/*
   *  acpi_tables.c - ACPI Boot-Time Table Parsing
   *
   *  Copyright (C) 2001 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
   *
   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   *  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.
   *

   * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   *
   */

  /* Uncomment next line to get verbose printout */
  /* #define DEBUG */

  #define pr_fmt(fmt) "ACPI: " fmt

  #include <linux/init.h>
  #include <linux/kernel.h>

  #include <linux/smp.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/irq.h>
  #include <linux/errno.h>
  #include <linux/acpi.h>
  #include <linux/bootmem.h>

  #include <linux/earlycpio.h>
  #include <linux/memblock.h>

  #include <linux/initrd.h>

  #include "internal.h"

  #ifdef CONFIG_ACPI_CUSTOM_DSDT
  #include CONFIG_ACPI_CUSTOM_DSDT_FILE
  #endif

  #define ACPI_MAX_TABLES		128

  static char *mps_inti_flags_polarity[] = { "dfl", "high", "res", "low" };
  static char *mps_inti_flags_trigger[] = { "dfl", "edge", "res", "level" };

  static struct acpi_table_desc initial_tables[ACPI_MAX_TABLES] __initdata;

  static int acpi_apic_instance __initdata;

  /*
   * Disable table checksum verification for the early stage due to the size
   * limitation of the current x86 early mapping implementation.
   */
  static bool acpi_verify_table_checksum __initdata = false;

  void acpi_table_print_madt_entry(struct acpi_subtable_header *header)

  {
  	if (!header)
  		return;
  
  	switch (header->type) {

  	case ACPI_MADT_TYPE_LOCAL_APIC:

  		{

  			struct acpi_madt_local_apic *p =
  			    (struct acpi_madt_local_apic *)header;

  			pr_debug("LAPIC (acpi_id[0x%02x] lapic_id[0x%02x] %s)
  ",
  				 p->processor_id, p->id,
  				 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");

  		}

  		break;

  	case ACPI_MADT_TYPE_LOCAL_X2APIC:
  		{
  			struct acpi_madt_local_x2apic *p =
  			    (struct acpi_madt_local_x2apic *)header;

  			pr_debug("X2APIC (apic_id[0x%02x] uid[0x%02x] %s)
  ",
  				 p->local_apic_id, p->uid,
  				 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");

  		}
  		break;

  	case ACPI_MADT_TYPE_IO_APIC:

  		{

  			struct acpi_madt_io_apic *p =
  			    (struct acpi_madt_io_apic *)header;

  			pr_debug("IOAPIC (id[0x%02x] address[0x%08x] gsi_base[%d])
  ",
  				 p->id, p->address, p->global_irq_base);

  		}

  		break;

  	case ACPI_MADT_TYPE_INTERRUPT_OVERRIDE:

  		{

  			struct acpi_madt_interrupt_override *p =
  			    (struct acpi_madt_interrupt_override *)header;

  			pr_info("INT_SRC_OVR (bus %d bus_irq %d global_irq %d %s %s)
  ",
  				p->bus, p->source_irq, p->global_irq,
  				mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
  				mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2]);

  			if (p->inti_flags  &
  			    ~(ACPI_MADT_POLARITY_MASK | ACPI_MADT_TRIGGER_MASK))

  				pr_info("INT_SRC_OVR unexpected reserved flags: 0x%x
  ",
  					p->inti_flags  &

  					~(ACPI_MADT_POLARITY_MASK | ACPI_MADT_TRIGGER_MASK));

  		}

  		break;

  	case ACPI_MADT_TYPE_NMI_SOURCE:

  		{

  			struct acpi_madt_nmi_source *p =
  			    (struct acpi_madt_nmi_source *)header;

  			pr_info("NMI_SRC (%s %s global_irq %d)
  ",
  				mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
  				mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
  				p->global_irq);

  		}

  		break;

  	case ACPI_MADT_TYPE_LOCAL_APIC_NMI:

