/*
* linux/mm/mincore.c
*
* Copyright (C) 1994-2006 Linus Torvalds
*/
/*
* The mincore() system call.
*/
#include <linux/pagemap.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/syscalls.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/hugetlb.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
static void mincore_hugetlb_page_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
#ifdef CONFIG_HUGETLB_PAGE
struct hstate *h;
h = hstate_vma(vma);
while (1) {
unsigned char present;
pte_t *ptep;
/*
* Huge pages are always in RAM for now, but
* theoretically it needs to be checked.
*/
ptep = huge_pte_offset(current->mm,
addr & huge_page_mask(h));
present = ptep && !huge_pte_none(huge_ptep_get(ptep));
while (1) {
*vec = present;
vec++;
addr += PAGE_SIZE;
if (addr == end)
return;
/* check hugepage border */
if (!(addr & ~huge_page_mask(h)))
break;
}
}
#else
BUG();
#endif
}
/*
* 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 address_space *mapping, pgoff_t pgoff)
{
unsigned char present = 0;
struct page *page;
/*
* When tmpfs swaps out a page from a file, any process mapping that
* file will not get a swp_entry_t in its pte, but rather it is like
* any other file mapping (ie. marked !present and faulted in with
* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
*
* However when tmpfs moves the page from pagecache and into swapcache,
* it is still in core, but the find_get_page below won't find it.
* No big deal, but make a note of it.
*/
page = find_get_page(mapping, pgoff);
if (page) {
present = PageUptodate(page);
page_cache_release(page);
}
return present;
}
static void mincore_unmapped_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
unsigned long nr = (end - addr) >> PAGE_SHIFT;
int i;
if (vma->vm_file) {
pgoff_t pgoff;
pgoff = linear_page_index(vma, addr);
for (i = 0; i < nr; i++, pgoff++)
vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
} else {
for (i = 0; i < nr; i++)
vec[i] = 0;
}
}
static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
unsigned long next;
spinlock_t *ptl;
pte_t *ptep;
ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
do {
pte_t pte = *ptep;
pgoff_t pgoff;
next = addr + PAGE_SIZE;
if (pte_none(pte))
mincore_unmapped_range(vma, addr, next, vec);
else if (pte_present(pte))
*vec = 1;
else if (pte_file(pte)) {
pgoff = pte_to_pgoff(pte);
*vec = mincore_page(vma->vm_file->f_mapping, pgoff);
} else { /* pte is a swap entry */
swp_entry_t entry = pte_to_swp_entry(pte);
if (is_migration_entry(entry)) {
/* migration entries are always uptodate */
*vec = 1;
} else {
#ifdef CONFIG_SWAP
pgoff = entry.val;
*vec = mincore_page(&swapper_space, pgoff);
#else
WARN_ON(1);
*vec = 1;
#endif
}
}
vec++;
} while (ptep++, addr = next, addr != end);
pte_unmap_unlock(ptep - 1, ptl);
}
static void mincore_pmd_range(struct vm_area_struct *vma, pud_t *pud,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
unsigned long next;
pmd_t *pmd;
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
if (mincore_huge_pmd(vma, pmd, addr, next, vec)) {
vec += (next - addr) >> PAGE_SHIFT;
continue;
}
/* fall through */
}
if (pmd_none_or_clear_bad(pmd))
mincore_unmapped_range(vma, addr, next, vec);
else
mincore_pte_range(vma, pmd, addr, next, vec);
vec += (next - addr) >> PAGE_SHIFT;
} while (pmd++, addr = next, addr != end);
}
static void mincore_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
unsigned long next;
pud_t *pud;
pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
mincore_unmapped_range(vma, addr, next, vec);
else
mincore_pmd_range(vma, pud, addr, next, vec);
vec += (next - addr) >> PAGE_SHIFT;
} while (pud++, addr = next, addr != end);
}
static void mincore_page_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
unsigned char *vec)
{
unsigned long next;
pgd_t *pgd;
pgd = pgd_offset(vma->vm_mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
mincore_unmapped_range(vma, addr, next, vec);
else
mincore_pud_range(vma, pgd, addr, next, vec);
vec += (next - addr) >> PAGE_SHIFT;
} while (pgd++, addr = next, addr != end);
}
/*
* 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 long pages, unsigned char *vec)
{
struct vm_area_struct *vma;
unsigned long end;
vma = find_vma(current->mm, addr);
if (!vma || addr < vma->vm_start)
return -ENOMEM;
end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
if (is_vm_hugetlb_page(vma)) {
mincore_hugetlb_page_range(vma, addr, end, vec);
return (end - addr) >> PAGE_SHIFT;
}
end = pmd_addr_end(addr, end);
if (is_vm_hugetlb_page(vma))
mincore_hugetlb_page_range(vma, addr, end, vec);
else
mincore_page_range(vma, addr, end, vec);
return (end - addr) >> PAGE_SHIFT;
}
/*
* 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.
*/
SYSCALL_DEFINE3(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, min(pages, PAGE_SIZE), tmp);
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;
}