xref: /openbmc/linux/mm/mlock.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *	linux/mm/mlock.c
3  *
4  *  (C) Copyright 1995 Linus Torvalds
5  *  (C) Copyright 2002 Christoph Hellwig
6  */
7 
8 #include <linux/mman.h>
9 #include <linux/mm.h>
10 #include <linux/mempolicy.h>
11 #include <linux/syscalls.h>
12 
13 
14 static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
15 	unsigned long start, unsigned long end, unsigned int newflags)
16 {
17 	struct mm_struct * mm = vma->vm_mm;
18 	pgoff_t pgoff;
19 	int pages;
20 	int ret = 0;
21 
22 	if (newflags == vma->vm_flags) {
23 		*prev = vma;
24 		goto out;
25 	}
26 
27 	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
28 	*prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
29 			  vma->vm_file, pgoff, vma_policy(vma));
30 	if (*prev) {
31 		vma = *prev;
32 		goto success;
33 	}
34 
35 	*prev = vma;
36 
37 	if (start != vma->vm_start) {
38 		ret = split_vma(mm, vma, start, 1);
39 		if (ret)
40 			goto out;
41 	}
42 
43 	if (end != vma->vm_end) {
44 		ret = split_vma(mm, vma, end, 0);
45 		if (ret)
46 			goto out;
47 	}
48 
49 success:
50 	/*
51 	 * vm_flags is protected by the mmap_sem held in write mode.
52 	 * It's okay if try_to_unmap_one unmaps a page just after we
53 	 * set VM_LOCKED, make_pages_present below will bring it back.
54 	 */
55 	vma->vm_flags = newflags;
56 
57 	/*
58 	 * Keep track of amount of locked VM.
59 	 */
60 	pages = (end - start) >> PAGE_SHIFT;
61 	if (newflags & VM_LOCKED) {
62 		pages = -pages;
63 		if (!(newflags & VM_IO))
64 			ret = make_pages_present(start, end);
65 	}
66 
67 	vma->vm_mm->locked_vm -= pages;
68 out:
69 	if (ret == -ENOMEM)
70 		ret = -EAGAIN;
71 	return ret;
72 }
73 
74 static int do_mlock(unsigned long start, size_t len, int on)
75 {
76 	unsigned long nstart, end, tmp;
77 	struct vm_area_struct * vma, * prev;
78 	int error;
79 
80 	len = PAGE_ALIGN(len);
81 	end = start + len;
82 	if (end < start)
83 		return -EINVAL;
84 	if (end == start)
85 		return 0;
86 	vma = find_vma_prev(current->mm, start, &prev);
87 	if (!vma || vma->vm_start > start)
88 		return -ENOMEM;
89 
90 	if (start > vma->vm_start)
91 		prev = vma;
92 
93 	for (nstart = start ; ; ) {
94 		unsigned int newflags;
95 
96 		/* Here we know that  vma->vm_start <= nstart < vma->vm_end. */
97 
98 		newflags = vma->vm_flags | VM_LOCKED;
99 		if (!on)
100 			newflags &= ~VM_LOCKED;
101 
102 		tmp = vma->vm_end;
103 		if (tmp > end)
104 			tmp = end;
105 		error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
106 		if (error)
107 			break;
108 		nstart = tmp;
109 		if (nstart < prev->vm_end)
110 			nstart = prev->vm_end;
111 		if (nstart >= end)
112 			break;
113 
114 		vma = prev->vm_next;
115 		if (!vma || vma->vm_start != nstart) {
116 			error = -ENOMEM;
117 			break;
118 		}
119 	}
120 	return error;
121 }
122 
123 asmlinkage long sys_mlock(unsigned long start, size_t len)
124 {
125 	unsigned long locked;
126 	unsigned long lock_limit;
127 	int error = -ENOMEM;
128 
129 	if (!can_do_mlock())
130 		return -EPERM;
131 
132 	down_write(&current->mm->mmap_sem);
133 	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
134 	start &= PAGE_MASK;
135 
136 	locked = len >> PAGE_SHIFT;
137 	locked += current->mm->locked_vm;
138 
139 	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
140 	lock_limit >>= PAGE_SHIFT;
141 
142 	/* check against resource limits */
143 	if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
144 		error = do_mlock(start, len, 1);
145 	up_write(&current->mm->mmap_sem);
146 	return error;
147 }
148 
149 asmlinkage long sys_munlock(unsigned long start, size_t len)
150 {
151 	int ret;
152 
153 	down_write(&current->mm->mmap_sem);
154 	len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
155 	start &= PAGE_MASK;
156 	ret = do_mlock(start, len, 0);
157 	up_write(&current->mm->mmap_sem);
158 	return ret;
159 }
160 
161 static int do_mlockall(int flags)
162 {
163 	struct vm_area_struct * vma, * prev = NULL;
164 	unsigned int def_flags = 0;
165 
166 	if (flags & MCL_FUTURE)
167 		def_flags = VM_LOCKED;
168 	current->mm->def_flags = def_flags;
169 	if (flags == MCL_FUTURE)
170 		goto out;
171 
172 	for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
173 		unsigned int newflags;
174 
175 		newflags = vma->vm_flags | VM_LOCKED;
176 		if (!(flags & MCL_CURRENT))
177 			newflags &= ~VM_LOCKED;
178 
179 		/* Ignore errors */
180 		mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
181 	}
182 out:
183 	return 0;
184 }
185 
186 asmlinkage long sys_mlockall(int flags)
187 {
188 	unsigned long lock_limit;
189 	int ret = -EINVAL;
190 
191 	if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
192 		goto out;
193 
194 	ret = -EPERM;
195 	if (!can_do_mlock())
196 		goto out;
197 
198 	down_write(&current->mm->mmap_sem);
199 
200 	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
201 	lock_limit >>= PAGE_SHIFT;
202 
203 	ret = -ENOMEM;
204 	if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
205 	    capable(CAP_IPC_LOCK))
206 		ret = do_mlockall(flags);
207 	up_write(&current->mm->mmap_sem);
208 out:
209 	return ret;
210 }
211 
212 asmlinkage long sys_munlockall(void)
213 {
214 	int ret;
215 
216 	down_write(&current->mm->mmap_sem);
217 	ret = do_mlockall(0);
218 	up_write(&current->mm->mmap_sem);
219 	return ret;
220 }
221 
222 /*
223  * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
224  * shm segments) get accounted against the user_struct instead.
225  */
226 static DEFINE_SPINLOCK(shmlock_user_lock);
227 
228 int user_shm_lock(size_t size, struct user_struct *user)
229 {
230 	unsigned long lock_limit, locked;
231 	int allowed = 0;
232 
233 	locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
234 	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
235 	lock_limit >>= PAGE_SHIFT;
236 	spin_lock(&shmlock_user_lock);
237 	if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
238 		goto out;
239 	get_uid(user);
240 	user->locked_shm += locked;
241 	allowed = 1;
242 out:
243 	spin_unlock(&shmlock_user_lock);
244 	return allowed;
245 }
246 
247 void user_shm_unlock(size_t size, struct user_struct *user)
248 {
249 	spin_lock(&shmlock_user_lock);
250 	user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
251 	spin_unlock(&shmlock_user_lock);
252 	free_uid(user);
253 }
254