parent
850b3660ae
commit
05edba96c2
@ -0,0 +1,464 @@
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/*
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* linux/mm/memory.c
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*
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* (C) 1991 Linus Torvalds
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*/
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/*
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* demand-loading started 01.12.91 - seems it is high on the list of
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* things wanted, and it should be easy to implement. - Linus
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*/
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/*
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* Ok, demand-loading was easy, shared pages a little bit tricker. Shared
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* pages started 02.12.91, seems to work. - Linus.
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*
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* Tested sharing by executing about 30 /bin/sh: under the old kernel it
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* would have taken more than the 6M I have free, but it worked well as
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* far as I could see.
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*
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* Also corrected some "invalidate()"s - I wasn't doing enough of them.
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*/
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#include <signal.h>
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#include <asm/system.h>
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#include <linux/sched.h>
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#include <linux/head.h>
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#include <linux/kernel.h>
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volatile void do_exit(long code);
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static inline volatile void oom(void)
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{
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printk("out of memory\n\r");
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do_exit(SIGSEGV);
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}
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#define invalidate() \
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__asm__("movl %%eax,%%cr3"::"a" (0))
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/* these are not to be changed without changing head.s etc */
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#define LOW_MEM 0x100000
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#define PAGING_MEMORY (15*1024*1024)
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#define PAGING_PAGES (PAGING_MEMORY>>12)
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#define MAP_NR(addr) (((addr)-LOW_MEM)>>12)
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#define USED 100
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#define CODE_SPACE(addr) ((((addr)+4095)&~4095) < \
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current->start_code + current->end_code)
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static long HIGH_MEMORY = 0;
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#define copy_page(from,to) \
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__asm__("cld ; rep ; movsl"::"S" (from),"D" (to),"c" (1024))
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static unsigned char mem_map [ PAGING_PAGES ] = {0,};
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/*
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* Get physical address of first (actually last :-) free page, and mark it
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* used. If no free pages left, return 0.
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*/
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unsigned long get_free_page(void)
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{
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register unsigned long __res asm("ax");
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__asm__("std ; repne ; scasb\n\t"
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"jne 1f\n\t"
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"movb $1,1(%%edi)\n\t"
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"sall $12,%%ecx\n\t"
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"addl %2,%%ecx\n\t"
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"movl %%ecx,%%edx\n\t"
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"movl $1024,%%ecx\n\t"
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"leal 4092(%%edx),%%edi\n\t"
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"rep ; stosl\n\t"
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"movl %%edx,%%eax\n\t"
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"1:"
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"cld\n\t" /* by wyj */
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:"=a" (__res)
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:"0" (0),"i" (LOW_MEM),"c" (PAGING_PAGES),
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"D" (mem_map+PAGING_PAGES-1)
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);
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return __res;
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}
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/*
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* Free a page of memory at physical address 'addr'. Used by
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* 'free_page_tables()'
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*/
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void free_page(unsigned long addr)
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{
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if (addr < LOW_MEM) return;
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if (addr >= HIGH_MEMORY)
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panic("trying to free nonexistent page");
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addr -= LOW_MEM;
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addr >>= 12;
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if (mem_map[addr]--) return;
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mem_map[addr]=0;
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panic("trying to free free page");
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}
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/*
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* This function frees a continuos block of page tables, as needed
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* by 'exit()'. As does copy_page_tables(), this handles only 4Mb blocks.
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*/
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int free_page_tables(unsigned long from,unsigned long size)
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{
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unsigned long *pg_table;
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unsigned long * dir, nr;
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if (from & 0x3fffff)
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panic("free_page_tables called with wrong alignment");
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if (!from)
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panic("Trying to free up swapper memory space");
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size = (size + 0x3fffff) >> 22;
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dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
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for ( ; size-->0 ; dir++) {
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if (!(1 & *dir))
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continue;
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pg_table = (unsigned long *) (0xfffff000 & *dir);
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for (nr=0 ; nr<1024 ; nr++) {
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if (1 & *pg_table)
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free_page(0xfffff000 & *pg_table);
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*pg_table = 0;
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pg_table++;
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}
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free_page(0xfffff000 & *dir);
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*dir = 0;
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}
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invalidate();
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return 0;
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}
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/*
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* Well, here is one of the most complicated functions in mm. It
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* copies a range of linerar addresses by copying only the pages.
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* Let's hope this is bug-free, 'cause this one I don't want to debug :-)
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*
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* Note! We don't copy just any chunks of memory - addresses have to
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* be divisible by 4Mb (one page-directory entry), as this makes the
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* function easier. It's used only by fork anyway.
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*
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* NOTE 2!! When from==0 we are copying kernel space for the first
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* fork(). Then we DONT want to copy a full page-directory entry, as
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* that would lead to some serious memory waste - we just copy the
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* first 160 pages - 640kB. Even that is more than we need, but it
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* doesn't take any more memory - we don't copy-on-write in the low
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* 1 Mb-range, so the pages can be shared with the kernel. Thus the
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* special case for nr=xxxx.
