xref: /linux/arch/arm64/kernel/vdso.c (revision 0526b56cbc3c489642bd6a5fe4b718dea7ef0ee8) 
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 {
73 	struct vdso_data	data[CS_BASES];
74 	u8			page[PAGE_SIZE];
75 } vdso_data_store __page_aligned_data;
76 struct vdso_data *vdso_data = vdso_data_store.data;
77 
78 static int vdso_mremap(const struct vm_special_mapping *sm,
79 		struct vm_area_struct *new_vma)
80 {
81 	current->mm->context.vdso = (void *)new_vma->vm_start;
82 
83 	return 0;
84 }
85 
86 static int __init __vdso_init(enum vdso_abi abi)
87 {
88 	int i;
89 	struct page **vdso_pagelist;
90 	unsigned long pfn;
91 
92 	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
93 		pr_err("vDSO is not a valid ELF object!\n");
94 		return -EINVAL;
95 	}
96 
97 	vdso_info[abi].vdso_pages = (
98 			vdso_info[abi].vdso_code_end -
99 			vdso_info[abi].vdso_code_start) >>
100 			PAGE_SHIFT;
101 
102 	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
103 				sizeof(struct page *),
104 				GFP_KERNEL);
105 	if (vdso_pagelist == NULL)
106 		return -ENOMEM;
107 
108 	/* Grab the vDSO code pages. */
109 	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
110 
111 	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
112 		vdso_pagelist[i] = pfn_to_page(pfn + i);
113 
114 	vdso_info[abi].cm->pages = vdso_pagelist;
115 
116 	return 0;
117 }
118 
119 #ifdef CONFIG_TIME_NS
120 struct vdso_data *arch_get_vdso_data(void *vvar_page)
121 {
122 	return (struct vdso_data *)(vvar_page);
123 }
124 
125 /*
126  * The vvar mapping contains data for a specific time namespace, so when a task
127  * changes namespace we must unmap its vvar data for the old namespace.
128  * Subsequent faults will map in data for the new namespace.
129  *
130  * For more details see timens_setup_vdso_data().
131  */
132 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
133 {
134 	struct mm_struct *mm = task->mm;
135 	struct vm_area_struct *vma;
136 	VMA_ITERATOR(vmi, mm, 0);
137 
138 	mmap_read_lock(mm);
139 
140 	for_each_vma(vmi, vma) {
141 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
142 			zap_vma_pages(vma);
143 #ifdef CONFIG_COMPAT_VDSO
144 		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
145 			zap_vma_pages(vma);
146 #endif
147 	}
148 
149 	mmap_read_unlock(mm);
150 	return 0;
151 }
152 #endif
153 
154 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
155 			     struct vm_area_struct *vma, struct vm_fault *vmf)
156 {
157 	struct page *timens_page = find_timens_vvar_page(vma);
158 	unsigned long pfn;
159 
160 	switch (vmf->pgoff) {
161 	case VVAR_DATA_PAGE_OFFSET:
162 		if (timens_page)
163 			pfn = page_to_pfn(timens_page);
164 		else
165 			pfn = sym_to_pfn(vdso_data);
166 		break;
167 #ifdef CONFIG_TIME_NS
168 	case VVAR_TIMENS_PAGE_OFFSET:
169 		/*
170 		 * If a task belongs to a time namespace then a namespace
171 		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
172 		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
173 		 * offset.
174 		 * See also the comment near timens_setup_vdso_data().
175 		 */
176 		if (!timens_page)
177 			return VM_FAULT_SIGBUS;
178 		pfn = sym_to_pfn(vdso_data);
179 		break;
180 #endif /* CONFIG_TIME_NS */
181 	default:
182 		return VM_FAULT_SIGBUS;
183 	}
184 
185 	return vmf_insert_pfn(vma, vmf->address, pfn);
186 }
187 
188 static int __setup_additional_pages(enum vdso_abi abi,
189 				    struct mm_struct *mm,
190 				    struct linux_binprm *bprm,
191 				    int uses_interp)
192 {
193 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
194 	unsigned long gp_flags = 0;
195 	void *ret;
196 
197 	BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
198 
199 	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
200 	/* Be sure to map the data page */
201 	vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
202 
203 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
204 	if (IS_ERR_VALUE(vdso_base)) {
205 		ret = ERR_PTR(vdso_base);
206 		goto up_fail;
207 	}
208 
209 	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
210 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
211 				       vdso_info[abi].dm);
212 	if (IS_ERR(ret))
213 		goto up_fail;
214 
215 	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
216 		gp_flags = VM_ARM64_BTI;
217 
218 	vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
219 	mm->context.vdso = (void *)vdso_base;
220 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
221 				       VM_READ|VM_EXEC|gp_flags|
222 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
223 				       vdso_info[abi].cm);
224 	if (IS_ERR(ret))
225 		goto up_fail;
226 
227 	return 0;
228 
229 up_fail:
230 	mm->context.vdso = NULL;
231 	return PTR_ERR(ret);
232 }
233 
234 #ifdef CONFIG_COMPAT
235 /*
236  * Create and map the vectors page for AArch32 tasks.
