vpnor/backend.cpp - openbmc/hiomapd - Gitiles

 // SPDX-License-Identifier: Apache-2.0
 // Copyright (C) 2018 IBM Corp.

 #include "config.h"

 #include <fcntl.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <syslog.h>
 #include <unistd.h>

 #include <algorithm>

 extern "C" {
 #include "backend.h"
 #include "common.h"
 #include "lpc.h"
 #include "mboxd.h"
 #include "protocol.h"
 #include "vpnor/backend.h"
 }

 #include "vpnor/partition.hpp"
 #include "vpnor/table.hpp"
 #include "xyz/openbmc_project/Common/error.hpp"

 #include <cassert>
 #include <exception>
 #include <filesystem>
 #include <memory>
 #include <phosphor-logging/elog-errors.hpp>
 #include <phosphor-logging/log.hpp>
 #include <stdexcept>
 #include <string>

 #include "vpnor/backend.h"

 namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
 namespace fs = std::filesystem;
 namespace vpnor = openpower::virtual_pnor;

 static constexpr uint32_t VPNOR_ERASE_SIZE = 4 * 1024;

 void vpnor_default_paths(vpnor_partition_paths* paths)
 {
     strncpy(paths->ro_loc, PARTITION_FILES_RO_LOC, PATH_MAX);
     paths->ro_loc[PATH_MAX - 1] = '\0';
     strncpy(paths->rw_loc, PARTITION_FILES_RW_LOC, PATH_MAX);
     paths->rw_loc[PATH_MAX - 1] = '\0';
     strncpy(paths->prsv_loc, PARTITION_FILES_PRSV_LOC, PATH_MAX);
     paths->prsv_loc[PATH_MAX - 1] = '\0';
     strncpy(paths->patch_loc, PARTITION_FILES_PATCH_LOC, PATH_MAX);
     paths->prsv_loc[PATH_MAX - 1] = '\0';
 }

 /** @brief Create a virtual PNOR partition table.
  *
  *  @param[in] backend - The backend context pointer
  *  @param[in] paths - A paths object pointer to initialise vpnor
  *
  *  This API should be called before calling any other APIs below. If a table
  *  already exists, this function will not do anything further. This function
  *  will not do anything if the context is NULL.
  *
  *  The content of the paths object is copied out, ownership is retained by the
  *  caller.
  *
  *  Returns 0 if the call succeeds, else a negative error code.
  */
 static int vpnor_init(struct backend* backend,
                       const vpnor_partition_paths* paths)
 {
     namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
     namespace fs = std::filesystem;
     namespace vpnor = openpower::virtual_pnor;

     vpnor_data* priv = new vpnor_data;
     assert(priv);

     priv->paths = *paths;
     backend->priv = priv;

     try
     {
         priv->vpnor = new vpnor_partition_table;
         priv->vpnor->table =
             new openpower::virtual_pnor::partition::Table(backend);
     }
     catch (vpnor::TocEntryError& e)
     {
         MSG_ERR("%s\n", e.what());
         try
         {
             phosphor::logging::commit<err::InternalFailure>();
         }
         catch (const std::exception& e)
         {
             MSG_ERR("Failed to commit InternalFailure: %s\n", e.what());
         }
         return -EINVAL;
     }

     return 0;
 }

 /** @brief Copy bootloader partition (alongwith TOC) to LPC memory
  *
  *  @param[in] backend - The backend context pointer
  *
  *  @returns 0 on success, negative error code on failure
  */
 int vpnor_copy_bootloader_partition(const struct backend* backend, void* buf,
                                     uint32_t count)
 {
     // The hostboot bootloader has certain size/offset assumptions, so
     // we need a special partition table here.
     // It assumes the PNOR is 64M, the TOC size is 32K, the erase block is
     // 4K, the page size is 4K.
     // It also assumes the TOC is at the 'end of pnor - toc size - 1 page size'
     // offset, and first looks for the TOC here, before proceeding to move up
     // page by page looking for the TOC. So it is optimal to place the TOC at
     // this offset.
     constexpr size_t eraseSize = 0x1000;
     constexpr size_t pageSize = 0x1000;
     constexpr size_t pnorSize = 0x4000000;
     constexpr size_t tocMaxSize = 0x8000;
     constexpr size_t tocStart = pnorSize - tocMaxSize - pageSize;
     constexpr auto blPartitionName = "HBB";

     namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
     namespace fs = std::filesystem;
     namespace vpnor = openpower::virtual_pnor;

     try
     {
         vpnor_partition_table vtbl{};
         struct vpnor_data priv;
         struct backend local = *backend;

         priv.vpnor = &vtbl;
         priv.paths = ((struct vpnor_data*)backend->priv)->paths;
         local.priv = &priv;
         local.block_size_shift = log_2(eraseSize);

         openpower::virtual_pnor::partition::Table blTable(&local);

         vtbl.table = &blTable;

         size_t tocOffset = 0;

         const pnor_partition& partition = blTable.partition(blPartitionName);
         size_t hbbOffset = partition.data.base * eraseSize;
         uint32_t hbbSize = partition.data.actual;

         if (count < tocStart + blTable.capacity() ||
             count < hbbOffset + hbbSize)
         {
             MSG_ERR("Reserved memory too small for dumb bootstrap\n");
             return -EINVAL;
         }

         uint8_t* buf8 = static_cast<uint8_t*>(buf);
         backend_copy(&local, tocOffset, buf8 + tocStart, blTable.capacity());
         backend_copy(&local, hbbOffset, buf8 + hbbOffset, hbbSize);
     }
     catch (err::InternalFailure& e)
     {
         phosphor::logging::commit<err::InternalFailure>();
         return -EIO;
     }
     catch (vpnor::ReasonedError& e)
     {
         MSG_ERR("%s\n", e.what());
         phosphor::logging::commit<err::InternalFailure>();
         return -EIO;
     }

     return 0;
 }

 int vpnor_dev_init(struct backend* backend, void* data)
 {
     vpnor_partition_paths* paths = (vpnor_partition_paths*)data;
     struct mtd_info_user mtd_info;
     const char* filename = NULL;
     int fd;
     int rc = 0;

     if (!(fs::is_directory(fs::status(paths->ro_loc)) &&
           fs::is_directory(fs::status(paths->rw_loc)) &&
           fs::is_directory(fs::status(paths->prsv_loc))))
     {
         return -EINVAL;
     }

     if (backend->flash_size == 0)
     {
         filename = get_dev_mtd();

         MSG_INFO("No flash size provided, using PNOR MTD size\n");

         if (!filename)
         {
             MSG_ERR("Couldn't find the flash /dev/mtd partition\n");
             return -errno;
         }

         MSG_DBG("Opening %s\n", filename);

         fd = open(filename, O_RDWR);
         if (fd < 0)
         {
             MSG_ERR("Couldn't open %s with flags O_RDWR: %s\n", filename,
                     strerror(errno));
             rc = -errno;
             goto cleanup_filename;
         }

         // Read the Flash Info
         if (ioctl(fd, MEMGETINFO, &mtd_info) == -1)
         {
             MSG_ERR("Couldn't get information about MTD: %s\n",
                     strerror(errno));
             rc = -errno;
             goto cleanup_fd;
         }

         close(fd);
         free((void*)filename);

         // See comment in flash.c on why
         // this is needed.
         backend->flash_size = mtd_info.size;
     }

     // Hostboot requires a 4K block-size to be used in the FFS flash structure
     backend->erase_size_shift = log_2(VPNOR_ERASE_SIZE);
     backend->block_size_shift = backend->erase_size_shift;

     return vpnor_init(backend, paths);

 cleanup_fd:
     close(fd);

 cleanup_filename:
     free((void*)filename);

     return rc;
 }

 static void vpnor_free(struct backend* backend)
 {
     struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

     if (priv)
     {
         if (priv->vpnor)
         {
             delete priv->vpnor->table;
         }
         delete priv->vpnor;
     }
     delete priv;
 }

