xref: /linux/arch/arm64/kernel/vdso.c (revision 74fc72e77dc5c8033d1b47d2c8a7229b4b83a746) 
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/timekeeper_internal.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 extern char vdso_start[], vdso_end[];
32 #ifdef CONFIG_COMPAT_VDSO
33 extern char vdso32_start[], vdso32_end[];
34 #endif /* CONFIG_COMPAT_VDSO */
35 
36 /* vdso_lookup arch_index */
37 enum arch_vdso_type {
38 	ARM64_VDSO = 0,
39 #ifdef CONFIG_COMPAT_VDSO
40 	ARM64_VDSO32 = 1,
41 #endif /* CONFIG_COMPAT_VDSO */
42 };
43 #ifdef CONFIG_COMPAT_VDSO
44 #define VDSO_TYPES		(ARM64_VDSO32 + 1)
45 #else
46 #define VDSO_TYPES		(ARM64_VDSO + 1)
47 #endif /* CONFIG_COMPAT_VDSO */
48 
49 struct __vdso_abi {
50 	const char *name;
51 	const char *vdso_code_start;
52 	const char *vdso_code_end;
53 	unsigned long vdso_pages;
54 	/* Data Mapping */
55 	struct vm_special_mapping *dm;
56 	/* Code Mapping */
57 	struct vm_special_mapping *cm;
58 };
59 
60 static struct __vdso_abi vdso_lookup[VDSO_TYPES] __ro_after_init = {
61 	{
62 		.name = "vdso",
63 		.vdso_code_start = vdso_start,
64 		.vdso_code_end = vdso_end,
65 	},
66 #ifdef CONFIG_COMPAT_VDSO
67 	{
68 		.name = "vdso32",
69 		.vdso_code_start = vdso32_start,
70 		.vdso_code_end = vdso32_end,
71 	},
72 #endif /* CONFIG_COMPAT_VDSO */
73 };
74 
75 /*
76  * The vDSO data page.
77  */
78 static union {
79 	struct vdso_data	data[CS_BASES];
80 	u8			page[PAGE_SIZE];
81 } vdso_data_store __page_aligned_data;
82 struct vdso_data *vdso_data = vdso_data_store.data;
83 
84 static int __vdso_remap(enum arch_vdso_type arch_index,
85 			const struct vm_special_mapping *sm,
86 			struct vm_area_struct *new_vma)
87 {
88 	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
89 	unsigned long vdso_size = vdso_lookup[arch_index].vdso_code_end -
90 				  vdso_lookup[arch_index].vdso_code_start;
91 
92 	if (vdso_size != new_size)
93 		return -EINVAL;
94 
95 	current->mm->context.vdso = (void *)new_vma->vm_start;
96 
97 	return 0;
98 }
99 
100 static int __vdso_init(enum arch_vdso_type arch_index)
101 {
102 	int i;
103 	struct page **vdso_pagelist;
104 	unsigned long pfn;
105 
106 	if (memcmp(vdso_lookup[arch_index].vdso_code_start, "\177ELF", 4)) {
107 		pr_err("vDSO is not a valid ELF object!\n");
108 		return -EINVAL;
109 	}
110 
111 	vdso_lookup[arch_index].vdso_pages = (
112 			vdso_lookup[arch_index].vdso_code_end -
113 			vdso_lookup[arch_index].vdso_code_start) >>
114 			PAGE_SHIFT;
115 
116 	/* Allocate the vDSO pagelist, plus a page for the data. */
117 	vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages + 1,
118 				sizeof(struct page *),
119 				GFP_KERNEL);
120 	if (vdso_pagelist == NULL)
121 		return -ENOMEM;
122 
123 	/* Grab the vDSO data page. */
124 	vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
125 
126 
127 	/* Grab the vDSO code pages. */
128 	pfn = sym_to_pfn(vdso_lookup[arch_index].vdso_code_start);
129 
130 	for (i = 0; i < vdso_lookup[arch_index].vdso_pages; i++)
131 		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
132 
133 	vdso_lookup[arch_index].dm->pages = &vdso_pagelist[0];
134 	vdso_lookup[arch_index].cm->pages = &vdso_pagelist[1];
135 
136 	return 0;
137 }
138 
139 static int __setup_additional_pages(enum arch_vdso_type arch_index,
140 				    struct mm_struct *mm,
141 				    struct linux_binprm *bprm,
142 				    int uses_interp)
143 {
144 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
145 	void *ret;
146 
147 	vdso_text_len = vdso_lookup[arch_index].vdso_pages << PAGE_SHIFT;
148 	/* Be sure to map the data page */
149 	vdso_mapping_len = vdso_text_len + PAGE_SIZE;
150 
151 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
152 	if (IS_ERR_VALUE(vdso_base)) {
153 		ret = ERR_PTR(vdso_base);
154 		goto up_fail;
155 	}
156 
157 	ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
158 				       VM_READ|VM_MAYREAD,
159 				       vdso_lookup[arch_index].dm);
160 	if (IS_ERR(ret))
161 		goto up_fail;
162 
163 	vdso_base += PAGE_SIZE;
164 	mm->context.vdso = (void *)vdso_base;
165 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
166 				       VM_READ|VM_EXEC|
167 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
168 				       vdso_lookup[arch_index].cm);
169 	if (IS_ERR(ret))
170 		goto up_fail;
171 
172 	return 0;
173 
174 up_fail:
175 	mm->context.vdso = NULL;
176 	return PTR_ERR(ret);
177 }
178 
179 #ifdef CONFIG_COMPAT
180 /*
181  * Create and map the vectors page for AArch32 tasks.
