drivers/sfi/sfi_core.c - kernel/msm-4.19 - Gitiles

 /* sfi_core.c Simple Firmware Interface - core internals */

 /*

   This file is provided under a dual BSD/GPLv2 license.  When using or
   redistributing this file, you may do so under either license.

   GPL LICENSE SUMMARY

   Copyright(c) 2009 Intel Corporation. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of version 2 of the GNU General Public License as
   published by the Free Software Foundation.

   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., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
   The full GNU General Public License is included in this distribution
   in the file called LICENSE.GPL.

   BSD LICENSE

   Copyright(c) 2009 Intel Corporation. All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in
       the documentation and/or other materials provided with the
       distribution.
     * Neither the name of Intel Corporation nor the names of its
       contributors may be used to endorse or promote products derived
       from this software without specific prior written permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

 #define KMSG_COMPONENT "SFI"
 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

 #include <linux/bootmem.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/acpi.h>
 #include <linux/init.h>
 #include <linux/sfi.h>

 #include "sfi_core.h"

 #define ON_SAME_PAGE(addr1, addr2) \
 	(((unsigned long)(addr1) & PAGE_MASK) == \
 	((unsigned long)(addr2) & PAGE_MASK))
 #define TABLE_ON_PAGE(page, table, size) (ON_SAME_PAGE(page, table) && \
 				ON_SAME_PAGE(page, table + size))

 int sfi_disabled __read_mostly;
 EXPORT_SYMBOL(sfi_disabled);

 static u64 syst_pa __read_mostly;
 static struct sfi_table_simple *syst_va __read_mostly;

 /*
  * FW creates and saves the SFI tables in memory. When these tables get
  * used, they may need to be mapped to virtual address space, and the mapping
  * can happen before or after the ioremap() is ready, so a flag is needed
  * to indicating this
  */
 static u32 sfi_use_ioremap __read_mostly;

 /*
  * sfi_un/map_memory calls early_ioremap/iounmap which is a __init function
  * and introduces section mismatch. So use __ref to make it calm.
  */
 static void __iomem * __ref sfi_map_memory(u64 phys, u32 size)
 {
 	if (!phys || !size)
 		return NULL;

 	if (sfi_use_ioremap)
 		return ioremap(phys, size);
 	else
 		return early_ioremap(phys, size);
 }

 static void __ref sfi_unmap_memory(void __iomem *virt, u32 size)
 {
 	if (!virt || !size)
 		return;

 	if (sfi_use_ioremap)
 		iounmap(virt);
 	else
 		early_iounmap(virt, size);
 }

 static void sfi_print_table_header(unsigned long long pa,
 				struct sfi_table_header *header)
 {
 	pr_info("%4.4s %llX, %04X (v%d %6.6s %8.8s)\n",
 		header->sig, pa,
 		header->len, header->rev, header->oem_id,
 		header->oem_table_id);
 }

 /*
  * sfi_verify_table()
  * Sanity check table lengh, calculate checksum
  */
 static __init int sfi_verify_table(struct sfi_table_header *table)
 {

 	u8 checksum = 0;
 	u8 *puchar = (u8 *)table;
 	u32 length = table->len;

 	/* Sanity check table length against arbitrary 1MB limit */
 	if (length > 0x100000) {
 		pr_err("Invalid table length 0x%x\n", length);
 		return -1;
 	}

 	while (length--)
 		checksum += *puchar++;

 	if (checksum) {
 		pr_err("Checksum %2.2X should be %2.2X\n",
 			table->csum, table->csum - checksum);
 		return -1;
 	}
 	return 0;
 }

 /*
  * sfi_map_table()
  *
  * Return address of mapped table
  * Check for common case that we can re-use mapping to SYST,
  * which requires syst_pa, syst_va to be initialized.
  */
 struct sfi_table_header *sfi_map_table(u64 pa)
 {
 	struct sfi_table_header *th;
 	u32 length;

 	if (!TABLE_ON_PAGE(syst_pa, pa, sizeof(struct sfi_table_header)))
 		th = sfi_map_memory(pa, sizeof(struct sfi_table_header));
 	else
 		th = (void *)syst_va + (pa - syst_pa);

