xref: /linux/arch/arm64/kernel/vdso.c (revision 77ec462536a13d4b428a1eead725c4818a49f0b1) 
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 extern char vdso_start[], vdso_end[];
33 extern char vdso32_start[], vdso32_end[];
34 
35 enum vdso_abi {
36 	VDSO_ABI_AA64,
37 	VDSO_ABI_AA32,
38 };
39 
40 enum vvar_pages {
41 	VVAR_DATA_PAGE_OFFSET,
42 	VVAR_TIMENS_PAGE_OFFSET,
43 	VVAR_NR_PAGES,
44 };
45 
46 struct vdso_abi_info {
47 	const char *name;
48 	const char *vdso_code_start;
49 	const char *vdso_code_end;
50 	unsigned long vdso_pages;
51 	/* Data Mapping */
52 	struct vm_special_mapping *dm;
53 	/* Code Mapping */
54 	struct vm_special_mapping *cm;
55 };
56 
57 static struct vdso_abi_info vdso_info[] __ro_after_init = {
58 	[VDSO_ABI_AA64] = {
59 		.name = "vdso",
60 		.vdso_code_start = vdso_start,
61 		.vdso_code_end = vdso_end,
62 	},
63 #ifdef CONFIG_COMPAT_VDSO
64 	[VDSO_ABI_AA32] = {
65 		.name = "vdso32",
66 		.vdso_code_start = vdso32_start,
67 		.vdso_code_end = vdso32_end,
68 	},
69 #endif /* CONFIG_COMPAT_VDSO */
70 };
71 
72 /*
73  * The vDSO data page.
74  */
75 static union {
76 	struct vdso_data	data[CS_BASES];
77 	u8			page[PAGE_SIZE];
78 } vdso_data_store __page_aligned_data;
79 struct vdso_data *vdso_data = vdso_data_store.data;
80 
81 static int vdso_mremap(const struct vm_special_mapping *sm,
82 		struct vm_area_struct *new_vma)
83 {
84 	current->mm->context.vdso = (void *)new_vma->vm_start;
85 
86 	return 0;
87 }
88 
89 static int __vdso_init(enum vdso_abi abi)
90 {
91 	int i;
92 	struct page **vdso_pagelist;
93 	unsigned long pfn;
94 
95 	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
96 		pr_err("vDSO is not a valid ELF object!\n");
97 		return -EINVAL;
98 	}
99 
100 	vdso_info[abi].vdso_pages = (
101 			vdso_info[abi].vdso_code_end -
102 			vdso_info[abi].vdso_code_start) >>
103 			PAGE_SHIFT;
104 
105 	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
106 				sizeof(struct page *),
107 				GFP_KERNEL);
108 	if (vdso_pagelist == NULL)
109 		return -ENOMEM;
110 
111 	/* Grab the vDSO code pages. */
112 	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
113 
114 	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
115 		vdso_pagelist[i] = pfn_to_page(pfn + i);
116 
117 	vdso_info[abi].cm->pages = vdso_pagelist;
118 
119 	return 0;
120 }
121 
122 #ifdef CONFIG_TIME_NS
123 struct vdso_data *arch_get_vdso_data(void *vvar_page)
124 {
125 	return (struct vdso_data *)(vvar_page);
126 }
127 
128 /*
129  * The vvar mapping contains data for a specific time namespace, so when a task
130  * changes namespace we must unmap its vvar data for the old namespace.
131  * Subsequent faults will map in data for the new namespace.
132  *
133  * For more details see timens_setup_vdso_data().
134  */
135 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
136 {
137 	struct mm_struct *mm = task->mm;
138 	struct vm_area_struct *vma;
139 
140 	mmap_read_lock(mm);
141 
142 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
143 		unsigned long size = vma->vm_end - vma->vm_start;
144 
145 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
146 			zap_page_range(vma, vma->vm_start, size);
147 #ifdef CONFIG_COMPAT_VDSO
148 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
149 			zap_page_range(vma, vma->vm_start, size);
150 #endif
151 	}
152 
153 	mmap_read_unlock(mm);
154 	return 0;
155 }
156 
157 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
158 {
159 	if (likely(vma->vm_mm == current->mm))
160 		return current->nsproxy->time_ns->vvar_page;
161 
162 	/*
163 	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
164 	 * through interfaces like /proc/$pid/mem or
165 	 * process_vm_{readv,writev}() as long as there's no .access()
166 	 * in special_mapping_vmops.
