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1 | /* | |
2 | * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds | |
3 | * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> | |
4 | * Copyright (C) 2002 Andi Kleen | |
5 | * | |
6 | * This handles calls from both 32bit and 64bit mode. | |
7 | */ | |
8 | ||
9 | #include <linux/errno.h> | |
10 | #include <linux/gfp.h> | |
11 | #include <linux/sched.h> | |
12 | #include <linux/string.h> | |
13 | #include <linux/mm.h> | |
14 | #include <linux/smp.h> | |
15 | #include <linux/vmalloc.h> | |
16 | #include <linux/uaccess.h> | |
17 | ||
18 | #include <asm/ldt.h> | |
19 | #include <asm/desc.h> | |
20 | #include <asm/mmu_context.h> | |
21 | #include <asm/syscalls.h> | |
22 | ||
23 | #ifdef CONFIG_SMP | |
24 | static void flush_ldt(void *current_mm) | |
25 | { | |
26 | if (current->active_mm == current_mm) | |
27 | load_LDT(¤t->active_mm->context); | |
28 | } | |
29 | #endif | |
30 | ||
31 | static int alloc_ldt(mm_context_t *pc, int mincount, int reload) | |
32 | { | |
33 | void *oldldt, *newldt; | |
34 | int oldsize; | |
35 | ||
36 | if (mincount <= pc->size) | |
37 | return 0; | |
38 | oldsize = pc->size; | |
39 | mincount = (mincount + (PAGE_SIZE / LDT_ENTRY_SIZE - 1)) & | |
40 | (~(PAGE_SIZE / LDT_ENTRY_SIZE - 1)); | |
41 | if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE) | |
42 | newldt = vmalloc(mincount * LDT_ENTRY_SIZE); | |
43 | else | |
44 | newldt = (void *)__get_free_page(GFP_KERNEL); | |
45 | ||
46 | if (!newldt) | |
47 | return -ENOMEM; | |
48 | ||
49 | if (oldsize) | |
50 | memcpy(newldt, pc->ldt, oldsize * LDT_ENTRY_SIZE); | |
51 | oldldt = pc->ldt; | |
52 | memset(newldt + oldsize * LDT_ENTRY_SIZE, 0, | |
53 | (mincount - oldsize) * LDT_ENTRY_SIZE); | |
54 | ||
55 | paravirt_alloc_ldt(newldt, mincount); | |
56 | ||
57 | #ifdef CONFIG_X86_64 | |
58 | /* CHECKME: Do we really need this ? */ | |
59 | wmb(); | |
60 | #endif | |
61 | pc->ldt = newldt; | |
62 | wmb(); | |
63 | pc->size = mincount; | |
64 | wmb(); | |
65 | ||
66 | if (reload) { | |
67 | #ifdef CONFIG_SMP | |
68 | preempt_disable(); | |
69 | load_LDT(pc); | |
70 | if (!cpumask_equal(mm_cpumask(current->mm), | |
71 | cpumask_of(smp_processor_id()))) | |
72 | smp_call_function(flush_ldt, current->mm, 1); | |
73 | preempt_enable(); | |
74 | #else | |
75 | load_LDT(pc); | |
76 | #endif | |
77 | } | |
78 | if (oldsize) { | |
79 | paravirt_free_ldt(oldldt, oldsize); | |
80 | if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE) | |
81 | vfree(oldldt); | |
82 | else | |
83 | put_page(virt_to_page(oldldt)); | |
84 | } | |
85 | return 0; | |
86 | } | |
87 | ||
88 | static inline int copy_ldt(mm_context_t *new, mm_context_t *old) | |
89 | { | |
90 | int err = alloc_ldt(new, old->size, 0); | |
91 | int i; | |
92 | ||
93 | if (err < 0) | |
94 | return err; | |
95 | ||
96 | for (i = 0; i < old->size; i++) | |
97 | write_ldt_entry(new->ldt, i, old->ldt + i * LDT_ENTRY_SIZE); | |
98 | return 0; | |
99 | } | |
100 | ||
101 | /* | |
102 | * we do not have to muck with descriptors here, that is | |
103 | * done in switch_mm() as needed. | |
104 | */ | |
105 | int init_new_context(struct task_struct *tsk, struct mm_struct *mm) | |
106 | { | |
107 | struct mm_struct *old_mm; | |
108 | int retval = 0; | |
109 | ||
110 | mutex_init(&mm->context.lock); | |
111 | mm->context.size = 0; | |
112 | old_mm = current->mm; | |
113 | if (old_mm && old_mm->context.size > 0) { | |
114 | mutex_lock(&old_mm->context.lock); | |
115 | retval = copy_ldt(&mm->context, &old_mm->context); | |
116 | mutex_unlock(&old_mm->context.lock); | |
117 | } | |
118 | return retval; | |
119 | } | |
120 | ||
121 | /* | |
122 | * No need to lock the MM as we are the last user | |
123 | * | |
124 | * 64bit: Don't touch the LDT register - we're already in the next thread. | |
125 | */ | |
126 | void destroy_context(struct mm_struct *mm) | |
127 | { | |
128 | if (mm->context.size) { | |
129 | #ifdef CONFIG_X86_32 | |
130 | /* CHECKME: Can this ever happen ? */ | |
131 | if (mm == current->active_mm) | |
132 | clear_LDT(); | |
133 | #endif | |