 	 /* If table fits on same page as its header, we are done */
 	if (TABLE_ON_PAGE(th, th, th->len))
 		return th;

 	/* Entire table does not fit on same page as SYST */
 	length = th->len;
 	if (!TABLE_ON_PAGE(syst_pa, pa, sizeof(struct sfi_table_header)))
 		sfi_unmap_memory(th, sizeof(struct sfi_table_header));

 	return sfi_map_memory(pa, length);
 }

 /*
  * sfi_unmap_table()
  *
  * Undoes effect of sfi_map_table() by unmapping table
  * if it did not completely fit on same page as SYST.
  */
 void sfi_unmap_table(struct sfi_table_header *th)
 {
 	if (!TABLE_ON_PAGE(syst_va, th, th->len))
 		sfi_unmap_memory(th, TABLE_ON_PAGE(th, th, th->len) ?
 					sizeof(*th) : th->len);
 }

 static int sfi_table_check_key(struct sfi_table_header *th,
 				struct sfi_table_key *key)
 {

 	if (strncmp(th->sig, key->sig, SFI_SIGNATURE_SIZE)
 		|| (key->oem_id && strncmp(th->oem_id,
 				key->oem_id, SFI_OEM_ID_SIZE))
 		|| (key->oem_table_id && strncmp(th->oem_table_id,
 				key->oem_table_id, SFI_OEM_TABLE_ID_SIZE)))
 		return -1;

 	return 0;
 }

 /*
  * This function will be used in 2 cases:
  * 1. used to enumerate and verify the tables addressed by SYST/XSDT,
  *    thus no signature will be given (in kernel boot phase)
  * 2. used to parse one specific table, signature must exist, and
  *    the mapped virt address will be returned, and the virt space
  *    will be released by call sfi_put_table() later
  *
  * This two cases are from two different functions with two different
  * sections and causes section mismatch warning. So use __ref to tell
  * modpost not to make any noise.
  *
  * Return value:
  *	NULL:			when can't find a table matching the key
  *	ERR_PTR(error):		error value
  *	virt table address:	when a matched table is found
  */
 struct sfi_table_header *
  __ref sfi_check_table(u64 pa, struct sfi_table_key *key)
 {
 	struct sfi_table_header *th;
 	void *ret = NULL;

 	th = sfi_map_table(pa);
 	if (!th)
 		return ERR_PTR(-ENOMEM);

 	if (!key->sig) {
 		sfi_print_table_header(pa, th);
 		if (sfi_verify_table(th))
 			ret = ERR_PTR(-EINVAL);
 	} else {
 		if (!sfi_table_check_key(th, key))
 			return th;	/* Success */
 	}

 	sfi_unmap_table(th);
 	return ret;
 }

 /*
  * sfi_get_table()
  *
  * Search SYST for the specified table with the signature in
  * the key, and return the mapped table
  */
 struct sfi_table_header *sfi_get_table(struct sfi_table_key *key)
 {
 	struct sfi_table_header *th;
 	u32 tbl_cnt, i;

 	tbl_cnt = SFI_GET_NUM_ENTRIES(syst_va, u64);
 	for (i = 0; i < tbl_cnt; i++) {
 		th = sfi_check_table(syst_va->pentry[i], key);
 		if (!IS_ERR(th) && th)
 			return th;
 	}

 	return NULL;
 }

 void sfi_put_table(struct sfi_table_header *th)
 {
 	sfi_unmap_table(th);
 }

 /* Find table with signature, run handler on it */
 int sfi_table_parse(char *signature, char *oem_id, char *oem_table_id,
 			sfi_table_handler handler)
 {
 	struct sfi_table_header *table = NULL;
 	struct sfi_table_key key;
 	int ret = -EINVAL;

 	if (sfi_disabled || !handler || !signature)
 		goto exit;

 	key.sig = signature;
 	key.oem_id = oem_id;
 	key.oem_table_id = oem_table_id;

 	table = sfi_get_table(&key);
 	if (!table)
 		goto exit;

 	ret = handler(table);
 	sfi_put_table(table);
 exit:
 	return ret;
 }
 EXPORT_SYMBOL_GPL(sfi_table_parse);

