src/drivers/storage/uefi_nv.c

/*
 * Copyright 2016 Google Inc.
 *
 * See file CREDITS for list of people who contributed to this
 * project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but without any warranty; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "base/container_of.h"
#include "base/fwdb.h"
#include "base/xalloc.h"
#include "drivers/storage/uefi_nv.h"

static EFI_GUID uefi_nv_default_vendor_guid =
{
	0x52bcc60a,
	0x91c7,
	0x4602,
	{ 0xa8, 0x7c, 0xc3, 0xbc, 0x7f, 0x89, 0x59, 0x9a }
};


static int uefi_nv_storage_write_variable(UefiNvStorage *storage)
{
	EFI_SYSTEM_TABLE *st = uefi_system_table_ptr();
	if (!st)
		return 1;
	EFI_RUNTIME_SERVICES *rs = st->RuntimeServices;

	UINTN attributes =
		EFI_VARIABLE_NON_VOLATILE |
		EFI_VARIABLE_BOOTSERVICE_ACCESS |
		EFI_VARIABLE_RUNTIME_ACCESS;

	// Write with size 0 to erase any existing version of this variable.
	EFI_STATUS status = rs->SetVariable(storage->name, storage->vendor,
					    0, 0, (void *)storage->data);
	if (status != EFI_SUCCESS && status != EFI_NOT_FOUND) {
		printf("Failed to erase previous version of nvstorage.\n");
		return 1;
	}
	status = rs->SetVariable(storage->name, storage->vendor, attributes,
				 storage->size, (void *)storage->data);
	if (status != EFI_SUCCESS) {
		printf("Error writing NV storage.\n");
		return 1;
	}

	return 0;
}

static int uefi_nv_storage_prepare(UefiNvStorage *storage)
{
	EFI_SYSTEM_TABLE *st = uefi_system_table_ptr();
	if (!st)
		return 1;
	EFI_RUNTIME_SERVICES *rs = st->RuntimeServices;

	UINTN old_size = 0;
	EFI_STATUS status = rs->GetVariable(storage->name, storage->vendor,
					    NULL, &old_size, NULL);

	if (status == EFI_NOT_FOUND || old_size != storage->size) {
		printf("UEFI NV variable not found or the wrong size.\n");
		storage->data = xzalloc(storage->size);

		if (uefi_nv_storage_write_variable(storage))
			return 1;
	} else {
		storage->data = xmalloc(storage->size);
		status = rs->GetVariable(storage->name, storage->vendor,
					 NULL, &old_size, storage->data);
	}

	return 0;
}


static int uefi_nv_storage_read(StorageOps *me, void *buffer,
				uint64_t offset, size_t size)
{
	UefiNvStorage *storage = container_of(me, UefiNvStorage, ops);

	if (!storage->data && uefi_nv_storage_prepare(storage))
		return 1;

	if (offset + size > storage->size) {
		printf("Read beyond the bounds of UEFI NV variable.\n");
		return 1;
	}

	memcpy(buffer, (uint8_t *)storage->data + offset, size);
	return 0;
}

static int uefi_nv_storage_write(StorageOps *me, const void *buffer,
				 uint64_t offset, size_t size)
{
	UefiNvStorage *storage = container_of(me, UefiNvStorage, ops);

	if (!storage->data && uefi_nv_storage_prepare(storage))
		return 1;

	if (offset + size > storage->size) {
		printf("Write beyond the bounds of UEFI NV variable.\n");
		return 1;
	}

	memcpy((uint8_t *)storage->data + offset, buffer, size);
	return uefi_nv_storage_write_variable(storage);
}

static int uefi_nv_storage_size(StorageOps *me)
{
	UefiNvStorage *storage = container_of(me, UefiNvStorage, ops);

	if (!storage->data && uefi_nv_storage_prepare(storage))
		return -1;

	return storage->size;
}

UefiNvStorage *new_uefi_nv_storage(size_t size, CHAR16 *name, EFI_GUID *vendor)
{
	UefiNvStorage *storage = xzalloc(sizeof(*storage));

	storage->ops.read = &uefi_nv_storage_read;
	storage->ops.write = &uefi_nv_storage_write;
	storage->ops.size = &uefi_nv_storage_size;

	storage->size = size;

	storage->name = name;
	storage->vendor = vendor ? vendor : &uefi_nv_default_vendor_guid;

	return storage;
}