1/*
2 *	linux/mm/mlock.c
3 *
4 *  (C) Copyright 1995 Linus Torvalds
5 *  (C) Copyright 2002 Christoph Hellwig
6 */
7
8#include <linux/capability.h>
9#include <linux/mman.h>
10#include <linux/mm.h>
11#include <linux/mempolicy.h>
12#include <linux/syscalls.h>
13#include <linux/sched.h>
14#include <linux/module.h>
15
16int can_do_mlock(void)
17{
18	if (capable(CAP_IPC_LOCK))
19		return 1;
20	if (current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur != 0)
21		return 1;
22	return 0;
23}
24EXPORT_SYMBOL(can_do_mlock);
25
26static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
27	unsigned long start, unsigned long end, unsigned int newflags)
28{
29	struct mm_struct * mm = vma->vm_mm;
30	pgoff_t pgoff;
31	int pages;
32	int ret = 0;
33
34	if (newflags == vma->vm_flags) {
35		*prev = vma;
36		goto out;
37	}
38
39	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
40	*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
41			  vma->vm_file, pgoff, vma_policy(vma));
42	if (*prev) {
43		vma = *prev;
44		goto success;
45	}
46
47	*prev = vma;
48
49	if (start != vma->vm_start) {
50		ret = split_vma(mm, vma, start, 1);
51		if (ret)
52			goto out;
53	}
54
55	if (end != vma->vm_end) {
56		ret = split_vma(mm, vma, end, 0);
57		if (ret)
58			goto out;
59	}
60
61success:
62	/*
63	 * vm_flags is protected by the mmap_sem held in write mode.
64	 * It's okay if try_to_unmap_one unmaps a page just after we
65	 * set VM_LOCKED, make_pages_present below will bring it back.
66	 */
67	vma->vm_flags = newflags;
68
69	/*
70	 * Keep track of amount of locked VM.
71	 */
72	pages = (end - start) >> PAGE_SHIFT;
73	if (newflags & VM_LOCKED) {
74		pages = -pages;
75		if (!(newflags & VM_IO))
76			ret = make_pages_present(start, end);
77	}
78
79	mm->locked_vm -= pages;
80out:
81	if (ret == -ENOMEM)
82		ret = -EAGAIN;
83	return ret;
84}
85
86static int do_mlock(unsigned long start, size_t len, int on)
87{
88	unsigned long nstart, end, tmp;
89	struct vm_area_struct * vma, * prev;
90	int error;
91
92	len = PAGE_ALIGN(len);
93	end = start + len;
94	if (end < start)
95		return -EINVAL;
96	if (end == start)
97		return 0;
98	vma = find_vma_prev(current->mm, start, &prev);
99	if (!vma || vma->vm_start > start)
100		return -ENOMEM;
101
102	if (start > vma->vm_start)
103		prev = vma;
104
105	for (nstart = start ; ; ) {
106		unsigned int newflags;
107
108		/* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
109
110		newflags = vma->vm_flags | VM_LOCKED;
111		if (!on)
112			newflags &= ~VM_LOCKED;
113
114		tmp = vma->vm_end;
115		if (tmp > end)
116			tmp = end;
117		error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
118		if (error)
119			break;
120		nstart = tmp;
121		if (nstart < prev->vm_end)
122			nstart = prev->vm_end;
123		if (nstart >= end)
124			break;
125
126		vma = prev->vm_next;
127		if (!vma || vma->vm_start != nstart) {
128			error = -ENOMEM;
129			break;
130		}
131	}
132	return error;
133}
134
135asmlinkage long sys_mlock(unsigned long start, size_t len)
136{
137	unsigned long locked;
138	unsigned long lock_limit;
139	int error = -ENOMEM;
140
141	if (!can_do_mlock())
142		return -EPERM;
143
144	down_write(&current->mm->mmap_sem);
145	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
146	start &= PAGE_MASK;
147
148	locked = len >> PAGE_SHIFT;
149	locked += current->mm->locked_vm;
150
151	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
152	lock_limit >>= PAGE_SHIFT;
153
154	/* check against resource limits */
155	if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
156		error = do_mlock(start, len, 1);
157	up_write(&current->mm->mmap_sem);
158	return error;
159}
160
161asmlinkage long sys_munlock(unsigned long start, size_t len)
162{
163	int ret;
164
165	down_write(&current->mm->mmap_sem);
166	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
167	start &= PAGE_MASK;
168	ret = do_mlock(start, len, 0);
169	up_write(&current->mm->mmap_sem);
170	return ret;
171}
172
173static int do_mlockall(int flags)
174{
175	struct vm_area_struct * vma, * prev = NULL;
176	unsigned int def_flags = 0;
177
178	if (flags & MCL_FUTURE)
179		def_flags = VM_LOCKED;
180	current->mm->def_flags = def_flags;
181	if (flags == MCL_FUTURE)
182		goto out;
183
184	for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
185		unsigned int newflags;
186
187		newflags = vma->vm_flags | VM_LOCKED;
188		if (!(flags & MCL_CURRENT))
189			newflags &= ~VM_LOCKED;
190
191		/* Ignore errors */
192		mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
193	}
194out:
195	return 0;
196}
197
198asmlinkage long sys_mlockall(int flags)
199{
200	unsigned long lock_limit;
201	int ret = -EINVAL;
202
203	if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
204		goto out;
205
206	ret = -EPERM;
207	if (!can_do_mlock())
208		goto out;
209
210	down_write(&current->mm->mmap_sem);
211
212	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
213	lock_limit >>= PAGE_SHIFT;
214
215	ret = -ENOMEM;
216	if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
217	    capable(CAP_IPC_LOCK))
218		ret = do_mlockall(flags);
219	up_write(&current->mm->mmap_sem);
220out:
221	return ret;
222}
223
224asmlinkage long sys_munlockall(void)
225{
226	int ret;
227
228	down_write(&current->mm->mmap_sem);
229	ret = do_mlockall(0);
230	up_write(&current->mm->mmap_sem);
231	return ret;
232}
233
234/*
235 * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
236 * shm segments) get accounted against the user_struct instead.
237 */
238static DEFINE_SPINLOCK(shmlock_user_lock);
239
240int user_shm_lock(size_t size, struct user_struct *user)
241{
242	unsigned long lock_limit, locked;
243	int allowed = 0;
244
245	locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
246	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
247	lock_limit >>= PAGE_SHIFT;
248	spin_lock(&shmlock_user_lock);
249	if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
250		goto out;
251	get_uid(user);
252	user->locked_shm += locked;
253	allowed = 1;
254out:
255	spin_unlock(&shmlock_user_lock);
256	return allowed;
257}
258
259void user_shm_unlock(size_t size, struct user_struct *user)
260{
261	spin_lock(&shmlock_user_lock);
262	user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
263	spin_unlock(&shmlock_user_lock);
264	free_uid(user);
265}
266