aboutsummaryrefslogtreecommitdiffstats
path: root/arch/um/sys-i386/ldt.c
blob: 67c0958eb984266e7e59eaf682754b3c25746642 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
/*
 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include "linux/mm.h"
#include "asm/unistd.h"
#include "os.h"
#include "proc_mm.h"
#include "skas.h"
#include "skas_ptrace.h"
#include "sysdep/tls.h"

extern int modify_ldt(int func, void *ptr, unsigned long bytecount);

long write_ldt_entry(struct mm_id * mm_idp, int func, struct user_desc * desc,
		     void **addr, int done)
{
	long res;

	if (proc_mm) {
		/*
		 * This is a special handling for the case, that the mm to
		 * modify isn't current->active_mm.
		 * If this is called directly by modify_ldt,
		 *     (current->active_mm->context.skas.u == mm_idp)
		 * will be true. So no call to __switch_mm(mm_idp) is done.
		 * If this is called in case of init_new_ldt or PTRACE_LDT,
		 * mm_idp won't belong to current->active_mm, but child->mm.
		 * So we need to switch child's mm into our userspace, then
		 * later switch back.
		 *
		 * Note: I'm unsure: should interrupts be disabled here?
		 */
		if (!current->active_mm || current->active_mm == &init_mm ||
		    mm_idp != &current->active_mm->context.id)
			__switch_mm(mm_idp);
	}

	if (ptrace_ldt) {
		struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
			.func = func,
			.ptr = desc,
			.bytecount = sizeof(*desc)};
		u32 cpu;
		int pid;

		if (!proc_mm)
			pid = mm_idp->u.pid;
		else {
			cpu = get_cpu();
			pid = userspace_pid[cpu];
		}

		res = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);

		if (proc_mm)
			put_cpu();
	}
	else {
		void *stub_addr;
		res = syscall_stub_data(mm_idp, (unsigned long *)desc,
					(sizeof(*desc) + sizeof(long) - 1) &
					    ~(sizeof(long) - 1),
					addr, &stub_addr);
		if (!res) {
			unsigned long args[] = { func,
						 (unsigned long)stub_addr,
						 sizeof(*desc),
						 0, 0, 0 };
			res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
					       0, addr, done);
		}
	}

	if (proc_mm) {
		/*
		 * This is the second part of special handling, that makes
		 * PTRACE_LDT possible to implement.
		 */
		if (current->active_mm && current->active_mm != &init_mm &&
		    mm_idp != &current->active_mm->context.id)
			__switch_mm(&current->active_mm->context.id);
	}

	return res;
}

static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
{
	int res, n;
	struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
			.func = 0,
			.bytecount = bytecount,
			.ptr = kmalloc(bytecount, GFP_KERNEL)};
	u32 cpu;

	if (ptrace_ldt.ptr == NULL)
		return -ENOMEM;

	/*
	 * This is called from sys_modify_ldt only, so userspace_pid gives
	 * us the right number
	 */

	cpu = get_cpu();
	res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
	put_cpu();
	if (res < 0)
		goto out;

	n = copy_to_user(ptr, ptrace_ldt.ptr, res);
	if (n != 0)
		res = -EFAULT;

  out:
	kfree(ptrace_ldt.ptr);

	return res;
}

/*
 * In skas mode, we hold our own ldt data in UML.
 * Thus, the code implementing sys_modify_ldt_skas
 * is very similar to (and mostly stolen from) sys_modify_ldt
 * for arch/i386/kernel/ldt.c
 * The routines copied and modified in part are:
 * - read_ldt
 * - read_default_ldt
 * - write_ldt
 * - sys_modify_ldt_skas
 */

static int read_ldt(void __user * ptr, unsigned long bytecount)
{
	int i, err = 0;
	unsigned long size;
	uml_ldt_t * ldt = &current->mm->context.ldt;

	if (!ldt->entry_count)
		goto out;
	if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
		bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
	err = bytecount;

	if (ptrace_ldt)
		return read_ldt_from_host(ptr, bytecount);

	down(&ldt->semaphore);
	if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
		size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
		if (size > bytecount)
			size = bytecount;
		if (copy_to_user(ptr, ldt->u.entries, size))
			err = -EFAULT;
		bytecount -= size;
		ptr += size;
	}
	else {
		for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
		     i++) {
			size = PAGE_SIZE;
			if (size > bytecount)
				size = bytecount;
			if (copy_to_user(ptr, ldt->u.pages[i], size)) {
				err = -EFAULT;
				break;
			}
			bytecount -= size;
			ptr += size;
		}
	}
	up(&ldt->semaphore);