 /*
  * vpnor_copy() - Copy data from the virtual pnor into a provided buffer
  * @context:    The backend context pointer
  * @offset:     The pnor offset to copy from (bytes)
  * @mem:        The buffer to copy into (must be of atleast 'size' bytes)
  * @size:       The number of bytes to copy
  * Return:      Number of bytes copied on success, otherwise negative error
  *              code. vpnor_copy will copy at most 'size' bytes, but it may
  *              copy less.
  */
 static int64_t vpnor_copy(struct backend* backend, uint32_t offset, void* mem,
                           uint32_t size)
 {
     struct vpnor_data* priv = (struct vpnor_data*)backend->priv;
     vpnor::partition::Table* table;
     int rc = size;

     if (!(priv->vpnor && priv->vpnor->table))
     {
         MSG_ERR("Trying to copy data with uninitialised context!\n");
         return -EINVAL;
     }

     table = priv->vpnor->table;

     MSG_DBG("Copy virtual pnor to %p for size 0x%.8x from offset 0x%.8x\n", mem,
             size, offset);

     /* The virtual PNOR partition table starts at offset 0 in the virtual
      * pnor image. Check if host asked for an offset that lies within the
      * partition table.
      */
     size_t sz = table->size();
     if (offset < sz)
     {
         const pnor_partition_table& toc = table->getHostTable();
         rc = std::min(sz - offset, static_cast<size_t>(size));
         memcpy(mem, ((uint8_t*)&toc) + offset, rc);
         return rc;
     }

     try
     {
         vpnor::Request req(backend, offset);
         rc = req.read(mem, size);
     }
     catch (vpnor::UnmappedOffset& e)
     {
         /*
          * Hooo boy. Pretend that this is valid flash so we don't have
          * discontiguous regions presented to the host. Instead, fill a window
          * with 0xff so the 'flash' looks erased. Writes to such regions are
          * dropped on the floor, see the implementation of vpnor_write() below.
          */
         MSG_INFO("Host requested unmapped region of %" PRId32
                  " bytes at offset 0x%" PRIx32 "\n",
                  size, offset);
         uint32_t span = e.next - e.base;
         rc = std::min(size, span);
         memset(mem, 0xff, rc);
     }
     catch (std::exception& e)
     {
         MSG_ERR("%s\n", e.what());
         phosphor::logging::commit<err::InternalFailure>();
         rc = -EIO;
     }
     return rc;
 }

 /*
  * vpnor_write() - Write to the virtual pnor from a provided buffer
  * @context: The backend context pointer
  * @offset:  The flash offset to write to (bytes)
  * @buf:     The buffer to write from (must be of atleast size)
  * @size:    The number of bytes to write
  *
  * Return:  0 on success otherwise negative error code
  */

 static int vpnor_write(struct backend* backend, uint32_t offset, void* buf,
                        uint32_t count)
 {
     assert(backend);

     struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

     if (!(priv && priv->vpnor && priv->vpnor->table))
     {
         MSG_ERR("Trying to write data with uninitialised context!\n");
         return -EINVAL;
     }

     vpnor::partition::Table* table = priv->vpnor->table;

     try
     {
         const struct pnor_partition& part = table->partition(offset);
         if (part.data.user.data[1] & PARTITION_READONLY)
         {
             MSG_ERR("Unreachable: Host attempted to write to read-only "
                     "partition %s\n",
                     part.data.name);
             return -EPERM;
         }

         MSG_DBG("Write flash @ 0x%.8x for 0x%.8x from %p\n", offset, count,
                 buf);
         vpnor::Request req(backend, offset);
         req.write(buf, count);
     }
     catch (vpnor::UnmappedOffset& e)
     {
         MSG_ERR("Unreachable: Host attempted to write %" PRIu32
                 " bytes to unmapped offset 0x%" PRIx32 "\n",
                 count, offset);
         return -EACCES;
     }
     catch (const vpnor::OutOfBoundsOffset& e)
     {
         MSG_ERR("%s\n", e.what());
         return -EINVAL;
     }
     catch (const std::exception& e)
     {
         MSG_ERR("%s\n", e.what());
         phosphor::logging::commit<err::InternalFailure>();
         return -EIO;
     }
     return 0;
 }

 static bool vpnor_partition_is_readonly(const pnor_partition& part)
 {
     return part.data.user.data[1] & PARTITION_READONLY;
 }

 static int vpnor_validate(struct backend* backend, uint32_t offset,
                           uint32_t size __attribute__((unused)), bool ro)
 {
     struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

