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/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2009 Pierre-Alexandre Meyer
 *
 *   Some parts borrowed from meminfo.c32:
 *
 *   Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
 *
 *   Some parts borrowed from Linux:
 *
 *   Copyright (C) 1991, 1992 Linus Torvalds
 *   Copyright 2007 rPath, Inc. - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author H. Peter Anvin
 *
 *   Interrupt list from Ralf Brown (http://www.cs.cmu.edu/~ralf/files.html)
 *
 *   This file is part of Syslinux, and is made available under
 *   the terms of the GNU General Public License version 2.
 *
 * ----------------------------------------------------------------------- */

#include <stdint.h>
#include <com32.h>
#include <string.h>
#include <memory.h>

const char * const e820_types[] = {
	"usable",
	"reserved",
	"ACPI reclaim",
	"ACPI NVS",
	"unusable",
};

struct e820_ext_entry {
	struct e820entry std;
	uint32_t ext_flags;
} __attribute__((packed));

#define SMAP	0x534d4150	/* ASCII "SMAP" */

void get_type(int type, char *type_ptr, int type_ptr_sz)
{
	unsigned int real_type = type - 1;
	if (real_type < sizeof(e820_types)/sizeof(e820_types[0]))
		strncpy(type_ptr, e820_types[real_type], type_ptr_sz);
}

/**
 *INT 15 - newer BIOSes - GET SYSTEM MEMORY MAP
 *	AX = E820h
 *	EAX = 0000E820h
 *	EDX = 534D4150h ('SMAP')
 *	EBX = continuation value or 00000000h to start at beginning of map
 *	ECX = size of buffer for result, in bytes (should be >= 20 bytes)
 *	ES:DI -> buffer for result (see #00581)
 *
 * Return: CF clear if successful
 *	    EAX = 534D4150h ('SMAP')
 *	    ES:DI buffer filled
 *	    EBX = next offset from which to copy or 00000000h if all done
 *	    ECX = actual length returned in bytes
 *	CF set on error
 *	    AH = error code (86h) (see #00496 at INT 15/AH=80h)
 *
 * Notes: originally introduced with the Phoenix BIOS v4.0, this function is
 *	  now supported by most newer BIOSes, since various versions of Windows
 *	  call it to find out about the system memory
 *	a maximum of 20 bytes will be transferred at one time, even if ECX is
 *	  higher; some BIOSes (e.g. Award Modular BIOS v4.50PG) ignore the
 *	  value of ECX on entry, and always copy 20 bytes
 *	some BIOSes expect the high word of EAX to be clear on entry, i.e.
 *	  EAX=0000E820h
 *	if this function is not supported, an application should fall back
 *	  to AX=E802h, AX=E801h, and then AH=88h
 *	the BIOS is permitted to return a nonzero continuation value in EBX
 *	  and indicate that the end of the list has already been reached by
 *	  returning with CF set on the next iteration
 *	this function will return base memory and ISA/PCI memory contiguous
 *	  with base memory as normal memory ranges; it will indicate
 *	  chipset-defined address holes which are not in use and motherboard
 *	  memory-mapped devices, and all occurrences of the system BIOS as
 *	  reserved; standard PC address ranges will not be reported
 **/
void detect_memory_e820(struct e820entry *desc, int size_map, int *size_found)
{
	int count = 0;
	static struct e820_ext_entry buf; /* static so it is zeroed */

	com32sys_t ireg, oreg;
	memset(&ireg, 0, sizeof ireg);

	ireg.eax.w[0] = 0xe820;
	ireg.edx.l    = SMAP;
	ireg.ecx.l    = sizeof(struct e820_ext_entry);
	ireg.edi.w[0] = OFFS(__com32.cs_bounce);
	ireg.es       = SEG(__com32.cs_bounce);

	/*
	 * Set this here so that if the BIOS doesn't change this field
	 * but still doesn't change %ecx, we're still okay...
	 */
	memset(&buf, 0, sizeof buf);
	buf.ext_flags = 1;

	do {
		memcpy(__com32.cs_bounce, &buf, sizeof buf);

