1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* file-nommu.c: no-MMU version of ramfs 3 * 4 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved. 5 * Written by David Howells (dhowells@redhat.com) 6 */ 7 8 #include <linux/module.h> 9 #include <linux/fs.h> 10 #include <linux/mm.h> 11 #include <linux/pagemap.h> 12 #include <linux/highmem.h> 13 #include <linux/init.h> 14 #include <linux/string.h> 15 #include <linux/backing-dev.h> 16 #include <linux/ramfs.h> 17 #include <linux/pagevec.h> 18 #include <linux/mman.h> 19 #include <linux/sched.h> 20 #include <linux/slab.h> 21 22 #include <linux/uaccess.h> 23 #include "internal.h" 24 25 static int ramfs_nommu_setattr(struct mnt_idmap *, struct dentry *, struct iattr *); 26 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 27 unsigned long addr, 28 unsigned long len, 29 unsigned long pgoff, 30 unsigned long flags); 31 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma); 32 33 static unsigned ramfs_mmap_capabilities(struct file *file) 34 { 35 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ | 36 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC; 37 } 38 39 const struct file_operations ramfs_file_operations = { 40 .mmap_capabilities = ramfs_mmap_capabilities, 41 .mmap = ramfs_nommu_mmap, 42 .get_unmapped_area = ramfs_nommu_get_unmapped_area, 43 .read_iter = generic_file_read_iter, 44 .write_iter = generic_file_write_iter, 45 .fsync = noop_fsync, 46 .splice_read = generic_file_splice_read, 47 .splice_write = iter_file_splice_write, 48 .llseek = generic_file_llseek, 49 }; 50 51 const struct inode_operations ramfs_file_inode_operations = { 52 .setattr = ramfs_nommu_setattr, 53 .getattr = simple_getattr, 54 }; 55 56 /*****************************************************************************/ 57 /* 58 * add a contiguous set of pages into a ramfs inode when it's truncated from 59 * size 0 on the assumption that it's going to be used for an mmap of shared 60 * memory 61 */ 62 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) 63 { 64 unsigned long npages, xpages, loop; 65 struct page *pages; 66 unsigned order; 67 void *data; 68 int ret; 69 gfp_t gfp = mapping_gfp_mask(inode->i_mapping); 70 71 /* make various checks */ 72 order = get_order(newsize); 73 if (unlikely(order >= MAX_ORDER)) 74 return -EFBIG; 75 76 ret = inode_newsize_ok(inode, newsize); 77 if (ret) 78 return ret; 79 80 i_size_write(inode, newsize); 81 82 /* allocate enough contiguous pages to be able to satisfy the 83 * request */ 84 pages = alloc_pages(gfp, order); 85 if (!pages) 86 return -ENOMEM; 87 88 /* split the high-order page into an array of single pages */ 89 xpages = 1UL << order; 90 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; 91 92 split_page(pages, order); 93 94 /* trim off any pages we don't actually require */ 95 for (loop = npages; loop < xpages; loop++) 96 __free_page(pages + loop); 97 98 /* clear the memory we allocated */ 99 newsize = PAGE_SIZE * npages; 100 data = page_address(pages); 101 memset(data, 0, newsize); 102 103 /* attach all the pages to the inode's address space */ 104 for (loop = 0; loop < npages; loop++) { 105 struct page *page = pages + loop; 106 107 ret = add_to_page_cache_lru(page, inode->i_mapping, loop, 108 gfp); 109 if (ret < 0) 110 goto add_error; 111 112 /* prevent the page from being discarded on memory pressure */ 113 SetPageDirty(page); 114 SetPageUptodate(page); 115 116 unlock_page(page); 117 put_page(page); 118 } 119 120 return 0; 121 122 add_error: 123 while (loop < npages) 124 __free_page(pages + loop++); 125 return ret; 126 } 127 128 /*****************************************************************************/ 129 /* 130 * 131 */ 132 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) 133 { 134 int ret; 135 136 /* assume a truncate from zero size is going to be for the purposes of 137 * shared mmap */ 138 if (size == 0) { 139 if (unlikely(newsize >> 32)) 140 return -EFBIG; 141 142 return ramfs_nommu_expand_for_mapping(inode, newsize); 143 } 144 145 /* check that a decrease in size doesn't cut off any shared mappings */ 146 if (newsize < size) { 147 ret = nommu_shrink_inode_mappings(inode, size, newsize); 148 if (ret < 0) 149 return ret; 150 } 151 152 truncate_setsize(inode, newsize); 153 return 0; 154 } 155 156 /*****************************************************************************/ 157 /* 158 * handle a change of attributes 159 * - we're specifically interested in a change of size 160 */ 161 static int ramfs_nommu_setattr(struct mnt_idmap *idmap, 162 struct dentry *dentry, struct iattr *ia) 163 { 164 struct inode *inode = d_inode(dentry); 165 unsigned int old_ia_valid = ia->ia_valid; 166 int ret = 0; 167 168 /* POSIX UID/GID verification for setting inode attributes */ 169 ret = setattr_prepare(&nop_mnt_idmap, dentry, ia); 170 if (ret) 171 return ret; 172 173 /* pick out size-changing events */ 174 if (ia->ia_valid & ATTR_SIZE) { 175 loff_t size = inode->i_size; 176 177 if (ia->ia_size != size) { 178 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 179 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 180 goto out; 181 } else { 182 /* we skipped the truncate but must still update 183 * timestamps 184 */ 185 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 186 } 187 } 188 189 setattr_copy(&nop_mnt_idmap, inode, ia); 190 out: 191 ia->ia_valid = old_ia_valid; 192 return ret; 193 } 194 195 /*****************************************************************************/ 196 /* 197 * try to determine where a shared mapping can be made 198 * - we require that: 199 * - the pages to be mapped must exist 200 * - the pages be physically contiguous in sequence 201 */ 202 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 203 unsigned long addr, unsigned long len, 204 unsigned long pgoff, unsigned long flags) 205 { 206 unsigned long maxpages, lpages, nr_folios, loop, ret, nr_pages, pfn; 207 struct inode *inode = file_inode(file); 208 struct folio_batch fbatch; 209 loff_t isize; 210 211 /* the mapping mustn't extend beyond the EOF */ 212 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 213 isize = i_size_read(inode); 214 215 ret = -ENOSYS; 216 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 217 if (pgoff >= maxpages) 218 goto out; 219 220 if (maxpages - pgoff < lpages) 221 goto out; 222 223 /* gang-find the pages */ 224 folio_batch_init(&fbatch); 225 nr_pages = 0; 226 repeat: 227 nr_folios = filemap_get_folios_contig(inode->i_mapping, &pgoff, 228 ULONG_MAX, &fbatch); 229 if (!nr_folios) { 230 ret = -ENOSYS; 231 return ret; 232 } 233 234 if (ret == -ENOSYS) { 235 ret = (unsigned long) folio_address(fbatch.folios[0]); 236 pfn = folio_pfn(fbatch.folios[0]); 237 } 238 /* check the pages for physical adjacency */ 239 for (loop = 0; loop < nr_folios; loop++) { 240 if (pfn + nr_pages != folio_pfn(fbatch.folios[loop])) { 241 ret = -ENOSYS; 242 goto out_free; /* leave if not physical adjacent */ 243 } 244 nr_pages += folio_nr_pages(fbatch.folios[loop]); 245 if (nr_pages >= lpages) 246 goto out_free; /* successfully found desired pages*/ 247 } 248 249 if (nr_pages < lpages) { 250 folio_batch_release(&fbatch); 251 goto repeat; /* loop if pages are missing */ 252 } 253 /* okay - all conditions fulfilled */ 254 255 out_free: 256 folio_batch_release(&fbatch); 257 out: 258 return ret; 259 } 260 261 /*****************************************************************************/ 262 /* 263 * set up a mapping for shared memory segments 264 */ 265 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 266 { 267 if (!is_nommu_shared_mapping(vma->vm_flags)) 268 return -ENOSYS; 269 270 file_accessed(file); 271 vma->vm_ops = &generic_file_vm_ops; 272 return 0; 273 } 274