134 | paravirt_free_ldt(mm->context.ldt, mm->context.size); | |
135 | if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE) | |
136 | vfree(mm->context.ldt); | |
137 | else | |
138 | put_page(virt_to_page(mm->context.ldt)); | |
139 | mm->context.size = 0; | |
140 | } | |
141 | } | |
142 | ||
143 | static int read_ldt(void __user *ptr, unsigned long bytecount) | |
144 | { | |
145 | int err; | |
146 | unsigned long size; | |
147 | struct mm_struct *mm = current->mm; | |
148 | ||
149 | if (!mm->context.size) | |
150 | return 0; | |
151 | if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES) | |
152 | bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES; | |
153 | ||
154 | mutex_lock(&mm->context.lock); | |
155 | size = mm->context.size * LDT_ENTRY_SIZE; | |
156 | if (size > bytecount) | |
157 | size = bytecount; | |
158 | ||
159 | err = 0; | |
160 | if (copy_to_user(ptr, mm->context.ldt, size)) | |
161 | err = -EFAULT; | |
162 | mutex_unlock(&mm->context.lock); | |
163 | if (err < 0) | |
164 | goto error_return; | |
165 | if (size != bytecount) { | |
166 | /* zero-fill the rest */ | |
167 | if (clear_user(ptr + size, bytecount - size) != 0) { | |
168 | err = -EFAULT; | |
169 | goto error_return; | |
170 | } | |
171 | } | |
172 | return bytecount; | |
173 | error_return: | |
174 | return err; | |
175 | } | |
176 | ||
177 | static int read_default_ldt(void __user *ptr, unsigned long bytecount) | |
178 | { | |
179 | /* CHECKME: Can we use _one_ random number ? */ | |
180 | #ifdef CONFIG_X86_32 | |
181 | unsigned long size = 5 * sizeof(struct desc_struct); | |
182 | #else | |
183 | unsigned long size = 128; | |
184 | #endif | |
185 | if (bytecount > size) | |
186 | bytecount = size; | |
187 | if (clear_user(ptr, bytecount)) | |
188 | return -EFAULT; | |
189 | return bytecount; | |
190 | } | |
191 | ||
192 | static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode) | |
193 | { | |
194 | struct mm_struct *mm = current->mm; | |
195 | struct desc_struct ldt; | |
196 | int error; | |
197 | struct user_desc ldt_info; | |
198 | ||
199 | error = -EINVAL; | |
200 | if (bytecount != sizeof(ldt_info)) | |
201 | goto out; | |
202 | error = -EFAULT; | |
203 | if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info))) | |
204 | goto out; | |
205 | ||
206 | error = -EINVAL; | |
207 | if (ldt_info.entry_number >= LDT_ENTRIES) | |
208 | goto out; | |
209 | if (ldt_info.contents == 3) { | |
210 | if (oldmode) | |
211 | goto out; | |
212 | if (ldt_info.seg_not_present == 0) | |
213 | goto out; | |
214 | } | |
215 | ||
216 | mutex_lock(&mm->context.lock); | |
217 | if (ldt_info.entry_number >= mm->context.size) { | |
218 | error = alloc_ldt(¤t->mm->context, | |
219 | ldt_info.entry_number + 1, 1); | |
220 | if (error < 0) | |
221 | goto out_unlock; | |
222 | } | |
223 | ||
224 | /* Allow LDTs to be cleared by the user. */ | |
225 | if (ldt_info.base_addr == 0 && ldt_info.limit == 0) { | |
226 | if (oldmode || LDT_empty(&ldt_info)) { | |
227 | memset(&ldt, 0, sizeof(ldt)); | |
228 | goto install; | |
229 | } | |
230 | } | |
231 | ||
232 | if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) { | |
233 | error = -EINVAL; | |
234 | goto out_unlock; | |
235 | } | |
236 | ||
237 | fill_ldt(&ldt, &ldt_info); | |
238 | if (oldmode) | |
239 | ldt.avl = 0; | |
240 | ||
241 | /* Install the new entry ... */ | |
242 | install: | |
243 | write_ldt_entry(mm->context.ldt, ldt_info.entry_number, &ldt); | |
244 | error = 0; | |
245 | ||
246 | out_unlock: | |
247 | mutex_unlock(&mm->context.lock); | |
248 | out: | |
249 | return error; | |
250 | } | |
251 | ||
252 | asmlinkage int sys_modify_ldt(int func, void __user *ptr, | |
253 | unsigned long bytecount) | |
254 | { | |
255 | int ret = -ENOSYS; | |
256 | ||
257 | switch (func) { | |
258 | case 0: | |
259 | ret = read_ldt(ptr, bytecount); | |
260 | break; | |
261 | case 1: | |
262 | ret = write_ldt(ptr, bytecount, 1); | |
263 | break; | |
264 | case 2: | |
265 | ret = read_default_ldt(ptr, bytecount); | |
266 | break; | |
267 | case 0x11: | |
268 | ret = write_ldt(ptr, bytecount, 0); | |
269 | break; | |
270 | } | |
271 | return ret; | |
272 | } |