	if (bytecount == 0 || err == -EFAULT)
		goto out;

	if (clear_user(ptr, bytecount))
		err = -EFAULT;

out:
	return err;
}

static int read_default_ldt(void __user * ptr, unsigned long bytecount)
{
	int err;

	if (bytecount > 5*LDT_ENTRY_SIZE)
		bytecount = 5*LDT_ENTRY_SIZE;

	err = bytecount;
	/*
	 * UML doesn't support lcall7 and lcall27.
	 * So, we don't really have a default ldt, but emulate
	 * an empty ldt of common host default ldt size.
	 */
	if (clear_user(ptr, bytecount))
		err = -EFAULT;

	return err;
}

static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
{
	uml_ldt_t * ldt = &current->mm->context.ldt;
	struct mm_id * mm_idp = &current->mm->context.id;
	int i, err;
	struct user_desc ldt_info;
	struct ldt_entry entry0, *ldt_p;
	void *addr = NULL;

	err = -EINVAL;
	if (bytecount != sizeof(ldt_info))
		goto out;
	err = -EFAULT;
	if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
		goto out;

	err = -EINVAL;
	if (ldt_info.entry_number >= LDT_ENTRIES)
		goto out;
	if (ldt_info.contents == 3) {
		if (func == 1)
			goto out;
		if (ldt_info.seg_not_present == 0)
			goto out;
	}

	if (!ptrace_ldt)
		down(&ldt->semaphore);

	err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
	if (err)
		goto out_unlock;
	else if (ptrace_ldt) {
		/* With PTRACE_LDT available, this is used as a flag only */
		ldt->entry_count = 1;
		goto out;
	}

	if (ldt_info.entry_number >= ldt->entry_count &&
	    ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
		for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
		     i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
		     i++) {
			if (i == 0)
				memcpy(&entry0, ldt->u.entries,
				       sizeof(entry0));
			ldt->u.pages[i] = (struct ldt_entry *)
				__get_free_page(GFP_KERNEL|__GFP_ZERO);
			if (!ldt->u.pages[i]) {
				err = -ENOMEM;
				/* Undo the change in host */
				memset(&ldt_info, 0, sizeof(ldt_info));
				write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
				goto out_unlock;
			}
			if (i == 0) {
				memcpy(ldt->u.pages[0], &entry0,
				       sizeof(entry0));
				memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
				       sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
			}
			ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
		}
	}
	if (ldt->entry_count <= ldt_info.entry_number)
		ldt->entry_count = ldt_info.entry_number + 1;

	if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
		ldt_p = ldt->u.entries + ldt_info.entry_number;
	else
		ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
			ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;

	if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
	   (func == 1 || LDT_empty(&ldt_info))) {
		ldt_p->a = 0;
		ldt_p->b = 0;
	}
	else{
		if (func == 1)
			ldt_info.useable = 0;
		ldt_p->a = LDT_entry_a(&ldt_info);
		ldt_p->b = LDT_entry_b(&ldt_info);
	}
	err = 0;

out_unlock:
	up(&ldt->semaphore);
out:
	return err;
}

static long do_modify_ldt_skas(int func, void __user *ptr,
			       unsigned long bytecount)
{
	int ret = -ENOSYS;

	switch (func) {
		case 0:
			ret = read_ldt(ptr, bytecount);
			break;
		case 1:
		case 0x11:
			ret = write_ldt(ptr, bytecount, func);
			break;
		case 2:
			ret = read_default_ldt(ptr, bytecount);
			break;
	}
	return ret;
}

static DEFINE_SPINLOCK(host_ldt_lock);
static short dummy_list[9] = {0, -1};
static short * host_ldt_entries = NULL;

static void ldt_get_host_info(void)
{
	long ret;
	struct ldt_entry * ldt;
	short *tmp;
	int i, size, k, order;

	spin_lock(&host_ldt_lock);

	if (host_ldt_entries != NULL) {
		spin_unlock(&host_ldt_lock);
		return;
	}
	host_ldt_entries = dummy_list+1;

	spin_unlock(&host_ldt_lock);

	for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
		;

	ldt = (struct ldt_entry *)
	      __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
	if (ldt == NULL) {
		printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
		       "for host ldt\n");
		return;
	}

	ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
	if (ret < 0) {
		printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
		goto out_free;
	}
	if (ret == 0) {
		/* default_ldt is active, simply write an empty entry 0 */
		host_ldt_entries = dummy_list;
		goto out_free;
	}

	for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
		if (ldt[i].a != 0 || ldt[i].b != 0)
			size++;
	}

	if (size < ARRAY_SIZE(dummy_list))
		host_ldt_entries = dummy_list;
	else {
		size = (size + 1) * sizeof(dummy_list[0]);
		tmp = kmalloc(size, GFP_KERNEL);
		if (tmp == NULL) {
			printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
			       "host ldt list\n");
			goto out_free;
		}
		host_ldt_entries = tmp;
	}

	for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
		if (ldt[i].a != 0 || ldt[i].b != 0)
			host_ldt_entries[k++] = i;
	}
	host_ldt_entries[k] = -1;

out_free:
	free_pages((unsigned long)ldt, order);
}

long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
{
	struct user_desc desc;
	short * num_p;
	int i;
	long page, err=0;
	void *addr = NULL;
	struct proc_mm_op copy;


	if (!ptrace_ldt)
		init_MUTEX(&new_mm->ldt.semaphore);

	if (!from_mm) {
		memset(&desc, 0, sizeof(desc));
		/*
		 * We have to initialize a clean ldt.
		 */
		if (proc_mm) {
			/*
			 * If the new mm was created using proc_mm, host's
			 * default-ldt currently is assigned, which normally
			 * contains the call-gates for lcall7 and lcall27.
			 * To remove these gates, we simply write an empty
			 * entry as number 0 to the host.
			 */
			err = write_ldt_entry(&new_mm->id, 1, &desc, &addr, 1);
		}
		else{
			/*
			 * Now we try to retrieve info about the ldt, we
			 * inherited from the host. All ldt-entries found
			 * will be reset in the following loop
			 */
			ldt_get_host_info();
			for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
				desc.entry_number = *num_p;
				err = write_ldt_entry(&new_mm->id, 1, &desc,
						      &addr, *(num_p + 1) == -1);
				if (err)
					break;
			}
		}
		new_mm->ldt.entry_count = 0;

		goto out;
	}

	if (proc_mm) {
		/*
		 * We have a valid from_mm, so we now have to copy the LDT of
		 * from_mm to new_mm, because using proc_mm an new mm with
		 * an empty/default LDT was created in new_mm()
		 */
		copy = ((struct proc_mm_op) { .op 	= MM_COPY_SEGMENTS,
					      .u 	=
					      { .copy_segments =
							from_mm->id.u.mm_fd } } );
		i = os_write_file(new_mm->id.u.mm_fd, &copy, sizeof(copy));
		if (i != sizeof(copy))
			printk(KERN_ERR "new_mm : /proc/mm copy_segments "
			       "failed, err = %d\n", -i);
	}

	if (!ptrace_ldt) {
		/*
		 * Our local LDT is used to supply the data for
		 * modify_ldt(READLDT), if PTRACE_LDT isn't available,
		 * i.e., we have to use the stub for modify_ldt, which
		 * can't handle the big read buffer of up to 64kB.
		 */
		down(&from_mm->ldt.semaphore);
		if (from_mm->ldt.entry_count <= LDT_DIRECT_ENTRIES)
			memcpy(new_mm->ldt.u.entries, from_mm->ldt.u.entries,
			       sizeof(new_mm->ldt.u.entries));
		else {
			i = from_mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
			while (i-->0) {
				page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
				if (!page) {
					err = -ENOMEM;
					break;
				}
				new_mm->ldt.u.pages[i] =
					(struct ldt_entry *) page;
				memcpy(new_mm->ldt.u.pages[i],
				       from_mm->ldt.u.pages[i], PAGE_SIZE);
			}
		}
		new_mm->ldt.entry_count = from_mm->ldt.entry_count;
		up(&from_mm->ldt.semaphore);
	}

    out:
	return err;
}


void free_ldt(struct mm_context *mm)
{
	int i;

	if (!ptrace_ldt && mm->ldt.entry_count > LDT_DIRECT_ENTRIES) {
		i = mm->ldt.entry_count / LDT_ENTRIES_PER_PAGE;
		while (i-- > 0)
			free_page((long) mm->ldt.u.pages[i]);
	}
	mm->ldt.entry_count = 0;
}

int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
{
	return do_modify_ldt_skas(func, ptr, bytecount);
}