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 #define COLOUR_ALIGN(addr, pgoff)                               \
  49         ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
  50          (((pgoff) << PAGE_SHIFT) & shm_align_mask))
  51
  52 enum mmap_allocation_direction {UP, DOWN};
  53
  54 static unsigned long arch_get_unmapped_area_common(struct file *filp,
  55         unsigned long addr0, unsigned long len, unsigned long pgoff,
  56         unsigned long flags, enum mmap_allocation_direction dir)
  57 {
  58         struct mm_struct *mm = current->mm;
  59         struct vm_area_struct *vma;
  60         unsigned long addr = addr0;
  61         int do_color_align;
  62         struct vm_unmapped_area_info info;
  63
  64         if (unlikely(len > TASK_SIZE))
  65                 return -ENOMEM;
  66
  67         if (flags & MAP_FIXED) {
  68                 /* Even MAP_FIXED mappings must reside within TASK_SIZE */
  69                 if (TASK_SIZE - len < addr)
  70                         return -EINVAL;
  71
  72                 /*
  73                  * We do not accept a shared mapping if it would violate
  74                  * cache aliasing constraints.
  75                  */
  76                 if ((flags & MAP_SHARED) &&
  77                     ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
  78                         return -EINVAL;
  79                 return addr;
  80         }
  81
  82         do_color_align = 0;
  83         if (filp || (flags & MAP_SHARED))
  84                 do_color_align = 1;
  85
  86         /* requesting a specific address */
  87         if (addr) {
  88                 if (do_color_align)
  89                         addr = COLOUR_ALIGN(addr, pgoff);
  90                 else
  91                         addr = PAGE_ALIGN(addr);
  92
  93                 vma = find_vma(mm, addr);
  94                 if (TASK_SIZE - len >= addr &&
  95                     (!vma || addr + len <= vma->vm_start))
  96                         return addr;
  97         }
  98
  99         info.length = len;
 100         info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
 101         info.align_offset = pgoff << PAGE_SHIFT;
 102
 103         if (dir == DOWN) {
 104                 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 105                 info.low_limit = PAGE_SIZE;
 106                 info.high_limit = mm->mmap_base;
 107                 addr = vm_unmapped_area(&info);
 108
 109                 if (!(addr & ~PAGE_MASK))
 110                         return addr;
 111
 112                 /*
 113                  * A failed mmap() very likely causes application failure,
 114                  * so fall back to the bottom-up function here. This scenario
 115                  * can happen with large stack limits and large mmap()
 116                  * allocations.
 117                  */
 118         }
 119
 120         info.flags = 0;
 121         info.low_limit = mm->mmap_base;
 122         info.high_limit = TASK_SIZE;
 123         return vm_unmapped_area(&info);
 124 }
 125
 126 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
 127         unsigned long len, unsigned long pgoff, unsigned long flags)
 128 {
 129         return arch_get_unmapped_area_common(filp,
 130                         addr0, len, pgoff, flags, UP);
 131 }
 132
 133 /*
 134  * There is no need to export this but sched.h declares the function as
 135  * extern so making it static here results in an error.
 136  */
 137 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 138         unsigned long addr0, unsigned long len, unsigned long pgoff,
 139         unsigned long flags)
 140 {
 141         return arch_get_unmapped_area_common(filp,
 142                         addr0, len, pgoff, flags, DOWN);
 143 }
 144
 145 void arch_pick_mmap_layout(struct mm_struct *mm)
 146 {
 147         unsigned long random_factor = 0UL;
 148
 149         if (current->flags & PF_RANDOMIZE) {
 150                 random_factor = get_random_int();
 151                 random_factor = random_factor << PAGE_SHIFT;
 152                 if (TASK_IS_32BIT_ADDR)
 153                         random_factor &= 0xfffffful;
 154                 else
 155                         random_factor &= 0xffffffful;
 156         }
 157
 158         if (mmap_is_legacy()) {
 159                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 160                 mm->get_unmapped_area = arch_get_unmapped_area;
 161                 mm->unmap_area = arch_unmap_area;
 162         } else {
 163                 mm->mmap_base = mmap_base(random_factor);
 164                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 165                 mm->unmap_area = arch_unmap_area_topdown;
 166         }
 167 }
 168
 169 static inline unsigned long brk_rnd(void)
 170 {
 171         unsigned long rnd = get_random_int();
 172
 173         rnd = rnd << PAGE_SHIFT;
 174         /* 8MB for 32bit, 256MB for 64bit */
 175         if (TASK_IS_32BIT_ADDR)
 176                 rnd = rnd & 0x7ffffful;
 177         else
 178                 rnd = rnd & 0xffffffful;
 179
 180         return rnd;
 181 }
 182
 183 unsigned long arch_randomize_brk(struct mm_struct *mm)
 184 {
 185         unsigned long base = mm->brk;
 186         unsigned long ret;
 187
 188         ret = PAGE_ALIGN(base + brk_rnd());
 189
 190         if (ret < mm->brk)
 191                 return mm->brk;
 192
 193         return ret;
 194 }