You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
467 lines
12 KiB
467 lines
12 KiB
/*
|
|
* linux/mm/memory.c
|
|
*
|
|
* (C) 1991 Linus Torvalds
|
|
*/
|
|
|
|
/*
|
|
* demand-loading started 01.12.91 - seems it is high on the list of
|
|
* things wanted, and it should be easy to implement. - Linus
|
|
*/
|
|
|
|
/*
|
|
* Ok, demand-loading was easy, shared pages a little bit tricker. Shared
|
|
* pages started 02.12.91, seems to work. - Linus.
|
|
*
|
|
* Tested sharing by executing about 30 /bin/sh: under the old kernel it
|
|
* would have taken more than the 6M I have free, but it worked well as
|
|
* far as I could see.
|
|
*
|
|
* Also corrected some "invalidate()"s - I wasn't doing enough of them.
|
|
*/
|
|
|
|
#include <signal.h>
|
|
|
|
#include <asm/system.h>
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/head.h>
|
|
#include <linux/kernel.h>
|
|
|
|
volatile void do_exit(long code);
|
|
|
|
static inline volatile void oom(void)
|
|
{
|
|
printk("out of memory\n\r");
|
|
do_exit(SIGSEGV);
|
|
}
|
|
|
|
#define invalidate() \
|
|
__asm__("movl %%eax,%%cr3"::"a" (0))
|
|
|
|
/* these are not to be changed without changing head.s etc */
|
|
#define LOW_MEM 0x100000
|
|
#define PAGING_MEMORY (15*1024*1024)
|
|
#define PAGING_PAGES (PAGING_MEMORY>>12)
|
|
#define MAP_NR(addr) (((addr)-LOW_MEM)>>12)
|
|
#define USED 100
|
|
|
|
#define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
|
|
current->start_code + current->end_code)
|
|
|
|
static long HIGH_MEMORY = 0;
|
|
|
|
#define copy_page(from,to) \
|
|
__asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024))
|
|
|
|
static unsigned char 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 ; scasb\n\t"
|
|
"jne 1f\n\t"
|
|
"movb $1,1(%%edi)\n\t"
|
|
"sall $12,%%ecx\n\t"
|
|
"addl %2,%%ecx\n\t"
|
|
"movl %%ecx,%%edx\n\t"
|
|
"movl $1024,%%ecx\n\t"
|
|
"leal 4092(%%edx),%%edi\n\t"
|
|
"rep ; stosl\n\t"
|
|
"movl %%edx,%%eax\n\t"
|
|
"1:"
|
|
"cld\n\t" /* by wyj */
|
|
:"=a" (__res)
|
|
:"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
|
|
"D" (mem_map+PAGING_PAGES-1)
|
|
);
|
|
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;
|
|
/* no need for invalidate */
|
|
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;
|
|
invalidate();
|
|
return;
|
|
}
|
|
if (!(new_page=get_free_page()))
|
|
oom();
|
|
if (old_page >= LOW_MEM)
|
|
mem_map[MAP_NR(old_page)]--;
|
|
*table_entry = new_page | 7;
|
|
invalidate();
|
|
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.
|
|
*
|
|
* If it's in code space we exit with a segment error.
|
|
*/
|
|
void do_wp_page(unsigned long error_code,unsigned long address)
|
|
{
|
|
#if 0
|
|
/* we cannot do this yet: the estdio library writes to code space */
|
|
/* stupid, stupid. I really want the libc.a from GNU */
|
|
if (CODE_SPACE(address))
|
|
do_exit(SIGSEGV);
|
|
#endif
|
|
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 get_empty_page(unsigned long address)
|
|
{
|
|
unsigned long tmp;
|
|
|
|
if (!(tmp=get_free_page()) || !put_page(tmp,address)) {
|
|
free_page(tmp); /* 0 is ok - ignored */
|
|
oom();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* try_to_share() checks the page at address "address" in the task "p",
|
|
* to see if it exists, and if it is clean. If so, share it with the current
|
|
* task.
|
|
*
|
|
* NOTE! This assumes we have checked that p != current, and that they
|
|
* share the same executable.
