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/vmalloc.h>
23 #include <vdso/datapage.h>
24 #include <vdso/helpers.h>
25 #include <vdso/vsyscall.h>
26
27 #include <asm/cacheflush.h>
28 #include <asm/signal32.h>
29 #include <asm/vdso.h>
30
31 enum vdso_abi {
32 VDSO_ABI_AA64,
33 VDSO_ABI_AA32,
34 };
35
36 struct vdso_abi_info {
37 const char *name;
38 const char *vdso_code_start;
39 const char *vdso_code_end;
40 unsigned long vdso_pages;
41 /* Code Mapping */
42 struct vm_special_mapping *cm;
43 };
44
45 static struct vdso_abi_info vdso_info[] __ro_after_init = {
46 [VDSO_ABI_AA64] = {
47 .name = "vdso",
48 .vdso_code_start = vdso_start,
49 .vdso_code_end = vdso_end,
50 },
51 #ifdef CONFIG_COMPAT_VDSO
52 [VDSO_ABI_AA32] = {
53 .name = "vdso32",
54 .vdso_code_start = vdso32_start,
55 .vdso_code_end = vdso32_end,
56 },
57 #endif /* CONFIG_COMPAT_VDSO */
58 };
59
60 /*
61 * The vDSO data page.
62 */
63 static union vdso_data_store vdso_data_store __page_aligned_data;
64 struct vdso_data *vdso_data = vdso_data_store.data;
65
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * new_vma)66 static int vdso_mremap(const struct vm_special_mapping *sm,
67 struct vm_area_struct *new_vma)
68 {
69 current->mm->context.vdso = (void *)new_vma->vm_start;
70
71 return 0;
72 }
73
__vdso_init(enum vdso_abi abi)74 static int __init __vdso_init(enum vdso_abi abi)
75 {
76 int i;
77 struct page **vdso_pagelist;
78 unsigned long pfn;
79
80 if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
81 pr_err("vDSO is not a valid ELF object!\n");
82 return -EINVAL;
83 }
84
85 vdso_info[abi].vdso_pages = (
86 vdso_info[abi].vdso_code_end -
87 vdso_info[abi].vdso_code_start) >>
88 PAGE_SHIFT;
89
90 vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
91 sizeof(struct page *),
92 GFP_KERNEL);
93 if (vdso_pagelist == NULL)
94 return -ENOMEM;
95
96 /* Grab the vDSO code pages. */
97 pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
98
99 for (i = 0; i < vdso_info[abi].vdso_pages; i++)
100 vdso_pagelist[i] = pfn_to_page(pfn + i);
101
102 vdso_info[abi].cm->pages = vdso_pagelist;
103
104 return 0;
105 }
106
107 #ifdef CONFIG_TIME_NS
arch_get_vdso_data(void * vvar_page)108 struct vdso_data *arch_get_vdso_data(void *vvar_page)
109 {
110 return (struct vdso_data *)(vvar_page);
111 }
112
113 static const struct vm_special_mapping vvar_map;
114
115 /*
116 * The vvar mapping contains data for a specific time namespace, so when a task
117 * changes namespace we must unmap its vvar data for the old namespace.
118 * Subsequent faults will map in data for the new namespace.
119 *
120 * For more details see timens_setup_vdso_data().
121 */
vdso_join_timens(struct task_struct * task,struct time_namespace * ns)122 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
123 {
124 struct mm_struct *mm = task->mm;
125 struct vm_area_struct *vma;
126 VMA_ITERATOR(vmi, mm, 0);
127
128 mmap_read_lock(mm);
129
130 for_each_vma(vmi, vma) {
131 if (vma_is_special_mapping(vma, &vvar_map))
132 zap_vma_pages(vma);
133 }
134
135 mmap_read_unlock(mm);
136 return 0;
137 }
138 #endif
139
vvar_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)140 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
141 struct vm_area_struct *vma, struct vm_fault *vmf)
142 {
143 struct page *timens_page = find_timens_vvar_page(vma);
144 unsigned long pfn;
145
146 switch (vmf->pgoff) {
147 case VVAR_DATA_PAGE_OFFSET:
148 if (timens_page)
149 pfn = page_to_pfn(timens_page);
150 else
151 pfn = sym_to_pfn(vdso_data);
152 break;
153 #ifdef CONFIG_TIME_NS
154 case VVAR_TIMENS_PAGE_OFFSET:
155 /*
156 * If a task belongs to a time namespace then a namespace
157 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
158 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
159 * offset.
