1 /*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 2011 Wind River Systems,
7 * written by Ralf Baechle <ralf@linux-mips.org>
8 */
9 #include <linux/compiler.h>
10 #include <linux/errno.h>
11 #include <linux/mm.h>
12 #include <linux/mman.h>
13 #include <linux/module.h>
14 #include <linux/personality.h>
15 #include <linux/random.h>
16 #include <linux/sched.h>
17
18 unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */
19 EXPORT_SYMBOL(shm_align_mask);
20
21 /* gap between mmap and stack */
22 #define MIN_GAP (128*1024*1024UL)
23 #define MAX_GAP ((TASK_SIZE)/6*5)
24
mmap_is_legacy(void)25 static int mmap_is_legacy(void)
26 {
27 if (current->personality & ADDR_COMPAT_LAYOUT)
28 return 1;
29
30 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
31 return 1;
32
33 return sysctl_legacy_va_layout;
34 }
35
mmap_base(unsigned long rnd)36 static unsigned long mmap_base(unsigned long rnd)
37 {
38 unsigned long gap = rlimit(RLIMIT_STACK);
39
40 if (gap < MIN_GAP)
41 gap = MIN_GAP;
42 else if (gap > MAX_GAP)
43 gap = MAX_GAP;
44
45 return PAGE_ALIGN(TASK_SIZE - gap - rnd);
46 }
47
COLOUR_ALIGN_DOWN(unsigned long addr,unsigned long pgoff)48 static inline unsigned long COLOUR_ALIGN_DOWN(unsigned long addr,
49 unsigned long pgoff)
50 {
51 unsigned long base = addr & ~shm_align_mask;
52 unsigned long off = (pgoff << PAGE_SHIFT) & shm_align_mask;
53
54 if (base + off <= addr)
55 return base + off;
56
57 return base - off;
58 }
59
60 #define COLOUR_ALIGN(addr, pgoff) \
61 ((((addr) + shm_align_mask) & ~shm_align_mask) + \
62 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
63
64 enum mmap_allocation_direction {UP, DOWN};
65
arch_get_unmapped_area_common(struct file * filp,unsigned long addr0,unsigned long len,unsigned long pgoff,unsigned long flags,enum mmap_allocation_direction dir)66 static unsigned long arch_get_unmapped_area_common(struct file *filp,
67 unsigned long addr0, unsigned long len, unsigned long pgoff,
68 unsigned long flags, enum mmap_allocation_direction dir)
69 {
70 struct mm_struct *mm = current->mm;
71 struct vm_area_struct *vma;
72 unsigned long addr = addr0;
73 int do_color_align;
74
75 if (unlikely(len > TASK_SIZE))
76 return -ENOMEM;
77
78 if (flags & MAP_FIXED) {
79 /* Even MAP_FIXED mappings must reside within TASK_SIZE */
80 if (TASK_SIZE - len < addr)
81 return -EINVAL;
82
83 /*
84 * We do not accept a shared mapping if it would violate
85 * cache aliasing constraints.
86 */
87 if ((flags & MAP_SHARED) &&
88 ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
89 return -EINVAL;
90 return addr;
91 }
92
93 do_color_align = 0;
94 if (filp || (flags & MAP_SHARED))
95 do_color_align = 1;
96
97 /* requesting a specific address */
98 if (addr) {
99 if (do_color_align)
100 addr = COLOUR_ALIGN(addr, pgoff);
101 else
102 addr = PAGE_ALIGN(addr);
103
104 vma = find_vma(mm, addr);
105 if (TASK_SIZE - len >= addr &&
106 (!vma || addr + len <= vma->vm_start))
107 return addr;
108 }
109
110 if (dir == UP) {
111 addr = mm->mmap_base;
112 if (do_color_align)
113 addr = COLOUR_ALIGN(addr, pgoff);
114 else
115 addr = PAGE_ALIGN(addr);
116
117 for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
118 /* At this point: (!vma || addr < vma->vm_end). */
119 if (TASK_SIZE - len < addr)
120 return -ENOMEM;
121 if (!vma || addr + len <= vma->vm_start)
122 return addr;
123 addr = vma->vm_end;
124 if (do_color_align)
125 addr = COLOUR_ALIGN(addr, pgoff);
126 }
127 } else {
128 /* check if free_area_cache is useful for us */
129 if (len <= mm->cached_hole_size) {
130 mm->cached_hole_size = 0;
131 mm->free_area_cache = mm->mmap_base;
132 }
133
134 /*
135 * either no address requested, or the mapping can't fit into
136 * the requested address hole
137 */
138 addr = mm->free_area_cache;
139 if (do_color_align) {
140 unsigned long base =
141 COLOUR_ALIGN_DOWN(addr - len, pgoff);
142 addr = base + len;
