xref: /linux/arch/arm64/kernel/vdso.c (revision 3fd6c59042dbba50391e30862beac979491145fe)
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