arch/arm/mm/mmap.c

   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 static inline unsigned long COLOUR_ALIGN_DOWN(unsigned long addr,
  15                                               unsigned long pgoff)
  16 {
  17         unsigned long base = addr & ~(SHMLBA-1);
  18         unsigned long off = (pgoff << PAGE_SHIFT) & (SHMLBA-1);
  19
  20         if (base + off <= addr)
  21                 return base + off;
  22
  23         return base - off;
  24 }
  25
  26 #define COLOUR_ALIGN(addr,pgoff)                \
  27         ((((addr)+SHMLBA-1)&~(SHMLBA-1)) +      \
  28          (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
  29
  30 /* gap between mmap and stack */
  31 #define MIN_GAP (128*1024*1024UL)
  32 #define MAX_GAP ((TASK_SIZE)/6*5)
  33
  34 static int mmap_is_legacy(void)
  35 {
  36         if (current->personality & ADDR_COMPAT_LAYOUT)
  37                 return 1;
  38
  39         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  40                 return 1;
  41
  42         return sysctl_legacy_va_layout;
  43 }
  44
  45 static unsigned long mmap_base(unsigned long rnd)
  46 {
  47         unsigned long gap = rlimit(RLIMIT_STACK);
  48
  49         if (gap < MIN_GAP)
  50                 gap = MIN_GAP;
  51         else if (gap > MAX_GAP)
  52                 gap = MAX_GAP;
  53
  54         return PAGE_ALIGN(TASK_SIZE - gap - rnd);
  55 }
  56
  57 /*
  58  * We need to ensure that shared mappings are correctly aligned to
  59  * avoid aliasing issues with VIPT caches.  We need to ensure that
  60  * a specific page of an object is always mapped at a multiple of
  61  * SHMLBA bytes.
  62  *
  63  * We unconditionally provide this function for all cases, however
  64  * in the VIVT case, we optimise out the alignment rules.
  65  */
  66 unsigned long
  67 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  68                 unsigned long len, unsigned long pgoff, unsigned long flags)
  69 {
  70         struct mm_struct *mm = current->mm;
  71         struct vm_area_struct *vma;
  72         unsigned long start_addr;
  73         int do_align = 0;
  74         int aliasing = cache_is_vipt_aliasing();
  75
  76         /*
  77          * We only need to do colour alignment if either the I or D
  78          * caches alias.
  79          */
  80         if (aliasing)
  81                 do_align = filp || (flags & MAP_SHARED);
  82
  83         /*
  84          * We enforce the MAP_FIXED case.
  85          */
  86         if (flags & MAP_FIXED) {
  87                 if (aliasing && flags & MAP_SHARED &&
  88                     (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
  89                         return -EINVAL;
  90                 return addr;
  91         }
  92
  93         if (len > TASK_SIZE)
  94                 return -ENOMEM;
  95
  96         if (addr) {
  97                 if (do_align)
  98                         addr = COLOUR_ALIGN(addr, pgoff);
  99                 else
 100                         addr = PAGE_ALIGN(addr);
 101
 102                 vma = find_vma(mm, addr);
 103                 if (TASK_SIZE - len >= addr &&
 104                     (!vma || addr + len <= vma->vm_start))
 105                         return addr;
 106         }
 107         if (len > mm->cached_hole_size) {
 108                 start_addr = addr = mm->free_area_cache;
 109         } else {
 110                 start_addr = addr = mm->mmap_base;
 111                 mm->cached_hole_size = 0;
 112         }
 113
 114 full_search:
 115         if (do_align)
 116                 addr = COLOUR_ALIGN(addr, pgoff);
 117         else
 118                 addr = PAGE_ALIGN(addr);
 119
 120         for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
 121                 /* At this point:  (!vma || addr < vma->vm_end). */
 122                 if (TASK_SIZE - len < addr) {
 123                         /*
 124                          * Start a new search - just in case we missed
 125                          * some holes.
 126                          */
 127                         if (start_addr != TASK_UNMAPPED_BASE) {
 128                                 start_addr = addr = TASK_UNMAPPED_BASE;
 129                                 mm->cached_hole_size = 0;
 130                                 goto full_search;
 131                         }
 132                         return -ENOMEM;
 133                 }
 134                 if (!vma || addr + len <= vma->vm_start) {
 135                         /*
 136                          * Remember the place where we stopped the search:
 137                          */
 138                         mm->free_area_cache = addr + len;
 139                         return addr;
 140                 }
 141                 if (addr + mm->cached_hole_size < vma->vm_start)
 142                         mm->cached_hole_size = vma->vm_start - addr;
 143                 addr = vma->vm_end;
 144                 if (do_align)
 145                         addr = COLOUR_ALIGN(addr, pgoff);
 146         }
 147 }
 148
 149 unsigned long
 150 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 151                         const unsigned long len, const unsigned long pgoff,
 152                         const unsigned long flags)
 153 {
 154         struct vm_area_struct *vma;
 155         struct mm_struct *mm = current->mm;
 156         unsigned long addr = addr0;
 157         int do_align = 0;
 158         int aliasing = cache_is_vipt_aliasing();
 159
 160         /*
 161          * We only need to do colour alignment if either the I or D
 162          * caches alias.
