1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * VDSO implementations.
4 *
5 * Copyright (C) 2012 ARM Limited
6 *
7 * Author: Will Deacon <will.deacon@arm.com>
8 */
9
10 #include <linux/cache.h>
11 #include <linux/clocksource.h>
12 #include <linux/elf.h>
13 #include <linux/err.h>
14 #include <linux/errno.h>
15 #include <linux/gfp.h>
16 #include <linux/kernel.h>
17 #include <linux/mm.h>
18 #include <linux/sched.h>
19 #include <linux/signal.h>
20 #include <linux/slab.h>
21 #include <linux/time_namespace.h>
22 #include <linux/timekeeper_internal.h>
23 #include <linux/vmalloc.h>
24 #include <vdso/datapage.h>
25 #include <vdso/helpers.h>
26 #include <vdso/vsyscall.h>
27
28 #include <asm/cacheflush.h>
29 #include <asm/signal32.h>
30 #include <asm/vdso.h>
31
32 enum vdso_abi {
33 VDSO_ABI_AA64,
34 VDSO_ABI_AA32,
35 };
36
37 enum vvar_pages {
38 VVAR_DATA_PAGE_OFFSET,
39 VVAR_TIMENS_PAGE_OFFSET,
40 VVAR_NR_PAGES,
41 };
42
43 struct vdso_abi_info {
44 const char *name;
45 const char *vdso_code_start;
46 const char *vdso_code_end;
47 unsigned long vdso_pages;
48 /* Data Mapping */
49 struct vm_special_mapping *dm;
50 /* Code Mapping */
51 struct vm_special_mapping *cm;
52 };
53
54 static struct vdso_abi_info vdso_info[] __ro_after_init = {
55 [VDSO_ABI_AA64] = {
56 .name = "vdso",
57 .vdso_code_start = vdso_start,
58 .vdso_code_end = vdso_end,
59 },
60 #ifdef CONFIG_COMPAT_VDSO
61 [VDSO_ABI_AA32] = {
62 .name = "vdso32",
63 .vdso_code_start = vdso32_start,
64 .vdso_code_end = vdso32_end,
65 },
66 #endif /* CONFIG_COMPAT_VDSO */
67 };
68
69 /*
70 * The vDSO data page.
71 */
72 static union vdso_data_store vdso_data_store __page_aligned_data;
73 struct vdso_data *vdso_data = vdso_data_store.data;
74
75 static int vdso_mremap(const struct vm_special_mapping *sm,
76 struct vm_area_struct *new_vma)
77 {
78 current->mm->context.vdso = (void *)new_vma->vm_start;
79
80 return 0;
81 }
82
83 static int __init __vdso_init(enum vdso_abi abi)
84 {
85 int i;
86 struct page **vdso_pagelist;
87 unsigned long pfn;
88
89 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
90 pr_err("vDSO is not a valid ELF object!\n");
91 return -EINVAL;
92 }
93
94 vdso_info[abi].vdso_pages = (
95 vdso_info[abi].vdso_code_end -
96 vdso_info[abi].vdso_code_start) >>
97 PAGE_SHIFT;
98
99 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
100 sizeof(struct page *),
101 GFP_KERNEL);
102 if (vdso_pagelist == NULL)
103 return -ENOMEM;
104
105 /* Grab the vDSO code pages. */
106 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
107
108 for (i = 0; i < vdso_info[abi].vdso_pages; i++)
109 vdso_pagelist[i] = pfn_to_page(pfn + i);
110
111 vdso_info[abi].cm->pages = vdso_pagelist;
112
113 return 0;
114 }
115
116 #ifdef CONFIG_TIME_NS
117 struct vdso_data *arch_get_vdso_data(void *vvar_page)
118 {
119 return (struct vdso_data *)(vvar_page);
120 }
121
122 /*
123 * The vvar mapping contains data for a specific time namespace, so when a task
124 * changes namespace we must unmap its vvar data for the old namespace.
125 * Subsequent faults will map in data for the new namespace.
126 *
127 * For more details see timens_setup_vdso_data().
