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