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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1da177e4 | 2 | /* |
1da177e4 LT |
3 | * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds |
4 | * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> | |
5 | * Copyright (C) 2002 Andi Kleen | |
78aa1f66 | 6 | * |
1da177e4 LT |
7 | * This handles calls from both 32bit and 64bit mode. |
8 | */ | |
9 | ||
10 | #include <linux/errno.h> | |
5a0e3ad6 | 11 | #include <linux/gfp.h> |
1da177e4 LT |
12 | #include <linux/sched.h> |
13 | #include <linux/string.h> | |
14 | #include <linux/mm.h> | |
15 | #include <linux/smp.h> | |
37868fe1 | 16 | #include <linux/slab.h> |
1da177e4 | 17 | #include <linux/vmalloc.h> |
423a5405 | 18 | #include <linux/uaccess.h> |
1da177e4 | 19 | |
1da177e4 LT |
20 | #include <asm/ldt.h> |
21 | #include <asm/desc.h> | |
70f5088d | 22 | #include <asm/mmu_context.h> |
bbc1f698 | 23 | #include <asm/syscalls.h> |
1da177e4 | 24 | |
a6323757 AL |
25 | static void refresh_ldt_segments(void) |
26 | { | |
27 | #ifdef CONFIG_X86_64 | |
28 | unsigned short sel; | |
29 | ||
30 | /* | |
31 | * Make sure that the cached DS and ES descriptors match the updated | |
32 | * LDT. | |
33 | */ | |
34 | savesegment(ds, sel); | |
35 | if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) | |
36 | loadsegment(ds, sel); | |
37 | ||
38 | savesegment(es, sel); | |
39 | if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) | |
40 | loadsegment(es, sel); | |
41 | #endif | |
42 | } | |
43 | ||
37868fe1 | 44 | /* context.lock is held for us, so we don't need any locking. */ |
3d28ebce | 45 | static void flush_ldt(void *__mm) |
1da177e4 | 46 | { |
3d28ebce | 47 | struct mm_struct *mm = __mm; |
37868fe1 AL |
48 | mm_context_t *pc; |
49 | ||
3d28ebce | 50 | if (this_cpu_read(cpu_tlbstate.loaded_mm) != mm) |
37868fe1 AL |
51 | return; |
52 | ||
3d28ebce | 53 | pc = &mm->context; |
bbf79d21 | 54 | set_ldt(pc->ldt->entries, pc->ldt->nr_entries); |
a6323757 AL |
55 | |
56 | refresh_ldt_segments(); | |
1da177e4 | 57 | } |
1da177e4 | 58 | |
37868fe1 | 59 | /* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */ |
bbf79d21 | 60 | static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) |
1da177e4 | 61 | { |
37868fe1 | 62 | struct ldt_struct *new_ldt; |
990e9dc3 | 63 | unsigned int alloc_size; |
37868fe1 | 64 | |
bbf79d21 | 65 | if (num_entries > LDT_ENTRIES) |
37868fe1 AL |
66 | return NULL; |
67 | ||
68 | new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL); | |
69 | if (!new_ldt) | |
70 | return NULL; | |
71 | ||
72 | BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct)); | |
bbf79d21 | 73 | alloc_size = num_entries * LDT_ENTRY_SIZE; |
37868fe1 AL |
74 | |
75 | /* | |
76 | * Xen is very picky: it requires a page-aligned LDT that has no | |
77 | * trailing nonzero bytes in any page that contains LDT descriptors. | |
78 | * Keep it simple: zero the whole allocation and never allocate less | |
79 | * than PAGE_SIZE. | |
80 | */ | |
81 | if (alloc_size > PAGE_SIZE) | |
82 | new_ldt->entries = vzalloc(alloc_size); | |
1da177e4 | 83 | else |
f454b478 | 84 | new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL); |
1da177e4 | 85 | |
37868fe1 AL |
86 | if (!new_ldt->entries) { |
87 | kfree(new_ldt); | |
88 | return NULL; | |
89 | } | |
77e463d1 | 90 | |
bbf79d21 | 91 | new_ldt->nr_entries = num_entries; |
37868fe1 AL |
92 | return new_ldt; |
93 | } | |
38ffbe66 | 94 | |
37868fe1 AL |
95 | /* After calling this, the LDT is immutable. */ |
96 | static void finalize_ldt_struct(struct ldt_struct *ldt) | |
97 | { | |
bbf79d21 | 98 | paravirt_alloc_ldt(ldt->entries, ldt->nr_entries); |
1da177e4 LT |
99 | } |
100 | ||
37868fe1 AL |
101 | /* context.lock is held */ |
102 | static void install_ldt(struct mm_struct *current_mm, | |
