memory.c

阿基米德操作系统的源代码

/////////////////////////////////////////////////////////////////////////
#include "general.h"
#include "invalidate.h"
/////////////////////////////////////////////////////////////////////////

unsigned long mem_map[1024];
unsigned long cur_user_sp;
unsigned long min_user_sp;

void init_mem(void)
{
	int i;
	
	for (i = 0; i < 1024; i++)
		mem_map[i] = 0;

	return;
}

unsigned long get_free_page(void)
{
	///////////////////////////////////////////
	unsigned long i;

	i = find_first_page(mem_map);
	if ((i >= 32768) || (i >= min_user_sp))
		return 0;

	set_bit(i,mem_map);

	i = LOW_MEM + (i << 12);
	clear_page(i);

	return i;

	///////////////////////////////////////////
	unsigned long __res;

	__asm__("std ; repne ; scasb\n\t"
			"jne 1f\n\t"
			"movb $1,1(%%edi)\n\t"
			"shll $12,%%ecx\n\t"
			"movl %%ecx,%%edx\n\t"
			"addl %2,%%edx\n\t"			
			"movl $1024,%%ecx\n\t"
			"leal 4092(%%edx),%%edi\n\t"
			"rep ; stosl\n\t"
			"movl %%edx,%%eax\n"
			"1:"
			:"=a" (__res)
			:"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
			"D" (mem_map + PAGING_PAGES - 1));
	return __res;
}

void free_page(unsigned long addr)
{
	////////////////////////////////////////////
	if ((addr < LOW_MEM) || (addr >= HIGH_MEM))
		return;
	addr	= addr - LOW_MEM;
	addr	= addr >> 12;

	clear_bit(addr, mem_map);

	return;
	////////////////////////////////////////////
	if ((addr < LOW_MEM) || (addr >= HIGH_MEM))
		return;
	addr  -= LOW_MEM;
	addr >>= 12;
	if (mem_map[addr]--) 
		return;
	mem_map[addr] = 0;
	return;
}

int free_page_tables(unsigned long from,unsigned long size)
{
	unsigned long * pg_table;
	unsigned long * dir , nr;

	if ((!from) || (from & 0x3fffff))
		return 0;
	size = (size + 0x3fffff) >> 22;
	dir = (unsigned long *) ((from >> 20) & 0xffc); 
	for ( ; size > 0 ; size-- , dir++) {
		if (!(*dir & 1))
			continue;
		pg_table = (unsigned long *) (*dir & 0xfffff000);
		for (nr = 0 ; nr < 1024 ; nr++ , pg_table++) {
			if (*pg_table & 1)
				free_page(*pg_table & 0xfffff000);
			*pg_table = 0;
		}
		free_page(*dir & 0xfffff000);
		*dir = 0;
	}
	invalidate();
	return 1;
}

unsigned long put_page(unsigned long page,unsigned long address)
{
	unsigned long tmp, * page_table;

	if ((page < LOW_MEM) || (page >= HIGH_MEM || (mem_map[(page - LOW_MEM) >> 12] != 1))
		return 0;
	page_table = (unsigned long *) ((address >> 20) & 0xffc);
	if ((*page_table) & 1)
		page_table = (unsigned long *)(*page_table & 0xfffff000);
	else {
		if (!(tmp = get_free_page()))
			return 0;
		*page_table = tmp | 7;
		page_table  = (unsigned long *) tmp;
	}
	page_table[(address >> 12) & 0x3ff] = page | 7;
	return page;
}