     /* All reads are allowed */
     if (ro)
     {
         return 0;
     }

     /* Only allow write windows on regions mapped by the ToC as writeable */
     try
     {
         const pnor_partition& part = priv->vpnor->table->partition(offset);
         if (vpnor_partition_is_readonly(part))
         {
             MSG_DBG("Try to write read only partition (part=%s, offset=0x%x)\n",
                     part.data.name, offset);
             return -EPERM;
         }
     }
     catch (const openpower::virtual_pnor::UnmappedOffset& e)
     {
         /*
          * Writes to unmapped areas are not meaningful, so deny the request.
          * This removes the ability for a compromised host to abuse unused
          * space if any data was to be persisted (which it isn't).
          */
         return -EACCES;
     }

     // Allowed.
     return 0;
 }

 /*
  * vpnor_reset() - Reset the lpc bus mapping
  * @context:     The mbox context pointer
  *
  * Return        0 on success otherwise negative error code
  */
 static int vpnor_reset(struct backend* backend, void* buf, uint32_t count)
 {
     const struct vpnor_data* priv = (const struct vpnor_data*)backend->priv;
     int rc;

     vpnor_partition_paths paths = priv->paths;

     vpnor_free(backend);

     rc = vpnor_init(backend, &paths);
     if (rc < 0)
         return rc;

     rc = vpnor_copy_bootloader_partition(backend, buf, count);
     if (rc < 0)
         return rc;

     return reset_lpc_memory;
 }

 /*
  * vpnor_align_offset() - Align the offset
  * @context:    The backend context pointer
  * @offset:	The flash offset
  * @window_size:The window size
  *
  * Return:      0 on success otherwise negative error code
  */
 static int vpnor_align_offset(struct backend* backend, uint32_t* offset,
                               uint32_t window_size)
 {
     const struct vpnor_data* priv = (const struct vpnor_data*)backend->priv;

     /* Adjust the offset to align with the offset of partition base */
     try
     {
         // Get the base of the partition
         const pnor_partition& part = priv->vpnor->table->partition(*offset);
         uint32_t base = part.data.base * VPNOR_ERASE_SIZE;

         // Get the base offset relative to the window_size
         uint32_t base_offset = base & (window_size - 1);

         // Adjust the offset to align with the base
         *offset = ((*offset - base_offset) & ~(window_size - 1)) + base_offset;
         MSG_DBG(
             "vpnor_align_offset: to @ 0x%.8x(base=0x%.8x base_offset=0x%.8x)\n",
             *offset, base, base_offset);
         return 0;
     }
     catch (const openpower::virtual_pnor::UnmappedOffset& e)
     {
         /*
          * Writes to unmapped areas are not meaningful, so deny the request.
          * This removes the ability for a compromised host to abuse unused
          * space if any data was to be persisted (which it isn't).
          */
         return -EACCES;
     }
 }

 static const struct backend_ops vpnor_ops = {
     .init = vpnor_dev_init,
     .free = vpnor_free,
     .copy = vpnor_copy,
     .set_bytemap = NULL,
     .erase = NULL,
     .write = vpnor_write,
     .validate = vpnor_validate,
     .reset = vpnor_reset,
     .align_offset = vpnor_align_offset,
 };

 struct backend backend_get_vpnor(void)
 {
     struct backend be = {0};

     be.ops = &vpnor_ops;

     return be;
 }

 int backend_probe_vpnor(struct backend* master,
                         const struct vpnor_partition_paths* paths)
 {
     struct backend with;

     assert(master);
     with = backend_get_vpnor();

     return backend_init(master, &with, (void*)paths);
 }
	// SPDX-License-Identifier: Apache-2.0
	// Copyright (C) 2018 IBM Corp.

