1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Set up the VMAs to tell the VM about the vDSO.
4 * Copyright 2007 Andi Kleen, SUSE Labs.
5 */
6
7 /*
8 * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
9 */
10
11 #include <linux/mm.h>
12 #include <linux/err.h>
13 #include <linux/sched.h>
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/linkage.h>
17 #include <linux/random.h>
18 #include <linux/elf.h>
19 #include <asm/cacheflush.h>
20 #include <asm/spitfire.h>
21 #include <asm/vdso.h>
22 #include <asm/vvar.h>
23 #include <asm/page.h>
24
25 unsigned int __read_mostly vdso_enabled = 1;
26
27 static struct vm_special_mapping vvar_mapping = {
28 .name = "[vvar]"
29 };
30
31 #ifdef CONFIG_SPARC64
32 static struct vm_special_mapping vdso_mapping64 = {
33 .name = "[vdso]"
34 };
35 #endif
36
37 #ifdef CONFIG_COMPAT
38 static struct vm_special_mapping vdso_mapping32 = {
39 .name = "[vdso]"
40 };
41 #endif
42
43 struct vvar_data *vvar_data;
44
45 struct vdso_elfinfo32 {
46 Elf32_Ehdr *hdr;
47 Elf32_Sym *dynsym;
48 unsigned long dynsymsize;
49 const char *dynstr;
50 unsigned long text;
51 };
52
53 struct vdso_elfinfo64 {
54 Elf64_Ehdr *hdr;
55 Elf64_Sym *dynsym;
56 unsigned long dynsymsize;
57 const char *dynstr;
58 unsigned long text;
59 };
60
61 struct vdso_elfinfo {
62 union {
63 struct vdso_elfinfo32 elf32;
64 struct vdso_elfinfo64 elf64;
65 } u;
66 };
67
one_section64(struct vdso_elfinfo64 * e,const char * name,unsigned long * size)68 static void *one_section64(struct vdso_elfinfo64 *e, const char *name,
69 unsigned long *size)
70 {
71 const char *snames;
72 Elf64_Shdr *shdrs;
73 unsigned int i;
74
75 shdrs = (void *)e->hdr + e->hdr->e_shoff;
76 snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
77 for (i = 1; i < e->hdr->e_shnum; i++) {
78 if (!strcmp(snames+shdrs[i].sh_name, name)) {
79 if (size)
80 *size = shdrs[i].sh_size;
81 return (void *)e->hdr + shdrs[i].sh_offset;
82 }
83 }
84 return NULL;
85 }
86
find_sections64(const struct vdso_image * image,struct vdso_elfinfo * _e)87 static int find_sections64(const struct vdso_image *image, struct vdso_elfinfo *_e)
88 {
89 struct vdso_elfinfo64 *e = &_e->u.elf64;
90
91 e->hdr = image->data;
92 e->dynsym = one_section64(e, ".dynsym", &e->dynsymsize);
93 e->dynstr = one_section64(e, ".dynstr", NULL);
94
95 if (!e->dynsym || !e->dynstr) {
96 pr_err("VDSO64: Missing symbol sections.\n");
97 return -ENODEV;
98 }
99 return 0;
100 }
101
find_sym64(const struct vdso_elfinfo64 * e,const char * name)102 static Elf64_Sym *find_sym64(const struct vdso_elfinfo64 *e, const char *name)
103 {
104 unsigned int i;
105
106 for (i = 0; i < (e->dynsymsize / sizeof(Elf64_Sym)); i++) {
107 Elf64_Sym *s = &e->dynsym[i];
108 if (s->st_name == 0)
109 continue;
110 if (!strcmp(e->dynstr + s->st_name, name))
111 return s;
112 }
113 return NULL;
114 }
115
patchsym64(struct vdso_elfinfo * _e,const char * orig,const char * new)116 static int patchsym64(struct vdso_elfinfo *_e, const char *orig,
117 const char *new)
118 {
119 struct vdso_elfinfo64 *e = &_e->u.elf64;
120 Elf64_Sym *osym = find_sym64(e, orig);
121 Elf64_Sym *nsym = find_sym64(e, new);
122
123 if (!nsym || !osym) {
124 pr_err("VDSO64: Missing symbols.\n");
125 return -ENODEV;
126 }
127 osym->st_value = nsym->st_value;
128 osym->st_size = nsym->st_size;
129 osym->st_info = nsym->st_info;
130 osym->st_other = nsym->st_other;
131 osym->st_shndx = nsym->st_shndx;
132
133 return 0;
134 }
135
one_section32(struct vdso_elfinfo32 * e,const char * name,unsigned long * size)136 static void *one_section32(struct vdso_elfinfo32 *e, const char *name,
137 unsigned long *size)
138 {
139 const char *snames;
140 Elf32_Shdr *shdrs;
141 unsigned int i;
142
143 shdrs = (void *)e->hdr + e->hdr->e_shoff;
144 snames = (void *)e->hdr + shdrs[e->hdr->e_shstrndx].sh_offset;
145 for (i = 1; i < e->hdr->e_shnum; i++) {
146 if (!strcmp(snames+shdrs[i].sh_name, name)) {
147 if (size)
148 *size = shdrs[i].sh_size;
