/* * 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 .nopage). 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. */ 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; }