1 /*
2 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6 #include <linux/mm.h>
7 #include <linux/sched.h>
8 #include <linux/slab.h>
9 #include <linux/syscalls.h>
10 #include <linux/uaccess.h>
11 #include <asm/unistd.h>
12 #include <os.h>
13 #include <skas.h>
14 #include <sysdep/tls.h>
15
modify_ldt(int func,void * ptr,unsigned long bytecount)16 static inline int modify_ldt (int func, void *ptr, unsigned long bytecount)
17 {
18 return syscall(__NR_modify_ldt, func, ptr, bytecount);
19 }
20
write_ldt_entry(struct mm_id * mm_idp,int func,struct user_desc * desc,void ** addr,int done)21 static long write_ldt_entry(struct mm_id *mm_idp, int func,
22 struct user_desc *desc, void **addr, int done)
23 {
24 long res;
25 void *stub_addr;
26 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
27 (sizeof(*desc) + sizeof(long) - 1) &
28 ~(sizeof(long) - 1),
29 addr, &stub_addr);
30 if (!res) {
31 unsigned long args[] = { func,
32 (unsigned long)stub_addr,
33 sizeof(*desc),
34 0, 0, 0 };
35 res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
36 0, addr, done);
37 }
38
39 return res;
40 }
41
42 /*
43 * In skas mode, we hold our own ldt data in UML.
44 * Thus, the code implementing sys_modify_ldt_skas
45 * is very similar to (and mostly stolen from) sys_modify_ldt
46 * for arch/i386/kernel/ldt.c
47 * The routines copied and modified in part are:
48 * - read_ldt
49 * - read_default_ldt
50 * - write_ldt
51 * - sys_modify_ldt_skas
52 */
53
read_ldt(void __user * ptr,unsigned long bytecount)54 static int read_ldt(void __user * ptr, unsigned long bytecount)
55 {
56 int i, err = 0;
57 unsigned long size;
58 uml_ldt_t *ldt = ¤t->mm->context.arch.ldt;
59
60 if (!ldt->entry_count)
61 goto out;
62 if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
63 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
64 err = bytecount;
65
66 mutex_lock(&ldt->lock);
67 if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
68 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
69 if (size > bytecount)
70 size = bytecount;
71 if (copy_to_user(ptr, ldt->u.entries, size))
72 err = -EFAULT;
73 bytecount -= size;
74 ptr += size;
75 }
76 else {
77 for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
78 i++) {
79 size = PAGE_SIZE;
80 if (size > bytecount)
81 size = bytecount;
82 if (copy_to_user(ptr, ldt->u.pages[i], size)) {
83 err = -EFAULT;
84 break;
85 }
86 bytecount -= size;
87 ptr += size;
88 }
89 }
90 mutex_unlock(&ldt->lock);
91
92 if (bytecount == 0 || err == -EFAULT)
93 goto out;
94
95 if (clear_user(ptr, bytecount))
96 err = -EFAULT;
97
98 out:
99 return err;
100 }
101
read_default_ldt(void __user * ptr,unsigned long bytecount)102 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
103 {
104 int err;
105
106 if (bytecount > 5*LDT_ENTRY_SIZE)
107 bytecount = 5*LDT_ENTRY_SIZE;
108
109 err = bytecount;
110 /*
111 * UML doesn't support lcall7 and lcall27.
112 * So, we don't really have a default ldt, but emulate
113 * an empty ldt of common host default ldt size.
114 */
115 if (clear_user(ptr, bytecount))
116 err = -EFAULT;
117
118 return err;
119 }
120
write_ldt(void __user * ptr,unsigned long bytecount,int func)121 static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
122 {
123 uml_ldt_t *ldt = ¤t->mm->context.arch.ldt;
124 struct mm_id * mm_idp = ¤t->mm->context.id;
125 int i, err;
126 struct user_desc ldt_info;
127 struct ldt_entry entry0, *ldt_p;
128 void *addr = NULL;
129
130 err = -EINVAL;
131 if (bytecount != sizeof(ldt_info))
132 goto out;
133 err = -EFAULT;
134 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
135 goto out;
136
137 err = -EINVAL;
138 if (ldt_info.entry_number >= LDT_ENTRIES)
139 goto out;
140 if (ldt_info.contents == 3) {
141 if (func == 1)
142 goto out;
143 if (ldt_info.seg_not_present == 0)
144 goto out;
145 }
146
147 mutex_lock(&ldt->lock);
148
149 err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
150 if (err)
151 goto out_unlock;
152
153 if (ldt_info.entry_number >= ldt->entry_count &&
154 ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
155 for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
156 i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
157 i++) {
158 if (i == 0)
159 memcpy(&entry0, ldt->u.entries,
160 sizeof(entry0));
161 ldt->u.pages[i] = (struct ldt_entry *)
162 __get_free_page(GFP_KERNEL|__GFP_ZERO);
163 if (!ldt->u.pages[i]) {
164 err = -ENOMEM;
165 /* Undo the change in host */
166 memset(&ldt_info, 0, sizeof(ldt_info));
167 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
168 goto out_unlock;
169 }
170 if (i == 0) {
171 memcpy(ldt->u.pages[0], &entry0,
172 sizeof(entry0));
173 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
174 sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
175 }
176 ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
177 }
178 }
179 if (ldt->entry_count <= ldt_info.entry_number)
180 ldt->entry_count = ldt_info.entry_number + 1;
181
182 if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
183 ldt_p = ldt->u.entries + ldt_info.entry_number;
184 else
185 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