 /*
  * sfi_parse_syst()
  * Checksum all the tables in SYST and print their headers
  *
  * success: set syst_va, return 0
  */
 static int __init sfi_parse_syst(void)
 {
 	struct sfi_table_key key = SFI_ANY_KEY;
 	int tbl_cnt, i;
 	void *ret;

 	syst_va = sfi_map_memory(syst_pa, sizeof(struct sfi_table_simple));
 	if (!syst_va)
 		return -ENOMEM;

 	tbl_cnt = SFI_GET_NUM_ENTRIES(syst_va, u64);
 	for (i = 0; i < tbl_cnt; i++) {
 		ret = sfi_check_table(syst_va->pentry[i], &key);
 		if (IS_ERR(ret))
 			return PTR_ERR(ret);
 	}

 	return 0;
 }

 /*
  * The OS finds the System Table by searching 16-byte boundaries between
  * physical address 0x000E0000 and 0x000FFFFF. The OS shall search this region
  * starting at the low address and shall stop searching when the 1st valid SFI
  * System Table is found.
  *
  * success: set syst_pa, return 0
  * fail: return -1
  */
 static __init int sfi_find_syst(void)
 {
 	unsigned long offset, len;
 	void *start;

 	len = SFI_SYST_SEARCH_END - SFI_SYST_SEARCH_BEGIN;
 	start = sfi_map_memory(SFI_SYST_SEARCH_BEGIN, len);
 	if (!start)
 		return -1;

 	for (offset = 0; offset < len; offset += 16) {
 		struct sfi_table_header *syst_hdr;

 		syst_hdr = start + offset;
 		if (strncmp(syst_hdr->sig, SFI_SIG_SYST,
 				SFI_SIGNATURE_SIZE))
 			continue;

 		if (syst_hdr->len > PAGE_SIZE)
 			continue;

 		sfi_print_table_header(SFI_SYST_SEARCH_BEGIN + offset,
 					syst_hdr);

 		if (sfi_verify_table(syst_hdr))
 			continue;

 		/*
 		 * Enforce SFI spec mandate that SYST reside within a page.
 		 */
 		if (!ON_SAME_PAGE(syst_pa, syst_pa + syst_hdr->len)) {
 			pr_info("SYST 0x%llx + 0x%x crosses page\n",
 					syst_pa, syst_hdr->len);
 			continue;
 		}

 		/* Success */
 		syst_pa = SFI_SYST_SEARCH_BEGIN + offset;
 		sfi_unmap_memory(start, len);
 		return 0;
 	}

 	sfi_unmap_memory(start, len);
 	return -1;
 }

 void __init sfi_init(void)
 {
 	if (!acpi_disabled)
 		disable_sfi();

 	if (sfi_disabled)
 		return;

 	pr_info("Simple Firmware Interface v0.7 http://simplefirmware.org\n");

 	if (sfi_find_syst() || sfi_parse_syst() || sfi_platform_init())
 		disable_sfi();

 	return;
 }

 void __init sfi_init_late(void)
 {
 	int length;

 	if (sfi_disabled)
 		return;

 	length = syst_va->header.len;
 	sfi_unmap_memory(syst_va, sizeof(struct sfi_table_simple));

 	/* Use ioremap now after it is ready */
 	sfi_use_ioremap = 1;
 	syst_va = sfi_map_memory(syst_pa, length);

 	sfi_acpi_init();
 }
	/* sfi_core.c Simple Firmware Interface - core internals */

	/*

	This file is provided under a dual BSD/GPLv2 license. When using or
	redistributing this file, you may do so under either license.