  		{

  			struct acpi_madt_local_apic_nmi *p =
  			    (struct acpi_madt_local_apic_nmi *)header;

  			pr_info("LAPIC_NMI (acpi_id[0x%02x] %s %s lint[0x%x])
  ",
  				p->processor_id,
  				mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK	],
  				mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
  				p->lint);

  		}
  		break;
  
  	case ACPI_MADT_TYPE_LOCAL_X2APIC_NMI:
  		{
  			u16 polarity, trigger;
  			struct acpi_madt_local_x2apic_nmi *p =
  			    (struct acpi_madt_local_x2apic_nmi *)header;
  
  			polarity = p->inti_flags & ACPI_MADT_POLARITY_MASK;
  			trigger = (p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2;

  			pr_info("X2APIC_NMI (uid[0x%02x] %s %s lint[0x%x])
  ",
  				p->uid,
  				mps_inti_flags_polarity[polarity],
  				mps_inti_flags_trigger[trigger],
  				p->lint);

  		}

  		break;

  	case ACPI_MADT_TYPE_LOCAL_APIC_OVERRIDE:

  		{

  			struct acpi_madt_local_apic_override *p =
  			    (struct acpi_madt_local_apic_override *)header;

  			pr_info("LAPIC_ADDR_OVR (address[%p])
  ",
  				(void *)(unsigned long)p->address);

  		}

  		break;

  	case ACPI_MADT_TYPE_IO_SAPIC:

  		{

  			struct acpi_madt_io_sapic *p =
  			    (struct acpi_madt_io_sapic *)header;

  			pr_debug("IOSAPIC (id[0x%x] address[%p] gsi_base[%d])
  ",
  				 p->id, (void *)(unsigned long)p->address,
  				 p->global_irq_base);

  		}

  		break;

  	case ACPI_MADT_TYPE_LOCAL_SAPIC:

  		{

  			struct acpi_madt_local_sapic *p =
  			    (struct acpi_madt_local_sapic *)header;

  			pr_debug("LSAPIC (acpi_id[0x%02x] lsapic_id[0x%02x] lsapic_eid[0x%02x] %s)
  ",
  				 p->processor_id, p->id, p->eid,
  				 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");

  		}

  		break;

  	case ACPI_MADT_TYPE_INTERRUPT_SOURCE:

  		{

  			struct acpi_madt_interrupt_source *p =
  			    (struct acpi_madt_interrupt_source *)header;

  			pr_info("PLAT_INT_SRC (%s %s type[0x%x] id[0x%04x] eid[0x%x] iosapic_vector[0x%x] global_irq[0x%x]
  ",
  				mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
  				mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
  				p->type, p->id, p->eid, p->io_sapic_vector,
  				p->global_irq);

  		}

  		break;

  	case ACPI_MADT_TYPE_GENERIC_INTERRUPT:
  		{
  			struct acpi_madt_generic_interrupt *p =
  				(struct acpi_madt_generic_interrupt *)header;
  			pr_debug("GICC (acpi_id[0x%04x] address[%llx] MPIDR[0x%llx] %s)
  ",
  				 p->uid, p->base_address,
  				 p->arm_mpidr,
  				 (p->flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");
  
  		}
  		break;
  
  	case ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR:
  		{
  			struct acpi_madt_generic_distributor *p =
  				(struct acpi_madt_generic_distributor *)header;
  			pr_debug("GIC Distributor (gic_id[0x%04x] address[%llx] gsi_base[%d])
  ",
  				 p->gic_id, p->base_address,
  				 p->global_irq_base);
  		}
  		break;

  	default:

  		pr_warn("Found unsupported MADT entry (type = 0x%x)
  ",
  			header->type);