103 | struct ldt_struct *ldt) | |
1da177e4 | 104 | { |
37868fe1 AL |
105 | /* Synchronizes with lockless_dereference in load_mm_ldt. */ |
106 | smp_store_release(¤t_mm->context.ldt, ldt); | |
107 | ||
108 | /* Activate the LDT for all CPUs using current_mm. */ | |
109 | on_each_cpu_mask(mm_cpumask(current_mm), flush_ldt, current_mm, true); | |
110 | } | |
78aa1f66 | 111 | |
37868fe1 AL |
112 | static void free_ldt_struct(struct ldt_struct *ldt) |
113 | { | |
114 | if (likely(!ldt)) | |
115 | return; | |
38ffbe66 | 116 | |
bbf79d21 BP |
117 | paravirt_free_ldt(ldt->entries, ldt->nr_entries); |
118 | if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE) | |
8d5341a6 | 119 | vfree_atomic(ldt->entries); |
37868fe1 | 120 | else |
f454b478 | 121 | free_page((unsigned long)ldt->entries); |
37868fe1 | 122 | kfree(ldt); |
1da177e4 LT |
123 | } |
124 | ||
125 | /* | |
126 | * we do not have to muck with descriptors here, that is | |
127 | * done in switch_mm() as needed. | |
128 | */ | |
39a0526f | 129 | int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm) |
1da177e4 | 130 | { |
37868fe1 | 131 | struct ldt_struct *new_ldt; |
78aa1f66 | 132 | struct mm_struct *old_mm; |
1da177e4 LT |
133 | int retval = 0; |
134 | ||
c7537ab2 | 135 | mutex_init(&mm->context.lock); |
1da177e4 | 136 | old_mm = current->mm; |
37868fe1 AL |
137 | if (!old_mm) { |
138 | mm->context.ldt = NULL; | |
139 | return 0; | |
1da177e4 | 140 | } |
37868fe1 AL |
141 | |
142 | mutex_lock(&old_mm->context.lock); | |
143 | if (!old_mm->context.ldt) { | |
144 | mm->context.ldt = NULL; | |
145 | goto out_unlock; | |
146 | } | |
147 | ||
bbf79d21 | 148 | new_ldt = alloc_ldt_struct(old_mm->context.ldt->nr_entries); |
37868fe1 AL |
149 | if (!new_ldt) { |
150 | retval = -ENOMEM; | |
151 | goto out_unlock; | |
152 | } | |
153 | ||
154 | memcpy(new_ldt->entries, old_mm->context.ldt->entries, | |
bbf79d21 | 155 | new_ldt->nr_entries * LDT_ENTRY_SIZE); |
37868fe1 AL |
156 | finalize_ldt_struct(new_ldt); |
157 | ||
158 | mm->context.ldt = new_ldt; | |
159 | ||
160 | out_unlock: | |
161 | mutex_unlock(&old_mm->context.lock); | |
1da177e4 LT |
162 | return retval; |
163 | } | |
164 | ||
165 | /* | |
77e463d1 TG |
166 | * No need to lock the MM as we are the last user |
167 | * | |
168 | * 64bit: Don't touch the LDT register - we're already in the next thread. | |
1da177e4 | 169 | */ |
39a0526f | 170 | void destroy_context_ldt(struct mm_struct *mm) |
1da177e4 | 171 | { |
37868fe1 AL |
172 | free_ldt_struct(mm->context.ldt); |
173 | mm->context.ldt = NULL; | |
1da177e4 LT |
174 | } |
175 | ||
78aa1f66 | 176 | static int read_ldt(void __user *ptr, unsigned long bytecount) |
1da177e4 | 177 | { |
78aa1f66 | 178 | struct mm_struct *mm = current->mm; |
bbf79d21 BP |
179 | unsigned long entries_size; |
180 | int retval; | |
1da177e4 | 181 | |
37868fe1 AL |
182 | mutex_lock(&mm->context.lock); |
183 | ||
184 | if (!mm->context.ldt) { | |
185 | retval = 0; | |
186 | goto out_unlock; | |
187 | } | |
188 | ||
78aa1f66 TG |
189 | if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES) |
190 | bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES; | |
1da177e4 | 191 | |
bbf79d21 BP |
192 | entries_size = mm->context.ldt->nr_entries * LDT_ENTRY_SIZE; |
193 | if (entries_size > bytecount) | |
194 | entries_size = bytecount; | |
1da177e4 | 195 | |
bbf79d21 | 196 | if (copy_to_user(ptr, mm->context.ldt->entries, entries_size)) { |
37868fe1 AL |
197 | retval = -EFAULT; |
198 | goto out_unlock; | |
199 | } | |
200 | ||
bbf79d21 | 201 | if (entries_size != bytecount) { |
37868fe1 | 202 | /* Zero-fill the rest and pretend we read bytecount bytes. */ |
bbf79d21 | 203 | if (clear_user(ptr + entries_size, bytecount - entries_size)) { |
37868fe1 AL |
204 | retval = -EFAULT; |
