1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
4 * <benh@kernel.crashing.org>
5 * Copyright (C) 2012 ARM Limited
6 * Copyright (C) 2015 Regents of the University of California
7 */
8
9 #include <linux/elf.h>
10 #include <linux/mm.h>
11 #include <linux/slab.h>
12 #include <linux/binfmts.h>
13 #include <linux/err.h>
14 #include <asm/page.h>
15 #include <asm/vdso.h>
16 #include <linux/time_namespace.h>
17 #include <vdso/datapage.h>
18 #include <vdso/vsyscall.h>
19
20 enum vvar_pages {
21 VVAR_DATA_PAGE_OFFSET,
22 VVAR_TIMENS_PAGE_OFFSET,
23 VVAR_NR_PAGES,
24 };
25
26 enum rv_vdso_map {
27 RV_VDSO_MAP_VVAR,
28 RV_VDSO_MAP_VDSO,
29 };
30
31 #define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT)
32
33 /*
34 * The vDSO data page.
35 */
36 static union {
37 struct vdso_data data;
38 u8 page[PAGE_SIZE];
39 } vdso_data_store __page_aligned_data;
40 struct vdso_data *vdso_data = &vdso_data_store.data;
41
42 struct __vdso_info {
43 const char *name;
44 const char *vdso_code_start;
45 const char *vdso_code_end;
46 unsigned long vdso_pages;
47 /* Data Mapping */
48 struct vm_special_mapping *dm;
49 /* Code Mapping */
50 struct vm_special_mapping *cm;
51 };
52
53 static struct __vdso_info vdso_info;
54 #ifdef CONFIG_COMPAT
55 static struct __vdso_info compat_vdso_info;
56 #endif
57
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * new_vma)58 static int vdso_mremap(const struct vm_special_mapping *sm,
59 struct vm_area_struct *new_vma)
60 {
61 current->mm->context.vdso = (void *)new_vma->vm_start;
62
63 return 0;
64 }
65
__vdso_init(struct __vdso_info * vdso_info)66 static void __init __vdso_init(struct __vdso_info *vdso_info)
67 {
68 unsigned int i;
69 struct page **vdso_pagelist;
70 unsigned long pfn;
71
72 if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4))
73 panic("vDSO is not a valid ELF object!\n");
74
75 vdso_info->vdso_pages = (
76 vdso_info->vdso_code_end -
77 vdso_info->vdso_code_start) >>
78 PAGE_SHIFT;
79
80 vdso_pagelist = kcalloc(vdso_info->vdso_pages,
81 sizeof(struct page *),
82 GFP_KERNEL);
83 if (vdso_pagelist == NULL)
84 panic("vDSO kcalloc failed!\n");
85
86 /* Grab the vDSO code pages. */
87 pfn = sym_to_pfn(vdso_info->vdso_code_start);
88
89 for (i = 0; i < vdso_info->vdso_pages; i++)
90 vdso_pagelist[i] = pfn_to_page(pfn + i);
91
92 vdso_info->cm->pages = vdso_pagelist;
93 }
94
95 #ifdef CONFIG_TIME_NS
arch_get_vdso_data(void * vvar_page)96 struct vdso_data *arch_get_vdso_data(void *vvar_page)
97 {
98 return (struct vdso_data *)(vvar_page);
99 }
100
101 /*
102 * The vvar mapping contains data for a specific time namespace, so when a task
103 * changes namespace we must unmap its vvar data for the old namespace.
104 * Subsequent faults will map in data for the new namespace.
105 *
106 * For more details see timens_setup_vdso_data().
107 */
vdso_join_timens(struct task_struct * task,struct time_namespace * ns)108 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
109 {
110 struct mm_struct *mm = task->mm;
111 struct vm_area_struct *vma;
112 VMA_ITERATOR(vmi, mm, 0);
113
114 mmap_read_lock(mm);
115
116 for_each_vma(vmi, vma) {
117 if (vma_is_special_mapping(vma, vdso_info.dm))
118 zap_vma_pages(vma);
119 #ifdef CONFIG_COMPAT
120 if (vma_is_special_mapping(vma, compat_vdso_info.dm))
121 zap_vma_pages(vma);
122 #endif
123 }
124
125 mmap_read_unlock(mm);
126 return 0;
127 }
128 #endif
129
vvar_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)130 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
131 struct vm_area_struct *vma, struct vm_fault *vmf)
132 {
133 struct page *timens_page = find_timens_vvar_page(vma);
134 unsigned long pfn;
135
136 switch (vmf->pgoff) {
137 case VVAR_DATA_PAGE_OFFSET:
138 if (timens_page)
139 pfn = page_to_pfn(timens_page);
140 else
141 pfn = sym_to_pfn(vdso_data);
142 break;
143 #ifdef CONFIG_TIME_NS
144 case VVAR_TIMENS_PAGE_OFFSET:
145 /*
146 * If a task belongs to a time namespace then a namespace
147 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
148 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
149 * offset.
