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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
24static 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
31static 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
88static 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 */
105int 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 */
126void 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
143static 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;
173error_return:
174 return err;
175}
176
177static 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
192static 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 fill_ldt(&ldt, &ldt_info);
233 if (oldmode)
234 ldt.avl = 0;
235
236 /* Install the new entry ... */
237install:
238 write_ldt_entry(mm->context.ldt, ldt_info.entry_number, &ldt);
239 error = 0;
240
241out_unlock:
242 mutex_unlock(&mm->context.lock);
243out:
244 return error;
245}
246
247asmlinkage int sys_modify_ldt(int func, void __user *ptr,
248 unsigned long bytecount)
249{
250 int ret = -ENOSYS;
251
252 switch (func) {
253 case 0:
254 ret = read_ldt(ptr, bytecount);
255 break;
256 case 1:
257 ret = write_ldt(ptr, bytecount, 1);
258 break;
259 case 2:
260 ret = read_default_ldt(ptr, bytecount);
261 break;
262 case 0x11:
263 ret = write_ldt(ptr, bytecount, 0);
264 break;
265 }
266 return ret;
267}
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/slab.h>
16#include <linux/vmalloc.h>
17#include <linux/uaccess.h>
18
19#include <asm/ldt.h>
20#include <asm/desc.h>
21#include <asm/mmu_context.h>
22#include <asm/syscalls.h>
23
24/* context.lock is held for us, so we don't need any locking. */
25static void flush_ldt(void *current_mm)
26{
27 mm_context_t *pc;
28
29 if (current->active_mm != current_mm)
30 return;
31
32 pc = ¤t->active_mm->context;
33 set_ldt(pc->ldt->entries, pc->ldt->size);
34}
35
36/* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
37static struct ldt_struct *alloc_ldt_struct(int size)
38{
39 struct ldt_struct *new_ldt;
40 int alloc_size;
41
42 if (size > LDT_ENTRIES)
43 return NULL;
44
45 new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL);
46 if (!new_ldt)
47 return NULL;
48
49 BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct));
50 alloc_size = size * LDT_ENTRY_SIZE;
51
52 /*
53 * Xen is very picky: it requires a page-aligned LDT that has no
54 * trailing nonzero bytes in any page that contains LDT descriptors.
55 * Keep it simple: zero the whole allocation and never allocate less
56 * than PAGE_SIZE.
57 */
58 if (alloc_size > PAGE_SIZE)
59 new_ldt->entries = vzalloc(alloc_size);
60 else
61 new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL);
62
63 if (!new_ldt->entries) {
64 kfree(new_ldt);
65 return NULL;
66 }
67
68 new_ldt->size = size;
69 return new_ldt;
70}
71
72/* After calling this, the LDT is immutable. */
73static void finalize_ldt_struct(struct ldt_struct *ldt)
74{
75 paravirt_alloc_ldt(ldt->entries, ldt->size);
76}
77
78/* context.lock is held */
79static void install_ldt(struct mm_struct *current_mm,
80 struct ldt_struct *ldt)
81{
82 /* Synchronizes with lockless_dereference in load_mm_ldt. */
83 smp_store_release(¤t_mm->context.ldt, ldt);
84
85 /* Activate the LDT for all CPUs using current_mm. */
86 on_each_cpu_mask(mm_cpumask(current_mm), flush_ldt, current_mm, true);
87}
88
89static void free_ldt_struct(struct ldt_struct *ldt)
90{
91 if (likely(!ldt))
92 return;
93
94 paravirt_free_ldt(ldt->entries, ldt->size);
95 if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE)
96 vfree(ldt->entries);
97 else
98 free_page((unsigned long)ldt->entries);
99 kfree(ldt);
100}
101
102/*
103 * we do not have to muck with descriptors here, that is
104 * done in switch_mm() as needed.
105 */
106int init_new_context_ldt(struct task_struct *tsk, struct mm_struct *mm)
107{
108 struct ldt_struct *new_ldt;
109 struct mm_struct *old_mm;
110 int retval = 0;
111
112 mutex_init(&mm->context.lock);
113 old_mm = current->mm;
114 if (!old_mm) {
115 mm->context.ldt = NULL;
116 return 0;
117 }
118
119 mutex_lock(&old_mm->context.lock);
120 if (!old_mm->context.ldt) {
121 mm->context.ldt = NULL;
122 goto out_unlock;
123 }
124
125 new_ldt = alloc_ldt_struct(old_mm->context.ldt->size);
126 if (!new_ldt) {
127 retval = -ENOMEM;
128 goto out_unlock;
129 }
130
131 memcpy(new_ldt->entries, old_mm->context.ldt->entries,
132 new_ldt->size * LDT_ENTRY_SIZE);
133 finalize_ldt_struct(new_ldt);
134
135 mm->context.ldt = new_ldt;
136
137out_unlock:
138 mutex_unlock(&old_mm->context.lock);
139 return retval;
140}
141
142/*
143 * No need to lock the MM as we are the last user
144 *
145 * 64bit: Don't touch the LDT register - we're already in the next thread.