	GPL LICENSE SUMMARY

	Copyright(c) 2009 Intel Corporation. All rights reserved.

	This program is free software; you can redistribute it and/or modify
	it under the terms of version 2 of the GNU General Public License as
	published by the Free Software Foundation.

	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., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
	The full GNU General Public License is included in this distribution
	in the file called LICENSE.GPL.

	BSD LICENSE

	Copyright(c) 2009 Intel Corporation. All rights reserved.

	Redistribution and use in source and binary forms, with or without
	modification, are permitted provided that the following conditions
	are met:

	* Redistributions of source code must retain the above copyright
	notice, this list of conditions and the following disclaimer.
	* Redistributions in binary form must reproduce the above copyright
	notice, this list of conditions and the following disclaimer in
	the documentation and/or other materials provided with the
	distribution.
	* Neither the name of Intel Corporation nor the names of its
	contributors may be used to endorse or promote products derived
	from this software without specific prior written permission.

	THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	*/

	#define KMSG_COMPONENT "SFI"
	#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

	#include <linux/bootmem.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/errno.h>
	#include <linux/types.h>
	#include <linux/acpi.h>
	#include <linux/init.h>
	#include <linux/sfi.h>

	#include "sfi_core.h"

	#define ON_SAME_PAGE(addr1, addr2) \
	(((unsigned long)(addr1) & PAGE_MASK) == \
	((unsigned long)(addr2) & PAGE_MASK))
	#define TABLE_ON_PAGE(page, table, size) (ON_SAME_PAGE(page, table) && \
	ON_SAME_PAGE(page, table + size))

	int sfi_disabled __read_mostly;
	EXPORT_SYMBOL(sfi_disabled);

	static u64 syst_pa __read_mostly;
	static struct sfi_table_simple *syst_va __read_mostly;

	/*
	* FW creates and saves the SFI tables in memory. When these tables get
	* used, they may need to be mapped to virtual address space, and the mapping
	* can happen before or after the ioremap() is ready, so a flag is needed
	* to indicating this
	*/
	static u32 sfi_use_ioremap __read_mostly;

	/*
	* sfi_un/map_memory calls early_ioremap/iounmap which is a __init function
	* and introduces section mismatch. So use __ref to make it calm.
	*/
	static void __iomem * __ref sfi_map_memory(u64 phys, u32 size)
	{
	if (!phys \|\| !size)
	return NULL;

	if (sfi_use_ioremap)
	return ioremap(phys, size);
	else
	return early_ioremap(phys, size);
	}

	static void __ref sfi_unmap_memory(void __iomem *virt, u32 size)
	{
	if (!virt \|\| !size)
	return;

	if (sfi_use_ioremap)
	iounmap(virt);
	else
	early_iounmap(virt, size);
	}

	static void sfi_print_table_header(unsigned long long pa,
	struct sfi_table_header *header)
	{
	pr_info("%4.4s %llX, %04X (v%d %6.6s %8.8s)\n",
	header->sig, pa,
	header->len, header->rev, header->oem_id,
	header->oem_table_id);
	}

	/*
	* sfi_verify_table()
	* Sanity check table lengh, calculate checksum
	*/
	static __init int sfi_verify_table(struct sfi_table_header *table)
	{

	u8 checksum = 0;
	u8 puchar = (u8 )table;
	u32 length = table->len;

	/* Sanity check table length against arbitrary 1MB limit */
	if (length > 0x100000) {
	pr_err("Invalid table length 0x%x\n", length);
	return -1;
	}

	while (length--)
	checksum += *puchar++;

	if (checksum) {
	pr_err("Checksum %2.2X should be %2.2X\n",
	table->csum, table->csum - checksum);
	return -1;
	}
	return 0;
	}

