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1da177e4 LT |
1 | /* |
2 | * linux/arch/x86_64/kernel/ldt.c | |
3 | * | |
4 | * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds | |
5 | * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com> | |
6 | * Copyright (C) 2002 Andi Kleen | |
7 | * | |
8 | * This handles calls from both 32bit and 64bit mode. | |
9 | */ | |
10 | ||
11 | #include <linux/errno.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/string.h> | |
14 | #include <linux/mm.h> | |
15 | #include <linux/smp.h> | |
16 | #include <linux/smp_lock.h> | |
17 | #include <linux/vmalloc.h> | |
18 | #include <linux/slab.h> | |
19 | ||
20 | #include <asm/uaccess.h> | |
21 | #include <asm/system.h> | |
22 | #include <asm/ldt.h> | |
23 | #include <asm/desc.h> | |
24 | #include <asm/proto.h> | |
25 | ||
26 | #ifdef CONFIG_SMP /* avoids "defined but not used" warnig */ | |
27 | static void flush_ldt(void *null) | |
28 | { | |
29 | if (current->active_mm) | |
30 | load_LDT(¤t->active_mm->context); | |
31 | } | |
32 | #endif | |
33 | ||
34 | static int alloc_ldt(mm_context_t *pc, unsigned mincount, int reload) | |
35 | { | |
36 | void *oldldt; | |
37 | void *newldt; | |
38 | unsigned oldsize; | |
39 | ||
40 | if (mincount <= (unsigned)pc->size) | |
41 | return 0; | |
42 | oldsize = pc->size; | |
43 | mincount = (mincount+511)&(~511); | |
44 | if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE) | |
45 | newldt = vmalloc(mincount*LDT_ENTRY_SIZE); | |
46 | else | |
47 | newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL); | |
48 | ||
49 | if (!newldt) | |
50 | return -ENOMEM; | |
51 | ||
52 | if (oldsize) | |
53 | memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE); | |
54 | oldldt = pc->ldt; | |
55 | memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE); | |
56 | wmb(); | |
57 | pc->ldt = newldt; | |
58 | wmb(); | |
59 | pc->size = mincount; | |
60 | wmb(); | |
61 | if (reload) { | |
62 | #ifdef CONFIG_SMP | |
63 | cpumask_t mask; | |
64 | ||
65 | preempt_disable(); | |
66 | mask = cpumask_of_cpu(smp_processor_id()); | |
67 | load_LDT(pc); | |
68 | if (!cpus_equal(current->mm->cpu_vm_mask, mask)) | |
69 | smp_call_function(flush_ldt, NULL, 1, 1); | |
70 | preempt_enable(); | |
71 | #else | |
72 | load_LDT(pc); | |
73 | #endif | |
74 | } | |
75 | if (oldsize) { | |
76 | if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE) | |
77 | vfree(oldldt); | |
78 | else | |
79 | kfree(oldldt); | |
80 | } | |
81 | return 0; | |
82 | } | |
83 | ||
84 | static inline int copy_ldt(mm_context_t *new, mm_context_t *old) | |
85 | { | |
86 | int err = alloc_ldt(new, old->size, 0); | |
87 | if (err < 0) | |
88 | return err; | |
89 | memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE); | |
90 | return 0; | |
91 | } | |
92 | ||
93 | /* | |
94 | * we do not have to muck with descriptors here, that is | |
95 | * done in switch_mm() as needed. | |
96 | */ | |
97 | int init_new_context(struct task_struct *tsk, struct mm_struct *mm) | |
98 | { | |
99 | struct mm_struct * old_mm; | |
100 | int retval = 0; | |
101 | ||
102 | init_MUTEX(&mm->context.sem); | |
103 | mm->context.size = 0; | |
104 | old_mm = current->mm; | |
105 | if (old_mm && old_mm->context.size > 0) { | |
106 | down(&old_mm->context.sem); | |
107 | retval = copy_ldt(&mm->context, &old_mm->context); | |
108 | up(&old_mm->context.sem); | |
109 | } | |
110 | return retval; | |
111 | } | |
112 | ||
113 | /* | |
114 | * | |
115 | * Don't touch the LDT register - we're already in the next thread. | |
116 | */ | |
117 | void destroy_context(struct mm_struct *mm) | |
118 | { | |
119 | if (mm->context.size) { | |
120 | if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE) | |
121 | vfree(mm->context.ldt); | |
122 | else | |