  		break;
  	}
  }

  /**
   * acpi_parse_entries_array - for each proc_num find a suitable subtable
   *
   * @id: table id (for debugging purposes)
   * @table_size: single entry size
   * @table_header: where does the table start?
   * @proc: array of acpi_subtable_proc struct containing entry id
   *        and associated handler with it
   * @proc_num: how big proc is?
   * @max_entries: how many entries can we process?
   *
   * For each proc_num find a subtable with proc->id and run proc->handler
   * on it. Assumption is that there's only single handler for particular
   * entry id.
   *
   * On success returns sum of all matching entries for all proc handlers.
   * Otherwise, -ENODEV or -EINVAL is returned.
   */
  static int __init
  acpi_parse_entries_array(char *id, unsigned long table_size,

  		struct acpi_table_header *table_header,

  		struct acpi_subtable_proc *proc, int proc_num,
  		unsigned int max_entries)

  {

  	struct acpi_subtable_header *entry;

  	unsigned long table_end;

  	int count = 0;

  	int errs = 0;

  	int i;

  	if (acpi_disabled)

  		return -ENODEV;

  	if (!id)

  		return -EINVAL;

  	if (!table_size)
  		return -EINVAL;

  	if (!table_header) {

  		pr_warn("%4.4s not present
  ", id);

  		return -ENODEV;
  	}

  	table_end = (unsigned long)table_header + table_header->length;

  
  	/* Parse all entries looking for a match. */

  	entry = (struct acpi_subtable_header *)

  	    ((unsigned long)table_header + table_size);

  	while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <

  	       table_end) {

  		if (max_entries && count >= max_entries)
  			break;
  
  		for (i = 0; i < proc_num; i++) {
  			if (entry->type != proc[i].id)
  				continue;

  			if (!proc[i].handler ||

  			     (!errs && proc[i].handler(entry, table_end))) {
  				errs++;
  				continue;
  			}

  			proc[i].count++;

  			break;

  		}

  		if (i != proc_num)
  			count++;

  		/*
  		 * If entry->length is 0, break from this loop to avoid
  		 * infinite loop.
  		 */
  		if (entry->length == 0) {

  			pr_err("[%4.4s:0x%02x] Invalid zero length
  ", id, proc->id);

  			return -EINVAL;

  		}

  		entry = (struct acpi_subtable_header *)

  		    ((unsigned long)entry + entry->length);

  	}

  	if (max_entries && count > max_entries) {

  		pr_warn("[%4.4s:0x%02x] found the maximum %i entries
  ",
  			id, proc->id, count);

  	}

  	return errs ? -EINVAL : count;

  }
  
  int __init

  acpi_parse_entries(char *id,
  			unsigned long table_size,
  			acpi_tbl_entry_handler handler,
  			struct acpi_table_header *table_header,
  			int entry_id, unsigned int max_entries)
  {
  	struct acpi_subtable_proc proc = {
  		.id		= entry_id,
  		.handler	= handler,
  	};
  
  	return acpi_parse_entries_array(id, table_size, table_header,
  			&proc, 1, max_entries);
  }
  
  int __init
  acpi_table_parse_entries_array(char *id,

  			 unsigned long table_size,

  			 struct acpi_subtable_proc *proc, int proc_num,

  			 unsigned int max_entries)
  {
  	struct acpi_table_header *table_header = NULL;
  	acpi_size tbl_size;
  	int count;
  	u32 instance = 0;
  
  	if (acpi_disabled)
  		return -ENODEV;

  	if (!id)

  		return -EINVAL;
  
  	if (!strncmp(id, ACPI_SIG_MADT, 4))
  		instance = acpi_apic_instance;
  
  	acpi_get_table_with_size(id, instance, &table_header, &tbl_size);
  	if (!table_header) {
  		pr_warn("%4.4s not present
  ", id);
  		return -ENODEV;
  	}

  	count = acpi_parse_entries_array(id, table_size, table_header,
  			proc, proc_num, max_entries);

  	early_acpi_os_unmap_memory((char *)table_header, tbl_size);

  	return count;

