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         unsigned long vm_start;
  74         int do_color_align;
  75
  76         if (unlikely(len > TASK_SIZE))
  77                 return -ENOMEM;
  78
  79         if (flags & MAP_FIXED) {
  80                 /* Even MAP_FIXED mappings must reside within TASK_SIZE */
  81                 if (TASK_SIZE - len < addr)
  82                         return -EINVAL;
  83
  84                 /*
  85                  * We do not accept a shared mapping if it would violate
  86                  * cache aliasing constraints.
  87                  */
  88                 if ((flags & MAP_SHARED) &&
  89                     ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
  90                         return -EINVAL;
  91                 return addr;
  92         }
  93
  94         do_color_align = 0;
  95         if (filp || (flags & MAP_SHARED))
  96                 do_color_align = 1;
  97
  98         /* requesting a specific address */
  99         if (addr) {
 100                 if (do_color_align)
 101                         addr = COLOUR_ALIGN(addr, pgoff);
 102                 else
 103                         addr = PAGE_ALIGN(addr);
 104
 105                 vma = find_vma(mm, addr);
 106                 if (TASK_SIZE - len >= addr &&
 107                     (!vma || addr + len <= vm_start_gap(vma)))
 108                         return addr;
 109         }
 110
 111         if (dir == UP) {
 112                 addr = mm->mmap_base;
 113                 if (do_color_align)
 114                         addr = COLOUR_ALIGN(addr, pgoff);
 115                 else
 116                         addr = PAGE_ALIGN(addr);
 117
 118                 for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
 119                         /* At this point:  (!vma || addr < vma->vm_end). */
 120                         if (TASK_SIZE - len < addr)
 121                                 return -ENOMEM;
 122                         if (!vma || addr + len <= vm_start_gap(vma))
 123                                 return addr;
 124                         addr = vma->vm_end;
 125                         if (do_color_align)
 126                                 addr = COLOUR_ALIGN(addr, pgoff);
 127                  }
 128          } else {
 129                 /* check if free_area_cache is useful for us */
 130                 if (len <= mm->cached_hole_size) {
 131                         mm->cached_hole_size = 0;
 132                         mm->free_area_cache = mm->mmap_base;
 133                 }
 134
 135                 /*
 136                  * either no address requested, or the mapping can't fit into
 137                  * the requested address hole
 138                  */
 139                 addr = mm->free_area_cache;
 140                 if (do_color_align) {
 141                         unsigned long base =
 142                                 COLOUR_ALIGN_DOWN(addr - len, pgoff);
 143                         addr = base + len;
 144                 }
 145
 146                 /* make sure it can fit in the remaining address space */
 147                 if (likely(addr > len)) {
 148                         vma = find_vma(mm, addr - len);
 149                         if (!vma || addr <= vm_start_gap(vma)) {
 150                                 /* cache the address as a hint for next time */
 151                                 return mm->free_area_cache = addr - len;
 152                         }
 153                 }
 154
 155                 if (unlikely(mm->mmap_base < len))
 156                         goto bottomup;
 157
 158                 addr = mm->mmap_base - len;
 159                 if (do_color_align)
 160                         addr = COLOUR_ALIGN_DOWN(addr, pgoff);
 161
 162                 do {
 163                         /*
 164                          * Lookup failure means no vma is above this address,
 165                          * else if new region fits below vma->vm_start,
 166                          * return with success:
 167                          */
 168                         vma = find_vma(mm, addr);
 169                         if (vma)
 170                                 vm_start = vm_start_gap(vma);
 171                         if (likely(!vma || addr + len <= vm_start)) {
 172                                 /* cache the address as a hint for next time */
 173                                 return mm->free_area_cache = addr;
 174                         }
 175
 176                         /* remember the largest hole we saw so far */
 177                         if (addr + mm->cached_hole_size < vm_start)
 178                                 mm->cached_hole_size = vm_start - addr;
 179
 180                         /* try just below the current vma->vm_start */
 181                         addr = vm_start - len;
 182                         if (do_color_align)
 183                                 addr = COLOUR_ALIGN_DOWN(addr, pgoff);
 184                 } while (likely(len < vm_start));
 185
 186 bottomup:
 187                 /*
 188                  * A failed mmap() very likely causes application failure,
 189                  * so fall back to the bottom-up function here. This scenario
 190                  * can happen with large stack limits and large mmap()
 191                  * allocations.
 192                  */
 193                 mm->cached_hole_size = ~0UL;
 194                 mm->free_area_cache = TASK_UNMAPPED_BASE;
 195                 addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 196                 /*
 197                  * Restore the topdown base:
 198                  */
 199                 mm->free_area_cache = mm->mmap_base;
 200                 mm->cached_hole_size = ~0UL;
 201
 202                 return addr;
 203         }
 204 }
 205
 206 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
 207         unsigned long len, unsigned long pgoff, unsigned long flags)
 208 {
 209         return arch_get_unmapped_area_common(filp,
 210                         addr0, len, pgoff, flags, UP);
 211 }
 212
 213 /*
 214  * There is no need to export this but sched.h declares the function as
 215  * extern so making it static here results in an error.
 216  */
 217 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 218         unsigned long addr0, unsigned long len, unsigned long pgoff,
 219         unsigned long flags)
 220 {
 221         return arch_get_unmapped_area_common(filp,
 222                         addr0, len, pgoff, flags, DOWN);
 223 }
 224
 225 void arch_pick_mmap_layout(struct mm_struct *mm)
 226 {
 227         unsigned long random_factor = 0UL;
 228
 229         if (current->flags & PF_RANDOMIZE) {
 230                 random_factor = get_random_int();
 231                 random_factor = random_factor << PAGE_SHIFT;
 232                 if (TASK_IS_32BIT_ADDR)
 233                         random_factor &= 0xfffffful;
 234                 else
 235                         random_factor &= 0xffffffful;
 236         }
 237
 238         if (mmap_is_legacy()) {
 239                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 240                 mm->get_unmapped_area = arch_get_unmapped_area;
 241                 mm->unmap_area = arch_unmap_area;
 242         } else {
 243                 mm->mmap_base = mmap_base(random_factor);
 244                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 245                 mm->unmap_area = arch_unmap_area_topdown;
 246         }
 247 }
 248
 249 static inline unsigned long brk_rnd(void)
 250 {
 251         unsigned long rnd = get_random_int();
 252
 253         rnd = rnd << PAGE_SHIFT;
 254         /* 8MB for 32bit, 256MB for 64bit */
 255         if (TASK_IS_32BIT_ADDR)
 256                 rnd = rnd & 0x7ffffful;
 257         else
 258                 rnd = rnd & 0xffffffful;
 259
 260         return rnd;
 261 }
 262
 263 unsigned long arch_randomize_brk(struct mm_struct *mm)
 264 {
 265         unsigned long base = mm->brk;
 266         unsigned long ret;
 267
 268         ret = PAGE_ALIGN(base + brk_rnd());
 269
 270         if (ret < mm->brk)
 271                 return mm->brk;
 272
 273         return ret;
 274 }