149 return (void *)e->hdr + shdrs[i].sh_offset;
150 }
151 }
152 return NULL;
153 }
154
find_sections32(const struct vdso_image * image,struct vdso_elfinfo * _e)155 static int find_sections32(const struct vdso_image *image, struct vdso_elfinfo *_e)
156 {
157 struct vdso_elfinfo32 *e = &_e->u.elf32;
158
159 e->hdr = image->data;
160 e->dynsym = one_section32(e, ".dynsym", &e->dynsymsize);
161 e->dynstr = one_section32(e, ".dynstr", NULL);
162
163 if (!e->dynsym || !e->dynstr) {
164 pr_err("VDSO32: Missing symbol sections.\n");
165 return -ENODEV;
166 }
167 return 0;
168 }
169
find_sym32(const struct vdso_elfinfo32 * e,const char * name)170 static Elf32_Sym *find_sym32(const struct vdso_elfinfo32 *e, const char *name)
171 {
172 unsigned int i;
173
174 for (i = 0; i < (e->dynsymsize / sizeof(Elf32_Sym)); i++) {
175 Elf32_Sym *s = &e->dynsym[i];
176 if (s->st_name == 0)
177 continue;
178 if (!strcmp(e->dynstr + s->st_name, name))
179 return s;
180 }
181 return NULL;
182 }
183
patchsym32(struct vdso_elfinfo * _e,const char * orig,const char * new)184 static int patchsym32(struct vdso_elfinfo *_e, const char *orig,
185 const char *new)
186 {
187 struct vdso_elfinfo32 *e = &_e->u.elf32;
188 Elf32_Sym *osym = find_sym32(e, orig);
189 Elf32_Sym *nsym = find_sym32(e, new);
190
191 if (!nsym || !osym) {
192 pr_err("VDSO32: Missing symbols.\n");
193 return -ENODEV;
194 }
195 osym->st_value = nsym->st_value;
196 osym->st_size = nsym->st_size;
197 osym->st_info = nsym->st_info;
198 osym->st_other = nsym->st_other;
199 osym->st_shndx = nsym->st_shndx;
200
201 return 0;
202 }
203
find_sections(const struct vdso_image * image,struct vdso_elfinfo * e,bool elf64)204 static int find_sections(const struct vdso_image *image, struct vdso_elfinfo *e,
205 bool elf64)
206 {
207 if (elf64)
208 return find_sections64(image, e);
209 else
210 return find_sections32(image, e);
211 }
212
patch_one_symbol(struct vdso_elfinfo * e,const char * orig,const char * new_target,bool elf64)213 static int patch_one_symbol(struct vdso_elfinfo *e, const char *orig,
214 const char *new_target, bool elf64)
215 {
216 if (elf64)
217 return patchsym64(e, orig, new_target);
218 else
219 return patchsym32(e, orig, new_target);
220 }
221
stick_patch(const struct vdso_image * image,struct vdso_elfinfo * e,bool elf64)222 static int stick_patch(const struct vdso_image *image, struct vdso_elfinfo *e, bool elf64)
223 {
224 int err;
225
226 err = find_sections(image, e, elf64);
227 if (err)
228 return err;
229
230 err = patch_one_symbol(e,
231 "__vdso_gettimeofday",
232 "__vdso_gettimeofday_stick", elf64);
233 if (err)
234 return err;
235
236 return patch_one_symbol(e,
237 "__vdso_clock_gettime",
238 "__vdso_clock_gettime_stick", elf64);
239 return 0;
240 }
241
242 /*
243 * Allocate pages for the vdso and vvar, and copy in the vdso text from the
244 * kernel image.
245 */
init_vdso_image(const struct vdso_image * image,struct vm_special_mapping * vdso_mapping,bool elf64)246 int __init init_vdso_image(const struct vdso_image *image,
247 struct vm_special_mapping *vdso_mapping, bool elf64)
248 {
249 int cnpages = (image->size) / PAGE_SIZE;
250 struct page *dp, **dpp = NULL;
251 struct page *cp, **cpp = NULL;
252 struct vdso_elfinfo ei;
253 int i, dnpages = 0;
254
255 if (tlb_type != spitfire) {
256 int err = stick_patch(image, &ei, elf64);
257 if (err)
258 return err;
259 }
260
261 /*
262 * First, the vdso text. This is initialied data, an integral number of
263 * pages long.
264 */
265 if (WARN_ON(image->size % PAGE_SIZE != 0))
266 goto oom;
267
268 cpp = kcalloc(cnpages, sizeof(struct page *), GFP_KERNEL);
269 vdso_mapping->pages = cpp;
270
271 if (!cpp)
272 goto oom;
273
274 for (i = 0; i < cnpages; i++) {
275 cp = alloc_page(GFP_KERNEL);
276 if (!cp)
277 goto oom;
278 cpp[i] = cp;
279 copy_page(page_address(cp), image->data + i * PAGE_SIZE);
280 }
281
282 /*
283 * Now the vvar page. This is uninitialized data.