128 */
129 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
130 {
131 struct mm_struct *mm = task->mm;
132 struct vm_area_struct *vma;
133 VMA_ITERATOR(vmi, mm, 0);
134
135 mmap_read_lock(mm);
136
137 for_each_vma(vmi, vma) {
138 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
139 zap_vma_pages(vma);
140 #ifdef CONFIG_COMPAT_VDSO
141 if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
142 zap_vma_pages(vma);
143 #endif
144 }
145
146 mmap_read_unlock(mm);
147 return 0;
148 }
149 #endif
150
151 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
152 struct vm_area_struct *vma, struct vm_fault *vmf)
153 {
154 struct page *timens_page = find_timens_vvar_page(vma);
155 unsigned long pfn;
156
157 switch (vmf->pgoff) {
158 case VVAR_DATA_PAGE_OFFSET:
159 if (timens_page)
160 pfn = page_to_pfn(timens_page);
161 else
162 pfn = sym_to_pfn(vdso_data);
163 break;
164 #ifdef CONFIG_TIME_NS
165 case VVAR_TIMENS_PAGE_OFFSET:
166 /*
167 * If a task belongs to a time namespace then a namespace
168 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
169 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
170 * offset.
171 * See also the comment near timens_setup_vdso_data().
172 */
173 if (!timens_page)
174 return VM_FAULT_SIGBUS;
175 pfn = sym_to_pfn(vdso_data);
176 break;
177 #endif /* CONFIG_TIME_NS */
178 default:
179 return VM_FAULT_SIGBUS;
180 }
181
182 return vmf_insert_pfn(vma, vmf->address, pfn);
183 }
184
185 static int __setup_additional_pages(enum vdso_abi abi,
186 struct mm_struct *mm,
187 struct linux_binprm *bprm,
188 int uses_interp)
189 {
190 unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
191 unsigned long gp_flags = 0;
192 void *ret;
193
194 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
195
196 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
197 /* Be sure to map the data page */
198 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
199
200 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
201 if (IS_ERR_VALUE(vdso_base)) {
202 ret = ERR_PTR(vdso_base);
203 goto up_fail;
204 }
205
206 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
207 VM_READ|VM_MAYREAD|VM_PFNMAP,
208 vdso_info[abi].dm);
209 if (IS_ERR(ret))
210 goto up_fail;
211
212 if (system_supports_bti_kernel())
213 gp_flags = VM_ARM64_BTI;
214
215 vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
216 mm->context.vdso = (void *)vdso_base;
217 ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
218 VM_READ|VM_EXEC|gp_flags|
219 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
220 vdso_info[abi].cm);
221 if (IS_ERR(ret))
222 goto up_fail;
223
224 return 0;
225
226 up_fail:
227 mm->context.vdso = NULL;
228 return PTR_ERR(ret);
229 }
230
231 #ifdef CONFIG_COMPAT
232 /*
233 * Create and map the vectors page for AArch32 tasks.
234 */
235 enum aarch32_map {
236 AA32_MAP_VECTORS, /* kuser helpers */
237 AA32_MAP_SIGPAGE,
238 AA32_MAP_VVAR,
239 AA32_MAP_VDSO,
240 };
241
242 static struct page *aarch32_vectors_page __ro_after_init;
243 static struct page *aarch32_sig_page __ro_after_init;
244
245 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
246 struct vm_area_struct *new_vma)
247 {
248 current->mm->context.sigpage = (void *)new_vma->vm_start;
249
250 return 0;
251 }
252
253 static struct vm_special_mapping aarch32_vdso_maps[] = {
254 [AA32_MAP_VECTORS] = {
255 .name = "[vectors]", /* ABI */
256 .pages = &aarch32_vectors_page,
257 },
258 [AA32_MAP_SIGPAGE] = {
259 .name = "[sigpage]", /* ABI */
260 .pages = &aarch32_sig_page,
261 .mremap = aarch32_sigpage_mremap,
262 },
263 [AA32_MAP_VVAR] = {
264 .name = "[vvar]",
265 .fault = vvar_fault,
266 },
267 [AA32_MAP_VDSO] = {
268 .name = "[vdso]",
269 .mremap = vdso_mremap,
270 },
271 };
272
273 static int aarch32_alloc_kuser_vdso_page(void)
274 {
275 extern char __kuser_helper_start[], __kuser_helper_end[];
276 int kuser_sz = __kuser_helper_end - __kuser_helper_start;
277 unsigned long vdso_page;
278
279 if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
280 return 0;
281
282 vdso_page = get_zeroed_page(GFP_KERNEL);
