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