  }

  int __init

  acpi_table_parse_entries(char *id,
  			unsigned long table_size,
  			int entry_id,
  			acpi_tbl_entry_handler handler,
  			unsigned int max_entries)
  {
  	struct acpi_subtable_proc proc = {
  		.id		= entry_id,
  		.handler	= handler,
  	};
  
  	return acpi_table_parse_entries_array(id, table_size, &proc, 1,
  						max_entries);
  }
  
  int __init

  acpi_table_parse_madt(enum acpi_madt_type id,

  		      acpi_tbl_entry_handler handler, unsigned int max_entries)

  {

  	return acpi_table_parse_entries(ACPI_SIG_MADT,

  					    sizeof(struct acpi_table_madt), id,
  					    handler, max_entries);

  }

  /**
   * acpi_table_parse - find table with @id, run @handler on it

   * @id: table id to find
   * @handler: handler to run
   *
   * Scan the ACPI System Descriptor Table (STD) for a table matching @id,

   * run @handler on it.
   *
   * Return 0 if table found, -errno if not.

   */

  int __init acpi_table_parse(char *id, acpi_tbl_table_handler handler)

  {

  	struct acpi_table_header *table = NULL;

  	acpi_size tbl_size;

  	if (acpi_disabled)

  		return -ENODEV;

  	if (!id || !handler)

  		return -EINVAL;

  	if (strncmp(id, ACPI_SIG_MADT, 4) == 0)

  		acpi_get_table_with_size(id, acpi_apic_instance, &table, &tbl_size);

  	else

  		acpi_get_table_with_size(id, 0, &table, &tbl_size);

  	if (table) {
  		handler(table);

  		early_acpi_os_unmap_memory(table, tbl_size);

  		return 0;

  	} else

  		return -ENODEV;

  }

  /* 
   * The BIOS is supposed to supply a single APIC/MADT,
   * but some report two.  Provide a knob to use either.
   * (don't you wish instance 0 and 1 were not the same?)
   */
  static void __init check_multiple_madt(void)
  {
  	struct acpi_table_header *table = NULL;

  	acpi_size tbl_size;

  	acpi_get_table_with_size(ACPI_SIG_MADT, 2, &table, &tbl_size);

  	if (table) {

  		pr_warn("BIOS bug: multiple APIC/MADT found, using %d
  ",
  			acpi_apic_instance);
  		pr_warn("If \"acpi_apic_instance=%d\" works better, "
  			"notify linux-acpi@vger.kernel.org
  ",
  			acpi_apic_instance ? 0 : 2);

  		early_acpi_os_unmap_memory(table, tbl_size);

  
  	} else
  		acpi_apic_instance = 0;
  
  	return;
  }

  static void acpi_table_taint(struct acpi_table_header *table)
  {
  	pr_warn("Override [%4.4s-%8.8s], this is unsafe: tainting kernel
  ",
  		table->signature, table->oem_table_id);
  	add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
  }

  #ifdef CONFIG_ACPI_TABLE_UPGRADE

  static u64 acpi_tables_addr;
  static int all_tables_size;
  
  /* Copied from acpica/tbutils.c:acpi_tb_checksum() */
  static u8 __init acpi_table_checksum(u8 *buffer, u32 length)
  {
  	u8 sum = 0;
  	u8 *end = buffer + length;
  
