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/** @file
Utility functions for serializing (persistently storing) and deserializing
OVMF's platform configuration.
Copyright (C) 2014, Red Hat, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>
#include <Guid/OvmfPlatformConfig.h>
#include "PlatformConfig.h"
//
// Name of the UEFI variable that we use for persistent storage.
//
STATIC CHAR16 mVariableName[] = L"PlatformConfig";
/**
Serialize and persistently save platform configuration.
@param[in] PlatformConfig The platform configuration to serialize and save.
@return Status codes returned by gRT->SetVariable().
**/
EFI_STATUS
EFIAPI
PlatformConfigSave (
IN PLATFORM_CONFIG *PlatformConfig
)
{
EFI_STATUS Status;
//
// We could implement any kind of translation here, as part of serialization.
// For example, we could expose the platform configuration in separate
// variables with human-readable contents, allowing other tools to access
// them more easily. For now, just save a binary dump.
//
Status = gRT->SetVariable (mVariableName, &gOvmfPlatformConfigGuid,
EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS |
EFI_VARIABLE_RUNTIME_ACCESS,
sizeof *PlatformConfig, PlatformConfig);
return Status;
}
/**
Load and deserialize platform configuration.
When the function fails, output parameters are indeterminate.
@param[out] PlatformConfig The platform configuration to receive the
loaded data.
@param[out] OptionalElements This bitmap describes the presence of optional
configuration elements that have been loaded.
PLATFORM_CONFIG_F_DOWNGRADE means that some
unknown elements, present in the wire format,
have been ignored.
@retval EFI_SUCCESS Loading & deserialization successful.
@return Error codes returned by GetVariable2().
**/
EFI_STATUS
EFIAPI
PlatformConfigLoad (
OUT PLATFORM_CONFIG *PlatformConfig,
OUT UINT64 *OptionalElements
)
{
VOID *Data;
UINTN DataSize;
EFI_STATUS Status;
//
// Any translation done in PlatformConfigSave() would have to be mirrored
// here. For now, just load the binary dump.
//
// Versioning of the binary wire format is implemented based on size
// (only incremental changes, ie. new fields), and on GUID.
// (Incompatible changes require a GUID change.)
//
Status = GetVariable2 (mVariableName, &gOvmfPlatformConfigGuid, &Data,
&DataSize);
if (EFI_ERROR (Status)) {
return Status;
}
*OptionalElements = 0;
if (DataSize > sizeof *PlatformConfig) {
//
// Handle firmware downgrade -- keep only leading part.
//
CopyMem (PlatformConfig, Data, sizeof *PlatformConfig);
*OptionalElements |= PLATFORM_CONFIG_F_DOWNGRADE;
} else {
CopyMem (PlatformConfig, Data, DataSize);
//
// Handle firmware upgrade -- zero out missing fields.
//
ZeroMem ((UINT8 *)PlatformConfig + DataSize,
sizeof *PlatformConfig - DataSize);
}
//
// Based on DataSize, report the optional features that we recognize.
//
if (DataSize >= (OFFSET_OF (PLATFORM_CONFIG, VerticalResolution) +
sizeof PlatformConfig->VerticalResolution)) {
*OptionalElements |= PLATFORM_CONFIG_F_GRAPHICS_RESOLUTION;
}
FreePool (Data);
return EFI_SUCCESS;
}
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