143 }
144
145 /* make sure it can fit in the remaining address space */
146 if (likely(addr > len)) {
147 vma = find_vma(mm, addr - len);
148 if (!vma || addr <= vma->vm_start) {
149 /* cache the address as a hint for next time */
150 return mm->free_area_cache = addr - len;
151 }
152 }
153
154 if (unlikely(mm->mmap_base < len))
155 goto bottomup;
156
157 addr = mm->mmap_base - len;
158 if (do_color_align)
159 addr = COLOUR_ALIGN_DOWN(addr, pgoff);
160
161 do {
162 /*
163 * Lookup failure means no vma is above this address,
164 * else if new region fits below vma->vm_start,
165 * return with success:
166 */
167 vma = find_vma(mm, addr);
168 if (likely(!vma || addr + len <= vma->vm_start)) {
169 /* cache the address as a hint for next time */
170 return mm->free_area_cache = addr;
171 }
172
173 /* remember the largest hole we saw so far */
174 if (addr + mm->cached_hole_size < vma->vm_start)
175 mm->cached_hole_size = vma->vm_start - addr;
176
177 /* try just below the current vma->vm_start */
178 addr = vma->vm_start - len;
179 if (do_color_align)
180 addr = COLOUR_ALIGN_DOWN(addr, pgoff);
181 } while (likely(len < vma->vm_start));
182
183 bottomup:
184 /*
185 * A failed mmap() very likely causes application failure,
186 * so fall back to the bottom-up function here. This scenario
187 * can happen with large stack limits and large mmap()
188 * allocations.
189 */
190 mm->cached_hole_size = ~0UL;
191 mm->free_area_cache = TASK_UNMAPPED_BASE;
192 addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
193 /*
194 * Restore the topdown base:
195 */
196 mm->free_area_cache = mm->mmap_base;
197 mm->cached_hole_size = ~0UL;
198
199 return addr;
200 }
201 }
202
arch_get_unmapped_area(struct file * filp,unsigned long addr0,unsigned long len,unsigned long pgoff,unsigned long flags)203 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
204 unsigned long len, unsigned long pgoff, unsigned long flags)
205 {
206 return arch_get_unmapped_area_common(filp,
207 addr0, len, pgoff, flags, UP);
208 }
209
210 /*
211 * There is no need to export this but sched.h declares the function as
212 * extern so making it static here results in an error.
213 */
arch_get_unmapped_area_topdown(struct file * filp,unsigned long addr0,unsigned long len,unsigned long pgoff,unsigned long flags)214 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
215 unsigned long addr0, unsigned long len, unsigned long pgoff,
216 unsigned long flags)
217 {
218 return arch_get_unmapped_area_common(filp,
219 addr0, len, pgoff, flags, DOWN);
220 }
221
arch_pick_mmap_layout(struct mm_struct * mm)222 void arch_pick_mmap_layout(struct mm_struct *mm)
223 {
224 unsigned long random_factor = 0UL;
225
226 if (current->flags & PF_RANDOMIZE) {
227 random_factor = get_random_int();
228 random_factor = random_factor << PAGE_SHIFT;
229 if (TASK_IS_32BIT_ADDR)
230 random_factor &= 0xfffffful;
231 else
232 random_factor &= 0xffffffful;
233 }
234
235 if (mmap_is_legacy()) {
236 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
237 mm->get_unmapped_area = arch_get_unmapped_area;
238 mm->unmap_area = arch_unmap_area;
239 } else {
240 mm->mmap_base = mmap_base(random_factor);
241 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
242 mm->unmap_area = arch_unmap_area_topdown;
243 }
244 }
245
brk_rnd(void)246 static inline unsigned long brk_rnd(void)
247 {
248 unsigned long rnd = get_random_int();
249
250 rnd = rnd << PAGE_SHIFT;
251 /* 8MB for 32bit, 256MB for 64bit */
252 if (TASK_IS_32BIT_ADDR)
253 rnd = rnd & 0x7ffffful;
254 else
255 rnd = rnd & 0xffffffful;
256
257 return rnd;
258 }
259
arch_randomize_brk(struct mm_struct * mm)260 unsigned long arch_randomize_brk(struct mm_struct *mm)
261 {
262 unsigned long base = mm->brk;
263 unsigned long ret;
264
265 ret = PAGE_ALIGN(base + brk_rnd());
266
267 if (ret < mm->brk)
268 return mm->brk;
269
270 return ret;
271 }
272