	/*
	* sfi_map_table()
	*
	* Return address of mapped table
	* Check for common case that we can re-use mapping to SYST,
	* which requires syst_pa, syst_va to be initialized.
	*/
	struct sfi_table_header *sfi_map_table(u64 pa)
	{
	struct sfi_table_header *th;
	u32 length;

	if (!TABLE_ON_PAGE(syst_pa, pa, sizeof(struct sfi_table_header)))
	th = sfi_map_memory(pa, sizeof(struct sfi_table_header));
	else
	th = (void *)syst_va + (pa - syst_pa);

	/* If table fits on same page as its header, we are done */
	if (TABLE_ON_PAGE(th, th, th->len))
	return th;

	/* Entire table does not fit on same page as SYST */
	length = th->len;
	if (!TABLE_ON_PAGE(syst_pa, pa, sizeof(struct sfi_table_header)))
	sfi_unmap_memory(th, sizeof(struct sfi_table_header));

	return sfi_map_memory(pa, length);
	}

	/*
	* sfi_unmap_table()
	*
	* Undoes effect of sfi_map_table() by unmapping table
	* if it did not completely fit on same page as SYST.
	*/
	void sfi_unmap_table(struct sfi_table_header *th)
	{
	if (!TABLE_ON_PAGE(syst_va, th, th->len))
	sfi_unmap_memory(th, TABLE_ON_PAGE(th, th, th->len) ?
	sizeof(*th) : th->len);
	}

	static int sfi_table_check_key(struct sfi_table_header *th,
	struct sfi_table_key *key)
	{

	if (strncmp(th->sig, key->sig, SFI_SIGNATURE_SIZE)
	\|\| (key->oem_id && strncmp(th->oem_id,
	key->oem_id, SFI_OEM_ID_SIZE))
	\|\| (key->oem_table_id && strncmp(th->oem_table_id,
	key->oem_table_id, SFI_OEM_TABLE_ID_SIZE)))
	return -1;

	return 0;
	}

	/*
	* This function will be used in 2 cases:
	* 1. used to enumerate and verify the tables addressed by SYST/XSDT,
	* thus no signature will be given (in kernel boot phase)
	* 2. used to parse one specific table, signature must exist, and
	* the mapped virt address will be returned, and the virt space
	* will be released by call sfi_put_table() later
	*
	* This two cases are from two different functions with two different
	* sections and causes section mismatch warning. So use __ref to tell
	* modpost not to make any noise.
	*
	* Return value:
	* NULL: when can't find a table matching the key
	* ERR_PTR(error): error value
	* virt table address: when a matched table is found
	*/
	struct sfi_table_header *
	__ref sfi_check_table(u64 pa, struct sfi_table_key *key)
	{
	struct sfi_table_header *th;
	void *ret = NULL;

	th = sfi_map_table(pa);
	if (!th)
	return ERR_PTR(-ENOMEM);

	if (!key->sig) {
	sfi_print_table_header(pa, th);
	if (sfi_verify_table(th))
	ret = ERR_PTR(-EINVAL);
	} else {
	if (!sfi_table_check_key(th, key))
	return th; /* Success */
	}

	sfi_unmap_table(th);
	return ret;
	}

	/*
	* sfi_get_table()
	*
	* Search SYST for the specified table with the signature in
	* the key, and return the mapped table
	*/
	struct sfi_table_header sfi_get_table(struct sfi_table_key key)
	{
	struct sfi_table_header *th;
	u32 tbl_cnt, i;

	tbl_cnt = SFI_GET_NUM_ENTRIES(syst_va, u64);
	for (i = 0; i < tbl_cnt; i++) {
	th = sfi_check_table(syst_va->pentry[i], key);
	if (!IS_ERR(th) && th)
	return th;
	}