182  */
183 #ifdef CONFIG_COMPAT_VDSO
184 static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
185 		struct vm_area_struct *new_vma)
186 {
187 	return __vdso_remap(ARM64_VDSO32, sm, new_vma);
188 }
189 #endif /* CONFIG_COMPAT_VDSO */
190 
191 /*
192  * aarch32_vdso_pages:
193  * 0 - kuser helpers
194  * 1 - sigreturn code
195  * or (CONFIG_COMPAT_VDSO):
196  * 0 - kuser helpers
197  * 1 - vdso data
198  * 2 - vdso code
199  */
200 #define C_VECTORS	0
201 #ifdef CONFIG_COMPAT_VDSO
202 #define C_VVAR		1
203 #define C_VDSO		2
204 #define C_PAGES		(C_VDSO + 1)
205 #else
206 #define C_SIGPAGE	1
207 #define C_PAGES		(C_SIGPAGE + 1)
208 #endif /* CONFIG_COMPAT_VDSO */
209 
210 static struct page *aarch32_vectors_page __ro_after_init;
211 #ifndef CONFIG_COMPAT_VDSO
212 static struct page *aarch32_sig_page __ro_after_init;
213 #endif
214 
215 static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
216 	{
217 		.name	= "[vectors]", /* ABI */
218 		.pages	= &aarch32_vectors_page,
219 	},
220 #ifdef CONFIG_COMPAT_VDSO
221 	{
222 		.name = "[vvar]",
223 	},
224 	{
225 		.name = "[vdso]",
226 		.mremap = aarch32_vdso_mremap,
227 	},
228 #else
229 	{
230 		.name	= "[sigpage]", /* ABI */
231 		.pages	= &aarch32_sig_page,
232 	},
233 #endif /* CONFIG_COMPAT_VDSO */
234 };
235 
236 static int aarch32_alloc_kuser_vdso_page(void)
237 {
238 	extern char __kuser_helper_start[], __kuser_helper_end[];
239 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
240 	unsigned long vdso_page;
241 
242 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
243 		return 0;
244 
245 	vdso_page = get_zeroed_page(GFP_ATOMIC);
246 	if (!vdso_page)
247 		return -ENOMEM;
248 
249 	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
250 	       kuser_sz);
251 	aarch32_vectors_page = virt_to_page(vdso_page);
252 	flush_dcache_page(aarch32_vectors_page);
253 	return 0;
254 }
255 
256 #ifdef CONFIG_COMPAT_VDSO
257 static int __aarch32_alloc_vdso_pages(void)
258 {
259 	int ret;
260 
261 	vdso_lookup[ARM64_VDSO32].dm = &aarch32_vdso_spec[C_VVAR];
262 	vdso_lookup[ARM64_VDSO32].cm = &aarch32_vdso_spec[C_VDSO];
263 
264 	ret = __vdso_init(ARM64_VDSO32);
265 	if (ret)
266 		return ret;
267 
268 	return aarch32_alloc_kuser_vdso_page();
269 }
270 #else
271 static int __aarch32_alloc_vdso_pages(void)
272 {
273 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
274 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
275 	unsigned long sigpage;
276 	int ret;
277 
278 	sigpage = get_zeroed_page(GFP_ATOMIC);
279 	if (!sigpage)
280 		return -ENOMEM;
281 
282 	memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
283 	aarch32_sig_page = virt_to_page(sigpage);
284 	flush_dcache_page(aarch32_sig_page);
285 
286 	ret = aarch32_alloc_kuser_vdso_page();
287 	if (ret)
288 		free_page(sigpage);
289 
290 	return ret;
291 }
292 #endif /* CONFIG_COMPAT_VDSO */
293 
294 static int __init aarch32_alloc_vdso_pages(void)
295 {
296 	return __aarch32_alloc_vdso_pages();
297 }
298 arch_initcall(aarch32_alloc_vdso_pages);
299 
300 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
301 {
302 	void *ret;
303 
304 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
305 		return 0;
306 
307 	/*
308 	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
309 	 * not safe to CoW the page containing the CPU exception vectors.