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*/
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int copy_page_tables(unsigned long from,unsigned long to,long size)
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{
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unsigned long * from_page_table;
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unsigned long * to_page_table;
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unsigned long this_page;
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unsigned long * from_dir, * to_dir;
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unsigned long nr;
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if ((from&0x3fffff) || (to&0x3fffff))
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panic("copy_page_tables called with wrong alignment");
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from_dir = (unsigned long *) ((from>>20) & 0xffc); /* _pg_dir = 0 */
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to_dir = (unsigned long *) ((to>>20) & 0xffc);
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size = ((unsigned) (size+0x3fffff)) >> 22;
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for( ; size-->0 ; from_dir++,to_dir++) {
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if (1 & *to_dir)
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panic("copy_page_tables: already exist");
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if (!(1 & *from_dir))
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continue;
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from_page_table = (unsigned long *) (0xfffff000 & *from_dir);
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if (!(to_page_table = (unsigned long *) get_free_page()))
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return -1; /* Out of memory, see freeing */
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*to_dir = ((unsigned long) to_page_table) | 7;
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nr = (from==0)?0xA0:1024;
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for ( ; nr-- > 0 ; from_page_table++,to_page_table++) {
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this_page = *from_page_table;
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if (!(1 & this_page))
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continue;
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this_page &= ~2;
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*to_page_table = this_page;
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if (this_page > LOW_MEM) {
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*from_page_table = this_page;
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this_page -= LOW_MEM;
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this_page >>= 12;
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mem_map[this_page]++;
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}
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}
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}
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invalidate();
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return 0;
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}
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/*
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* This function puts a page in memory at the wanted address.
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* It returns the physical address of the page gotten, 0 if
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* out of memory (either when trying to access page-table or
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* page.)
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*/
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unsigned long put_page(unsigned long page,unsigned long address)
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{
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unsigned long tmp, *page_table;
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/* NOTE !!! This uses the fact that _pg_dir=0 */
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if (page < LOW_MEM || page >= HIGH_MEMORY)
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printk("Trying to put page %p at %p\n",page,address);
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if (mem_map[(page-LOW_MEM)>>12] != 1)
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printk("mem_map disagrees with %p at %p\n",page,address);
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page_table = (unsigned long *) ((address>>20) & 0xffc);
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if ((*page_table)&1)
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page_table = (unsigned long *) (0xfffff000 & *page_table);
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else {
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if (!(tmp=get_free_page()))
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return 0;
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*page_table = tmp|7;
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page_table = (unsigned long *) tmp;
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}
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page_table[(address>>12) & 0x3ff] = page | 7;
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/* no need for invalidate */
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return page;
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}
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void un_wp_page(unsigned long * table_entry)
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{
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unsigned long old_page,new_page;
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old_page = 0xfffff000 & *table_entry;
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if (old_page >= LOW_MEM && mem_map[MAP_NR(old_page)]==1) {
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*table_entry |= 2;
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invalidate();
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return;
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}
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if (!(new_page=get_free_page()))
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oom();
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if (old_page >= LOW_MEM)
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mem_map[MAP_NR(old_page)]--;
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*table_entry = new_page | 7;
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invalidate();
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copy_page(old_page,new_page);
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}
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/*
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* This routine handles present pages, when users try to write
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* to a shared page. It is done by copying the page to a new address
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* and decrementing the shared-page counter for the old page.
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*
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* If it's in code space we exit with a segment error.
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*/
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void do_wp_page(unsigned long error_code,unsigned long address)
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{
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#if 0
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/* we cannot do this yet: the estdio library writes to code space */
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/* stupid, stupid. I really want the libc.a from GNU */
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if (CODE_SPACE(address))
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do_exit(SIGSEGV);
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#endif
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un_wp_page((unsigned long *)
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(((address>>10) & 0xffc) + (0xfffff000 &
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*((unsigned long *) ((address>>20) &0xffc)))));
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}
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void write_verify(unsigned long address)
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{
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unsigned long page;
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if (!( (page = *((unsigned long *) ((address>>20) & 0xffc)) )&1))
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return;
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page &= 0xfffff000;
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page += ((address>>10) & 0xffc);
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if ((3 & *(unsigned long *) page) == 1) /* non-writeable, present */
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un_wp_page((unsigned long *) page);
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return;
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}
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void get_empty_page(unsigned long address)
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{
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unsigned long tmp;
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if (!(tmp=get_free_page()) || !put_page(tmp,address)) {
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free_page(tmp); /* 0 is ok - ignored */
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oom();
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}
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}
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/*
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* try_to_share() checks the page at address "address" in the task "p",
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* to see if it exists, and if it is clean. If so, share it with the current
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* task.
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*
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* NOTE! This assumes we have checked that p != current, and that they
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* share the same executable.
