efi_loader: prepare for read only OP-TEE variables

We currently have two implementations of UEFI variables:

* variables provided via an OP-TEE module
* variables stored in the U-Boot environment

Read only variables are up to now only implemented in the U-Boot
environment implementation.

Provide a common interface for both implementations that allows handling
read-only variables.

As variable access is limited to very few source files put variable
related definitions into new include efi_variable.h instead of efi_loader.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

1 files changed, 78 insertions, 0 deletions

diff --git a/lib/efi_loader/efi_var_common.c b/lib/efi_loader/efi_var_common.c
new file mode 100644
index 0000000000..6a4efa3f27
--- /dev/null
+++ b/lib/efi_loader/efi_var_common.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * UEFI runtime variable services
+ *
+ * Copyright (c) 2020, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <efi_loader.h>
+#include <efi_variable.h>
+
+/**
+ * efi_efi_get_variable() - retrieve value of a UEFI variable
+ *
+ * This function implements the GetVariable runtime service.
+ *
+ * See the Unified Extensible Firmware Interface (UEFI) specification for
+ * details.
+ *
+ * @variable_name:	name of the variable
+ * @vendor:		vendor GUID
+ * @attributes:		attributes of the variable
+ * @data_size:		size of the buffer to which the variable value is copied
+ * @data:		buffer to which the variable value is copied
+ * Return:		status code
+ */
+efi_status_t EFIAPI efi_get_variable(u16 *variable_name,
+				     const efi_guid_t *vendor, u32 *attributes,
+				     efi_uintn_t *data_size, void *data)
+{
+	efi_status_t ret;
+
+	EFI_ENTRY("\"%ls\" %pUl %p %p %p", variable_name, vendor, attributes,
+		  data_size, data);
+
+	ret = efi_get_variable_int(variable_name, vendor, attributes,
+				   data_size, data, NULL);
+
+	/* Remove EFI_VARIABLE_READ_ONLY flag */
+	if (attributes)
+		*attributes &= EFI_VARIABLE_MASK;
+
+	return EFI_EXIT(ret);
+}
+
+/**
+ * efi_set_variable() - set value of a UEFI variable
+ *
+ * This function implements the SetVariable runtime service.
+ *
+ * See the Unified Extensible Firmware Interface (UEFI) specification for
+ * details.
+ *
+ * @variable_name:	name of the variable
+ * @vendor:		vendor GUID
+ * @attributes:		attributes of the variable
+ * @data_size:		size of the buffer with the variable value
+ * @data:		buffer with the variable value
+ * Return:		status code
+ */
+efi_status_t EFIAPI efi_set_variable(u16 *variable_name,
+				     const efi_guid_t *vendor, u32 attributes,
+				     efi_uintn_t data_size, const void *data)
+{
+	efi_status_t ret;
+
+	EFI_ENTRY("\"%ls\" %pUl %x %zu %p", variable_name, vendor, attributes,
+		  data_size, data);
+
+	/* Make sure that the EFI_VARIABLE_READ_ONLY flag is not set */
+	if (attributes & ~(u32)EFI_VARIABLE_MASK)
+		ret = EFI_INVALID_PARAMETER;
+	else
+		ret = efi_set_variable_int(variable_name, vendor, attributes,
+					   data_size, data, true);
+
+	return EFI_EXIT(ret);
+}