186 ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
187
188 if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
189 (func == 1 || LDT_empty(&ldt_info))) {
190 ldt_p->a = 0;
191 ldt_p->b = 0;
192 }
193 else{
194 if (func == 1)
195 ldt_info.useable = 0;
196 ldt_p->a = LDT_entry_a(&ldt_info);
197 ldt_p->b = LDT_entry_b(&ldt_info);
198 }
199 err = 0;
200
201 out_unlock:
202 mutex_unlock(&ldt->lock);
203 out:
204 return err;
205 }
206
do_modify_ldt_skas(int func,void __user * ptr,unsigned long bytecount)207 static long do_modify_ldt_skas(int func, void __user *ptr,
208 unsigned long bytecount)
209 {
210 int ret = -ENOSYS;
211
212 switch (func) {
213 case 0:
214 ret = read_ldt(ptr, bytecount);
215 break;
216 case 1:
217 case 0x11:
218 ret = write_ldt(ptr, bytecount, func);
219 break;
220 case 2:
221 ret = read_default_ldt(ptr, bytecount);
222 break;
223 }
224 return ret;
225 }
226
227 static DEFINE_SPINLOCK(host_ldt_lock);
228 static short dummy_list[9] = {0, -1};
229 static short * host_ldt_entries = NULL;
230
ldt_get_host_info(void)231 static void ldt_get_host_info(void)
232 {
233 long ret;
234 struct ldt_entry * ldt;
235 short *tmp;
236 int i, size, k, order;
237
238 spin_lock(&host_ldt_lock);
239
240 if (host_ldt_entries != NULL) {
241 spin_unlock(&host_ldt_lock);
242 return;
243 }
244 host_ldt_entries = dummy_list+1;
245
246 spin_unlock(&host_ldt_lock);
247
248 for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
249 ;
250
251 ldt = (struct ldt_entry *)
252 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
253 if (ldt == NULL) {
254 printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
255 "for host ldt\n");
256 return;
257 }
258
259 ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
260 if (ret < 0) {
261 printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
262 goto out_free;
263 }
264 if (ret == 0) {
265 /* default_ldt is active, simply write an empty entry 0 */
266 host_ldt_entries = dummy_list;
267 goto out_free;
268 }
269
270 for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
271 if (ldt[i].a != 0 || ldt[i].b != 0)
272 size++;
273 }
274
275 if (size < ARRAY_SIZE(dummy_list))
276 host_ldt_entries = dummy_list;
277 else {
278 size = (size + 1) * sizeof(dummy_list[0]);
279 tmp = kmalloc(size, GFP_KERNEL);
280 if (tmp == NULL) {
281 printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
282 "host ldt list\n");
283 goto out_free;
284 }
285 host_ldt_entries = tmp;
286 }
287
288 for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
289 if (ldt[i].a != 0 || ldt[i].b != 0)
290 host_ldt_entries[k++] = i;
291 }
292 host_ldt_entries[k] = -1;
293
294 out_free:
295 free_pages((unsigned long)ldt, order);
296 }
297
init_new_ldt(struct mm_context * new_mm,struct mm_context * from_mm)298 long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
299 {
300 struct user_desc desc;
301 short * num_p;
302 int i;
303 long page, err=0;
304 void *addr = NULL;
305
306
307 mutex_init(&new_mm->arch.ldt.lock);
308
309 if (!from_mm) {
310 memset(&desc, 0, sizeof(desc));
311 /*
312 * Now we try to retrieve info about the ldt, we
313 * inherited from the host. All ldt-entries found
314 * will be reset in the following loop
315 */
316 ldt_get_host_info();
317 for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
318 desc.entry_number = *num_p;
319 err = write_ldt_entry(&new_mm->id, 1, &desc,
320 &addr, *(num_p + 1) == -1);
321 if (err)
322 break;
323 }
324 new_mm->arch.ldt.entry_count = 0;
325
326 goto out;
327 }
328
329 /*
330 * Our local LDT is used to supply the data for
331 * modify_ldt(READLDT), if PTRACE_LDT isn't available,
332 * i.e., we have to use the stub for modify_ldt, which
333 * can't handle the big read buffer of up to 64kB.
334 */
335 mutex_lock(&from_mm->arch.ldt.lock);
336 if (from_mm->arch.ldt.entry_count <= LDT_DIRECT_ENTRIES)
337 memcpy(new_mm->arch.ldt.u.entries, from_mm->arch.ldt.u.entries,
338 sizeof(new_mm->arch.ldt.u.entries));
339 else {
340 i = from_mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
341 while (i-->0) {
342 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
343 if (!page) {
344 err = -ENOMEM;
345 break;
346 }
347 new_mm->arch.ldt.u.pages[i] =
348 (struct ldt_entry *) page;
349 memcpy(new_mm->arch.ldt.u.pages[i],
350 from_mm->arch.ldt.u.pages[i], PAGE_SIZE);
351 }
352 }
353 new_mm->arch.ldt.entry_count = from_mm->arch.ldt.entry_count;
354 mutex_unlock(&from_mm->arch.ldt.lock);
355
356 out:
357 return err;
358 }
359
360
free_ldt(struct mm_context * mm)361 void free_ldt(struct mm_context *mm)
362 {
363 int i;
364
365 if (mm->arch.ldt.entry_count > LDT_DIRECT_ENTRIES) {
366 i = mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
367 while (i-- > 0)
368 free_page((long) mm->arch.ldt.u.pages[i]);
369 }
370 mm->arch.ldt.entry_count = 0;
371 }
372
SYSCALL_DEFINE3(modify_ldt,int,func,void __user *,ptr,unsigned long,bytecount)373 SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr ,
374 unsigned long , bytecount)
375 {
376 /* See non-um modify_ldt() for why we do this cast */
377 return (unsigned int)do_modify_ldt_skas(func, ptr, bytecount);
378 }
379