	#include "config.h"

	#include <fcntl.h>
	#include <stdint.h>
	#include <stdlib.h>
	#include <sys/ioctl.h>
	#include <sys/mman.h>
	#include <syslog.h>
	#include <unistd.h>

	#include <algorithm>

	extern "C" {
	#include "backend.h"
	#include "common.h"
	#include "lpc.h"
	#include "mboxd.h"
	#include "protocol.h"
	#include "vpnor/backend.h"
	}

	#include "vpnor/partition.hpp"
	#include "vpnor/table.hpp"
	#include "xyz/openbmc_project/Common/error.hpp"

	#include <cassert>
	#include <exception>
	#include <filesystem>
	#include <memory>
	#include <phosphor-logging/elog-errors.hpp>
	#include <phosphor-logging/log.hpp>
	#include <stdexcept>
	#include <string>

	#include "vpnor/backend.h"

	namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
	namespace fs = std::filesystem;
	namespace vpnor = openpower::virtual_pnor;

	static constexpr uint32_t VPNOR_ERASE_SIZE = 4 * 1024;

	void vpnor_default_paths(vpnor_partition_paths* paths)
	{
	strncpy(paths->ro_loc, PARTITION_FILES_RO_LOC, PATH_MAX);
	paths->ro_loc[PATH_MAX - 1] = '\0';
	strncpy(paths->rw_loc, PARTITION_FILES_RW_LOC, PATH_MAX);
	paths->rw_loc[PATH_MAX - 1] = '\0';
	strncpy(paths->prsv_loc, PARTITION_FILES_PRSV_LOC, PATH_MAX);
	paths->prsv_loc[PATH_MAX - 1] = '\0';
	strncpy(paths->patch_loc, PARTITION_FILES_PATCH_LOC, PATH_MAX);
	paths->prsv_loc[PATH_MAX - 1] = '\0';
	}

	/** @brief Create a virtual PNOR partition table.
	*
	* @param[in] backend - The backend context pointer
	* @param[in] paths - A paths object pointer to initialise vpnor
	*
	* This API should be called before calling any other APIs below. If a table
	* already exists, this function will not do anything further. This function
	* will not do anything if the context is NULL.
	*
	* The content of the paths object is copied out, ownership is retained by the
	* caller.
	*
	* Returns 0 if the call succeeds, else a negative error code.
	*/
	static int vpnor_init(struct backend* backend,
	const vpnor_partition_paths* paths)
	{
	namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
	namespace fs = std::filesystem;
	namespace vpnor = openpower::virtual_pnor;

	vpnor_data* priv = new vpnor_data;
	assert(priv);

	priv->paths = *paths;
	backend->priv = priv;

	try
	{
	priv->vpnor = new vpnor_partition_table;
	priv->vpnor->table =
	new openpower::virtual_pnor::partition::Table(backend);
	}
	catch (vpnor::TocEntryError& e)
	{
	MSG_ERR("%s\n", e.what());
	try
	{
	phosphor::logging::commit<err::InternalFailure>();
	}
	catch (const std::exception& e)
	{
	MSG_ERR("Failed to commit InternalFailure: %s\n", e.what());
	}
	return -EINVAL;
	}

	return 0;
	}

	/** @brief Copy bootloader partition (alongwith TOC) to LPC memory
	*
	* @param[in] backend - The backend context pointer
	*
	* @returns 0 on success, negative error code on failure
	*/
	int vpnor_copy_bootloader_partition(const struct backend* backend, void* buf,
	uint32_t count)
	{
	// The hostboot bootloader has certain size/offset assumptions, so
	// we need a special partition table here.
	// It assumes the PNOR is 64M, the TOC size is 32K, the erase block is
	// 4K, the page size is 4K.
	// It also assumes the TOC is at the 'end of pnor - toc size - 1 page size'
	// offset, and first looks for the TOC here, before proceeding to move up
	// page by page looking for the TOC. So it is optimal to place the TOC at
	// this offset.
	constexpr size_t eraseSize = 0x1000;
	constexpr size_t pageSize = 0x1000;
	constexpr size_t pnorSize = 0x4000000;
	constexpr size_t tocMaxSize = 0x8000;
	constexpr size_t tocStart = pnorSize - tocMaxSize - pageSize;
	constexpr auto blPartitionName = "HBB";

