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 <asm/unistd.h>
9 #include "os.h"
10 #include "proc_mm.h"
11 #include "skas.h"
12 #include "skas_ptrace.h"
13 #include "sysdep/tls.h"
14
15 extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
16
17 static long write_ldt_entry(struct mm_id *mm_idp, int func,
18 struct user_desc *desc, void **addr, int done)
19 {
20 long res;
21
22 if (proc_mm) {
23 /*
24 * This is a special handling for the case, that the mm to
25 * modify isn't current->active_mm.
26 * If this is called directly by modify_ldt,
27 * (current->active_mm->context.skas.u == mm_idp)
28 * will be true. So no call to __switch_mm(mm_idp) is done.
29 * If this is called in case of init_new_ldt or PTRACE_LDT,
30 * mm_idp won't belong to current->active_mm, but child->mm.
31 * So we need to switch child's mm into our userspace, then
32 * later switch back.
33 *
34 * Note: I'm unsure: should interrupts be disabled here?
35 */
36 if (!current->active_mm || current->active_mm == &init_mm ||
37 mm_idp != ¤t->active_mm->context.id)
38 __switch_mm(mm_idp);
39 }
40
41 if (ptrace_ldt) {
42 struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
43 .func = func,
44 .ptr = desc,
45 .bytecount = sizeof(*desc)};
46 u32 cpu;
47 int pid;
48
49 if (!proc_mm)
50 pid = mm_idp->u.pid;
51 else {
52 cpu = get_cpu();
53 pid = userspace_pid[cpu];
54 }
55
56 res = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);
57
58 if (proc_mm)
59 put_cpu();
60 }
61 else {
62 void *stub_addr;
63 res = syscall_stub_data(mm_idp, (unsigned long *)desc,
64 (sizeof(*desc) + sizeof(long) - 1) &
65 ~(sizeof(long) - 1),
66 addr, &stub_addr);
67 if (!res) {
68 unsigned long args[] = { func,
69 (unsigned long)stub_addr,
70 sizeof(*desc),
71 0, 0, 0 };
72 res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
73 0, addr, done);
74 }
75 }
76
77 if (proc_mm) {
78 /*
79 * This is the second part of special handling, that makes
80 * PTRACE_LDT possible to implement.
81 */
82 if (current->active_mm && current->active_mm != &init_mm &&
83 mm_idp != ¤t->active_mm->context.id)
84 __switch_mm(¤t->active_mm->context.id);
85 }
86
87 return res;
88 }
89
90 static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
91 {
92 int res, n;
93 struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
94 .func = 0,
95 .bytecount = bytecount,
96 .ptr = kmalloc(bytecount, GFP_KERNEL)};
97 u32 cpu;
98
99 if (ptrace_ldt.ptr == NULL)
100 return -ENOMEM;
101
102 /*
103 * This is called from sys_modify_ldt only, so userspace_pid gives
104 * us the right number
105 */
106
107 cpu = get_cpu();
108 res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
109 put_cpu();
110 if (res < 0)
111 goto out;
112
113 n = copy_to_user(ptr, ptrace_ldt.ptr, res);
114 if (n != 0)
115 res = -EFAULT;
116
117 out:
118 kfree(ptrace_ldt.ptr);
119
120 return res;
121 }
122
123 /*
124 * In skas mode, we hold our own ldt data in UML.
125 * Thus, the code implementing sys_modify_ldt_skas
126 * is very similar to (and mostly stolen from) sys_modify_ldt
127 * for arch/i386/kernel/ldt.c
128 * The routines copied and modified in part are:
129 * - read_ldt
130 * - read_default_ldt
131 * - write_ldt
132 * - sys_modify_ldt_skas
133 */
134
135 static int read_ldt(void __user * ptr, unsigned long bytecount)
136 {
137 int i, err = 0;
138 unsigned long size;
139 uml_ldt_t * ldt = ¤t->mm->context.ldt;
140
141 if (!ldt->entry_count)
142 goto out;
143 if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
144 bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
145 err = bytecount;
146
147 if (ptrace_ldt)
148 return read_ldt_from_host(ptr, bytecount);
149
150 mutex_lock(&ldt->lock);
151 if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
152 size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
153 if (size > bytecount)
154 size = bytecount;
155 if (copy_to_user(ptr, ldt->u.entries, size))
156 err = -EFAULT;
157 bytecount -= size;
158 ptr += size;
159 }
160 else {
161 for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
162 i++) {
163 size = PAGE_SIZE;
164 if (size > bytecount)
165 size = bytecount;
166 if (copy_to_user(ptr, ldt->u.pages[i], size)) {
167 err = -EFAULT;
168 break;
169 }
170 bytecount -= size;
171 ptr += size;
172 }
173 }
174 mutex_unlock(&ldt->lock);
175
176 if (bytecount == 0 || err == -EFAULT)
177 goto out;
178
179 if (clear_user(ptr, bytecount))
180 err = -EFAULT;
181
182 out:
183 return err;
184 }
185
186 static int read_default_ldt(void __user * ptr, unsigned long bytecount)
187 {
188 int err;
189
190 if (bytecount > 5*LDT_ENTRY_SIZE)
191 bytecount = 5*LDT_ENTRY_SIZE;
192
193 err = bytecount;
194 /*
195 * UML doesn't support lcall7 and lcall27.
