arch/mips/mm/mmap.c

   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
  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
  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
  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
  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
 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  */
 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
 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
 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
 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 }