150 * See also the comment near timens_setup_vdso_data().
151 */
152 if (!timens_page)
153 return VM_FAULT_SIGBUS;
154 pfn = sym_to_pfn(vdso_data);
155 break;
156 #endif /* CONFIG_TIME_NS */
157 default:
158 return VM_FAULT_SIGBUS;
159 }
160
161 return vmf_insert_pfn(vma, vmf->address, pfn);
162 }
163
164 static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
165 [RV_VDSO_MAP_VVAR] = {
166 .name = "[vvar]",
167 .fault = vvar_fault,
168 },
169 [RV_VDSO_MAP_VDSO] = {
170 .name = "[vdso]",
171 .mremap = vdso_mremap,
172 },
173 };
174
175 static struct __vdso_info vdso_info __ro_after_init = {
176 .name = "vdso",
177 .vdso_code_start = vdso_start,
178 .vdso_code_end = vdso_end,
179 .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
180 .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
181 };
182
183 #ifdef CONFIG_COMPAT
184 static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = {
185 [RV_VDSO_MAP_VVAR] = {
186 .name = "[vvar]",
187 .fault = vvar_fault,
188 },
189 [RV_VDSO_MAP_VDSO] = {
190 .name = "[vdso]",
191 .mremap = vdso_mremap,
192 },
193 };
194
195 static struct __vdso_info compat_vdso_info __ro_after_init = {
196 .name = "compat_vdso",
197 .vdso_code_start = compat_vdso_start,
198 .vdso_code_end = compat_vdso_end,
199 .dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR],
200 .cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO],
201 };
202 #endif
203
vdso_init(void)204 static int __init vdso_init(void)
205 {
206 __vdso_init(&vdso_info);
207 #ifdef CONFIG_COMPAT
208 __vdso_init(&compat_vdso_info);
209 #endif
210
211 return 0;
212 }
213 arch_initcall(vdso_init);
214
__setup_additional_pages(struct mm_struct * mm,struct linux_binprm * bprm,int uses_interp,struct __vdso_info * vdso_info)215 static int __setup_additional_pages(struct mm_struct *mm,
216 struct linux_binprm *bprm,
217 int uses_interp,
218 struct __vdso_info *vdso_info)
219 {
220 unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
221 void *ret;
222
223 BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
224
225 vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
226 /* Be sure to map the data page */
227 vdso_mapping_len = vdso_text_len + VVAR_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_SIZE,
236 (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm);
237 if (IS_ERR(ret))
238 goto up_fail;
239
240 vdso_base += VVAR_SIZE;
241 mm->context.vdso = (void *)vdso_base;
242
243 ret =
244 _install_special_mapping(mm, vdso_base, vdso_text_len,
245 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
246 vdso_info->cm);
247
248 if (IS_ERR(ret))
249 goto up_fail;
250
251 return 0;
252
253 up_fail:
254 mm->context.vdso = NULL;
255 return PTR_ERR(ret);
256 }
257
258 #ifdef CONFIG_COMPAT
compat_arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)259 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
260 int uses_interp)
261 {
262 struct mm_struct *mm = current->mm;
263 int ret;
264
265 if (mmap_write_lock_killable(mm))
266 return -EINTR;
267
268 ret = __setup_additional_pages(mm, bprm, uses_interp,
269 &compat_vdso_info);
270 mmap_write_unlock(mm);
271
272 return ret;
273 }
274 #endif
275
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)276 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
277 {
278 struct mm_struct *mm = current->mm;
279 int ret;
280
281 if (mmap_write_lock_killable(mm))
282 return -EINTR;
283
284 ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
285 mmap_write_unlock(mm);
286
287 return ret;
288 }
289