146 */
147void destroy_context_ldt(struct mm_struct *mm)
148{
149 free_ldt_struct(mm->context.ldt);
150 mm->context.ldt = NULL;
151}
152
153static int read_ldt(void __user *ptr, unsigned long bytecount)
154{
155 int retval;
156 unsigned long size;
157 struct mm_struct *mm = current->mm;
158
159 mutex_lock(&mm->context.lock);
160
161 if (!mm->context.ldt) {
162 retval = 0;
163 goto out_unlock;
164 }
165
166 if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
167 bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
168
169 size = mm->context.ldt->size * LDT_ENTRY_SIZE;
170 if (size > bytecount)
171 size = bytecount;
172
173 if (copy_to_user(ptr, mm->context.ldt->entries, size)) {
174 retval = -EFAULT;
175 goto out_unlock;
176 }
177
178 if (size != bytecount) {
179 /* Zero-fill the rest and pretend we read bytecount bytes. */
180 if (clear_user(ptr + size, bytecount - size)) {
181 retval = -EFAULT;
182 goto out_unlock;
183 }
184 }
185 retval = bytecount;
186
187out_unlock:
188 mutex_unlock(&mm->context.lock);
189 return retval;
190}
191
192static int read_default_ldt(void __user *ptr, unsigned long bytecount)
193{
194 /* CHECKME: Can we use _one_ random number ? */
195#ifdef CONFIG_X86_32
196 unsigned long size = 5 * sizeof(struct desc_struct);
197#else
198 unsigned long size = 128;
199#endif
200 if (bytecount > size)
201 bytecount = size;
202 if (clear_user(ptr, bytecount))
203 return -EFAULT;
204 return bytecount;
205}
206
207static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
208{
209 struct mm_struct *mm = current->mm;
210 struct desc_struct ldt;
211 int error;
212 struct user_desc ldt_info;
213 int oldsize, newsize;
214 struct ldt_struct *new_ldt, *old_ldt;
215
216 error = -EINVAL;
217 if (bytecount != sizeof(ldt_info))
218 goto out;
219 error = -EFAULT;
220 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
221 goto out;
222
223 error = -EINVAL;
224 if (ldt_info.entry_number >= LDT_ENTRIES)
225 goto out;
226 if (ldt_info.contents == 3) {
227 if (oldmode)
228 goto out;
229 if (ldt_info.seg_not_present == 0)
230 goto out;
231 }
232
233 if ((oldmode && !ldt_info.base_addr && !ldt_info.limit) ||
234 LDT_empty(&ldt_info)) {
235 /* The user wants to clear the entry. */
236 memset(&ldt, 0, sizeof(ldt));
237 } else {
238 if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) {
239 error = -EINVAL;
240 goto out;
241 }
242
243 fill_ldt(&ldt, &ldt_info);
244 if (oldmode)
245 ldt.avl = 0;
246 }
247
248 mutex_lock(&mm->context.lock);
249
250 old_ldt = mm->context.ldt;
251 oldsize = old_ldt ? old_ldt->size : 0;
252 newsize = max((int)(ldt_info.entry_number + 1), oldsize);
253
254 error = -ENOMEM;
255 new_ldt = alloc_ldt_struct(newsize);
256 if (!new_ldt)
257 goto out_unlock;
258
259 if (old_ldt)
260 memcpy(new_ldt->entries, old_ldt->entries, oldsize * LDT_ENTRY_SIZE);
261 new_ldt->entries[ldt_info.entry_number] = ldt;
262 finalize_ldt_struct(new_ldt);
263
264 install_ldt(mm, new_ldt);
265 free_ldt_struct(old_ldt);
266 error = 0;
267
268out_unlock:
269 mutex_unlock(&mm->context.lock);
270out:
271 return error;
272}
273
274asmlinkage int sys_modify_ldt(int func, void __user *ptr,
275 unsigned long bytecount)
276{
277 int ret = -ENOSYS;
278
279 switch (func) {
280 case 0:
281 ret = read_ldt(ptr, bytecount);
282 break;
283 case 1:
284 ret = write_ldt(ptr, bytecount, 1);
285 break;
286 case 2:
287 ret = read_default_ldt(ptr, bytecount);
288 break;
289 case 0x11:
290 ret = write_ldt(ptr, bytecount, 0);
291 break;
292 }
293 return ret;
294}