  	while (buffer < end)
  		sum = (u8) (sum + *(buffer++));
  	return sum;
  }
  
  /* All but ACPI_SIG_RSDP and ACPI_SIG_FACS: */
  static const char * const table_sigs[] = {
  	ACPI_SIG_BERT, ACPI_SIG_CPEP, ACPI_SIG_ECDT, ACPI_SIG_EINJ,
  	ACPI_SIG_ERST, ACPI_SIG_HEST, ACPI_SIG_MADT, ACPI_SIG_MSCT,
  	ACPI_SIG_SBST, ACPI_SIG_SLIT, ACPI_SIG_SRAT, ACPI_SIG_ASF,
  	ACPI_SIG_BOOT, ACPI_SIG_DBGP, ACPI_SIG_DMAR, ACPI_SIG_HPET,
  	ACPI_SIG_IBFT, ACPI_SIG_IVRS, ACPI_SIG_MCFG, ACPI_SIG_MCHI,
  	ACPI_SIG_SLIC, ACPI_SIG_SPCR, ACPI_SIG_SPMI, ACPI_SIG_TCPA,
  	ACPI_SIG_UEFI, ACPI_SIG_WAET, ACPI_SIG_WDAT, ACPI_SIG_WDDT,
  	ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT, ACPI_SIG_PSDT,
  	ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT, NULL };
  
  #define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)

  #define NR_ACPI_INITRD_TABLES 64
  static struct cpio_data __initdata acpi_initrd_files[NR_ACPI_INITRD_TABLES];
  static DECLARE_BITMAP(acpi_initrd_installed, NR_ACPI_INITRD_TABLES);

  
  #define MAP_CHUNK_SIZE   (NR_FIX_BTMAPS << PAGE_SHIFT)

  void __init acpi_table_upgrade(void)

  {

  	void *data = (void *)initrd_start;
  	size_t size = initrd_end - initrd_start;

  	int sig, no, table_nr = 0, total_offset = 0;
  	long offset = 0;
  	struct acpi_table_header *table;
  	char cpio_path[32] = "kernel/firmware/acpi/";
  	struct cpio_data file;
  
  	if (data == NULL || size == 0)
  		return;

  	for (no = 0; no < NR_ACPI_INITRD_TABLES; no++) {

  		file = find_cpio_data(cpio_path, data, size, &offset);
  		if (!file.data)
  			break;
  
  		data += offset;
  		size -= offset;
  
  		if (file.size < sizeof(struct acpi_table_header)) {
  			pr_err("ACPI OVERRIDE: Table smaller than ACPI header [%s%s]
  ",
  				cpio_path, file.name);
  			continue;
  		}
  
  		table = file.data;
  
  		for (sig = 0; table_sigs[sig]; sig++)
  			if (!memcmp(table->signature, table_sigs[sig], 4))
  				break;
  
  		if (!table_sigs[sig]) {
  			pr_err("ACPI OVERRIDE: Unknown signature [%s%s]
  ",
  				cpio_path, file.name);
  			continue;
  		}
  		if (file.size != table->length) {
  			pr_err("ACPI OVERRIDE: File length does not match table length [%s%s]
  ",
  				cpio_path, file.name);
  			continue;
  		}
  		if (acpi_table_checksum(file.data, table->length)) {
  			pr_err("ACPI OVERRIDE: Bad table checksum [%s%s]
  ",
  				cpio_path, file.name);
  			continue;
  		}
  
  		pr_info("%4.4s ACPI table found in initrd [%s%s][0x%x]
  ",
  			table->signature, cpio_path, file.name, table->length);
  
  		all_tables_size += table->length;
  		acpi_initrd_files[table_nr].data = file.data;
  		acpi_initrd_files[table_nr].size = file.size;
  		table_nr++;
  	}
  	if (table_nr == 0)
  		return;
  
  	acpi_tables_addr =

  		memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,

  				       all_tables_size, PAGE_SIZE);
  	if (!acpi_tables_addr) {
  		WARN_ON(1);
  		return;
  	}
  	/*
  	 * Only calling e820_add_reserve does not work and the
  	 * tables are invalid (memory got used) later.
  	 * memblock_reserve works as expected and the tables won't get modified.
  	 * But it's not enough on X86 because ioremap will
  	 * complain later (used by acpi_os_map_memory) that the pages
  	 * that should get mapped are not marked "reserved".
  	 * Both memblock_reserve and e820_add_region (via arch_reserve_mem_area)
  	 * works fine.
  	 */
  	memblock_reserve(acpi_tables_addr, all_tables_size);
  	arch_reserve_mem_area(acpi_tables_addr, all_tables_size);
  