|
|
*/
|
|
static int try_to_share(unsigned long address, struct task_struct * p)
|
|
{
|
|
unsigned long from;
|
|
unsigned long to;
|
|
unsigned long from_page;
|
|
unsigned long to_page;
|
|
unsigned long phys_addr;
|
|
|
|
from_page = to_page = ((address>>20) & 0xffc);
|
|
from_page += ((p->start_code>>20) & 0xffc);
|
|
to_page += ((current->start_code>>20) & 0xffc);
|
|
/* is there a page-directory at from? */
|
|
from = *(unsigned long *) from_page;
|
|
if (!(from & 1))
|
|
return 0;
|
|
from &= 0xfffff000;
|
|
from_page = from + ((address>>10) & 0xffc);
|
|
phys_addr = *(unsigned long *) from_page;
|
|
/* is the page clean and present? */
|
|
if ((phys_addr & 0x41) != 0x01)
|
|
return 0;
|
|
phys_addr &= 0xfffff000;
|
|
if (phys_addr >= HIGH_MEMORY || phys_addr < LOW_MEM)
|
|
return 0;
|
|
to = *(unsigned long *) to_page;
|
|
if (!(to & 1))
|
|
if (to = get_free_page())
|
|
*(unsigned long *) to_page = to | 7;
|
|
else
|
|
oom();
|
|
to &= 0xfffff000;
|
|
to_page = to + ((address>>10) & 0xffc);
|
|
if (1 & *(unsigned long *) to_page)
|
|
panic("try_to_share: to_page already exists");
|
|
/* share them: write-protect */
|
|
*(unsigned long *) from_page &= ~2;
|
|
*(unsigned long *) to_page = *(unsigned long *) from_page;
|
|
invalidate();
|
|
phys_addr -= LOW_MEM;
|
|
phys_addr >>= 12;
|
|
mem_map[phys_addr]++;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* share_page() tries to find a process that could share a page with
|
|
* the current one. Address is the address of the wanted page relative
|
|
* to the current data space.
|
|
*
|
|
* We first check if it is at all feasible by checking executable->i_count.
|
|
* It should be >1 if there are other tasks sharing this inode.
|
|
*/
|
|
static int share_page(unsigned long address)
|
|
{
|
|
struct task_struct ** p;
|
|
|
|
if (!current->executable)
|
|
return 0;
|
|
if (current->executable->i_count < 2)
|
|
return 0;
|
|
for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
|
|
if (!*p)
|
|
continue;
|
|
if (current == *p)
|
|
continue;
|
|
if ((*p)->executable != current->executable)
|
|
continue;
|
|
if (try_to_share(address,*p))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
void do_no_page(unsigned long error_code,unsigned long address)
|
|
{
|
|
int nr[4];
|
|
unsigned long tmp;
|
|
unsigned long page;
|
|
int block,i;
|
|
|
|
|
|
address &= 0xfffff000;
|
|
tmp = address - current->start_code;
|
|
if (!current->executable || tmp >= current->end_data) {
|
|
get_empty_page(address);
|
|
return;
|
|
}
|
|
if (share_page(tmp))
|
|
return;
|
|
if (!(page = get_free_page()))
|
|
oom();
|
|
/* remember that 1 block is used for header */
|
|
block = 1 + tmp/BLOCK_SIZE;
|
|
for (i=0 ; i<4 ; block++,i++)
|
|
nr[i] = bmap(current->executable,block);
|
|
bread_page(page,current->executable->i_dev,nr);
|
|
i = tmp + 4096 - current->end_data;
|
|
tmp = page + 4096;
|
|
while (i-- > 0) {
|
|
tmp--;
|
|
*(char *)tmp = 0;
|
|
}
|
|
if (put_page(page,address))
|
|
return;
|
|
free_page(page);
|
|
oom();
|
|
}
|
|
void do_no_page2(unsigned long error_code,unsigned long address)
|
|
{
|
|
int nr[4];
|
|
unsigned long tmp;
|
|
unsigned long page;
|
|
int block,i;
|
|
|
|
address &= 0xfffff000;
|
|
tmp = address - current->start_code;
|
|
if (!current->executable || tmp >= current->end_data) {
|
|
get_empty_page(address);
|
|
return;
|
|
}
|
|
if (share_page(tmp))
|
|
return;
|
|
if (!(page = get_free_page()))
|
|
oom();
|
|
/* remember that 1 block is used for header */
|
|
block = 1 + tmp/BLOCK_SIZE;
|
|
for (i=0 ; i<4 ; block++,i++)
|
|
nr[i] = bmap(current->executable,block);
|
|
bread_page(page,current->executable->i_dev,nr);
|
|
i = tmp + 4096 - current->end_data;
|
|
tmp = page + 4096;
|
|
while (i-- > 0) {
|
|
tmp--;
|
|
*(char *)tmp = 0;
|
|
}
|
|
if (put_page(page,address))
|
|
return;
|
|
free_page(page);
|
|
oom();
|
|
}
|
|
|
|
|
|
void mem_init(long start_mem, long end_mem)
|
|
{
|
|
int i;
|
|
|
|
HIGH_MEMORY = end_mem;
|
|
for (i=0 ; i<PAGING_PAGES ; i++)
|
|
mem_map[i] = USED;
|
|
i = MAP_NR(start_mem);
|
|
end_mem -= start_mem;
|
|
end_mem >>= 12;
|
|
while (end_mem-->0)
|
|
mem_map[i++]=0;
|
|
}
|
|
|
|
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);
|
|
}
|
|
}
|
|
}
|