196 * So, we don't really have a default ldt, but emulate
197 * an empty ldt of common host default ldt size.
198 */
199 if (clear_user(ptr, bytecount))
200 err = -EFAULT;
201
202 return err;
203 }
204
205 static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
206 {
207 uml_ldt_t * ldt = ¤t->mm->context.ldt;
208 struct mm_id * mm_idp = ¤t->mm->context.id;
209 int i, err;
210 struct user_desc ldt_info;
211 struct ldt_entry entry0, *ldt_p;
212 void *addr = NULL;
213
214 err = -EINVAL;
215 if (bytecount != sizeof(ldt_info))
216 goto out;
217 err = -EFAULT;
218 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
219 goto out;
220
221 err = -EINVAL;
222 if (ldt_info.entry_number >= LDT_ENTRIES)
223 goto out;
224 if (ldt_info.contents == 3) {
225 if (func == 1)
226 goto out;
227 if (ldt_info.seg_not_present == 0)
228 goto out;
229 }
230
231 if (!ptrace_ldt)
232 mutex_lock(&ldt->lock);
233
234 err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
235 if (err)
236 goto out_unlock;
237 else if (ptrace_ldt) {
238 /* With PTRACE_LDT available, this is used as a flag only */
239 ldt->entry_count = 1;
240 goto out;
241 }
242
243 if (ldt_info.entry_number >= ldt->entry_count &&
244 ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
245 for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
246 i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
247 i++) {
248 if (i == 0)
249 memcpy(&entry0, ldt->u.entries,
250 sizeof(entry0));
251 ldt->u.pages[i] = (struct ldt_entry *)
252 __get_free_page(GFP_KERNEL|__GFP_ZERO);
253 if (!ldt->u.pages[i]) {
254 err = -ENOMEM;
255 /* Undo the change in host */
256 memset(&ldt_info, 0, sizeof(ldt_info));
257 write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
258 goto out_unlock;
259 }
260 if (i == 0) {
261 memcpy(ldt->u.pages[0], &entry0,
262 sizeof(entry0));
263 memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
264 sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
265 }
266 ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
267 }
268 }
269 if (ldt->entry_count <= ldt_info.entry_number)
270 ldt->entry_count = ldt_info.entry_number + 1;
271
272 if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
273 ldt_p = ldt->u.entries + ldt_info.entry_number;
274 else
275 ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
276 ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
277
278 if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
279 (func == 1 || LDT_empty(&ldt_info))) {
280 ldt_p->a = 0;
281 ldt_p->b = 0;
282 }
283 else{
284 if (func == 1)
285 ldt_info.useable = 0;
286 ldt_p->a = LDT_entry_a(&ldt_info);
287 ldt_p->b = LDT_entry_b(&ldt_info);
288 }
289 err = 0;
290
291 out_unlock:
292 mutex_unlock(&ldt->lock);
293 out:
294 return err;
295 }
296
297 static long do_modify_ldt_skas(int func, void __user *ptr,
298 unsigned long bytecount)
299 {
300 int ret = -ENOSYS;
301
302 switch (func) {
303 case 0:
304 ret = read_ldt(ptr, bytecount);
305 break;
306 case 1:
307 case 0x11:
308 ret = write_ldt(ptr, bytecount, func);
309 break;
310 case 2:
311 ret = read_default_ldt(ptr, bytecount);
312 break;
313 }
314 return ret;
315 }
316
317 static DEFINE_SPINLOCK(host_ldt_lock);
318 static short dummy_list[9] = {0, -1};
319 static short * host_ldt_entries = NULL;
320
321 static void ldt_get_host_info(void)
322 {
323 long ret;
324 struct ldt_entry * ldt;
325 short *tmp;
326 int i, size, k, order;
327
328 spin_lock(&host_ldt_lock);
329
330 if (host_ldt_entries != NULL) {
331 spin_unlock(&host_ldt_lock);
332 return;
333 }
334 host_ldt_entries = dummy_list+1;
335
336 spin_unlock(&host_ldt_lock);
337
338 for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
339 ;
340
341 ldt = (struct ldt_entry *)
342 __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
343 if (ldt == NULL) {
344 printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
345 "for host ldt\n");
346 return;
347 }
348
349 ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
350 if (ret < 0) {
351 printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
