/* * 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_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; }