237  */
238 enum aarch32_map {
239 	AA32_MAP_VECTORS, /* kuser helpers */
240 	AA32_MAP_SIGPAGE,
241 	AA32_MAP_VVAR,
242 	AA32_MAP_VDSO,
243 };
244 
245 static struct page *aarch32_vectors_page __ro_after_init;
246 static struct page *aarch32_sig_page __ro_after_init;
247 
248 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
249 				  struct vm_area_struct *new_vma)
250 {
251 	current->mm->context.sigpage = (void *)new_vma->vm_start;
252 
253 	return 0;
254 }
255 
256 static struct vm_special_mapping aarch32_vdso_maps[] = {
257 	[AA32_MAP_VECTORS] = {
258 		.name	= "[vectors]", /* ABI */
259 		.pages	= &aarch32_vectors_page,
260 	},
261 	[AA32_MAP_SIGPAGE] = {
262 		.name	= "[sigpage]", /* ABI */
263 		.pages	= &aarch32_sig_page,
264 		.mremap	= aarch32_sigpage_mremap,
265 	},
266 	[AA32_MAP_VVAR] = {
267 		.name = "[vvar]",
268 		.fault = vvar_fault,
269 	},
270 	[AA32_MAP_VDSO] = {
271 		.name = "[vdso]",
272 		.mremap = vdso_mremap,
273 	},
274 };
275 
276 static int aarch32_alloc_kuser_vdso_page(void)
277 {
278 	extern char __kuser_helper_start[], __kuser_helper_end[];
279 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
280 	unsigned long vdso_page;
281 
282 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
283 		return 0;
284 
285 	vdso_page = get_zeroed_page(GFP_KERNEL);
286 	if (!vdso_page)
287 		return -ENOMEM;
288 
289 	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
290 	       kuser_sz);
291 	aarch32_vectors_page = virt_to_page((void *)vdso_page);
292 	return 0;
293 }
294 
295 #define COMPAT_SIGPAGE_POISON_WORD	0xe7fddef1
296 static int aarch32_alloc_sigpage(void)
297 {
298 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
299 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
300 	__le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
301 	void *sigpage;
302 
303 	sigpage = (void *)__get_free_page(GFP_KERNEL);
304 	if (!sigpage)
305 		return -ENOMEM;
306 
307 	memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
308 	memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
309 	aarch32_sig_page = virt_to_page(sigpage);
310 	return 0;
311 }
312 
313 static int __init __aarch32_alloc_vdso_pages(void)
314 {
315 
316 	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
317 		return 0;
318 
319 	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
320 	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
321 
322 	return __vdso_init(VDSO_ABI_AA32);
323 }
324 
325 static int __init aarch32_alloc_vdso_pages(void)
326 {
327 	int ret;
328 
329 	ret = __aarch32_alloc_vdso_pages();
330 	if (ret)
331 		return ret;
332 
333 	ret = aarch32_alloc_sigpage();
334 	if (ret)
335 		return ret;
336 
337 	return aarch32_alloc_kuser_vdso_page();
338 }
339 arch_initcall(aarch32_alloc_vdso_pages);
340 
341 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
342 {
343 	void *ret;
344 
345 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
346 		return 0;
347 
348 	/*
349 	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
350 	 * not safe to CoW the page containing the CPU exception vectors.
351 	 */
352 	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
353 				       VM_READ | VM_EXEC |
354 				       VM_MAYREAD | VM_MAYEXEC,
355 				       &aarch32_vdso_maps[AA32_MAP_VECTORS]);
356 
357 	return PTR_ERR_OR_ZERO(ret);
358 }
359 
360 static int aarch32_sigreturn_setup(struct mm_struct *mm)
361 {
362 	unsigned long addr;
363 	void *ret;
364 
365 	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
366 	if (IS_ERR_VALUE(addr)) {
367 		ret = ERR_PTR(addr);
368 		goto out;
369 	}
370 
371 	/*
372 	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
373 	 * set breakpoints.
374 	 */
375 	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
376 				       VM_READ | VM_EXEC | VM_MAYREAD |
377 				       VM_MAYWRITE | VM_MAYEXEC,
378 				       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
379 	if (IS_ERR(ret))
380 		goto out;
381 
382 	mm->context.sigpage = (void *)addr;
383 
384 out:
385 	return PTR_ERR_OR_ZERO(ret);
386 }
387 
388 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
389 {
390 	struct mm_struct *mm = current->mm;
391 	int ret;
392 
393 	if (mmap_write_lock_killable(mm))
394 		return -EINTR;
395 
396 	ret = aarch32_kuser_helpers_setup(mm);
397 	if (ret)
398 		goto out;
399 
400 	if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
401 		ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
402 					       uses_interp);
403 		if (ret)
404 			goto out;
405 	}
406 
407 	ret = aarch32_sigreturn_setup(mm);
408 out:
409 	mmap_write_unlock(mm);
410 	return ret;
411 }
412 #endif /* CONFIG_COMPAT */
413 
414 enum aarch64_map {
415 	AA64_MAP_VVAR,
416 	AA64_MAP_VDSO,
417 };
418 
419 static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
420 	[AA64_MAP_VVAR] = {
421 		.name	= "[vvar]",
422 		.fault = vvar_fault,
423 	},
424 	[AA64_MAP_VDSO] = {
425 		.name	= "[vdso]",
426 		.mremap = vdso_mremap,
427 	},
428 };
429 
430 static int __init vdso_init(void)
431 {
432 	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
433 	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
434 
435 	return __vdso_init(VDSO_ABI_AA64);
436 }
437 arch_initcall(vdso_init);
438 
439 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
440 {
441 	struct mm_struct *mm = current->mm;
442 	int ret;
443 
444 	if (mmap_write_lock_killable(mm))
445 		return -EINTR;
446 
447 	ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
448 	mmap_write_unlock(mm);
449 
450 	return ret;
451 }
452