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/*
* linux/mm/mincore.c
*
* Copyright (C) 1994-1999 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;
}
static long mincore_vma(struct vm_area_struct * vma,
unsigned long start, unsigned long end, unsigned char __user * vec)
{
long error, i, remaining;
unsigned char * tmp;
error = -ENOMEM;
if (!vma->vm_file)
return error;
start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
if (end > vma->vm_end)
end = vma->vm_end;
end = ((end - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
error = -EAGAIN;
tmp = (unsigned char *) __get_free_page(GFP_KERNEL);
if (!tmp)
return error;
/* (end - start) is # of pages, and also # of bytes in "vec */
remaining = (end - start),
error = 0;
for (i = 0; remaining > 0; remaining -= PAGE_SIZE, i++) {
int j = 0;
long thispiece = (remaining < PAGE_SIZE) ?
remaining : PAGE_SIZE;
while (j < thispiece)
tmp[j++] = mincore_page(vma, start++);
if (copy_to_user(vec + PAGE_SIZE * i, tmp, thispiece)) {
error = -EFAULT;
break;
}
}
free_page((unsigned long) tmp);
return error;
}
/*
* 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)
{
int index = 0;
unsigned long end, limit;
struct vm_area_struct * vma;
size_t max;
int unmapped_error = 0;
long error;
/* check the arguments */
if (start & ~PAGE_CACHE_MASK)
goto einval;
limit = TASK_SIZE;
if (start >= limit)
goto enomem;
if (!len)
return 0;
max = limit - start;
len = PAGE_CACHE_ALIGN(len);
if (len > max || !len)
goto enomem;
end = start + len;
/* check the output buffer whilst holding the lock */
error = -EFAULT;
down_read(¤t->mm->mmap_sem);
if (!access_ok(VERIFY_WRITE, vec, len >> PAGE_SHIFT))
goto out;
/*
* If the interval [start,end) covers some unmapped address
* ranges, just ignore them, but return -ENOMEM at the end.
*/
error = 0;
vma = find_vma(current->mm, start);
while (vma) {
/* Here start < vma->vm_end. */
if (start < vma->vm_start) {
unmapped_error = -ENOMEM;
start = vma->vm_start;
}
/* Here vma->vm_start <= start < vma->vm_end. */
if (end <= vma->vm_end) {
if (start < end) {
error = mincore_vma(vma, start, end,
&vec[index]);
if (error)
goto out;
}
error = unmapped_error;
goto out;
}
/* Here vma->vm_start <= start < vma->vm_end < end. */
error = mincore_vma(vma, start, vma->vm_end, &vec[index]);
if (error)
goto out;
index += (vma->vm_end - start) >> PAGE_CACHE_SHIFT;
start = vma->vm_end;
vma = vma->vm_next;
}
/* we found a hole in the area queried if we arrive here */
error = -ENOMEM;
out:
up_read(¤t->mm->mmap_sem);
return error;
einval:
return -EINVAL;
enomem:
return -ENOMEM;
}
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