283 if (!vdso_page)
284 return -ENOMEM;
285
286 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
287 kuser_sz);
288 aarch32_vectors_page = virt_to_page((void *)vdso_page);
289 return 0;
290 }
291
292 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1
293 static int aarch32_alloc_sigpage(void)
294 {
295 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
296 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
297 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
298 void *sigpage;
299
300 sigpage = (void *)__get_free_page(GFP_KERNEL);
301 if (!sigpage)
302 return -ENOMEM;
303
304 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
305 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
306 aarch32_sig_page = virt_to_page(sigpage);
307 return 0;
308 }
309
310 static int __init __aarch32_alloc_vdso_pages(void)
311 {
312
313 if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
314 return 0;
315
316 vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
317 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
318
319 return __vdso_init(VDSO_ABI_AA32);
320 }
321
322 static int __init aarch32_alloc_vdso_pages(void)
323 {
324 int ret;
325
326 ret = __aarch32_alloc_vdso_pages();
327 if (ret)
328 return ret;
329
330 ret = aarch32_alloc_sigpage();
331 if (ret)
332 return ret;
333
334 return aarch32_alloc_kuser_vdso_page();
335 }
336 arch_initcall(aarch32_alloc_vdso_pages);
337
338 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
339 {
340 void *ret;
341
342 if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
343 return 0;
344
345 /*
346 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
347 * not safe to CoW the page containing the CPU exception vectors.
348 */
349 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
350 VM_READ | VM_EXEC |
351 VM_MAYREAD | VM_MAYEXEC,
352 &aarch32_vdso_maps[AA32_MAP_VECTORS]);
353
354 return PTR_ERR_OR_ZERO(ret);
355 }
356
357 static int aarch32_sigreturn_setup(struct mm_struct *mm)
358 {
359 unsigned long addr;
360 void *ret;
361
362 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
363 if (IS_ERR_VALUE(addr)) {
364 ret = ERR_PTR(addr);
365 goto out;
366 }
367
368 /*
369 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
370 * set breakpoints.
371 */
372 ret = _install_special_mapping(mm, addr, PAGE_SIZE,
373 VM_READ | VM_EXEC | VM_MAYREAD |
374 VM_MAYWRITE | VM_MAYEXEC,
375 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
376 if (IS_ERR(ret))
377 goto out;
378
379 mm->context.sigpage = (void *)addr;
380
381 out:
382 return PTR_ERR_OR_ZERO(ret);
383 }
384
385 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
386 {
387 struct mm_struct *mm = current->mm;
388 int ret;
389
390 if (mmap_write_lock_killable(mm))
391 return -EINTR;
392
393 ret = aarch32_kuser_helpers_setup(mm);
394 if (ret)
395 goto out;
396
397 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
398 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
399 uses_interp);
400 if (ret)
401 goto out;
402 }
403
404 ret = aarch32_sigreturn_setup(mm);
405 out:
406 mmap_write_unlock(mm);
407 return ret;
408 }
409 #endif /* CONFIG_COMPAT */
410
411 enum aarch64_map {
412 AA64_MAP_VVAR,
413 AA64_MAP_VDSO,
414 };
415
416 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
417 [AA64_MAP_VVAR] = {
418 .name = "[vvar]",
419 .fault = vvar_fault,
420 },
421 [AA64_MAP_VDSO] = {
422 .name = "[vdso]",
423 .mremap = vdso_mremap,
424 },
425 };
426
427 static int __init vdso_init(void)
428 {
429 vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
430 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
431
432 return __vdso_init(VDSO_ABI_AA64);
433 }
434 arch_initcall(vdso_init);
435
436 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
437 {
438 struct mm_struct *mm = current->mm;
439 int ret;
440
441 if (mmap_write_lock_killable(mm))
442 return -EINTR;
443
444 ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
445 mmap_write_unlock(mm);
446
447 return ret;
448 }
449
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