diff options
Diffstat (limited to 'mm/mincore.c')
| -rw-r--r-- | mm/mincore.c | 229 |
1 files changed, 229 insertions, 0 deletions
diff --git a/mm/mincore.c b/mm/mincore.c new file mode 100644 index 0000000..8cb508f --- /dev/null +++ b/mm/mincore.c @@ -0,0 +1,229 @@ +/* + * 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 <linux/swap.h> +#include <linux/swapops.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 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; +} + +/* + * 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) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *ptep; + spinlock_t *ptl; + unsigned long nr; + int i; + pgoff_t 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; + + /* + * Calculate how many pages there are left in the last level of the + * PTE array for our address. + */ + nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)); + + /* + * Don't overrun this vma + */ + nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT); + + /* + * Don't return more than the caller asked for + */ + nr = min(nr, pages); + + pgd = pgd_offset(vma->vm_mm, addr); + if (pgd_none_or_clear_bad(pgd)) + goto none_mapped; + pud = pud_offset(pgd, addr); + if (pud_none_or_clear_bad(pud)) + goto none_mapped; + pmd = pmd_offset(pud, addr); + if (pmd_none_or_clear_bad(pmd)) + goto none_mapped; + + ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); + for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) { + unsigned char present; + pte_t pte = *ptep; + + if (pte_present(pte)) { + present = 1; + + } else if (pte_none(pte)) { + if (vma->vm_file) { + pgoff = linear_page_index(vma, addr); + present = mincore_page(vma->vm_file->f_mapping, + pgoff); + } else + present = 0; + + } else if (pte_file(pte)) { + pgoff = pte_to_pgoff(pte); + present = 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 */ + present = 1; + } else { +#ifdef CONFIG_SWAP + pgoff = entry.val; + present = mincore_page(&swapper_space, pgoff); +#else + WARN_ON(1); + present = 1; +#endif + } + } + + vec[i] = present; + } + pte_unmap_unlock(ptep-1, ptl); + + return nr; + +none_mapped: + if (vma->vm_file) { + 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; + } + + 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. + */ +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, 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; +} |