160 * See also the comment near timens_setup_vdso_data().
161 */
162 if (!timens_page)
163 return VM_FAULT_SIGBUS;
164 pfn = sym_to_pfn(vdso_data);
165 break;
166 #endif /* CONFIG_TIME_NS */
167 default:
168 return VM_FAULT_SIGBUS;
169 }
170
171 return vmf_insert_pfn(vma, vmf->address, pfn);
172 }
173
174 static const struct vm_special_mapping vvar_map = {
175 .name = "[vvar]",
176 .fault = vvar_fault,
177 };
178
__setup_additional_pages(enum vdso_abi abi,struct mm_struct * mm,struct linux_binprm * bprm,int uses_interp)179 static int __setup_additional_pages(enum vdso_abi abi,
180 struct mm_struct *mm,
181 struct linux_binprm *bprm,
182 int uses_interp)
183 {
184 unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
185 unsigned long gp_flags = 0;
186 void *ret;
187
188 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
189
190 vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
191 /* Be sure to map the data page */
192 vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
193
194 vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
195 if (IS_ERR_VALUE(vdso_base)) {
196 ret = ERR_PTR(vdso_base);
197 goto up_fail;
198 }
199
200 ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
201 VM_READ|VM_MAYREAD|VM_PFNMAP,
202 &vvar_map);
203 if (IS_ERR(ret))
204 goto up_fail;
205
206 if (system_supports_bti_kernel())
207 gp_flags = VM_ARM64_BTI;
208
209 vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
210 mm->context.vdso = (void *)vdso_base;
211 ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
212 VM_READ|VM_EXEC|gp_flags|
213 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
214 vdso_info[abi].cm);
215 if (IS_ERR(ret))
216 goto up_fail;
217
218 return 0;
219
220 up_fail:
221 mm->context.vdso = NULL;
222 return PTR_ERR(ret);
223 }
224
225 #ifdef CONFIG_COMPAT
226 /*
227 * Create and map the vectors page for AArch32 tasks.
228 */
229 enum aarch32_map {
230 AA32_MAP_VECTORS, /* kuser helpers */
231 AA32_MAP_SIGPAGE,
232 AA32_MAP_VDSO,
233 };
234
235 static struct page *aarch32_vectors_page __ro_after_init;
236 static struct page *aarch32_sig_page __ro_after_init;
237
aarch32_sigpage_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * new_vma)238 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
239 struct vm_area_struct *new_vma)
240 {
241 current->mm->context.sigpage = (void *)new_vma->vm_start;
242
243 return 0;
244 }
245
246 static struct vm_special_mapping aarch32_vdso_maps[] = {
247 [AA32_MAP_VECTORS] = {
248 .name = "[vectors]", /* ABI */
249 .pages = &aarch32_vectors_page,
250 },
251 [AA32_MAP_SIGPAGE] = {
252 .name = "[sigpage]", /* ABI */
253 .pages = &aarch32_sig_page,
254 .mremap = aarch32_sigpage_mremap,
255 },
256 [AA32_MAP_VDSO] = {
257 .name = "[vdso]",
258 .mremap = vdso_mremap,
259 },
260 };
261
aarch32_alloc_kuser_vdso_page(void)262 static int aarch32_alloc_kuser_vdso_page(void)
263 {
264 extern char __kuser_helper_start[], __kuser_helper_end[];
265 int kuser_sz = __kuser_helper_end - __kuser_helper_start;
266 unsigned long vdso_page;
267
268 if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
269 return 0;
270
271 vdso_page = get_zeroed_page(GFP_KERNEL);
272 if (!vdso_page)
273 return -ENOMEM;
274
275 memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
276 kuser_sz);
277 aarch32_vectors_page = virt_to_page((void *)vdso_page);
278 return 0;
279 }
280
281 #define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1
aarch32_alloc_sigpage(void)282 static int aarch32_alloc_sigpage(void)
283 {
284 extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
285 int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