123 | kfree(mm->context.ldt); | |
124 | mm->context.size = 0; | |
125 | } | |
126 | } | |
127 | ||
128 | static int read_ldt(void __user * ptr, unsigned long bytecount) | |
129 | { | |
130 | int err; | |
131 | unsigned long size; | |
132 | struct mm_struct * mm = current->mm; | |
133 | ||
134 | if (!mm->context.size) | |
135 | return 0; | |
136 | if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES) | |
137 | bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES; | |
138 | ||
139 | down(&mm->context.sem); | |
140 | size = mm->context.size*LDT_ENTRY_SIZE; | |
141 | if (size > bytecount) | |
142 | size = bytecount; | |
143 | ||
144 | err = 0; | |
145 | if (copy_to_user(ptr, mm->context.ldt, size)) | |
146 | err = -EFAULT; | |
147 | up(&mm->context.sem); | |
148 | if (err < 0) | |
149 | goto error_return; | |
150 | if (size != bytecount) { | |
151 | /* zero-fill the rest */ | |
152 | if (clear_user(ptr+size, bytecount-size) != 0) { | |
153 | err = -EFAULT; | |
154 | goto error_return; | |
155 | } | |
156 | } | |
157 | return bytecount; | |
158 | error_return: | |
159 | return err; | |
160 | } | |
161 | ||
162 | static int read_default_ldt(void __user * ptr, unsigned long bytecount) | |
163 | { | |
164 | /* Arbitrary number */ | |
165 | /* x86-64 default LDT is all zeros */ | |
166 | if (bytecount > 128) | |
167 | bytecount = 128; | |
168 | if (clear_user(ptr, bytecount)) | |
169 | return -EFAULT; | |
170 | return bytecount; | |
171 | } | |
172 | ||
173 | static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode) | |
174 | { | |
175 | struct task_struct *me = current; | |
176 | struct mm_struct * mm = me->mm; | |
177 | __u32 entry_1, entry_2, *lp; | |
178 | int error; | |
179 | struct user_desc ldt_info; | |
180 | ||
181 | error = -EINVAL; | |
182 | ||
183 | if (bytecount != sizeof(ldt_info)) | |
184 | goto out; | |
185 | error = -EFAULT; | |
186 | if (copy_from_user(&ldt_info, ptr, bytecount)) | |
187 | goto out; | |
188 | ||
189 | error = -EINVAL; | |
190 | if (ldt_info.entry_number >= LDT_ENTRIES) | |
191 | goto out; | |
192 | if (ldt_info.contents == 3) { | |
193 | if (oldmode) | |
194 | goto out; | |
195 | if (ldt_info.seg_not_present == 0) | |
196 | goto out; | |
197 | } | |
198 | ||
199 | down(&mm->context.sem); | |
200 | if (ldt_info.entry_number >= (unsigned)mm->context.size) { | |
201 | error = alloc_ldt(¤t->mm->context, ldt_info.entry_number+1, 1); | |
202 | if (error < 0) | |
203 | goto out_unlock; | |
204 | } | |
205 | ||
206 | lp = (__u32 *) ((ldt_info.entry_number << 3) + (char *) mm->context.ldt); | |
207 | ||
208 | /* Allow LDTs to be cleared by the user. */ | |
209 | if (ldt_info.base_addr == 0 && ldt_info.limit == 0) { | |
210 | if (oldmode || LDT_empty(&ldt_info)) { | |
211 | entry_1 = 0; | |
212 | entry_2 = 0; | |
213 | goto install; | |
214 | } | |
215 | } | |
216 | ||
217 | entry_1 = LDT_entry_a(&ldt_info); | |
218 | entry_2 = LDT_entry_b(&ldt_info); | |
219 | if (oldmode) | |
220 | entry_2 &= ~(1 << 20); | |
221 | ||
222 | /* Install the new entry ... */ | |
223 | install: | |
224 | *lp = entry_1; | |
225 | *(lp+1) = entry_2; | |
226 | error = 0; | |
227 | ||
228 | out_unlock: | |
229 | up(&mm->context.sem); | |
230 | out: | |
231 | return error; | |
232 | } | |
233 | ||
234 | asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount) | |
235 | { | |
236 | int ret = -ENOSYS; | |
237 | ||
238 | switch (func) { | |
239 | case 0: | |
240 | ret = read_ldt(ptr, bytecount); | |
241 | break; | |
242 | case 1: | |
243 | ret = write_ldt(ptr, bytecount, 1); | |
244 | break; | |
245 | case 2: | |
246 | ret = read_default_ldt(ptr, bytecount); | |
247 | break; | |
248 | case 0x11: | |
249 | ret = write_ldt(ptr, bytecount, 0); | |
250 | break; | |
251 | } | |
252 | return ret; | |
253 | } |