		/* Important: %edx and %esi are clobbered by some BIOSes,
		   so they must be either used for the error output
		   or explicitly marked clobbered.  Given that, assume there
		   is something out there clobbering %ebp and %edi, too. */
		__intcall(0x15, &ireg, &oreg);

		/* Some BIOSes stop returning SMAP in the middle of
		   the search loop.  We don't know exactly how the BIOS
		   screwed up the map at that point, we might have a
		   partial map, the full map, or complete garbage, so
		   just return failure. */
		if (oreg.eax.l != SMAP) {
			count = 0;
			break;
		}

		if (oreg.eflags.l & EFLAGS_CF ||
		    oreg.ecx.l < 20)
			break;

		memcpy(&buf, __com32.cs_bounce, sizeof buf);

		/*
		 * ACPI 3.0 added the extended flags support.  If bit 0
		 * in the extended flags is zero, we're supposed to simply
		 * ignore the entry -- a backwards incompatible change!
		 */
		if (oreg.ecx.l > 20 && !(buf.ext_flags & 1))
			continue;

		memcpy(&desc[count], &buf, sizeof buf);
		count++;

		/* Set continuation value */
		ireg.ebx.l = oreg.ebx.l;
	} while (ireg.ebx.l && count < size_map);

	*size_found = count;
}

/**
 * detect_memory_e801
 *
 *INT 15 - Phoenix BIOS v4.0 - GET MEMORY SIZE FOR >64M CONFIGURATIONS
 *	AX = E801h
 *
 * Return: CF clear if successful
 *	    AX = extended memory between 1M and 16M, in K (max 3C00h = 15MB)
 *	    BX = extended memory above 16M, in 64K blocks
 *	    CX = configured memory 1M to 16M, in K
 *	    DX = configured memory above 16M, in 64K blocks
 *	CF set on error
 *
 * Notes: supported by the A03 level (6/14/94) and later XPS P90 BIOSes, as well
 *	as the Compaq Contura, 3/8/93 DESKPRO/i, and 7/26/93 LTE Lite 386 ROM
 *	BIOS
 *	supported by AMI BIOSes dated 8/23/94 or later
 *	on some systems, the BIOS returns AX=BX=0000h; in this case, use CX
 *	  and DX instead of AX and BX
 *	this interface is used by Windows NT 3.1, OS/2 v2.11/2.20, and is
 *	  used as a fall-back by newer versions if AX=E820h is not supported
 *	this function is not used by MS-DOS 6.0 HIMEM.SYS when an EISA machine
 *	  (for example with parameter /EISA) (see also MEM F000h:FFD9h), or no
 *	  Compaq machine was detected, or parameter /NOABOVE16 was given.
 **/
int detect_memory_e801(int* mem_size_below_16, int* mem_size_above_16)
{
	com32sys_t ireg, oreg;
	memset(&ireg, 0, sizeof ireg);

	ireg.eax.w[0] = 0xe801;

	__intcall(0x15, &ireg, &oreg);

	if (oreg.eflags.l & EFLAGS_CF)
		return -1;

	if (oreg.eax.w[0] > 0x3c00)
		return -1;	/* Bogus! */

	/* Linux seems to use ecx and edx by default if they are defined */
	if (oreg.eax.w[0] || oreg.eax.w[0]) {
		oreg.eax.w[0] = oreg.ecx.w[0];
		oreg.ebx.w[0] = oreg.edx.w[0];
	}

	*mem_size_below_16 = oreg.eax.w[0]; /* 1K blocks */
	*mem_size_above_16 = oreg.ebx.w[0]; /* 64K blocks */

	return 0;
}

int detect_memory_88(int* mem_size)
{
	com32sys_t ireg, oreg;
	memset(&ireg, 0, sizeof ireg);

	ireg.eax.w[0] = 0x8800;

