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 25static int ramfs_nommu_setattr(struct dentry *, struct iattr *); 26static 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); 31static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma); 32 33static 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 39const 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 51const 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 */ 62int 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 122add_error: 123 while (loop < npages) 124 __free_page(pages + loop++); 125 return ret; 126} 127 128/*****************************************************************************/ 129/* 130 * 131 */ 132static 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 */ 161static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) 162{ 163 struct inode *inode = d_inode(dentry); 164 unsigned int old_ia_valid = ia->ia_valid; 165 int ret = 0; 166 167 /* POSIX UID/GID verification for setting inode attributes */ 168 ret = setattr_prepare(dentry, ia); 169 if (ret) 170 return ret; 171 172 /* pick out size-changing events */ 173 if (ia->ia_valid & ATTR_SIZE) { 174 loff_t size = inode->i_size; 175 176 if (ia->ia_size != size) { 177 ret = ramfs_nommu_resize(inode, ia->ia_size, size); 178 if (ret < 0 || ia->ia_valid == ATTR_SIZE) 179 goto out; 180 } else { 181 /* we skipped the truncate but must still update 182 * timestamps 183 */ 184 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; 185 } 186 } 187 188 setattr_copy(inode, ia); 189 out: 190 ia->ia_valid = old_ia_valid; 191 return ret; 192} 193 194/*****************************************************************************/ 195/* 196 * try to determine where a shared mapping can be made 197 * - we require that: 198 * - the pages to be mapped must exist 199 * - the pages be physically contiguous in sequence 200 */ 201static unsigned long ramfs_nommu_get_unmapped_area(struct file *file, 202 unsigned long addr, unsigned long len, 203 unsigned long pgoff, unsigned long flags) 204{ 205 unsigned long maxpages, lpages, nr, loop, ret; 206 struct inode *inode = file_inode(file); 207 struct page **pages = NULL, **ptr, *page; 208 loff_t isize; 209 210 /* the mapping mustn't extend beyond the EOF */ 211 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; 212 isize = i_size_read(inode); 213 214 ret = -ENOSYS; 215 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; 216 if (pgoff >= maxpages) 217 goto out; 218 219 if (maxpages - pgoff < lpages) 220 goto out; 221 222 /* gang-find the pages */ 223 pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL); 224 if (!pages) 225 goto out_free; 226 227 nr = find_get_pages_contig(inode->i_mapping, pgoff, lpages, pages); 228 if (nr != lpages) 229 goto out_free_pages; /* leave if some pages were missing */ 230 231 /* check the pages for physical adjacency */ 232 ptr = pages; 233 page = *ptr++; 234 page++; 235 for (loop = lpages; loop > 1; loop--) 236 if (*ptr++ != page++) 237 goto out_free_pages; 238 239 /* okay - all conditions fulfilled */ 240 ret = (unsigned long) page_address(pages[0]); 241 242out_free_pages: 243 ptr = pages; 244 for (loop = nr; loop > 0; loop--) 245 put_page(*ptr++); 246out_free: 247 kfree(pages); 248out: 249 return ret; 250} 251 252/*****************************************************************************/ 253/* 254 * set up a mapping for shared memory segments 255 */ 256static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) 257{ 258 if (!(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) 259 return -ENOSYS; 260 261 file_accessed(file); 262 vma->vm_ops = &generic_file_vm_ops; 263 return 0; 264} 265