205 | goto out_unlock; | |
1da177e4 LT |
206 | } |
207 | } | |
37868fe1 AL |
208 | retval = bytecount; |
209 | ||
210 | out_unlock: | |
211 | mutex_unlock(&mm->context.lock); | |
212 | return retval; | |
1da177e4 LT |
213 | } |
214 | ||
78aa1f66 | 215 | static int read_default_ldt(void __user *ptr, unsigned long bytecount) |
1da177e4 | 216 | { |
77e463d1 TG |
217 | /* CHECKME: Can we use _one_ random number ? */ |
218 | #ifdef CONFIG_X86_32 | |
219 | unsigned long size = 5 * sizeof(struct desc_struct); | |
220 | #else | |
221 | unsigned long size = 128; | |
222 | #endif | |
223 | if (bytecount > size) | |
224 | bytecount = size; | |
1da177e4 LT |
225 | if (clear_user(ptr, bytecount)) |
226 | return -EFAULT; | |
78aa1f66 | 227 | return bytecount; |
1da177e4 LT |
228 | } |
229 | ||
78aa1f66 | 230 | static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) |
1da177e4 | 231 | { |
70f5088d | 232 | struct mm_struct *mm = current->mm; |
990e9dc3 | 233 | struct ldt_struct *new_ldt, *old_ldt; |
bbf79d21 | 234 | unsigned int old_nr_entries, new_nr_entries; |
990e9dc3 | 235 | struct user_desc ldt_info; |
5af72502 | 236 | struct desc_struct ldt; |
1da177e4 | 237 | int error; |
1da177e4 LT |
238 | |
239 | error = -EINVAL; | |
1da177e4 LT |
240 | if (bytecount != sizeof(ldt_info)) |
241 | goto out; | |
78aa1f66 | 242 | error = -EFAULT; |
70f5088d | 243 | if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info))) |
1da177e4 LT |
244 | goto out; |
245 | ||
246 | error = -EINVAL; | |
247 | if (ldt_info.entry_number >= LDT_ENTRIES) | |
248 | goto out; | |
249 | if (ldt_info.contents == 3) { | |
250 | if (oldmode) | |
251 | goto out; | |
252 | if (ldt_info.seg_not_present == 0) | |
253 | goto out; | |
254 | } | |
255 | ||
37868fe1 AL |
256 | if ((oldmode && !ldt_info.base_addr && !ldt_info.limit) || |
257 | LDT_empty(&ldt_info)) { | |
258 | /* The user wants to clear the entry. */ | |
259 | memset(&ldt, 0, sizeof(ldt)); | |
260 | } else { | |
261 | if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) { | |
262 | error = -EINVAL; | |
263 | goto out; | |
1da177e4 | 264 | } |
37868fe1 AL |
265 | |
266 | fill_ldt(&ldt, &ldt_info); | |
267 | if (oldmode) | |
268 | ldt.avl = 0; | |
1da177e4 LT |
269 | } |
270 | ||
37868fe1 AL |
271 | mutex_lock(&mm->context.lock); |
272 | ||
bbf79d21 BP |
273 | old_ldt = mm->context.ldt; |
274 | old_nr_entries = old_ldt ? old_ldt->nr_entries : 0; | |
275 | new_nr_entries = max(ldt_info.entry_number + 1, old_nr_entries); | |
37868fe1 AL |
276 | |
277 | error = -ENOMEM; | |
bbf79d21 | 278 | new_ldt = alloc_ldt_struct(new_nr_entries); |
37868fe1 | 279 | if (!new_ldt) |
34273f41 | 280 | goto out_unlock; |
34273f41 | 281 | |
37868fe1 | 282 | if (old_ldt) |
bbf79d21 BP |
283 | memcpy(new_ldt->entries, old_ldt->entries, old_nr_entries * LDT_ENTRY_SIZE); |
284 | ||
37868fe1 AL |
285 | new_ldt->entries[ldt_info.entry_number] = ldt; |
286 | finalize_ldt_struct(new_ldt); | |
1da177e4 | 287 | |
37868fe1 AL |
288 | install_ldt(mm, new_ldt); |
289 | free_ldt_struct(old_ldt); | |
1da177e4 LT |
290 | error = 0; |
291 | ||
292 | out_unlock: | |
c7537ab2 | 293 | mutex_unlock(&mm->context.lock); |
1da177e4 LT |
294 | out: |
295 | return error; | |
296 | } | |
297 | ||
78aa1f66 TG |
298 | asmlinkage int sys_modify_ldt(int func, void __user *ptr, |
299 | unsigned long bytecount) | |
1da177e4 LT |
300 | { |
301 | int ret = -ENOSYS; | |
302 | ||
303 | switch (func) { | |
304 | case 0: | |
305 | ret = read_ldt(ptr, bytecount); | |
306 | break; | |
307 | case 1: | |
308 | ret = write_ldt(ptr, bytecount, 1); | |
309 | break; | |
310 | case 2: | |
311 | ret = read_default_ldt(ptr, bytecount); | |
312 | break; | |
313 | case 0x11: | |
314 | ret = write_ldt(ptr, bytecount, 0); | |
315 | break; | |
316 | } | |
317 | return ret; | |
318 | } |