167 	 * For more details check_vma_flags() and __access_remote_vm()
168 	 */
169 	WARN(1, "vvar_page accessed remotely");
170 
171 	return NULL;
172 }
173 #else
174 static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
175 {
176 	return NULL;
177 }
178 #endif
179 
180 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
181 			     struct vm_area_struct *vma, struct vm_fault *vmf)
182 {
183 	struct page *timens_page = find_timens_vvar_page(vma);
184 	unsigned long pfn;
185 
186 	switch (vmf->pgoff) {
187 	case VVAR_DATA_PAGE_OFFSET:
188 		if (timens_page)
189 			pfn = page_to_pfn(timens_page);
190 		else
191 			pfn = sym_to_pfn(vdso_data);
192 		break;
193 #ifdef CONFIG_TIME_NS
194 	case VVAR_TIMENS_PAGE_OFFSET:
195 		/*
196 		 * If a task belongs to a time namespace then a namespace
197 		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
198 		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
199 		 * offset.
200 		 * See also the comment near timens_setup_vdso_data().
201 		 */
202 		if (!timens_page)
203 			return VM_FAULT_SIGBUS;
204 		pfn = sym_to_pfn(vdso_data);
205 		break;
206 #endif /* CONFIG_TIME_NS */
207 	default:
208 		return VM_FAULT_SIGBUS;
209 	}
210 
211 	return vmf_insert_pfn(vma, vmf->address, pfn);
212 }
213 
214 static int __setup_additional_pages(enum vdso_abi abi,
215 				    struct mm_struct *mm,
216 				    struct linux_binprm *bprm,
217 				    int uses_interp)
218 {
219 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
220 	unsigned long gp_flags = 0;
221 	void *ret;
222 
223 	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
224 
225 	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
226 	/* Be sure to map the data page */
227 	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
228 
229 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
230 	if (IS_ERR_VALUE(vdso_base)) {
231 		ret = ERR_PTR(vdso_base);
232 		goto up_fail;
233 	}
234 
235 	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
236 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
237 				       vdso_info[abi].dm);
238 	if (IS_ERR(ret))
239 		goto up_fail;
240 
241 	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
242 		gp_flags = VM_ARM64_BTI;
243 
244 	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
245 	mm->context.vdso = (void *)vdso_base;
246 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
247 				       VM_READ|VM_EXEC|gp_flags|
248 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
249 				       vdso_info[abi].cm);
250 	if (IS_ERR(ret))
251 		goto up_fail;
252 
253 	return 0;
254 
255 up_fail:
256 	mm->context.vdso = NULL;
257 	return PTR_ERR(ret);
258 }
259 
260 #ifdef CONFIG_COMPAT
261 /*
262  * Create and map the vectors page for AArch32 tasks.
263  */
264 enum aarch32_map {
265 	AA32_MAP_VECTORS, /* kuser helpers */
266 	AA32_MAP_SIGPAGE,
267 	AA32_MAP_VVAR,
268 	AA32_MAP_VDSO,
269 };
270 
271 static struct page *aarch32_vectors_page __ro_after_init;
272 static struct page *aarch32_sig_page __ro_after_init;
273 
274 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
275 				  struct vm_area_struct *new_vma)
276 {
277 	current->mm->context.sigpage = (void *)new_vma->vm_start;
278 
279 	return 0;
280 }
281 
282 static struct vm_special_mapping aarch32_vdso_maps[] = {
283 	[AA32_MAP_VECTORS] = {
284 		.name	= "[vectors]", /* ABI */
285 		.pages	= &aarch32_vectors_page,
286 	},
287 	[AA32_MAP_SIGPAGE] = {
288 		.name	= "[sigpage]", /* ABI */
289 		.pages	= &aarch32_sig_page,
290 		.mremap	= aarch32_sigpage_mremap,
291 	},
292 	[AA32_MAP_VVAR] = {
293 		.name = "[vvar]",
294 		.fault = vvar_fault,
295 	},
296 	[AA32_MAP_VDSO] = {
297 		.name = "[vdso]",
298 		.mremap = vdso_mremap,
299 	},
300 };
301 
302 static int aarch32_alloc_kuser_vdso_page(void)
303 {
304 	extern char __kuser_helper_start[], __kuser_helper_end[];
305 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
306 	unsigned long vdso_page;
307 
308 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
309 		return 0;
310 
