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/vdso_datastore.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 static int vdso_mremap(const struct vm_special_mapping *sm,
61 		struct vm_area_struct *new_vma)
62 {
63 	current->mm->context.vdso = (void *)new_vma->vm_start;
64 
65 	return 0;
66 }
67 
68 static int __init __vdso_init(enum vdso_abi abi)
69 {
70 	int i;
71 	struct page **vdso_pagelist;
72 	unsigned long pfn;
73 
74 	if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
75 		pr_err("vDSO is not a valid ELF object!\n");
76 		return -EINVAL;
77 	}
78 
79 	vdso_info[abi].vdso_pages = (
80 			vdso_info[abi].vdso_code_end -
81 			vdso_info[abi].vdso_code_start) >>
82 			PAGE_SHIFT;
83 
84 	vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
85 				sizeof(struct page *),
86 				GFP_KERNEL);
87 	if (vdso_pagelist == NULL)
88 		return -ENOMEM;
89 
90 	/* Grab the vDSO code pages. */
91 	pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
92 
93 	for (i = 0; i < vdso_info[abi].vdso_pages; i++)
94 		vdso_pagelist[i] = pfn_to_page(pfn + i);
95 
96 	vdso_info[abi].cm->pages = vdso_pagelist;
97 
98 	return 0;
99 }
100 
101 static int __setup_additional_pages(enum vdso_abi abi,
102 				    struct mm_struct *mm,
103 				    struct linux_binprm *bprm,
104 				    int uses_interp)
105 {
106 	unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
107 	unsigned long gp_flags = 0;
108 	void *ret;
109 
110 	BUILD_BUG_ON(VDSO_NR_PAGES != __VDSO_PAGES);
111 
112 	vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
113 	/* Be sure to map the data page */
114 	vdso_mapping_len = vdso_text_len + VDSO_NR_PAGES * PAGE_SIZE;
115 
116 	vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
117 	if (IS_ERR_VALUE(vdso_base)) {
118 		ret = ERR_PTR(vdso_base);
119 		goto up_fail;
120 	}
121 
122 	ret = vdso_install_vvar_mapping(mm, vdso_base);
123 	if (IS_ERR(ret))
124 		goto up_fail;
125 
126 	if (system_supports_bti_kernel())
127 		gp_flags = VM_ARM64_BTI;
128 
129 	vdso_base += VDSO_NR_PAGES * PAGE_SIZE;
130 	mm->context.vdso = (void *)vdso_base;
131 	ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
132 				       VM_READ|VM_EXEC|gp_flags|
133 				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
134 				       VM_SEALED_SYSMAP,
135 				       vdso_info[abi].cm);
136 	if (IS_ERR(ret))
137 		goto up_fail;
138 
139 	return 0;
140 
141 up_fail:
142 	mm->context.vdso = NULL;
143 	return PTR_ERR(ret);
144 }
145 
146 #ifdef CONFIG_COMPAT
147 /*
148  * Create and map the vectors page for AArch32 tasks.
149  */
150 enum aarch32_map {
151 	AA32_MAP_VECTORS, /* kuser helpers */
152 	AA32_MAP_SIGPAGE,
153 	AA32_MAP_VDSO,
154 };
155 
156 static struct page *aarch32_vectors_page __ro_after_init;
157 static struct page *aarch32_sig_page __ro_after_init;
158 
159 static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm,
160 				  struct vm_area_struct *new_vma)
161 {
162 	current->mm->context.sigpage = (void *)new_vma->vm_start;
163 
164 	return 0;
165 }
166 
167 static struct vm_special_mapping aarch32_vdso_maps[] = {
168 	[AA32_MAP_VECTORS] = {
169 		.name	= "[vectors]", /* ABI */
170 		.pages	= &aarch32_vectors_page,
171 	},
172 	[AA32_MAP_SIGPAGE] = {
173 		.name	= "[sigpage]", /* ABI */
174 		.pages	= &aarch32_sig_page,
175 		.mremap	= aarch32_sigpage_mremap,
176 	},
177 	[AA32_MAP_VDSO] = {
178 		.name = "[vdso]",
179 		.mremap = vdso_mremap,
180 	},
181 };
182 
183 static int aarch32_alloc_kuser_vdso_page(void)
184 {
185 	extern char __kuser_helper_start[], __kuser_helper_end[];
186 	int kuser_sz = __kuser_helper_end - __kuser_helper_start;
187 	unsigned long vdso_page;
188 
189 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
190 		return 0;
191 
192 	vdso_page = get_zeroed_page(GFP_KERNEL);
193 	if (!vdso_page)
194 		return -ENOMEM;
195 
196 	memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
197 	       kuser_sz);