  	/*
  	 * early_ioremap only can remap 256k one time. If we map all
  	 * tables one time, we will hit the limit. Need to map chunks
  	 * one by one during copying the same as that in relocate_initrd().
  	 */
  	for (no = 0; no < table_nr; no++) {
  		unsigned char *src_p = acpi_initrd_files[no].data;
  		phys_addr_t size = acpi_initrd_files[no].size;
  		phys_addr_t dest_addr = acpi_tables_addr + total_offset;
  		phys_addr_t slop, clen;
  		char *dest_p;
  
  		total_offset += size;
  
  		while (size) {
  			slop = dest_addr & ~PAGE_MASK;
  			clen = size;
  			if (clen > MAP_CHUNK_SIZE - slop)
  				clen = MAP_CHUNK_SIZE - slop;

  			dest_p = early_memremap(dest_addr & PAGE_MASK,
  						clen + slop);

  			memcpy(dest_p + slop, src_p, clen);

  			early_memunmap(dest_p, clen + slop);

  			src_p += clen;
  			dest_addr += clen;
  			size -= clen;
  		}
  	}
  }
  
  static acpi_status
  acpi_table_initrd_override(struct acpi_table_header *existing_table,
  			   acpi_physical_address *address, u32 *length)
  {
  	int table_offset = 0;
  	int table_index = 0;
  	struct acpi_table_header *table;
  	u32 table_length;
  
  	*length = 0;
  	*address = 0;
  	if (!acpi_tables_addr)
  		return AE_OK;
  
  	while (table_offset + ACPI_HEADER_SIZE <= all_tables_size) {
  		table = acpi_os_map_memory(acpi_tables_addr + table_offset,
  					   ACPI_HEADER_SIZE);
  		if (table_offset + table->length > all_tables_size) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			WARN_ON(1);
  			return AE_OK;
  		}
  
  		table_length = table->length;
  
  		/* Only override tables matched */

  		if (memcmp(existing_table->signature, table->signature, 4) ||
  		    memcmp(table->oem_id, existing_table->oem_id,
  			   ACPI_OEM_ID_SIZE) ||

  		    memcmp(table->oem_table_id, existing_table->oem_table_id,
  			   ACPI_OEM_TABLE_ID_SIZE)) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			goto next_table;
  		}

  		/*
  		 * Mark the table to avoid being used in
  		 * acpi_table_initrd_scan() and check the revision.
  		 */
  		if (test_and_set_bit(table_index, acpi_initrd_installed) ||
  		    existing_table->oem_revision >= table->oem_revision) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			goto next_table;
  		}

  
  		*length = table_length;
  		*address = acpi_tables_addr + table_offset;

  		pr_info("Table Upgrade: override [%4.4s-%6.6s-%8.8s]
  ",
  			table->signature, table->oem_id,
  			table->oem_table_id);

  		acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);

  		break;
  
  next_table:
  		table_offset += table_length;
  		table_index++;
  	}
  	return AE_OK;
  }
  
  static void __init acpi_table_initrd_scan(void)
  {
  	int table_offset = 0;
  	int table_index = 0;
  	u32 table_length;
  	struct acpi_table_header *table;
  
  	if (!acpi_tables_addr)
  		return;
  
  	while (table_offset + ACPI_HEADER_SIZE <= all_tables_size) {
  		table = acpi_os_map_memory(acpi_tables_addr + table_offset,
  					   ACPI_HEADER_SIZE);
  		if (table_offset + table->length > all_tables_size) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			WARN_ON(1);
  			return;
  		}
  
  		table_length = table->length;
  