311 	vdso_page = get_zeroed_page(GFP_KERNEL);
312 	if (!vdso_page)
313 		return -ENOMEM;
314 
315 	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
316 	       kuser_sz);
317 	aarch32_vectors_page = virt_to_page(vdso_page);
318 	return 0;
319 }
320 
321 static int aarch32_alloc_sigpage(void)
322 {
323 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
324 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
325 	unsigned long sigpage;
326 
327 	sigpage = get_zeroed_page(GFP_KERNEL);
328 	if (!sigpage)
329 		return -ENOMEM;
330 
331 	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
332 	aarch32_sig_page = virt_to_page(sigpage);
333 	return 0;
334 }
335 
336 static int __aarch32_alloc_vdso_pages(void)
337 {
338 
339 	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
340 		return 0;
341 
342 	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
343 	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
344 
345 	return __vdso_init(VDSO_ABI_AA32);
346 }
347 
348 static int __init aarch32_alloc_vdso_pages(void)
349 {
350 	int ret;
351 
352 	ret = __aarch32_alloc_vdso_pages();
353 	if (ret)
354 		return ret;
355 
356 	ret = aarch32_alloc_sigpage();
357 	if (ret)
358 		return ret;
359 
360 	return aarch32_alloc_kuser_vdso_page();
361 }
362 arch_initcall(aarch32_alloc_vdso_pages);
363 
364 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
365 {
366 	void *ret;
367 
368 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
369 		return 0;
370 
371 	/*
372 	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
373 	 * not safe to CoW the page containing the CPU exception vectors.
374 	 */
375 	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
376 				       VM_READ | VM_EXEC |
377 				       VM_MAYREAD | VM_MAYEXEC,
378 				       &aarch32_vdso_maps[AA32_MAP_VECTORS]);
379 
380 	return PTR_ERR_OR_ZERO(ret);
381 }
382 
383 static int aarch32_sigreturn_setup(struct mm_struct *mm)
384 {
385 	unsigned long addr;
386 	void *ret;
387 
388 	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
389 	if (IS_ERR_VALUE(addr)) {
390 		ret = ERR_PTR(addr);
391 		goto out;
392 	}
393 
394 	/*
395 	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
396 	 * set breakpoints.
397 	 */
398 	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
399 				       VM_READ | VM_EXEC | VM_MAYREAD |
400 				       VM_MAYWRITE | VM_MAYEXEC,
401 				       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
402 	if (IS_ERR(ret))
403 		goto out;
404 
405 	mm->context.sigpage = (void *)addr;
406 
407 out:
408 	return PTR_ERR_OR_ZERO(ret);
409 }
410 
411 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
412 {
413 	struct mm_struct *mm = current->mm;
414 	int ret;
415 
416 	if (mmap_write_lock_killable(mm))
417 		return -EINTR;
418 
419 	ret = aarch32_kuser_helpers_setup(mm);
420 	if (ret)
421 		goto out;
422 
423 	if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
424 		ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
425 					       uses_interp);
426 		if (ret)
427 			goto out;
428 	}
429 
430 	ret = aarch32_sigreturn_setup(mm);
431 out:
432 	mmap_write_unlock(mm);
433 	return ret;
434 }
435 #endif /* CONFIG_COMPAT */
436 
437 enum aarch64_map {
438 	AA64_MAP_VVAR,
439 	AA64_MAP_VDSO,
440 };
441 
442 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
443 	[AA64_MAP_VVAR] = {
444 		.name	= "[vvar]",
445 		.fault = vvar_fault,
446 	},
447 	[AA64_MAP_VDSO] = {
448 		.name	= "[vdso]",
449 		.mremap = vdso_mremap,
450 	},
451 };
452 
453 static int __init vdso_init(void)
454 {
455 	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
456 	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
457 
458 	return __vdso_init(VDSO_ABI_AA64);
459 }
460 arch_initcall(vdso_init);
461 
462 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
463 {
464 	struct mm_struct *mm = current->mm;
465 	int ret;
466 
467 	if (mmap_write_lock_killable(mm))
468 		return -EINTR;
469 
470 	ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
471 	mmap_write_unlock(mm);
472 
473 	return ret;
474 }
475