	__intcall(0x15, &ireg, &oreg);

	if (oreg.eflags.l & EFLAGS_CF)
		return -1;

	*mem_size = oreg.eax.w[0];
	return 0;
}

/*
 * Sanitize the BIOS e820 map.
 *
 * This code come from the memtest86 project. It have been adjusted to match
 * the syslinux environement.
 * Some e820 responses include overlapping entries.  The following 
 * replaces the original e820 map with a new one, removing overlaps.
 *
 */
int sanitize_e820_map(struct e820entry *orig_map, struct e820entry *new_bios,
	short old_nr)
{
	struct change_member {
		struct e820entry *pbios; /* pointer to original bios entry */
		unsigned long long addr; /* address for this change point */
	};
	struct change_member change_point_list[2*E820MAX];
	struct change_member *change_point[2*E820MAX];
	struct e820entry *overlap_list[E820MAX];
	struct e820entry biosmap[E820MAX];
	struct change_member *change_tmp;
	unsigned long current_type, last_type;
	unsigned long long last_addr;
	int chgidx, still_changing;
	int overlap_entries;
	int new_bios_entry;
	int i;

	/*
		Visually we're performing the following (1,2,3,4 = memory types)...
		Sample memory map (w/overlaps):
		   ____22__________________
		   ______________________4_
		   ____1111________________
		   _44_____________________
		   11111111________________
		   ____________________33__
		   ___________44___________
		   __________33333_________
		   ______________22________
		   ___________________2222_
		   _________111111111______
		   _____________________11_
		   _________________4______

		Sanitized equivalent (no overlap):
		   1_______________________
		   _44_____________________
		   ___1____________________
		   ____22__________________
		   ______11________________
		   _________1______________
		   __________3_____________
		   ___________44___________
		   _____________33_________
		   _______________2________
		   ________________1_______
		   _________________4______
		   ___________________2____
		   ____________________33__
		   ______________________4_
	*/
	/* First make a copy of the map */
	for (i=0; i<old_nr; i++) {
		biosmap[i].addr = orig_map[i].addr;
		biosmap[i].size = orig_map[i].size;
		biosmap[i].type = orig_map[i].type;
	}

	/* bail out if we find any unreasonable addresses in bios map */
	for (i=0; i<old_nr; i++) {
		if (biosmap[i].addr + biosmap[i].size < biosmap[i].addr)
			return 0;
	}

	/* create pointers for initial change-point information (for sorting) */
	for (i=0; i < 2*old_nr; i++)
		change_point[i] = &change_point_list[i];

	/* record all known change-points (starting and ending addresses) */
	chgidx = 0;
	for (i=0; i < old_nr; i++)	{
		change_point[chgidx]->addr = biosmap[i].addr;
		change_point[chgidx++]->pbios = &biosmap[i];
		change_point[chgidx]->addr = biosmap[i].addr + biosmap[i].size;
		change_point[chgidx++]->pbios = &biosmap[i];
	}

	/* sort change-point list by memory addresses (low -> high) */
	still_changing = 1;
	while (still_changing)	{
		still_changing = 0;
		for (i=1; i < 2*old_nr; i++)  {
			/* if <current_addr> > <last_addr>, swap */
			/* or, if current=<start_addr> & last=<end_addr>, swap */
			if ((change_point[i]->addr < change_point[i-1]->addr) ||
				((change_point[i]->addr == change_point[i-1]->addr) &&
				 (change_point[i]->addr == change_point[i]->pbios->addr) &&
				 (change_point[i-1]->addr != change_point[i-1]->pbios->addr))
			   )
			{
				change_tmp = change_point[i];
				change_point[i] = change_point[i-1];
				change_point[i-1] = change_tmp;
				still_changing=1;
			}
		}
	}