	namespace err = sdbusplus::xyz::openbmc_project::Common::Error;
	namespace fs = std::filesystem;
	namespace vpnor = openpower::virtual_pnor;

	try
	{
	vpnor_partition_table vtbl{};
	struct vpnor_data priv;
	struct backend local = *backend;

	priv.vpnor = &vtbl;
	priv.paths = ((struct vpnor_data*)backend->priv)->paths;
	local.priv = &priv;
	local.block_size_shift = log_2(eraseSize);

	openpower::virtual_pnor::partition::Table blTable(&local);

	vtbl.table = &blTable;

	size_t tocOffset = 0;

	const pnor_partition& partition = blTable.partition(blPartitionName);
	size_t hbbOffset = partition.data.base * eraseSize;
	uint32_t hbbSize = partition.data.actual;

	if (count < tocStart + blTable.capacity() \|\|
	count < hbbOffset + hbbSize)
	{
	MSG_ERR("Reserved memory too small for dumb bootstrap\n");
	return -EINVAL;
	}

	uint8_t* buf8 = static_cast<uint8_t*>(buf);
	backend_copy(&local, tocOffset, buf8 + tocStart, blTable.capacity());
	backend_copy(&local, hbbOffset, buf8 + hbbOffset, hbbSize);
	}
	catch (err::InternalFailure& e)
	{
	phosphor::logging::commit<err::InternalFailure>();
	return -EIO;
	}
	catch (vpnor::ReasonedError& e)
	{
	MSG_ERR("%s\n", e.what());
	phosphor::logging::commit<err::InternalFailure>();
	return -EIO;
	}

	return 0;
	}

	int vpnor_dev_init(struct backend* backend, void* data)
	{
	vpnor_partition_paths* paths = (vpnor_partition_paths*)data;
	struct mtd_info_user mtd_info;
	const char* filename = NULL;
	int fd;
	int rc = 0;

	if (!(fs::is_directory(fs::status(paths->ro_loc)) &&
	fs::is_directory(fs::status(paths->rw_loc)) &&
	fs::is_directory(fs::status(paths->prsv_loc))))
	{
	return -EINVAL;
	}

	if (backend->flash_size == 0)
	{
	filename = get_dev_mtd();

	MSG_INFO("No flash size provided, using PNOR MTD size\n");

	if (!filename)
	{
	MSG_ERR("Couldn't find the flash /dev/mtd partition\n");
	return -errno;
	}

	MSG_DBG("Opening %s\n", filename);

	fd = open(filename, O_RDWR);
	if (fd < 0)
	{
	MSG_ERR("Couldn't open %s with flags O_RDWR: %s\n", filename,
	strerror(errno));
	rc = -errno;
	goto cleanup_filename;
	}

	// Read the Flash Info
	if (ioctl(fd, MEMGETINFO, &mtd_info) == -1)
	{
	MSG_ERR("Couldn't get information about MTD: %s\n",
	strerror(errno));
	rc = -errno;
	goto cleanup_fd;
	}

	close(fd);
	free((void*)filename);

	// See comment in flash.c on why
	// this is needed.
	backend->flash_size = mtd_info.size;
	}

	// Hostboot requires a 4K block-size to be used in the FFS flash structure
	backend->erase_size_shift = log_2(VPNOR_ERASE_SIZE);
	backend->block_size_shift = backend->erase_size_shift;

	return vpnor_init(backend, paths);

	cleanup_fd:
	close(fd);

	cleanup_filename:
	free((void*)filename);

	return rc;
	}

	static void vpnor_free(struct backend* backend)
	{
	struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

	if (priv)
	{
	if (priv->vpnor)
	{
	delete priv->vpnor->table;
	}
	delete priv->vpnor;
	}
	delete priv;
	}

