfs_create_mount_point(efi_kobj, "efivars");
+		if (error) {
+			pr_err("efivars: Subsystem registration failed.\n");
+			goto err_remove_group;
+		}
 	}
 
 	if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
-- 
2.16.4