	/* create a new bios memory map, removing overlaps */
	overlap_entries=0;	 /* number of entries in the overlap table */
	new_bios_entry=0;	 /* index for creating new bios map entries */
	last_type = 0;		 /* start with undefined memory type */
	last_addr = 0;		 /* start with 0 as last starting address */
	/* loop through change-points, determining affect on the new bios map */
	for (chgidx=0; chgidx < 2*old_nr; chgidx++)
	{
		/* keep track of all overlapping bios entries */
		if (change_point[chgidx]->addr == change_point[chgidx]->pbios->addr)
		{
			/* add map entry to overlap list (> 1 entry implies an overlap) */
			overlap_list[overlap_entries++]=change_point[chgidx]->pbios;
		}
		else
		{
			/* remove entry from list (order independent, so swap with last) */
			for (i=0; i<overlap_entries; i++)
			{
				if (overlap_list[i] == change_point[chgidx]->pbios)
					overlap_list[i] = overlap_list[overlap_entries-1];
			}
			overlap_entries--;
		}
		/* if there are overlapping entries, decide which "type" to use */
		/* (larger value takes precedence -- 1=usable, 2,3,4,4+=unusable) */
		current_type = 0;
		for (i=0; i<overlap_entries; i++)
			if (overlap_list[i]->type > current_type)
				current_type = overlap_list[i]->type;
		/* continue building up new bios map based on this information */
		if (current_type != last_type)	{
			if (last_type != 0)	 {
				new_bios[new_bios_entry].size =
					change_point[chgidx]->addr - last_addr;
				/* move forward only if the new size was non-zero */
				if (new_bios[new_bios_entry].size != 0)
					if (++new_bios_entry >= E820MAX)
						break; 	/* no more space left for new bios entries */
			}
			if (current_type != 0)	{
				new_bios[new_bios_entry].addr = change_point[chgidx]->addr;
				new_bios[new_bios_entry].type = current_type;
				last_addr=change_point[chgidx]->addr;
			}
			last_type = current_type;
		}
	}
	return(new_bios_entry);
}

unsigned long detect_memsize(void) {
	unsigned long memory_size=0;

	/* Try to detect memory via e820 */
	struct e820entry map[E820MAX];
        int count = 0;
	detect_memory_e820(map, E820MAX, &count);
	memory_size=memsize_e820(map,count);
	if (memory_size > 0) return memory_size;

	/*e820 failed, let's try e801 */
	int mem_low, mem_high = 0;
        if (!detect_memory_e801(&mem_low, &mem_high))
		return mem_low + (mem_high << 6);
	
	/*e801 failed, let's try e88 */
	int mem_size = 0;
        if (!detect_memory_88(&mem_size))
		return mem_size;

	/* We were enable to detect any kind of memory */
	return 0;
}

unsigned long memsize_e820(struct e820entry *e820, int e820_nr) {
	int i, n, nr;
	unsigned long memory_size=0;
	struct e820entry nm[E820MAX];

	/* Clean up, adjust and copy the BIOS-supplied E820-map. */
	nr = sanitize_e820_map(e820, nm, e820_nr);

	/* If there is not a good 820 map returning 0 to indicate 
	that we don't have any idea of the amount of ram we have */
	if (nr < 1 || nr > E820MAX) {
		return 0;
	}

	/* Build the memory map for testing */
	n = 0;
	for (i=0; i<nr; i++) {
		if (nm[i].type == E820_RAM || nm[i].type == E820_ACPI) {
			unsigned long long start;
			unsigned long long end;
			start = nm[i].addr;
			end = start + nm[i].size;

			/* Don't ever use memory between 640 and 1024k */
			if (start > RES_START && start < RES_END) {
				if (end < RES_END) {
					continue;
				}
				start = RES_END;
			}
			if (end > RES_START && end < RES_END) {
				end = RES_START;
			}
			memory_size += (end>>12) - ((start + 4095)>>12);
			n++;
		} else if (nm[i].type == E820_NVS) {
			memory_size += nm[i].size >> 12;
		}
	}
	return memory_size*4;
}