1/*
2 * linux/arch/x86_64/kernel/ldt.c
3 *
4 * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
5 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
6 * Copyright (C) 2002 Andi Kleen
7 *
8 * This handles calls from both 32bit and 64bit mode.
9 */
10
11#include <linux/errno.h>
12#include <linux/sched.h>
13#include <linux/string.h>
14#include <linux/mm.h>
15#include <linux/smp.h>
16#include <linux/vmalloc.h>
17#include <linux/slab.h>
18
19#include <asm/uaccess.h>
20#include <asm/system.h>
21#include <asm/ldt.h>
22#include <asm/desc.h>
23#include <asm/proto.h>
24
25#ifdef CONFIG_SMP     /* avoids "defined but not used" warnig */
26static void flush_ldt(void *null)
27{
28	if (current->active_mm)
29               load_LDT(&current->active_mm->context);
30}
31#endif
32
33static int alloc_ldt(mm_context_t *pc, unsigned mincount, int reload)
34{
35	void *oldldt;
36	void *newldt;
37	unsigned oldsize;
38
39	if (mincount <= (unsigned)pc->size)
40		return 0;
41	oldsize = pc->size;
42	mincount = (mincount+511)&(~511);
43	if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
44		newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
45	else
46		newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
47
48	if (!newldt)
49		return -ENOMEM;
50
51	if (oldsize)
52		memcpy(newldt, pc->ldt, oldsize*LDT_ENTRY_SIZE);
53	oldldt = pc->ldt;
54	memset(newldt+oldsize*LDT_ENTRY_SIZE, 0, (mincount-oldsize)*LDT_ENTRY_SIZE);
55	wmb();
56	pc->ldt = newldt;
57	wmb();
58	pc->size = mincount;
59	wmb();
60	if (reload) {
61#ifdef CONFIG_SMP
62		cpumask_t mask;
63
64		preempt_disable();
65		mask = cpumask_of_cpu(smp_processor_id());
66		load_LDT(pc);
67		if (!cpus_equal(current->mm->cpu_vm_mask, mask))
68			smp_call_function(flush_ldt, NULL, 1, 1);
69		preempt_enable();
70#else
71		load_LDT(pc);
72#endif
73	}
74	if (oldsize) {
75		if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
76			vfree(oldldt);
77		else
78			kfree(oldldt);
79	}
80	return 0;
81}
82
83static inline int copy_ldt(mm_context_t *new, mm_context_t *old)
84{
85	int err = alloc_ldt(new, old->size, 0);
86	if (err < 0)
87		return err;
88	memcpy(new->ldt, old->ldt, old->size*LDT_ENTRY_SIZE);
89	return 0;
90}
91
92/*
93 * we do not have to muck with descriptors here, that is
94 * done in switch_mm() as needed.
95 */
96int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
97{
98	struct mm_struct * old_mm;
99	int retval = 0;
100
101	init_MUTEX(&mm->context.sem);
102	mm->context.size = 0;
103	old_mm = current->mm;
104	if (old_mm && old_mm->context.size > 0) {
105		down(&old_mm->context.sem);
106		retval = copy_ldt(&mm->context, &old_mm->context);
107		up(&old_mm->context.sem);
108	}
109	return retval;
110}
111
112/*
113 *
114 * Don't touch the LDT register - we're already in the next thread.
115 */
116void destroy_context(struct mm_struct *mm)
117{
118	if (mm->context.size) {
119		if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
120			vfree(mm->context.ldt);
121		else
122			kfree(mm->context.ldt);
123		mm->context.size = 0;
124	}
125}
126
127static int read_ldt(void __user * ptr, unsigned long bytecount)
128{
129	int err;
130	unsigned long size;
131	struct mm_struct * mm = current->mm;
132
133	if (!mm->context.size)
134		return 0;
135	if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
136		bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
137
138	down(&mm->context.sem);
139	size = mm->context.size*LDT_ENTRY_SIZE;
140	if (size > bytecount)
141		size = bytecount;
142
143	err = 0;
144	if (copy_to_user(ptr, mm->context.ldt, size))
145		err = -EFAULT;
146	up(&mm->context.sem);
147	if (err < 0)
148		goto error_return;
149	if (size != bytecount) {
150		/* zero-fill the rest */
151		if (clear_user(ptr+size, bytecount-size) != 0) {
152			err = -EFAULT;
153			goto error_return;
154		}
155	}
156	return bytecount;
157error_return:
158	return err;
159}
160
161static int read_default_ldt(void __user * ptr, unsigned long bytecount)
162{
163	/* Arbitrary number */
164	/* x86-64 default LDT is all zeros */
165	if (bytecount > 128)
166		bytecount = 128;
167	if (clear_user(ptr, bytecount))
168		return -EFAULT;
169	return bytecount;
170}
171
172static int write_ldt(void __user * ptr, unsigned long bytecount, int oldmode)
173{
174	struct task_struct *me = current;
175	struct mm_struct * mm = me->mm;
176	__u32 entry_1, entry_2, *lp;
177	int error;
178	struct user_desc ldt_info;
179
180	error = -EINVAL;
181
182	if (bytecount != sizeof(ldt_info))
183		goto out;
184	error = -EFAULT;
185	if (copy_from_user(&ldt_info, ptr, bytecount))
186		goto out;
187
188	error = -EINVAL;
189	if (ldt_info.entry_number >= LDT_ENTRIES)
190		goto out;
191	if (ldt_info.contents == 3) {
192		if (oldmode)
193			goto out;
194		if (ldt_info.seg_not_present == 0)
195			goto out;
196	}
197
198	down(&mm->context.sem);
199	if (ldt_info.entry_number >= (unsigned)mm->context.size) {
200		error = alloc_ldt(&current->mm->context, ldt_info.entry_number+1, 1);
201		if (error < 0)
202			goto out_unlock;
203	}
204
205	lp = (__u32 *) ((ldt_info.entry_number << 3) + (char *) mm->context.ldt);
206
207   	/* Allow LDTs to be cleared by the user. */
208   	if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
209		if (oldmode || LDT_empty(&ldt_info)) {
210			entry_1 = 0;
211			entry_2 = 0;
212			goto install;
213		}
214	}
215
216	entry_1 = LDT_entry_a(&ldt_info);
217	entry_2 = LDT_entry_b(&ldt_info);
218	if (oldmode)
219		entry_2 &= ~(1 << 20);
220
221	/* Install the new entry ...  */
222install:
223	*lp	= entry_1;
224	*(lp+1)	= entry_2;
225	error = 0;
226
227out_unlock:
228	up(&mm->context.sem);
229out:
230	return error;
231}
232
233asmlinkage int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
234{
235	int ret = -ENOSYS;
236
237	switch (func) {
238	case 0:
239		ret = read_ldt(ptr, bytecount);
240		break;
241	case 1:
242		ret = write_ldt(ptr, bytecount, 1);
243		break;
244	case 2:
245		ret = read_default_ldt(ptr, bytecount);
246		break;
247	case 0x11:
248		ret = write_ldt(ptr, bytecount, 0);
249		break;
250	}
251	return ret;
252}
253