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118 lines
2.8 KiB
118 lines
2.8 KiB
void breading(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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{
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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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{
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return;
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}
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if(!(page = get_free_page()))
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{
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oom();
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}
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block = 1 + tmp/BLOCK_SIZE;
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for(i = 0; i < 4; block++, i++)
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{
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nr[i] = bmap(current->executable, block);
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}
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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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{
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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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{
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return ;
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}
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free_page(page);
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oom();
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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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} |