 163          */
 164         if (aliasing)
 165                 do_align = filp || (flags & MAP_SHARED);
 166
 167         /* requested length too big for entire address space */
 168         if (len > TASK_SIZE)
 169                 return -ENOMEM;
 170
 171         if (flags & MAP_FIXED) {
 172                 if (aliasing && flags & MAP_SHARED &&
 173                     (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1))
 174                         return -EINVAL;
 175                 return addr;
 176         }
 177
 178         /* requesting a specific address */
 179         if (addr) {
 180                 if (do_align)
 181                         addr = COLOUR_ALIGN(addr, pgoff);
 182                 else
 183                         addr = PAGE_ALIGN(addr);
 184                 vma = find_vma(mm, addr);
 185                 if (TASK_SIZE - len >= addr &&
 186                                 (!vma || addr + len <= vma->vm_start))
 187                         return addr;
 188         }
 189
 190         /* check if free_area_cache is useful for us */
 191         if (len <= mm->cached_hole_size) {
 192                 mm->cached_hole_size = 0;
 193                 mm->free_area_cache = mm->mmap_base;
 194         }
 195
 196         /* either no address requested or can't fit in requested address hole */
 197         addr = mm->free_area_cache;
 198         if (do_align) {
 199                 unsigned long base = COLOUR_ALIGN_DOWN(addr - len, pgoff);
 200                 addr = base + len;
 201         }
 202
 203         /* make sure it can fit in the remaining address space */
 204         if (addr > len) {
 205                 vma = find_vma(mm, addr-len);
 206                 if (!vma || addr <= vma->vm_start)
 207                         /* remember the address as a hint for next time */
 208                         return (mm->free_area_cache = addr-len);
 209         }
 210
 211         if (mm->mmap_base < len)
 212                 goto bottomup;
 213
 214         addr = mm->mmap_base - len;
 215         if (do_align)
 216                 addr = COLOUR_ALIGN_DOWN(addr, pgoff);
 217
 218         do {
 219                 /*
 220                  * Lookup failure means no vma is above this address,
 221                  * else if new region fits below vma->vm_start,
 222                  * return with success:
 223                  */
 224                 vma = find_vma(mm, addr);
 225                 if (!vma || addr+len <= vma->vm_start)
 226                         /* remember the address as a hint for next time */
 227                         return (mm->free_area_cache = addr);
 228
 229                 /* remember the largest hole we saw so far */
 230                 if (addr + mm->cached_hole_size < vma->vm_start)
 231                         mm->cached_hole_size = vma->vm_start - addr;
 232
 233                 /* try just below the current vma->vm_start */
 234                 addr = vma->vm_start - len;
 235                 if (do_align)
 236                         addr = COLOUR_ALIGN_DOWN(addr, pgoff);
 237         } while (len < vma->vm_start);
 238
 239 bottomup:
 240         /*
 241          * A failed mmap() very likely causes application failure,
 242          * so fall back to the bottom-up function here. This scenario
 243          * can happen with large stack limits and large mmap()
 244          * allocations.
 245          */
 246         mm->cached_hole_size = ~0UL;
 247         mm->free_area_cache = TASK_UNMAPPED_BASE;
 248         addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 249         /*
 250          * Restore the topdown base:
 251          */
 252         mm->free_area_cache = mm->mmap_base;
 253         mm->cached_hole_size = ~0UL;
 254
 255         return addr;
 256 }
 257
 258 void arch_pick_mmap_layout(struct mm_struct *mm)
 259 {
 260         unsigned long random_factor = 0UL;
 261
 262         /* 8 bits of randomness in 20 address space bits */
 263         if ((current->flags & PF_RANDOMIZE) &&
 264             !(current->personality & ADDR_NO_RANDOMIZE))
 265                 random_factor = (get_random_int() % (1 << 8)) << PAGE_SHIFT;
 266
 267         if (mmap_is_legacy()) {
 268                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 269                 mm->get_unmapped_area = arch_get_unmapped_area;
 270                 mm->unmap_area = arch_unmap_area;
 271         } else {
 272                 mm->mmap_base = mmap_base(random_factor);
 273                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 274                 mm->unmap_area = arch_unmap_area_topdown;
 275         }
 276 }
 277
 278 /*
 279  * You really shouldn't be using read() or write() on /dev/mem.  This
 280  * might go away in the future.
 281  */
 282 int valid_phys_addr_range(unsigned long addr, size_t size)
 283 {
 284         if (addr < PHYS_OFFSET)
 285                 return 0;
 286         if (addr + size > __pa(high_memory - 1) + 1)
 287                 return 0;
 288
 289         return 1;
 290 }
 291
 292 /*
 293  * We don't use supersection mappings for mmap() on /dev/mem, which
 294  * means that we can't map the memory area above the 4G barrier into
 295  * userspace.
 296  */
 297 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
 298 {
 299         return !(pfn + (size >> PAGE_SHIFT) > 0x00100000);
 300 }
 301
 302 #ifdef CONFIG_STRICT_DEVMEM
 303
 304 #include <linux/ioport.h>
 305
 306 /*
 307  * devmem_is_allowed() checks to see if /dev/mem access to a certain
 308  * address is valid. The argument is a physical page number.
 309  * We mimic x86 here by disallowing access to system RAM as well as
 310  * device-exclusive MMIO regions. This effectively disable read()/write()
 311  * on /dev/mem.
 312  */
 313 int devmem_is_allowed(unsigned long pfn)
 314 {
 315         if (iomem_is_exclusive(pfn << PAGE_SHIFT))
 316                 return 0;
 317         if (!page_is_ram(pfn))
 318                 return 1;
 319         return 0;
 320 }
 321
 322 #endif