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*/
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static int try_to_share(unsigned long address, struct task_struct * p)
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{
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unsigned long from;
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unsigned long to;
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unsigned long from_page;
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unsigned long to_page;
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unsigned long phys_addr;
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from_page = to_page = ((address>>20) & 0xffc);
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from_page += ((p->start_code>>20) & 0xffc);
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to_page += ((current->start_code>>20) & 0xffc);
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/* is there a page-directory at from? */
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from = *(unsigned long *) from_page;
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if (!(from & 1))
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return 0;
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from &= 0xfffff000;
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from_page = from + ((address>>10) & 0xffc);
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phys_addr = *(unsigned long *) from_page;
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/* is the page clean and present? */
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if ((phys_addr & 0x41) != 0x01)
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return 0;
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phys_addr &= 0xfffff000;
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if (phys_addr >= HIGH_MEMORY || phys_addr < LOW_MEM)
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return 0;
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to = *(unsigned long *) to_page;
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if (!(to & 1))
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if (to = get_free_page())
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*(unsigned long *) to_page = to | 7;
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else
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oom();
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to &= 0xfffff000;
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to_page = to + ((address>>10) & 0xffc);
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if (1 & *(unsigned long *) to_page)
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panic("try_to_share: to_page already exists");
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/* share them: write-protect */
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*(unsigned long *) from_page &= ~2;
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*(unsigned long *) to_page = *(unsigned long *) from_page;
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invalidate();
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phys_addr -= LOW_MEM;
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phys_addr >>= 12;
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mem_map[phys_addr]++;
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return 1;
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}
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/*
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* share_page() tries to find a process that could share a page with
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* the current one. Address is the address of the wanted page relative
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* to the current data space.
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*
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* We first check if it is at all feasible by checking executable->i_count.
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* It should be >1 if there are other tasks sharing this inode.
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*/
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static int share_page(unsigned long address)
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{
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struct task_struct ** p;
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if (!current->executable)
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return 0;
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if (current->executable->i_count < 2)
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return 0;
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for (p = &LAST_TASK ; p > &FIRST_TASK ; --p) {
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if (!*p)
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continue;
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if (current == *p)
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continue;
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if ((*p)->executable != current->executable)
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continue;
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if (try_to_share(address,*p))
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return 1;
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}
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return 0;
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}
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void do_no_page(unsigned long error_code,unsigned long address)
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{
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int nr[4];
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unsigned long tmp;
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unsigned long page;
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int block,i;
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if (current->pid > 5)
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printk(" --do_no_page: address=%x, pid=%d\n", address, current->pid);
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address &= 0xfffff000;
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tmp = address - current->start_code;
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if (!current->executable || tmp >= current->end_data) {
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get_empty_page(address);
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return;
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}
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if (share_page(tmp))
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return;
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if (!(page = get_free_page()))
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oom();
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/* remember that 1 block is used for header */
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block = 1 + tmp/BLOCK_SIZE;
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for (i=0 ; i<4 ; block++,i++)
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nr[i] = bmap(current->executable,block);
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bread_page(page,current->executable->i_dev,nr);
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i = tmp + 4096 - current->end_data;
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tmp = page + 4096;
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while (i-- > 0) {
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tmp--;
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*(char *)tmp = 0;
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}
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if (put_page(page,address))
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return;
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free_page(page);
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oom();
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}
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void do_no_page1(unsigned long address)
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{
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int nr[4];
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unsigned long tmp;
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unsigned long page;
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int block,i;
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address &= 0xfffff000;
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tmp = address - current->start_code;
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if (!current->executable || tmp >= current->end_data) {
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get_empty_page(address);
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return;
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}
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if (share_page(tmp))
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return;
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if (!(page = get_free_page()))
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oom();
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block = 1 + tmp/BLOCK_SIZE;
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for (i=0 ; i<4 ; block++,i++)
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nr[i] = bmap(current->executable,block);
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bread_page(page,current->executable->i_dev,nr);
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i = tmp + 4096 - current->end_data;
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tmp = page + 4096;
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while (i-- > 0) {
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tmp--;
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*(char *)tmp = 0;
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}
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if (put_page(page,address))
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return;
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free_page(page);
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oom();
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}
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void mem_init(long start_mem, long end_mem)
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{
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int i;
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HIGH_MEMORY = end_mem;
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for (i=0 ; i<PAGING_PAGES ; i++)
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mem_map[i] = USED;
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i = MAP_NR(start_mem);
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end_mem -= start_mem;
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end_mem >>= 12;
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while (end_mem-->0)
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mem_map[i++]=0;
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}
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void calc_mem(void)
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{
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int i,j,k,free=0;
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long * pg_tbl;
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for(i=0 ; i<PAGING_PAGES ; i++)
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if (!mem_map[i]) free++;
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printk("%d pages free (of %d)\n\r",free,PAGING_PAGES);
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for(i=2 ; i<1024 ; i++) {
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if (1&pg_dir[i]) {
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pg_tbl=(long *) (0xfffff000 & pg_dir[i]);
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for(j=k=0 ; j<1024 ; j++)
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if (pg_tbl[j]&1)
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k++;
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printk("Pg-dir[%d] uses %d pages\n",i,k);
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}
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}
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}
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Loading…
Reference in new issue