198 	aarch32_vectors_page = virt_to_page((void *)vdso_page);
199 	return 0;
200 }
201 
202 #define COMPAT_SIGPAGE_POISON_WORD	0xe7fddef1
203 static int aarch32_alloc_sigpage(void)
204 {
205 	extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
206 	int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
207 	__le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD);
208 	void *sigpage;
209 
210 	sigpage = (void *)__get_free_page(GFP_KERNEL);
211 	if (!sigpage)
212 		return -ENOMEM;
213 
214 	memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison));
215 	memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz);
216 	aarch32_sig_page = virt_to_page(sigpage);
217 	return 0;
218 }
219 
220 static int __init __aarch32_alloc_vdso_pages(void)
221 {
222 
223 	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
224 		return 0;
225 
226 	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
227 
228 	return __vdso_init(VDSO_ABI_AA32);
229 }
230 
231 static int __init aarch32_alloc_vdso_pages(void)
232 {
233 	int ret;
234 
235 	ret = __aarch32_alloc_vdso_pages();
236 	if (ret)
237 		return ret;
238 
239 	ret = aarch32_alloc_sigpage();
240 	if (ret)
241 		return ret;
242 
243 	return aarch32_alloc_kuser_vdso_page();
244 }
245 arch_initcall(aarch32_alloc_vdso_pages);
246 
247 static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
248 {
249 	void *ret;
250 
251 	if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
252 		return 0;
253 
254 	/*
255 	 * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
256 	 * not safe to CoW the page containing the CPU exception vectors.
257 	 */
258 	ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
259 				       VM_READ | VM_EXEC |
260 				       VM_MAYREAD | VM_MAYEXEC |
261 				       VM_SEALED_SYSMAP,
262 				       &aarch32_vdso_maps[AA32_MAP_VECTORS]);
263 
264 	return PTR_ERR_OR_ZERO(ret);
265 }
266 
267 static int aarch32_sigreturn_setup(struct mm_struct *mm)
268 {
269 	unsigned long addr;
270 	void *ret;
271 
272 	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
273 	if (IS_ERR_VALUE(addr)) {
274 		ret = ERR_PTR(addr);
275 		goto out;
276 	}
277 
278 	/*
279 	 * VM_MAYWRITE is required to allow gdb to Copy-on-Write and
280 	 * set breakpoints.
281 	 */
282 	ret = _install_special_mapping(mm, addr, PAGE_SIZE,
283 				       VM_READ | VM_EXEC | VM_MAYREAD |
284 				       VM_MAYWRITE | VM_MAYEXEC |
285 				       VM_SEALED_SYSMAP,
286 				       &aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
287 	if (IS_ERR(ret))
288 		goto out;
289 
290 	mm->context.sigpage = (void *)addr;
291 
292 out:
293 	return PTR_ERR_OR_ZERO(ret);
294 }
295 
296 int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
297 {
298 	struct mm_struct *mm = current->mm;
299 	int ret;
300 
301 	if (mmap_write_lock_killable(mm))
302 		return -EINTR;
303 
304 	ret = aarch32_kuser_helpers_setup(mm);
305 	if (ret)
306 		goto out;
307 
308 	if (IS_ENABLED(CONFIG_COMPAT_VDSO)) {
309 		ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm,
310 					       uses_interp);
311 		if (ret)
312 			goto out;
313 	}
314 
315 	ret = aarch32_sigreturn_setup(mm);
316 out:
317 	mmap_write_unlock(mm);
318 	return ret;
319 }
320 #endif /* CONFIG_COMPAT */
321 
322 static struct vm_special_mapping aarch64_vdso_map __ro_after_init = {
323 	.name	= "[vdso]",
324 	.mremap = vdso_mremap,
325 };
326 
327 static int __init vdso_init(void)
328 {
329 	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_map;
330 
331 	return __vdso_init(VDSO_ABI_AA64);
332 }
333 arch_initcall(vdso_init);
334 
335 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
336 {
337 	struct mm_struct *mm = current->mm;
338 	int ret;
339 
340 	if (mmap_write_lock_killable(mm))
341 		return -EINTR;
342 
343 	ret = __setup_additional_pages(VDSO_ABI_AA64, mm, bprm, uses_interp);
344 	mmap_write_unlock(mm);
345 
346 	return ret;
347 }
348