  		/* Skip RSDT/XSDT which should only be used for override */

  		if (ACPI_COMPARE_NAME(table->signature, ACPI_SIG_RSDT) ||

  		    ACPI_COMPARE_NAME(table->signature, ACPI_SIG_XSDT)) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			goto next_table;
  		}

  		/*
  		 * Mark the table to avoid being used in
  		 * acpi_table_initrd_override(). Though this is not possible
  		 * because override is disabled in acpi_install_table().
  		 */
  		if (test_and_set_bit(table_index, acpi_initrd_installed)) {
  			acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  			goto next_table;
  		}

  		pr_info("Table Upgrade: install [%4.4s-%6.6s-%8.8s]
  ",
  			table->signature, table->oem_id,
  			table->oem_table_id);

  		acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
  		acpi_install_table(acpi_tables_addr + table_offset, TRUE);

  next_table:
  		table_offset += table_length;
  		table_index++;
  	}
  }
  #else

  static acpi_status
  acpi_table_initrd_override(struct acpi_table_header *existing_table,
  			   acpi_physical_address *address,
  			   u32 *table_length)
  {
  	*table_length = 0;
  	*address = 0;
  	return AE_OK;
  }
  
  static void __init acpi_table_initrd_scan(void)
  {
  }

  #endif /* CONFIG_ACPI_TABLE_UPGRADE */

  
  acpi_status
  acpi_os_physical_table_override(struct acpi_table_header *existing_table,
  				acpi_physical_address *address,
  				u32 *table_length)
  {
  	return acpi_table_initrd_override(existing_table, address,
  					  table_length);
  }
  
  acpi_status
  acpi_os_table_override(struct acpi_table_header *existing_table,
  		       struct acpi_table_header **new_table)
  {
  	if (!existing_table || !new_table)
  		return AE_BAD_PARAMETER;
  
  	*new_table = NULL;
  
  #ifdef CONFIG_ACPI_CUSTOM_DSDT
  	if (strncmp(existing_table->signature, "DSDT", 4) == 0)
  		*new_table = (struct acpi_table_header *)AmlCode;
  #endif
  	if (*new_table != NULL)
  		acpi_table_taint(existing_table);
  	return AE_OK;
  }

  /*
   * acpi_table_init()
   *
   * find RSDP, find and checksum SDT/XSDT.
   * checksum all tables, print SDT/XSDT

   *

   * result: sdt_entry[] is initialized
   */

  int __init acpi_table_init(void)

  {

  	acpi_status status;

  	if (acpi_verify_table_checksum) {
  		pr_info("Early table checksum verification enabled
  ");
  		acpi_gbl_verify_table_checksum = TRUE;
  	} else {
  		pr_info("Early table checksum verification disabled
  ");
  		acpi_gbl_verify_table_checksum = FALSE;
  	}

  	status = acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0);
  	if (ACPI_FAILURE(status))

  		return -EINVAL;

  	acpi_table_initrd_scan();

  	check_multiple_madt();
  	return 0;
  }
  
  static int __init acpi_parse_apic_instance(char *str)
  {

  	if (!str)
  		return -EINVAL;

  	if (kstrtoint(str, 0, &acpi_apic_instance))
  		return -EINVAL;

  	pr_notice("Shall use APIC/MADT table %d
  ", acpi_apic_instance);

  	return 0;
  }

  
  early_param("acpi_apic_instance", acpi_parse_apic_instance);

  
  static int __init acpi_force_table_verification_setup(char *s)
  {
  	acpi_verify_table_checksum = true;
  
  	return 0;
  }
  
  early_param("acpi_force_table_verification", acpi_force_table_verification_setup);

  
  static int __init acpi_force_32bit_fadt_addr(char *s)
  {
  	pr_info("Forcing 32 Bit FADT addresses
  ");
  	acpi_gbl_use32_bit_fadt_addresses = TRUE;
  
  	return 0;
  }
  
  early_param("acpi_force_32bit_fadt_addr", acpi_force_32bit_fadt_addr);