selftests/kexec: remove broken EFI_VARS secure boot fallback check

Commit b433a52 ("selftests/kexec: update get_secureboot_mode")
refactored the code that discovers the EFI secure boot mode so it only
depends on either the efivars pseudo filesystem or the efivars sysfs
interface, but never both.

However, the latter version was not implemented correctly, given the
fact that the local 'efi_vars' variable never assumes a value. This
means the fallback has been dead code ever since it was introduced.

So let's drop the fallback altogether. The sysfs interface has been
deprecated for ~10 years now, and is only enabled on x86 to begin with,
so it is time to get rid of it entirely.

Reviewed-by:  Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

tools/testing/selftests/kexec/kexec_common_lib.sh

@@ -65,32 +65,6 @@ get_efivarfs_secureboot_mode()
 	return 0;
 }
 
-get_efi_var_secureboot_mode()
-{
-	local efi_vars
-	local secure_boot_file
-	local setup_mode_file
-	local secureboot_mode
-	local setup_mode
-
-	if [ ! -d "$efi_vars" ]; then
-		log_skip "efi_vars is not enabled\n"
-	fi
-	secure_boot_file=$(find "$efi_vars" -name SecureBoot-* 2>/dev/null)
-	setup_mode_file=$(find "$efi_vars" -name SetupMode-* 2>/dev/null)
-	if [ -f "$secure_boot_file/data" ] && \
-	   [ -f "$setup_mode_file/data" ]; then
-		secureboot_mode=`od -An -t u1 "$secure_boot_file/data"`
-		setup_mode=`od -An -t u1 "$setup_mode_file/data"`
-
-		if [ $secureboot_mode -eq 1 ] && [ $setup_mode -eq 0 ]; then
-			log_info "secure boot mode enabled (CONFIG_EFI_VARS)"
-			return 1;
-		fi
-	fi
-	return 0;
-}
-
 # On powerpc platform, check device-tree property
 # /proc/device-tree/ibm,secureboot/os-secureboot-enforcing
 # to detect secureboot state.
@@ -113,9 +87,8 @@ get_arch()
 }
 
 # Check efivar SecureBoot-$(the UUID) and SetupMode-$(the UUID).
-# The secure boot mode can be accessed either as the last integer
-# of "od -An -t u1 /sys/firmware/efi/efivars/SecureBoot-*" or from
-# "od -An -t u1 /sys/firmware/efi/vars/SecureBoot-*/data".  The efi
+# The secure boot mode can be accessed as the last integer of
+# "od -An -t u1 /sys/firmware/efi/efivars/SecureBoot-*".  The efi
 # SetupMode can be similarly accessed.
 # Return 1 for SecureBoot mode enabled and SetupMode mode disabled.
 get_secureboot_mode()
@@ -129,11 +102,6 @@ get_secureboot_mode()
 	else
 		get_efivarfs_secureboot_mode
 		secureboot_mode=$?
-		# fallback to using the efi_var files
-		if [ $secureboot_mode -eq 0 ]; then
-			get_efi_var_secureboot_mode
-			secureboot_mode=$?
-		fi
 	fi
 
 	if [ $secureboot_mode -eq 0 ]; then