162 lines
4.2 KiB
C
162 lines
4.2 KiB
C
/*
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* linux/mm/mincore.c
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*
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* Copyright (C) 1994-2006 Linus Torvalds
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*/
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/*
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* The mincore() system call.
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*/
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#include <linux/slab.h>
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#include <linux/pagemap.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/syscalls.h>
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#include <asm/uaccess.h>
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#include <asm/pgtable.h>
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/*
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* Later we can get more picky about what "in core" means precisely.
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* For now, simply check to see if the page is in the page cache,
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* and is up to date; i.e. that no page-in operation would be required
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* at this time if an application were to map and access this page.
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*/
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static unsigned char mincore_page(struct vm_area_struct * vma,
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unsigned long pgoff)
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{
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unsigned char present = 0;
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struct address_space * as = vma->vm_file->f_mapping;
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struct page * page;
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page = find_get_page(as, pgoff);
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if (page) {
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present = PageUptodate(page);
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page_cache_release(page);
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}
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return present;
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}
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/*
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* Do a chunk of "sys_mincore()". We've already checked
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* all the arguments, we hold the mmap semaphore: we should
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* just return the amount of info we're asked for.
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*/
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static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages)
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{
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unsigned long i, nr, pgoff;
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struct vm_area_struct *vma = find_vma(current->mm, addr);
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/*
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* find_vma() didn't find anything above us, or we're
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* in an unmapped hole in the address space: ENOMEM.
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*/
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if (!vma || addr < vma->vm_start)
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return -ENOMEM;
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/*
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* Ok, got it. But check whether it's a segment we support
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* mincore() on. Right now, we don't do any anonymous mappings.
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*
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* FIXME: This is just stupid. And returning ENOMEM is
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* stupid too. We should just look at the page tables. But
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* this is what we've traditionally done, so we'll just
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* continue doing it.
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*/
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if (!vma->vm_file)
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return -ENOMEM;
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/*
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* Calculate how many pages there are left in the vma, and
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* what the pgoff is for our address.
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*/
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nr = (vma->vm_end - addr) >> PAGE_SHIFT;
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if (nr > pages)
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nr = pages;
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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/* And then we just fill the sucker in.. */
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for (i = 0 ; i < nr; i++, pgoff++)
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vec[i] = mincore_page(vma, pgoff);
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return nr;
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}
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/*
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* The mincore(2) system call.
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*
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* mincore() returns the memory residency status of the pages in the
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* current process's address space specified by [addr, addr + len).
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* The status is returned in a vector of bytes. The least significant
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* bit of each byte is 1 if the referenced page is in memory, otherwise
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* it is zero.
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*
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* Because the status of a page can change after mincore() checks it
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* but before it returns to the application, the returned vector may
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* contain stale information. Only locked pages are guaranteed to
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* remain in memory.
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*
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* return values:
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* zero - success
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* -EFAULT - vec points to an illegal address
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* -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
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* -ENOMEM - Addresses in the range [addr, addr + len] are
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* invalid for the address space of this process, or
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* specify one or more pages which are not currently
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* mapped
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* -EAGAIN - A kernel resource was temporarily unavailable.
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*/
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asmlinkage long sys_mincore(unsigned long start, size_t len,
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unsigned char __user * vec)
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{
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long retval;
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unsigned long pages;
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unsigned char *tmp;
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/* Check the start address: needs to be page-aligned.. */
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if (start & ~PAGE_CACHE_MASK)
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return -EINVAL;
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/* ..and we need to be passed a valid user-space range */
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if (!access_ok(VERIFY_READ, (void __user *) start, len))
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return -ENOMEM;
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/* This also avoids any overflows on PAGE_CACHE_ALIGN */
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pages = len >> PAGE_SHIFT;
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pages += (len & ~PAGE_MASK) != 0;
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if (!access_ok(VERIFY_WRITE, vec, pages))
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return -EFAULT;
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tmp = (void *) __get_free_page(GFP_USER);
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if (!tmp)
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return -EAGAIN;
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retval = 0;
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while (pages) {
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/*
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* Do at most PAGE_SIZE entries per iteration, due to
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* the temporary buffer size.
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*/
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down_read(¤t->mm->mmap_sem);
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retval = do_mincore(start, tmp, min(pages, PAGE_SIZE));
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up_read(¤t->mm->mmap_sem);
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if (retval <= 0)
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break;
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if (copy_to_user(vec, tmp, retval)) {
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retval = -EFAULT;
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break;
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}
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pages -= retval;
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vec += retval;
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start += retval << PAGE_SHIFT;
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retval = 0;
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}
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free_page((unsigned long) tmp);
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return retval;
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}
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