	/*
	* vpnor_copy() - Copy data from the virtual pnor into a provided buffer
	* @context: The backend context pointer
	* @offset: The pnor offset to copy from (bytes)
	* @mem: The buffer to copy into (must be of atleast 'size' bytes)
	* @size: The number of bytes to copy
	* Return: Number of bytes copied on success, otherwise negative error
	* code. vpnor_copy will copy at most 'size' bytes, but it may
	* copy less.
	*/
	static int64_t vpnor_copy(struct backend* backend, uint32_t offset, void* mem,
	uint32_t size)
	{
	struct vpnor_data* priv = (struct vpnor_data*)backend->priv;
	vpnor::partition::Table* table;
	int rc = size;

	if (!(priv->vpnor && priv->vpnor->table))
	{
	MSG_ERR("Trying to copy data with uninitialised context!\n");
	return -EINVAL;
	}

	table = priv->vpnor->table;

	MSG_DBG("Copy virtual pnor to %p for size 0x%.8x from offset 0x%.8x\n", mem,
	size, offset);

	/* The virtual PNOR partition table starts at offset 0 in the virtual
	* pnor image. Check if host asked for an offset that lies within the
	* partition table.
	*/
	size_t sz = table->size();
	if (offset < sz)
	{
	const pnor_partition_table& toc = table->getHostTable();
	rc = std::min(sz - offset, static_cast<size_t>(size));
	memcpy(mem, ((uint8_t*)&toc) + offset, rc);
	return rc;
	}

	try
	{
	vpnor::Request req(backend, offset);
	rc = req.read(mem, size);
	}
	catch (vpnor::UnmappedOffset& e)
	{
	/*
	* Hooo boy. Pretend that this is valid flash so we don't have
	* discontiguous regions presented to the host. Instead, fill a window
	* with 0xff so the 'flash' looks erased. Writes to such regions are
	* dropped on the floor, see the implementation of vpnor_write() below.
	*/
	MSG_INFO("Host requested unmapped region of %" PRId32
	" bytes at offset 0x%" PRIx32 "\n",
	size, offset);
	uint32_t span = e.next - e.base;
	rc = std::min(size, span);
	memset(mem, 0xff, rc);
	}
	catch (std::exception& e)
	{
	MSG_ERR("%s\n", e.what());
	phosphor::logging::commit<err::InternalFailure>();
	rc = -EIO;
	}
	return rc;
	}

	/*
	* vpnor_write() - Write to the virtual pnor from a provided buffer
	* @context: The backend context pointer
	* @offset: The flash offset to write to (bytes)
	* @buf: The buffer to write from (must be of atleast size)
	* @size: The number of bytes to write
	*
	* Return: 0 on success otherwise negative error code
	*/

	static int vpnor_write(struct backend* backend, uint32_t offset, void* buf,
	uint32_t count)
	{
	assert(backend);

	struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

	if (!(priv && priv->vpnor && priv->vpnor->table))
	{
	MSG_ERR("Trying to write data with uninitialised context!\n");
	return -EINVAL;
	}

	vpnor::partition::Table* table = priv->vpnor->table;

	try
	{
	const struct pnor_partition& part = table->partition(offset);
	if (part.data.user.data[1] & PARTITION_READONLY)
	{
	MSG_ERR("Unreachable: Host attempted to write to read-only "
	"partition %s\n",
	part.data.name);
	return -EPERM;
	}

	MSG_DBG("Write flash @ 0x%.8x for 0x%.8x from %p\n", offset, count,
	buf);
	vpnor::Request req(backend, offset);
	req.write(buf, count);
	}
	catch (vpnor::UnmappedOffset& e)
	{
	MSG_ERR("Unreachable: Host attempted to write %" PRIu32
	" bytes to unmapped offset 0x%" PRIx32 "\n",
	count, offset);
	return -EACCES;
	}
	catch (const vpnor::OutOfBoundsOffset& e)
	{
	MSG_ERR("%s\n", e.what());
	return -EINVAL;
	}
	catch (const std::exception& e)
	{
	MSG_ERR("%s\n", e.what());
	phosphor::logging::commit<err::InternalFailure>();
	return -EIO;
	}
	return 0;
	}

	static bool vpnor_partition_is_readonly(const pnor_partition& part)
	{
	return part.data.user.data[1] & PARTITION_READONLY;
	}

	static int vpnor_validate(struct backend* backend, uint32_t offset,
	uint32_t size __attribute__((unused)), bool ro)
	{
	struct vpnor_data* priv = (struct vpnor_data*)backend->priv;

