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 = filemap_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(mapping: inode->i_mapping); |
70 | |
71 | /* make various checks */ |
72 | order = get_order(size: newsize); |
73 | if (unlikely(order > MAX_ORDER)) |
74 | return -EFBIG; |
75 | |
76 | ret = inode_newsize_ok(inode, offset: newsize); |
77 | if (ret) |
78 | return ret; |
79 | |
80 | i_size_write(inode, i_size: 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(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, mapping: inode->i_mapping, index: 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, newsize: 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, attr: 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(f: 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: &fbatch); |
225 | nr_pages = 0; |
226 | repeat: |
227 | nr_folios = filemap_get_folios_contig(mapping: inode->i_mapping, start: &pgoff, |
228 | ULONG_MAX, fbatch: &fbatch); |
229 | if (!nr_folios) { |
230 | ret = -ENOSYS; |
231 | return ret; |
232 | } |
233 | |
234 | if (ret == -ENOSYS) { |
235 | ret = (unsigned long) folio_address(folio: fbatch.folios[0]); |
236 | pfn = folio_pfn(folio: 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(folio: fbatch.folios[loop])) { |
241 | ret = -ENOSYS; |
242 | goto out_free; /* leave if not physical adjacent */ |
243 | } |
244 | nr_pages += folio_nr_pages(folio: 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: &fbatch); |
251 | goto repeat; /* loop if pages are missing */ |
252 | } |
253 | /* okay - all conditions fulfilled */ |
254 | |
255 | out_free: |
256 | folio_batch_release(fbatch: &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 | |