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1 /*
2 * linux/arch/arm/mm/mmap.c
3 */
4 #include <linux/fs.h>
5 #include <linux/mm.h>
6 #include <linux/mman.h>
7 #include <linux/shm.h>
8 #include <linux/sched.h>
9 #include <linux/io.h>
10 #include <linux/personality.h>
11 #include <linux/random.h>
12 #include <asm/cachetype.h>
13
14 #define COLOUR_ALIGN(addr,pgoff) \
15 ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \
16 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
17
18 /* gap between mmap and stack */
19 #define MIN_GAP (128*1024*1024UL)
20 #define MAX_GAP ((TASK_SIZE)/6*5)
21
22 static int mmap_is_legacy(void)
23 {
24 if (current->personality & ADDR_COMPAT_LAYOUT)
25 return 1;
26
27 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
28 return 1;
29
30 return sysctl_legacy_va_layout;
31 }
32
33 static unsigned long mmap_base(unsigned long rnd)
34 {
35 unsigned long gap = rlimit(RLIMIT_STACK);
36
37 if (gap < MIN_GAP)
38 gap = MIN_GAP;
39 else if (gap > MAX_GAP)
40 gap = MAX_GAP;
41
42 return PAGE_ALIGN(TASK_SIZE - gap - rnd);
43 }
44
45 /*
46 * We need to ensure that shared mappings are correctly aligned to
47 * avoid aliasing issues with VIPT caches. We need to ensure that
48 * a specific page of an object is always mapped at a multiple of
49 * SHMLBA bytes.
50 *
51 * We unconditionally provide this function for all cases, however
52 * in the VIVT case, we optimise out the alignment rules.
53 */
54 unsigned long
55 arch_get_unmapped_area(struct file *filp, unsigned long addr,
56 unsigned long len, unsigned long pgoff, unsigned long flags)
57 {
58 struct mm_struct *mm = current->mm;
59 struct vm_area_struct *vma;
60 int do_align = 0;
61 int aliasing = cache_is_vipt_aliasing();
62 struct vm_unmapped_area_info info;
63
64 /*
65 * We only need to do colour alignment if either the I or D
66 * caches alias.
67 */
68 if (aliasing)
69 do_align = filp || (flags & MAP_SHARED);
70
71 /*
72 * We enforce the MAP_FIXED case.
73 */
74 if (flags & MAP_FIXED) {
75 if (aliasing && flags & MAP_SHARED &&
76 (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
77 return -EINVAL;
78 return addr;
79 }
80
81 if (len > TASK_SIZE)
82 return -ENOMEM;
83
84 if (addr) {
85 if (do_align)
86 addr = COLOUR_ALIGN(addr, pgoff);
87 else
88 addr = PAGE_ALIGN(addr);
89
90 vma = find_vma(mm, addr);
91 if (TASK_SIZE - len >= addr &&
92 (!vma || addr + len <= vma->vm_start))
93 return addr;
94 }
95
96 info.flags = 0;
97 info.length = len;
98 info.low_limit = mm->mmap_base;
99 info.high_limit = TASK_SIZE;
100 info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
101 info.align_offset = pgoff << PAGE_SHIFT;
102 return vm_unmapped_area(&info);
103 }
104
105 unsigned long
106 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
107 const unsigned long len, const unsigned long pgoff,
108 const unsigned long flags)
109 {
110 struct vm_area_struct *vma;
111 struct mm_struct *mm = current->mm;
112 unsigned long addr = addr0;
113 int do_align = 0;
114 int aliasing = cache_is_vipt_aliasing();
115 struct vm_unmapped_area_info info;
116
117 /*
118 * We only need to do colour alignment if either the I or D
119 * caches alias.
120 */
121 if (aliasing)
122 do_align = filp || (flags & MAP_SHARED);
123
124 /* requested length too big for entire address space */
125 if (len > TASK_SIZE)
126 return -ENOMEM;
127
128 if (flags & MAP_FIXED) {
129 if (aliasing && flags & MAP_SHARED &&
130 (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
131 return -EINVAL;
132 return addr;
133 }
134
135 /* requesting a specific address */
136 if (addr) {
137 if (do_align)
138 addr = COLOUR_ALIGN(addr, pgoff);
139 else
140 addr = PAGE_ALIGN(addr);
141 vma = find_vma(mm, addr);
142 if (TASK_SIZE - len >= addr &&
143 (!vma || addr + len <= vma->vm_start))
144 return addr;
145 }
146
147 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
148 info.length = len;
149 info.low_limit = FIRST_USER_ADDRESS;
150 info.high_limit = mm->mmap_base;
151 info.align_mask = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
152 info.align_offset = pgoff << PAGE_SHIFT;
153 addr = vm_unmapped_area(&info);
154
155 /*
156 * A failed mmap() very likely causes application failure,
157 * so fall back to the bottom-up function here. This scenario
158 * can happen with large stack limits and large mmap()
159 * allocations.
160 */
161 if (addr & ~PAGE_MASK) {
162 VM_BUG_ON(addr != -ENOMEM);
163 info.flags = 0;
164 info.low_limit = mm->mmap_base;
165 info.high_limit = TASK_SIZE;
166 addr = vm_unmapped_area(&info);
167 }
168
169 return addr;
170 }
171
172 unsigned long arch_mmap_rnd(void)
173 {
174 unsigned long rnd;
175
176 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
177
178 return rnd << PAGE_SHIFT;
179 }
180
181 void arch_pick_mmap_layout(struct mm_struct *mm)
182 {
183 unsigned long random_factor = 0UL;
184
185 if (current->flags & PF_RANDOMIZE)
186 random_factor = arch_mmap_rnd();
187
188 if (mmap_is_legacy()) {
189 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
190 mm->get_unmapped_area = arch_get_unmapped_area;
191 } else {
192 mm->mmap_base = mmap_base(random_factor);
193 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
194 }
195 }
196
197 /*
198 * You really shouldn't be using read() or write() on /dev/mem. This
199 * might go away in the future.
200 */
201 int valid_phys_addr_range(phys_addr_t addr, size_t size)
202 {
203 if (addr < PHYS_OFFSET)
204 return 0;
205 if (addr + size > __pa(high_memory - 1) + 1)
206 return 0;
207
208 return 1;
209 }
210
211 /*
212 * Do not allow /dev/mem mappings beyond the supported physical range.
213 */
214 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
215 {
216 return (pfn + (size >> PAGE_SHIFT)) <= (1 + (PHYS_MASK >> PAGE_SHIFT));
217 }
218
219 #ifdef CONFIG_STRICT_DEVMEM
220
221 #include <linux/ioport.h>
222
223 /*
224 * devmem_is_allowed() checks to see if /dev/mem access to a certain
225 * address is valid. The argument is a physical page number.
226 * We mimic x86 here by disallowing access to system RAM as well as
227 * device-exclusive MMIO regions. This effectively disable read()/write()
228 * on /dev/mem.
229 */
230 int devmem_is_allowed(unsigned long pfn)
231 {
232 if (iomem_is_exclusive(pfn << PAGE_SHIFT))
233 return 0;
234 if (!page_is_ram(pfn))
235 return 1;
236 return 0;
237 }
238
239 #endif