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8#include <linux/errno.h>
9#include <linux/sched.h>
10#include <linux/string.h>
11#include <linux/mm.h>
12#include <linux/smp.h>
13#include <linux/vmalloc.h>
14#include <linux/slab.h>
15
16#include <asm/uaccess.h>
17#include <asm/system.h>
18#include <asm/ldt.h>
19#include <asm/desc.h>
20#include <asm/mmu_context.h>
21
22#ifdef CONFIG_SMP
23static void flush_ldt(void *null)
24{
25 if (current->active_mm)
26 load_LDT(¤t->active_mm->context);
27}
28#endif
29
30static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
31{
32 void *oldldt;
33 void *newldt;
34 int oldsize;
35
36 if (mincount <= pc->size)
37 return 0;
38 oldsize = pc->size;
39 mincount = (mincount+511)&(~511);
40 if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
41 newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
42 else
43 newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
44
45 if (!newldt)
46 return -ENOMEM;
47
48 if (oldsize)
49 memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
50 oldldt = pc->ldt;
51 memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
52 pc->ldt = newldt;
53 wmb();
54 pc->size = mincount;
55 wmb();
56
57 if (reload) {
58#ifdef CONFIG_SMP
59 cpumask_t mask;
60 preempt_disable();
61 load_LDT(pc);
62 mask = cpumask_of_cpu(smp_processor_id());
63 if (!cpus_equal(current->mm->cpu_vm_mask, mask))
64 smp_call_function(flush_ldt, NULL, 1, 1);
65 preempt_enable();
66#else
67 load_LDT(pc);
68#endif
69 }
70 if (oldsize) {
71 if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
72 vfree(oldldt);
73 else
74 kfree(oldldt);
75 }
76 return 0;
77}
78
79static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
80{
81 int err = alloc_ldt(new, old->size, 0);
82 if (err < 0)
83 return err;
84 memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
85 return 0;
86}
87
88
89
90
91
92int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
93{
94 struct mm_struct * old_mm;
95 int retval = 0;
96
97 init_MUTEX(&mm->context.sem);
98 mm->context.size = 0;
99 old_mm = current->mm;
100 if (old_mm && old_mm->context.size > 0) {
101 down(&old_mm->context.sem);
102 retval = copy_ldt(&mm->context, &old_mm->context);
103 up(&old_mm->context.sem);
104 }
105 return retval;
106}
107
108
109
110
111void destroy_context(struct mm_struct *mm)
112{
113 if (mm->context.size) {
114 if (mm == current->active_mm)
115 clear_LDT();
116 if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
117 vfree(mm->context.ldt);
118 else
119 kfree(mm->context.ldt);
120 mm->context.size = 0;
121 }
122}
123
124static int read_ldt(void __user * ptr, unsigned long bytecount)
125{
126 int err;
127 unsigned long size;
128 struct mm_struct * mm = current->mm;
129
130 if (!mm->context.size)
131 return 0;
132 if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
133 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
134
135 down(&mm->context.sem);
136 size = mm->context.size*LDT_ENTRY_SIZE;
137 if (size > bytecount)
138 size = bytecount;
139
140 err = 0;
141 if (copy_to_user(ptr, mm->context.ldt, size))
142 err = -EFAULT;
143 up(&mm->context.sem);
144 if (err < 0)
145 goto error_return;
146 if (size != bytecount) {
147
148 if (clear_user(ptr+size, bytecount-size) != 0) {
149 err = -EFAULT;
150 goto error_return;
151 }
152 }
153 return bytecount;
154error_return:
155 return err;
156}
157
158static int read_default_ldt(void __user * ptr, unsigned long bytecount)
159{
160 int err;
161 unsigned long size;
162
163 err = 0;
164 size = 5*sizeof(struct desc_struct);
165 if (size > bytecount)
166 size = bytecount;
167
168 err = size;
169 if (clear_user(ptr, size))
170 err = -EFAULT;
171
172 return err;
173}
174
175static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
176{
177 struct mm_struct * mm = current->mm;
178 __u32 entry_1, entry_2;
179 int error;
180 struct user_desc ldt_info;
181
182 error = -EINVAL;
183 if (bytecount != sizeof(ldt_info))
184 goto out;
185 error = -EFAULT;
186 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
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 >= 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
207 if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
208 if (oldmode || LDT_empty(&ldt_info)) {
209 entry_1 = 0;
210 entry_2 = 0;
211 goto install;
212 }
213 }
214
215 entry_1 = LDT_entry_a(&ldt_info);
216 entry_2 = LDT_entry_b(&ldt_info);
217 if (oldmode)
218 entry_2 &= ~(1 << 20);
219
220
221install:
222 write_ldt_entry(mm->context.ldt, ldt_info.entry_number, entry_1, entry_2);
223 error = 0;
224
225out_unlock:
226 up(&mm->context.sem);
227out:
228 return error;
229}
230
231asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
232{
233 int ret = -ENOSYS;
234
235 switch (func) {
236 case 0:
237 ret = read_ldt(ptr, bytecount);
238 break;
239 case 1:
240 ret = write_ldt(ptr, bytecount, 1);
241 break;
242 case 2:
243 ret = read_default_ldt(ptr, bytecount);
244 break;
245 case 0x11:
246 ret = write_ldt(ptr, bytecount, 0);
247 break;
248 }
249 return ret;
250}
251
