LXR linux/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
  18unsigned long shm_align_mask = PAGE_SIZE - 1;   /* Sane caches */
  19EXPORT_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
  25static 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
  36static 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
  48static 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
  64enum mmap_allocation_direction {UP, DOWN};
  65
  66static 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
 183bottomup:
 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
 203unsigned 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 */
 214unsigned 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
 222void 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
 246static 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
 260unsigned 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