284 */
285
286 if (vvar_data == NULL) {
287 dnpages = (sizeof(struct vvar_data) / PAGE_SIZE) + 1;
288 if (WARN_ON(dnpages != 1))
289 goto oom;
290 dpp = kcalloc(dnpages, sizeof(struct page *), GFP_KERNEL);
291 vvar_mapping.pages = dpp;
292
293 if (!dpp)
294 goto oom;
295
296 dp = alloc_page(GFP_KERNEL);
297 if (!dp)
298 goto oom;
299
300 dpp[0] = dp;
301 vvar_data = page_address(dp);
302 memset(vvar_data, 0, PAGE_SIZE);
303
304 vvar_data->seq = 0;
305 }
306
307 return 0;
308 oom:
309 if (cpp != NULL) {
310 for (i = 0; i < cnpages; i++) {
311 if (cpp[i] != NULL)
312 __free_page(cpp[i]);
313 }
314 kfree(cpp);
315 vdso_mapping->pages = NULL;
316 }
317
318 if (dpp != NULL) {
319 for (i = 0; i < dnpages; i++) {
320 if (dpp[i] != NULL)
321 __free_page(dpp[i]);
322 }
323 kfree(dpp);
324 vvar_mapping.pages = NULL;
325 }
326
327 pr_warn("Cannot allocate vdso\n");
328 vdso_enabled = 0;
329 return -ENOMEM;
330 }
331
init_vdso(void)332 static int __init init_vdso(void)
333 {
334 int err = 0;
335 #ifdef CONFIG_SPARC64
336 err = init_vdso_image(&vdso_image_64_builtin, &vdso_mapping64, true);
337 if (err)
338 return err;
339 #endif
340
341 #ifdef CONFIG_COMPAT
342 err = init_vdso_image(&vdso_image_32_builtin, &vdso_mapping32, false);
343 #endif
344 return err;
345
346 }
347 subsys_initcall(init_vdso);
348
349 struct linux_binprm;
350
351 /* Shuffle the vdso up a bit, randomly. */
vdso_addr(unsigned long start,unsigned int len)352 static unsigned long vdso_addr(unsigned long start, unsigned int len)
353 {
354 unsigned int offset;
355
356 /* This loses some more bits than a modulo, but is cheaper */
357 offset = get_random_int() & (PTRS_PER_PTE - 1);
358 return start + (offset << PAGE_SHIFT);
359 }
360
map_vdso(const struct vdso_image * image,struct vm_special_mapping * vdso_mapping)361 static int map_vdso(const struct vdso_image *image,
362 struct vm_special_mapping *vdso_mapping)
363 {
364 struct mm_struct *mm = current->mm;
365 struct vm_area_struct *vma;
366 unsigned long text_start, addr = 0;
367 int ret = 0;
368
369 down_write(&mm->mmap_sem);
370
371 /*
372 * First, get an unmapped region: then randomize it, and make sure that
373 * region is free.
374 */
375 if (current->flags & PF_RANDOMIZE) {
376 addr = get_unmapped_area(NULL, 0,
377 image->size - image->sym_vvar_start,
378 0, 0);
379 if (IS_ERR_VALUE(addr)) {
380 ret = addr;
381 goto up_fail;
382 }
383 addr = vdso_addr(addr, image->size - image->sym_vvar_start);
384 }
385 addr = get_unmapped_area(NULL, addr,
386 image->size - image->sym_vvar_start, 0, 0);
387 if (IS_ERR_VALUE(addr)) {
388 ret = addr;
389 goto up_fail;
390 }
391
392 text_start = addr - image->sym_vvar_start;
393 current->mm->context.vdso = (void __user *)text_start;
394
395 /*
396 * MAYWRITE to allow gdb to COW and set breakpoints
397 */
398 vma = _install_special_mapping(mm,
399 text_start,
400 image->size,
401 VM_READ|VM_EXEC|
402 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
403 vdso_mapping);
404
405 if (IS_ERR(vma)) {
406 ret = PTR_ERR(vma);
407 goto up_fail;
408 }
409
410 vma = _install_special_mapping(mm,
411 addr,
412 -image->sym_vvar_start,
413 VM_READ|VM_MAYREAD,
414 &vvar_mapping);
415
416 if (IS_ERR(vma)) {
417 ret = PTR_ERR(vma);
418 do_munmap(mm, text_start, image->size, NULL);
419 }
420
421 up_fail:
422 if (ret)
423 current->mm->context.vdso = NULL;
424
425 up_write(&mm->mmap_sem);
426 return ret;
427 }
428
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)429 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
430 {
431
432 if (!vdso_enabled)
433 return 0;
434
435 #if defined CONFIG_COMPAT
436 if (!(is_32bit_task()))
437 return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
438 else
439 return map_vdso(&vdso_image_32_builtin, &vdso_mapping32);
440 #else
441 return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
442 #endif
443
444 }
445
vdso_setup(char * s)446 static __init int vdso_setup(char *s)
447 {
448 int err;
449 unsigned long val;
450
451 err = kstrtoul(s, 10, &val);
452 if (!err)
453 vdso_enabled = val;
454 return 1;
455 }
456 __setup("vdso=", vdso_setup);
457