310 	 */
311 	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
312 				       VM_READ | VM_EXEC |
313 				       VM_MAYREAD | VM_MAYEXEC,
314 				       &aarch32_vdso_spec[C_VECTORS]);
315 
316 	return PTR_ERR_OR_ZERO(ret);
317 }
318 
319 #ifndef CONFIG_COMPAT_VDSO
320 static int aarch32_sigreturn_setup(struct mm_struct *mm)
321 {
322 	unsigned long addr;
323 	void *ret;
324 
325 	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
326 	if (IS_ERR_VALUE(addr)) {
327 		ret = ERR_PTR(addr);
328 		goto out;
329 	}
330 
331 	/*
332 	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
333 	 * set breakpoints.
334 	 */
335 	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
336 				       VM_READ | VM_EXEC | VM_MAYREAD |
337 				       VM_MAYWRITE | VM_MAYEXEC,
338 				       &aarch32_vdso_spec[C_SIGPAGE]);
339 	if (IS_ERR(ret))
340 		goto out;
341 
342 	mm->context.vdso = (void *)addr;
343 
344 out:
345 	return PTR_ERR_OR_ZERO(ret);
346 }
347 #endif /* !CONFIG_COMPAT_VDSO */
348 
349 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
350 {
351 	struct mm_struct *mm = current->mm;
352 	int ret;
353 
354 	if (down_write_killable(&mm->mmap_sem))
355 		return -EINTR;
356 
357 	ret = aarch32_kuser_helpers_setup(mm);
358 	if (ret)
359 		goto out;
360 
361 #ifdef CONFIG_COMPAT_VDSO
362 	ret = __setup_additional_pages(ARM64_VDSO32,
363 				       mm,
364 				       bprm,
365 				       uses_interp);
366 #else
367 	ret = aarch32_sigreturn_setup(mm);
368 #endif /* CONFIG_COMPAT_VDSO */
369 
370 out:
371 	up_write(&mm->mmap_sem);
372 	return ret;
373 }
374 #endif /* CONFIG_COMPAT */
375 
376 static int vdso_mremap(const struct vm_special_mapping *sm,
377 		struct vm_area_struct *new_vma)
378 {
379 	return __vdso_remap(ARM64_VDSO, sm, new_vma);
380 }
381 
382 /*
383  * aarch64_vdso_pages:
384  * 0 - vvar
385  * 1 - vdso
386  */
387 #define A_VVAR		0
388 #define A_VDSO		1
389 #define A_PAGES		(A_VDSO + 1)
390 static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
391 	{
392 		.name	= "[vvar]",
393 	},
394 	{
395 		.name	= "[vdso]",
396 		.mremap = vdso_mremap,
397 	},
398 };
399 
400 static int __init vdso_init(void)
401 {
402 	vdso_lookup[ARM64_VDSO].dm = &vdso_spec[A_VVAR];
403 	vdso_lookup[ARM64_VDSO].cm = &vdso_spec[A_VDSO];
404 
405 	return __vdso_init(ARM64_VDSO);
406 }
407 arch_initcall(vdso_init);
408 
409 int arch_setup_additional_pages(struct linux_binprm *bprm,
410 				int uses_interp)
411 {
412 	struct mm_struct *mm = current->mm;
413 	int ret;
414 
415 	if (down_write_killable(&mm->mmap_sem))
416 		return -EINTR;
417 
418 	ret = __setup_additional_pages(ARM64_VDSO,
419 				       mm,
420 				       bprm,
421 				       uses_interp);
422 
423 	up_write(&mm->mmap_sem);
424 
425 	return ret;
426 }
427