1/* 2 * linux/mm/fremap.c 3 * 4 * Explicit pagetable population and nonlinear (random) mappings support. 5 * 6 * started by Ingo Molnar, Copyright (C) 2002, 2003 7 */ 8#include <linux/export.h> 9#include <linux/backing-dev.h> 10#include <linux/mm.h> 11#include <linux/swap.h> 12#include <linux/file.h> 13#include <linux/mman.h> 14#include <linux/pagemap.h> 15#include <linux/swapops.h> 16#include <linux/rmap.h> 17#include <linux/syscalls.h> 18#include <linux/mmu_notifier.h> 19 20#include <asm/mmu_context.h> 21#include <asm/cacheflush.h> 22#include <asm/tlbflush.h> 23 24#include "internal.h" 25 26static int mm_counter(struct page *page) 27{ 28 return PageAnon(page) ? MM_ANONPAGES : MM_FILEPAGES; 29} 30 31static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma, 32 unsigned long addr, pte_t *ptep) 33{ 34 pte_t pte = *ptep; 35 struct page *page; 36 swp_entry_t entry; 37 38 if (pte_present(pte)) { 39 flush_cache_page(vma, addr, pte_pfn(pte)); 40 pte = ptep_clear_flush(vma, addr, ptep); 41 page = vm_normal_page(vma, addr, pte); 42 if (page) { 43 if (pte_dirty(pte)) 44 set_page_dirty(page); 45 update_hiwater_rss(mm); 46 dec_mm_counter(mm, mm_counter(page)); 47 page_remove_rmap(page); 48 page_cache_release(page); 49 } 50 } else { /* zap_pte() is not called when pte_none() */ 51 if (!pte_file(pte)) { 52 update_hiwater_rss(mm); 53 entry = pte_to_swp_entry(pte); 54 if (non_swap_entry(entry)) { 55 if (is_migration_entry(entry)) { 56 page = migration_entry_to_page(entry); 57 dec_mm_counter(mm, mm_counter(page)); 58 } 59 } else { 60 free_swap_and_cache(entry); 61 dec_mm_counter(mm, MM_SWAPENTS); 62 } 63 } 64 pte_clear_not_present_full(mm, addr, ptep, 0); 65 } 66} 67 68/* 69 * Install a file pte to a given virtual memory address, release any 70 * previously existing mapping. 71 */ 72static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma, 73 unsigned long addr, unsigned long pgoff, pgprot_t prot) 74{ 75 int err = -ENOMEM; 76 pte_t *pte, ptfile; 77 spinlock_t *ptl; 78 79 pte = get_locked_pte(mm, addr, &ptl); 80 if (!pte) 81 goto out; 82 83 ptfile = pgoff_to_pte(pgoff); 84 85 if (!pte_none(*pte)) 86 zap_pte(mm, vma, addr, pte); 87 88 set_pte_at(mm, addr, pte, pte_file_mksoft_dirty(ptfile)); 89 /* 90 * We don't need to run update_mmu_cache() here because the "file pte" 91 * being installed by install_file_pte() is not a real pte - it's a 92 * non-present entry (like a swap entry), noting what file offset should 93 * be mapped there when there's a fault (in a non-linear vma where 94 * that's not obvious). 95 */ 96 pte_unmap_unlock(pte, ptl); 97 err = 0; 98out: 99 return err; 100} 101 102int generic_file_remap_pages(struct vm_area_struct *vma, unsigned long addr, 103 unsigned long size, pgoff_t pgoff) 104{ 105 struct mm_struct *mm = vma->vm_mm; 106 int err; 107 108 do { 109 err = install_file_pte(mm, vma, addr, pgoff, vma->vm_page_prot); 110 if (err) 111 return err; 112 113 size -= PAGE_SIZE; 114 addr += PAGE_SIZE; 115 pgoff++; 116 } while (size); 117 118 return 0; 119} 120EXPORT_SYMBOL(generic_file_remap_pages); 121 122/** 123 * sys_remap_file_pages - remap arbitrary pages of an existing VM_SHARED vma 124 * @start: start of the remapped virtual memory range 125 * @size: size of the remapped virtual memory range 126 * @prot: new protection bits of the range (see NOTE) 127 * @pgoff: to-be-mapped page of the backing store file 128 * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO. 129 * 130 * sys_remap_file_pages remaps arbitrary pages of an existing VM_SHARED vma 131 * (shared backing store file). 132 * 133 * This syscall works purely via pagetables, so it's the most efficient 134 * way to map the same (large) file into a given virtual window. Unlike 135 * mmap()/mremap() it does not create any new vmas. The new mappings are 136 * also safe across swapout. 137 * 138 * NOTE: the @prot parameter right now is ignored (but must be zero), 139 * and the vma's default protection is used. Arbitrary protections 140 * might be implemented in the future. 