	return NULL;
	}

	void sfi_put_table(struct sfi_table_header *th)
	{
	sfi_unmap_table(th);
	}

	/* Find table with signature, run handler on it */
	int sfi_table_parse(char signature, char oem_id, char *oem_table_id,
	sfi_table_handler handler)
	{
	struct sfi_table_header *table = NULL;
	struct sfi_table_key key;
	int ret = -EINVAL;

	if (sfi_disabled \|\| !handler \|\| !signature)
	goto exit;

	key.sig = signature;
	key.oem_id = oem_id;
	key.oem_table_id = oem_table_id;

	table = sfi_get_table(&key);
	if (!table)
	goto exit;

	ret = handler(table);
	sfi_put_table(table);
	exit:
	return ret;
	}
	EXPORT_SYMBOL_GPL(sfi_table_parse);

	/*
	* sfi_parse_syst()
	* Checksum all the tables in SYST and print their headers
	*
	* success: set syst_va, return 0
	*/
	static int __init sfi_parse_syst(void)
	{
	struct sfi_table_key key = SFI_ANY_KEY;
	int tbl_cnt, i;
	void *ret;

	syst_va = sfi_map_memory(syst_pa, sizeof(struct sfi_table_simple));
	if (!syst_va)
	return -ENOMEM;

	tbl_cnt = SFI_GET_NUM_ENTRIES(syst_va, u64);
	for (i = 0; i < tbl_cnt; i++) {
	ret = sfi_check_table(syst_va->pentry[i], &key);
	if (IS_ERR(ret))
	return PTR_ERR(ret);
	}

	return 0;
	}

	/*
	* The OS finds the System Table by searching 16-byte boundaries between
	* physical address 0x000E0000 and 0x000FFFFF. The OS shall search this region
	* starting at the low address and shall stop searching when the 1st valid SFI
	* System Table is found.
	*
	* success: set syst_pa, return 0
	* fail: return -1
	*/
	static __init int sfi_find_syst(void)
	{
	unsigned long offset, len;
	void *start;

	len = SFI_SYST_SEARCH_END - SFI_SYST_SEARCH_BEGIN;
	start = sfi_map_memory(SFI_SYST_SEARCH_BEGIN, len);
	if (!start)
	return -1;

	for (offset = 0; offset < len; offset += 16) {
	struct sfi_table_header *syst_hdr;

	syst_hdr = start + offset;
	if (strncmp(syst_hdr->sig, SFI_SIG_SYST,
	SFI_SIGNATURE_SIZE))
	continue;

	if (syst_hdr->len > PAGE_SIZE)
	continue;

	sfi_print_table_header(SFI_SYST_SEARCH_BEGIN + offset,
	syst_hdr);

	if (sfi_verify_table(syst_hdr))
	continue;

	/*
	* Enforce SFI spec mandate that SYST reside within a page.
	*/
	if (!ON_SAME_PAGE(syst_pa, syst_pa + syst_hdr->len)) {
	pr_info("SYST 0x%llx + 0x%x crosses page\n",
	syst_pa, syst_hdr->len);
	continue;
	}

	/* Success */
	syst_pa = SFI_SYST_SEARCH_BEGIN + offset;
	sfi_unmap_memory(start, len);
	return 0;
	}

	sfi_unmap_memory(start, len);
	return -1;
	}

	void __init sfi_init(void)
	{
	if (!acpi_disabled)
	disable_sfi();

	if (sfi_disabled)
	return;

	pr_info("Simple Firmware Interface v0.7 http://simplefirmware.org\n");

	if (sfi_find_syst() \|\| sfi_parse_syst() \|\| sfi_platform_init())
	disable_sfi();

	return;
	}

	void __init sfi_init_late(void)
	{
	int length;

	if (sfi_disabled)
	return;

	length = syst_va->header.len;
	sfi_unmap_memory(syst_va, sizeof(struct sfi_table_simple));

	/* Use ioremap now after it is ready */
	sfi_use_ioremap = 1;
	syst_va = sfi_map_memory(syst_pa, length);

	sfi_acpi_init();
	}