352 goto out_free;
353 }
354 if (ret == 0) {
355 /* default_ldt is active, simply write an empty entry 0 */
356 host_ldt_entries = dummy_list;
357 goto out_free;
358 }
359
360 for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
361 if (ldt[i].a != 0 || ldt[i].b != 0)
362 size++;
363 }
364
365 if (size < ARRAY_SIZE(dummy_list))
366 host_ldt_entries = dummy_list;
367 else {
368 size = (size + 1) * sizeof(dummy_list[0]);
369 tmp = kmalloc(size, GFP_KERNEL);
370 if (tmp == NULL) {
371 printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
372 "host ldt list\n");
373 goto out_free;
374 }
375 host_ldt_entries = tmp;
376 }
377
378 for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
379 if (ldt[i].a != 0 || ldt[i].b != 0)
380 host_ldt_entries[k++] = i;
381 }
382 host_ldt_entries[k] = -1;
383
384 out_free:
385 free_pages((unsigned long)ldt, order);
386 }
387
388 long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
389 {
390 struct user_desc desc;
391 short * num_p;
392 int i;
393 long page, err=0;
394 void *addr = NULL;
395 struct proc_mm_op copy;
396
397
398 if (!ptrace_ldt)
399 mutex_init(&new_mm->ldt.lock);
400
401 if (!from_mm) {
402 memset(&desc, 0, sizeof(desc));
403 /*
404 * We have to initialize a clean ldt.
405 */
406 if (proc_mm) {
407 /*
408 * If the new mm was created using proc_mm, host's
409 * default-ldt currently is assigned, which normally
410 * contains the call-gates for lcall7 and lcall27.
411 * To remove these gates, we simply write an empty
412 * entry as number 0 to the host.
413 */
414 err = write_ldt_entry(&new_mm->id, 1, &desc, &addr, 1);
415 }
416 else{
417 /*
418 * Now we try to retrieve info about the ldt, we
419 * inherited from the host. All ldt-entries found
420 * will be reset in the following loop
421 */
422 ldt_get_host_info();
423 for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
424 desc.entry_number = *num_p;
425 err = write_ldt_entry(&new_mm->id, 1, &desc,
426 &addr, *(num_p + 1) == -1);
427 if (err)
428 break;
429 }
430 }
431 new_mm->ldt.entry_count = 0;
432
433 goto out;
434 }
435
436 if (proc_mm) {
437 /*
438 * We have a valid from_mm, so we now have to copy the LDT of
439 * from_mm to new_mm, because using proc_mm an new mm with
440 * an empty/default LDT was created in new_mm()
441 */
442 copy = ((struct proc_mm_op) { .op = MM_COPY_SEGMENTS,
443 .u =
444 { .copy_segments =
445 from_mm->id.u.mm_fd } } );
446 i = os_write_file(new_mm->id.u.mm_fd, ©, sizeof(copy));
447 if (i != sizeof(copy))
448 printk(KERN_ERR "new_mm : /proc/mm copy_segments "
449 "failed, err = %d\n", -i);
450 }
451
452 if (!ptrace_ldt) {
453 /*
454 * Our local LDT is used to supply the data for
455 * modify_ldt(READLDT), if PTRACE_LDT isn't available,
456 * i.e., we have to use the stub for modify_ldt, which
457 * can't handle the big read buffer of up to 64kB.
458 */
459 mutex_lock(&from_mm->ldt.lock);
460 if (from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES)
461 memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
462 sizeof(new_mm->ldt.u.entries));
463 else {
464 i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
465 while (i-->0) {
466 page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
467 if (!page) {
468 err = -ENOMEM;
469 break;
470 }
471 new_mm->ldt.u.pages[i] =
472 (struct ldt_entry *) page;
473 memcpy(new_mm->ldt.u.pages[i],
474 from_mm->ldt.u.pages[i], PAGE_SIZE);
475 }
476 }
477 new_mm->ldt.entry_count = from_mm->ldt.entry_count;
478 mutex_unlock(&from_mm->ldt.lock);
479 }
480
481 out:
482 return err;
483 }
484
485
486 void free_ldt(struct mm_context *mm)
487 {
488 int i;
489
490 if (!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES) {
491 i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
492 while (i-- > 0)
493 free_page((long) mm->ldt.u.pages[i]);
494 }
495 mm->ldt.entry_count = 0;
496 }
497
498 int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
499 {
500 return do_modify_ldt_skas(func, ptr, bytecount);
501 }
502
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