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
16static inline int modify_ldt (int func, void *ptr, unsigned long bytecount)
17{
18 return syscall(__NR_modify_ldt, func, ptr, bytecount);
19}
20
21static 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
27 BUILD_BUG_ON(sizeof(*desc) % sizeof(long));
28
29 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
30 sizeof(*desc) / sizeof(long),
31 addr, &stub_addr);
32 if (!res) {
33 unsigned long args[] = { func,
34 (unsigned long)stub_addr,
35 sizeof(*desc),
36 0, 0, 0 };
37 res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
38 0, addr, done);
39 }
40
41 return res;
42}
43
44/*
45 * In skas mode, we hold our own ldt data in UML.
46 * Thus, the code implementing sys_modify_ldt_skas
47 * is very similar to (and mostly stolen from) sys_modify_ldt
48 * for arch/i386/kernel/ldt.c
49 * The routines copied and modified in part are:
50 * - read_ldt
51 * - read_default_ldt
52 * - write_ldt
53 * - sys_modify_ldt_skas
54 */
55
56static int read_ldt(void __user * ptr, unsigned long bytecount)
57{
58 int i, err = 0;
59 unsigned long size;
60 uml_ldt_t *ldt = &current->mm->context.arch.ldt;
61
62 if (!ldt->entry_count)
63 goto out;
64 if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
65 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
66 err = bytecount;
67
68 mutex_lock(&ldt->lock);
69 if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
70 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
71 if (size > bytecount)
72 size = bytecount;
73 if (copy_to_user(to: ptr, from: ldt->u.entries, n: size))
74 err = -EFAULT;
75 bytecount -= size;
76 ptr += size;
77 }
78 else {
79 for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
80 i++) {
81 size = PAGE_SIZE;
82 if (size > bytecount)
83 size = bytecount;
84 if (copy_to_user(ptr, ldt->u.pages[i], size)) {
85 err = -EFAULT;
86 break;
87 }
88 bytecount -= size;
89 ptr += size;
90 }
91 }
92 mutex_unlock(lock: &ldt->lock);
93
94 if (bytecount == 0 || err == -EFAULT)
95 goto out;
96
97 if (clear_user(to: ptr, n: bytecount))
98 err = -EFAULT;
99
100out:
101 return err;
102}
103
104static int read_default_ldt(void __user * ptr, unsigned long bytecount)
105{
106 int err;
107
108 if (bytecount > 5*LDT_ENTRY_SIZE)
109 bytecount = 5*LDT_ENTRY_SIZE;
110
111 err = bytecount;
112 /*
113 * UML doesn't support lcall7 and lcall27.
114 * So, we don't really have a default ldt, but emulate
115 * an empty ldt of common host default ldt size.
116 */
117 if (clear_user(to: ptr, n: bytecount))
118 err = -EFAULT;
119
120 return err;
121}
122
123static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
124{
125 uml_ldt_t *ldt = &current->mm->context.arch.ldt;
126 struct mm_id * mm_idp = &current->mm->context.id;
127 int i, err;
128 struct user_desc ldt_info;
129 struct ldt_entry entry0, *ldt_p;
130 void *addr = NULL;
131
132 err = -EINVAL;
133 if (bytecount != sizeof(ldt_info))
134 goto out;
135 err = -EFAULT;
136 if (copy_from_user(to: &ldt_info, from: ptr, n: sizeof(ldt_info)))
137 goto out;
138
139 err = -EINVAL;
140 if (ldt_info.entry_number >= LDT_ENTRIES)
141 goto out;
142 if (ldt_info.contents == 3) {
143 if (func == 1)
144 goto out;
145 if (ldt_info.seg_not_present == 0)
146 goto out;
147 }
148
149 mutex_lock(&ldt->lock);
150
151 err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
152 if (err)
153 goto out_unlock;
154
155 if (ldt_info.entry_number >= ldt->entry_count &&
156 ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
157 for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
158 i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
159 i++) {
160 if (i == 0)
161 memcpy(&entry0, ldt->u.entries,
162 sizeof(entry0));
163 ldt->u.pages[i] = (struct ldt_entry *)
164 __get_free_page(GFP_KERNEL|__GFP_ZERO);
165 if (!ldt->u.pages[i]) {
166 err = -ENOMEM;
167 /* Undo the change in host */
168 memset(&ldt_info, 0, sizeof(ldt_info));
169 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
170 goto out_unlock;
171 }
172 if (i == 0) {
173 memcpy(ldt->u.pages[0], &entry0,
174 sizeof(entry0));
175 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
176 sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
177 }
178 ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
179 }
180 }
181 if (ldt->entry_count <= ldt_info.entry_number)
182 ldt->entry_count = ldt_info.entry_number + 1;
183
184 if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
185 ldt_p = ldt->u.entries + ldt_info.entry_number;
186 else
187 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
188 ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
189
190 if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
191 (func == 1 || LDT_empty(&ldt_info))) {
192 ldt_p->a = 0;
