लिनक्स/linux-0.01.tar/mm/memory.c
< लिनक्स | linux-0.01.tar
#include <signal.h>
#include <linux/config.h>
#include <linux/head.h>
#include <linux/kernel.h>
#include <asm/system.h>
int do_exit(long code);
#define invalidate() \
__asm__("movl %%eax,%%cr3"::"a" (0))
#if (BUFFER_END < 0x100000)
#define LOW_MEM 0x100000
#else
#define LOW_MEM BUFFER_END
#endif
/* these are not to be changed - thay are calculated from the above */
#define PAGING_MEMORY (HIGH_MEMORY - LOW_MEM)
#define PAGING_PAGES (PAGING_MEMORY/4096)
#define MAP_NR(addr) (((addr)-LOW_MEM)>>12)
#if (PAGING_PAGES < 10)
#error "Won't work"
#endif
#define copy_page(from,to) \
__asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024):"cx","di","si")
static unsigned short mem_map [ PAGING_PAGES ] = {0,};
/*
* Get physical address of first (actually last :-) free page, and mark it
* used. If no free pages left, return 0.
*/
unsigned long get_free_page(void)
{
register unsigned long __res asm("ax");
__asm__("std ; repne ; scasw\n\t"
"jne 1f\n\t"
"movw $1,2(%%edi)\n\t"
"sall $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)
:"di","cx","dx");
return __res;
}
/*
* Free a page of memory at physical address 'addr'. Used by
* 'free_page_tables()'
*/
void free_page(unsigned long addr)
{
if (addr<LOW_MEM) return;
if (addr>HIGH_MEMORY)
panic("trying to free nonexistent page");
addr -= LOW_MEM;
addr >>= 12;
if (mem_map[addr]--) return;
mem_map[addr]=0;
panic("trying to free free page");
}
/*
* This function frees a continuos block of page tables, as needed
* by 'exit()'. As does copy_page_tables(), this handles only 4Mb blocks.
*/
int free_page_tables(unsigned long from,unsigned long size)
{
unsigned long *pg_table;
unsigned long * dir, nr;
if (from & 0x3fffff)
panic("free_page_tables called with wrong alignment");
if (!from)
panic("Trying to free up swapper memory space");
size = (size + 0x3fffff) >> 22;
dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
for ( ; size-->0 ; dir++) {
if (!(1 & *dir))
continue;
pg_table = (unsigned long *) (0xfffff000 & *dir);
for (nr=0 ; nr<1024 ; nr++) {
if (1 & *pg_table)
free_page(0xfffff000 & *pg_table);
*pg_table = 0;
pg_table++;
}
free_page(0xfffff000 & *dir);
*dir = 0;
}
invalidate();
return 0;
}
/*
* Well, here is one of the most complicated functions in mm. It
* copies a range of linerar addresses by copying only the pages.
* Let's hope this is bug-free, 'cause this one I don't want to debug :-)
*
* Note! We don't copy just any chunks of memory - addresses have to
* be divisible by 4Mb (one page-directory entry), as this makes the
* function easier. It's used only by fork anyway.
*
* NOTE 2!! When from==0 we are copying kernel space for the first
* fork(). Then we DONT want to copy a full page-directory entry, as
* that would lead to some serious memory waste - we just copy the
* first 160 pages - 640kB. Even that is more than we need, but it
* doesn't take any more memory - we don't copy-on-write in the low
* 1 Mb-range, so the pages can be shared with the kernel. Thus the
* special case for nr=xxxx.
*/
int copy_page_tables(unsigned long from,unsigned long to,long size)
{
unsigned long * from_page_table;
unsigned long * to_page_table;
unsigned long this_page;
unsigned long * from_dir, * to_dir;
unsigned long nr;
if ((from&0x3fffff) || (to&0x3fffff))
panic("copy_page_tables called with wrong alignment");
from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
to_dir = (unsigned long *) ((to>>20) & 0xffc);
size = ((unsigned) (size+0x3fffff)) >> 22;
for( ; size-->0 ; from_dir++,to_dir++) {
if (1 & *to_dir)
panic("copy_page_tables: already exist");
if (!(1 & *from_dir))
continue;
from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
if (!(to_page_table = (unsigned long *) get_free_page()))
return -1; /* Out of memory, see freeing */
*to_dir = ((unsigned long) to_page_table) | 7;
nr = (from==0)?0xA0:1024;
for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
this_page = *from_page_table;
if (!(1 & this_page))
continue;
this_page &= ~2;
*to_page_table = this_page;
if (this_page > LOW_MEM) {
*from_page_table = this_page;
this_page -= LOW_MEM;
this_page >>= 12;
mem_map[this_page]++;
}
}
}
invalidate();
return 0;
}
/*
* This function puts a page in memory at the wanted address.
* It returns the physical address of the page gotten, 0 if
* out of memory (either when trying to access page-table or
* page.)
*/
unsigned long put_page(unsigned long page,unsigned long address)
{
unsigned long tmp, *page_table;
/* NOTE !!! This uses the fact that _pg_dir=0 */
if (page < LOW_MEM || page > HIGH_MEMORY)
printk("Trying to put page %p at %p\n",page,address);
if (mem_map[(page-LOW_MEM)>>12] != 1)
printk("mem_map disagrees with %p at %p\n",page,address);
page_table = (unsigned long *) ((address>>20) & 0xffc);
if ((*page_table)&1)
page_table = (unsigned long *) (0xfffff000 & *page_table);
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;
}
void un_wp_page(unsigned long * table_entry)
{
unsigned long old_page,new_page;
old_page = 0xfffff000 & *table_entry;
if (old_page >= LOW_MEM && mem_map[MAP_NR(old_page)]==1) {
*table_entry |= 2;
return;
}
if (!(new_page=get_free_page()))
do_exit(SIGSEGV);
if (old_page >= LOW_MEM)
mem_map[MAP_NR(old_page)]--;
*table_entry = new_page | 7;
copy_page(old_page,new_page);
}
/*
* This routine handles present pages, when users try to write
* to a shared page. It is done by copying the page to a new address
* and decrementing the shared-page counter for the old page.
*/
void do_wp_page(unsigned long error_code,unsigned long address)
{
un_wp_page((unsigned long *)
(((address>>10) & 0xffc) + (0xfffff000 &
*((unsigned long *) ((address>>20) &0xffc)))));
}
void write_verify(unsigned long address)
{
unsigned long page;
if (!( (page = *((unsigned long *) ((address>>20) & 0xffc)) )&1))
return;
page &= 0xfffff000;
page += ((address>>10) & 0xffc);
if ((3 & *(unsigned long *) page) == 1) /* non-writeable, present */
un_wp_page((unsigned long *) page);
return;
}
void do_no_page(unsigned long error_code,unsigned long address)
{
unsigned long tmp;
if (tmp=get_free_page())
if (put_page(tmp,address))
return;
do_exit(SIGSEGV);
}
void calc_mem(void)
{
int i,j,k,free=0;
long * pg_tbl;
for(i=0 ; i<PAGING_PAGES ; i++)
if (!mem_map[i]) free++;
printk("%d pages free (of %d)\n\r",free,PAGING_PAGES);
for(i=2 ; i<1024 ; i++) {
if (1&pg_dir[i]) {
pg_tbl=(long *) (0xfffff000 & pg_dir[i]);
for(j=k=0 ; j<1024 ; j++)
if (pg_tbl[j]&1)
k++;
printk("Pg-dir[%d] uses %d pages\n",i,k);
}
}
}