286 __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
287 void *sigpage;
288
289 sigpage = (void *)__get_free_page(GFP_KERNEL);
290 if (!sigpage)
291 return -ENOMEM;
292
293 memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
294 memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
295 aarch32_sig_page = virt_to_page(sigpage);
296 return 0;
297 }
298
__aarch32_alloc_vdso_pages(void)299 static int __init __aarch32_alloc_vdso_pages(void)
300 {
301
302 if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
303 return 0;
304
305 vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
306
307 return __vdso_init(VDSO_ABI_AA32);
308 }
309
aarch32_alloc_vdso_pages(void)310 static int __init aarch32_alloc_vdso_pages(void)
311 {
312 int ret;
313
314 ret = __aarch32_alloc_vdso_pages();
315 if (ret)
316 return ret;
317
318 ret = aarch32_alloc_sigpage();
319 if (ret)
320 return ret;
321
322 return aarch32_alloc_kuser_vdso_page();
323 }
324 arch_initcall(aarch32_alloc_vdso_pages);
325
aarch32_kuser_helpers_setup(struct mm_struct * mm)326 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
327 {
328 void *ret;
329
330 if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
331 return 0;
332
333 /*
334 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
335 * not safe to CoW the page containing the CPU exception vectors.
336 */
337 ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
338 VM_READ | VM_EXEC |
339 VM_MAYREAD | VM_MAYEXEC,
340 &aarch32_vdso_maps[AA32_MAP_VECTORS]);
341
342 return PTR_ERR_OR_ZERO(ret);
343 }
344
aarch32_sigreturn_setup(struct mm_struct * mm)345 static int aarch32_sigreturn_setup(struct mm_struct *mm)
346 {
347 unsigned long addr;
348 void *ret;
349
350 addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
351 if (IS_ERR_VALUE(addr)) {
352 ret = ERR_PTR(addr);
353 goto out;
354 }
355
356 /*
357 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
358 * set breakpoints.
359 */
360 ret = _install_special_mapping(mm, addr, PAGE_SIZE,
361 VM_READ | VM_EXEC | VM_MAYREAD |
362 VM_MAYWRITE | VM_MAYEXEC,
363 &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
364 if (IS_ERR(ret))
365 goto out;
366
367 mm->context.sigpage = (void *)addr;
368
369 out:
370 return PTR_ERR_OR_ZERO(ret);
371 }
372
aarch32_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)373 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
374 {
375 struct mm_struct *mm = current->mm;
376 int ret;
377
378 if (mmap_write_lock_killable(mm))
379 return -EINTR;
380
381 ret = aarch32_kuser_helpers_setup(mm);
382 if (ret)
383 goto out;
384
385 if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
386 ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
387 uses_interp);
388 if (ret)
389 goto out;
390 }
391
392 ret = aarch32_sigreturn_setup(mm);
393 out:
394 mmap_write_unlock(mm);
395 return ret;
396 }
397 #endif /* CONFIG_COMPAT */
398
399 static struct vm_special_mapping aarch64_vdso_map __ro_after_init = {
400 .name = "[vdso]",
401 .mremap = vdso_mremap,
402 };
403
vdso_init(void)404 static int __init vdso_init(void)
405 {
406 vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_map;
407
408 return __vdso_init(VDSO_ABI_AA64);
409 }
410 arch_initcall(vdso_init);
411
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)412 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
413 {
414 struct mm_struct *mm = current->mm;
415 int ret;
416
417 if (mmap_write_lock_killable(mm))
418 return -EINTR;
419
420 ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
421 mmap_write_unlock(mm);
422
423 return ret;
424 }
425