193 ldt_p->b = 0;
194 }
195 else{
196 if (func == 1)
197 ldt_info.useable = 0;
198 ldt_p->a = LDT_entry_a(&ldt_info);
199 ldt_p->b = LDT_entry_b(&ldt_info);
200 }
201 err = 0;
202
203out_unlock:
204 mutex_unlock(&ldt->lock);
205out:
206 return err;
207}
208
209static long do_modify_ldt_skas(int func, void __user *ptr,
210 unsigned long bytecount)
211{
212 int ret = -ENOSYS;
213
214 switch (func) {
215 case 0:
216 ret = read_ldt(ptr, bytecount);
217 break;
218 case 1:
219 case 0x11:
220 ret = write_ldt(ptr, bytecount, func);
221 break;
222 case 2:
223 ret = read_default_ldt(ptr, bytecount);
224 break;
225 }
226 return ret;
227}
228
229static DEFINE_SPINLOCK(host_ldt_lock);
230static short dummy_list[9] = {0, -1};
231static short * host_ldt_entries = NULL;
232
233static void ldt_get_host_info(void)
234{
235 long ret;
236 struct ldt_entry * ldt;
237 short *tmp;
238 int i, size, k, order;
239
240 spin_lock(lock: &host_ldt_lock);
241
242 if (host_ldt_entries != NULL) {
243 spin_unlock(lock: &host_ldt_lock);
244 return;
245 }
246 host_ldt_entries = dummy_list+1;
247
248 spin_unlock(lock: &host_ldt_lock);
249
250 for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
251 ;
252
253 ldt = (struct ldt_entry *)
254 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
255 if (ldt == NULL) {
256 printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
257 "for host ldt\n");
258 return;
259 }
260
261 ret = modify_ldt(func: 0, ptr: ldt, bytecount: (1<<order)*PAGE_SIZE);
262 if (ret < 0) {
263 printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
264 goto out_free;
265 }
266 if (ret == 0) {
267 /* default_ldt is active, simply write an empty entry 0 */
268 host_ldt_entries = dummy_list;
269 goto out_free;
270 }
271
272 for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
273 if (ldt[i].a != 0 || ldt[i].b != 0)
274 size++;
275 }
276
277 if (size < ARRAY_SIZE(dummy_list))
278 host_ldt_entries = dummy_list;
279 else {
280 size = (size + 1) * sizeof(dummy_list[0]);
281 tmp = kmalloc(size, GFP_KERNEL);
282 if (tmp == NULL) {
283 printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
284 "host ldt list\n");
285 goto out_free;
286 }
287 host_ldt_entries = tmp;
288 }
289
290 for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
291 if (ldt[i].a != 0 || ldt[i].b != 0)
292 host_ldt_entries[k++] = i;
293 }
294 host_ldt_entries[k] = -1;
295
296out_free:
297 free_pages(addr: (unsigned long)ldt, order);
298}
299
300long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
301{
302 struct user_desc desc;
303 short * num_p;
304 int i;
305 long page, err=0;
306 void *addr = NULL;
307
308
309 mutex_init(&new_mm->arch.ldt.lock);
310
311 if (!from_mm) {
312 memset(&desc, 0, sizeof(desc));
313 /*
314 * Now we try to retrieve info about the ldt, we
315 * inherited from the host. All ldt-entries found
316 * will be reset in the following loop
317 */
318 ldt_get_host_info();
319 for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
320 desc.entry_number = *num_p;
321 err = write_ldt_entry(dt: &new_mm->id, entry: 1, desc: &desc,
322 &addr, *(num_p + 1) == -1);
323 if (err)
324 break;
325 }
326 new_mm->arch.ldt.entry_count = 0;
327
328 goto out;
329 }
330
331 /*
332 * Our local LDT is used to supply the data for
333 * modify_ldt(READLDT), if PTRACE_LDT isn't available,
334 * i.e., we have to use the stub for modify_ldt, which
335 * can't handle the big read buffer of up to 64kB.
336 */
337 mutex_lock(&from_mm->arch.ldt.lock);
338 if (from_mm->arch.ldt.entry_count <= LDT_DIRECT_ENTRIES)
339 memcpy(new_mm->arch.ldt.u.entries, from_mm->arch.ldt.u.entries,
340 sizeof(new_mm->arch.ldt.u.entries));
341 else {
342 i = from_mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
343 while (i-->0) {
344 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
345 if (!page) {
346 err = -ENOMEM;
347 break;
348 }
349 new_mm->arch.ldt.u.pages[i] =
350 (struct ldt_entry *) page;
351 memcpy(new_mm->arch.ldt.u.pages[i],
352 from_mm->arch.ldt.u.pages[i], PAGE_SIZE);
353 }
354 }
355 new_mm->arch.ldt.entry_count = from_mm->arch.ldt.entry_count;
356 mutex_unlock(lock: &from_mm->arch.ldt.lock);
357
358 out:
359 return err;
360}
361
362
363void free_ldt(struct mm_context *mm)
364{
365 int i;
366
367 if (mm->arch.ldt.entry_count > LDT_DIRECT_ENTRIES) {
368 i = mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
369 while (i-- > 0)
370 free_page((long) mm->arch.ldt.u.pages[i]);
371 }
372 mm->arch.ldt.entry_count = 0;
373}
374
375SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr ,
376 unsigned long , bytecount)
377{
378 /* See non-um modify_ldt() for why we do this cast */
379 return (unsigned int)do_modify_ldt_skas(func, ptr, bytecount);
380}
381

source code of linux/arch/x86/um/ldt.c