	/* All reads are allowed */
	if (ro)
	{
	return 0;
	}

	/* Only allow write windows on regions mapped by the ToC as writeable */
	try
	{
	const pnor_partition& part = priv->vpnor->table->partition(offset);
	if (vpnor_partition_is_readonly(part))
	{
	MSG_DBG("Try to write read only partition (part=%s, offset=0x%x)\n",
	part.data.name, offset);
	return -EPERM;
	}
	}
	catch (const openpower::virtual_pnor::UnmappedOffset& e)
	{
	/*
	* Writes to unmapped areas are not meaningful, so deny the request.
	* This removes the ability for a compromised host to abuse unused
	* space if any data was to be persisted (which it isn't).
	*/
	return -EACCES;
	}

	// Allowed.
	return 0;
	}

	/*
	* vpnor_reset() - Reset the lpc bus mapping
	* @context: The mbox context pointer
	*
	* Return 0 on success otherwise negative error code
	*/
	static int vpnor_reset(struct backend* backend, void* buf, uint32_t count)
	{
	const struct vpnor_data* priv = (const struct vpnor_data*)backend->priv;
	int rc;

	vpnor_partition_paths paths = priv->paths;

	vpnor_free(backend);

	rc = vpnor_init(backend, &paths);
	if (rc < 0)
	return rc;

	rc = vpnor_copy_bootloader_partition(backend, buf, count);
	if (rc < 0)
	return rc;

	return reset_lpc_memory;
	}

	/*
	* vpnor_align_offset() - Align the offset
	* @context: The backend context pointer
	* @offset: The flash offset
	* @window_size:The window size
	*
	* Return: 0 on success otherwise negative error code
	*/
	static int vpnor_align_offset(struct backend* backend, uint32_t* offset,
	uint32_t window_size)
	{
	const struct vpnor_data* priv = (const struct vpnor_data*)backend->priv;

	/* Adjust the offset to align with the offset of partition base */
	try
	{
	// Get the base of the partition
	const pnor_partition& part = priv->vpnor->table->partition(*offset);
	uint32_t base = part.data.base * VPNOR_ERASE_SIZE;

	// Get the base offset relative to the window_size
	uint32_t base_offset = base & (window_size - 1);

	// Adjust the offset to align with the base
	offset = ((offset - base_offset) & ~(window_size - 1)) + base_offset;
	MSG_DBG(
	"vpnor_align_offset: to @ 0x%.8x(base=0x%.8x base_offset=0x%.8x)\n",
	*offset, base, base_offset);
	return 0;
	}
	catch (const openpower::virtual_pnor::UnmappedOffset& e)
	{
	/*
	* Writes to unmapped areas are not meaningful, so deny the request.
	* This removes the ability for a compromised host to abuse unused
	* space if any data was to be persisted (which it isn't).
	*/
	return -EACCES;
	}
	}

	static const struct backend_ops vpnor_ops = {
	.init = vpnor_dev_init,
	.free = vpnor_free,
	.copy = vpnor_copy,
	.set_bytemap = NULL,
	.erase = NULL,
	.write = vpnor_write,
	.validate = vpnor_validate,
	.reset = vpnor_reset,
	.align_offset = vpnor_align_offset,
	};

	struct backend backend_get_vpnor(void)
	{
	struct backend be = {0};

	be.ops = &vpnor_ops;

	return be;
	}

	int backend_probe_vpnor(struct backend* master,
	const struct vpnor_partition_paths* paths)
	{
	struct backend with;

	assert(master);
	with = backend_get_vpnor();

	return backend_init(master, &with, (void*)paths);
	}