141 */ 142SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, 143 unsigned long, prot, unsigned long, pgoff, unsigned long, flags) 144{ 145 struct mm_struct *mm = current->mm; 146 struct address_space *mapping; 147 struct vm_area_struct *vma; 148 int err = -EINVAL; 149 int has_write_lock = 0; 150 vm_flags_t vm_flags = 0; 151 152 pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. " 153 "See Documentation/vm/remap_file_pages.txt.\n", 154 current->comm, current->pid); 155 156 if (prot) 157 return err; 158 /* 159 * Sanitize the syscall parameters: 160 */ 161 start = start & PAGE_MASK; 162 size = size & PAGE_MASK; 163 164 /* Does the address range wrap, or is the span zero-sized? */ 165 if (start + size <= start) 166 return err; 167 168 /* Does pgoff wrap? */ 169 if (pgoff + (size >> PAGE_SHIFT) < pgoff) 170 return err; 171 172 /* Can we represent this offset inside this architecture's pte's? */ 173#if PTE_FILE_MAX_BITS < BITS_PER_LONG 174 if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS)) 175 return err; 176#endif 177 178 /* We need down_write() to change vma->vm_flags. */ 179 down_read(&mm->mmap_sem); 180 retry: 181 vma = find_vma(mm, start); 182 183 /* 184 * Make sure the vma is shared, that it supports prefaulting, 185 * and that the remapped range is valid and fully within 186 * the single existing vma. 187 */ 188 if (!vma || !(vma->vm_flags & VM_SHARED)) 189 goto out; 190 191 if (!vma->vm_ops || !vma->vm_ops->remap_pages) 192 goto out; 193 194 if (start < vma->vm_start || start + size > vma->vm_end) 195 goto out; 196 197 /* Must set VM_NONLINEAR before any pages are populated. */ 198 if (!(vma->vm_flags & VM_NONLINEAR)) { 199 /* 200 * vm_private_data is used as a swapout cursor 201 * in a VM_NONLINEAR vma. 202 */ 203 if (vma->vm_private_data) 204 goto out; 205 206 /* Don't need a nonlinear mapping, exit success */ 207 if (pgoff == linear_page_index(vma, start)) { 208 err = 0; 209 goto out; 210 } 211 212 if (!has_write_lock) { 213get_write_lock: 214 up_read(&mm->mmap_sem); 215 down_write(&mm->mmap_sem); 216 has_write_lock = 1; 217 goto retry; 218 } 219 mapping = vma->vm_file->f_mapping; 220 /* 221 * page_mkclean doesn't work on nonlinear vmas, so if 222 * dirty pages need to be accounted, emulate with linear 223 * vmas. 224 */ 225 if (mapping_cap_account_dirty(mapping)) { 226 unsigned long addr; 227 struct file *file = get_file(vma->vm_file); 228 /* mmap_region may free vma; grab the info now */ 229 vm_flags = vma->vm_flags; 230 231 addr = mmap_region(file, start, size, vm_flags, pgoff); 232 fput(file); 233 if (IS_ERR_VALUE(addr)) { 234 err = addr; 235 } else { 236 BUG_ON(addr != start); 237 err = 0; 238 } 239 goto out_freed; 240 } 241 mutex_lock(&mapping->i_mmap_mutex); 242 flush_dcache_mmap_lock(mapping); 243 vma->vm_flags |= VM_NONLINEAR; 244 vma_interval_tree_remove(vma, &mapping->i_mmap); 245 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); 246 flush_dcache_mmap_unlock(mapping); 247 mutex_unlock(&mapping->i_mmap_mutex); 248 } 249 250 if (vma->vm_flags & VM_LOCKED) { 251 /* 252 * drop PG_Mlocked flag for over-mapped range 253 */ 254 if (!has_write_lock) 255 goto get_write_lock; 256 vm_flags = vma->vm_flags; 257 munlock_vma_pages_range(vma, start, start + size); 258 vma->vm_flags = vm_flags; 259 } 260 261 mmu_notifier_invalidate_range_start(mm, start, start + size); 262 err = vma->vm_ops->remap_pages(vma, start, size, pgoff); 263 mmu_notifier_invalidate_range_end(mm, start, start + size); 264 265 /* 266 * We can't clear VM_NONLINEAR because we'd have to do 267 * it after ->populate completes, and that would prevent 268 * downgrading the lock. (Locks can't be upgraded). 269 */ 270 271out: 272 if (vma) 273 vm_flags = vma->vm_flags; 274out_freed: 275 if (likely(!has_write_lock)) 276 up_read(&mm->mmap_sem); 277 else 278 up_write(&mm->mmap_sem); 279 if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK))) 280 mm_populate(start, size); 281 282 return err; 283} 284