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/export.h>
  14 #include <linux/personality.h>
  15 #include <linux/random.h>
  16 #include <linux/sched/signal.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 unsigned long arch_mmap_rnd(void)
 146 {
 147         unsigned long rnd;
 148
 149 #ifdef CONFIG_COMPAT
 150         if (TASK_IS_32BIT_ADDR)
 151                 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
 152         else
 153 #endif /* CONFIG_COMPAT */
 154                 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
 155
 156         return rnd << PAGE_SHIFT;
 157 }
 158
 159 void arch_pick_mmap_layout(struct mm_struct *mm)
 160 {
 161         unsigned long random_factor = 0UL;
 162
 163         if (current->flags & PF_RANDOMIZE)
 164                 random_factor = arch_mmap_rnd();
 165
 166         if (mmap_is_legacy()) {
 167                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 168                 mm->get_unmapped_area = arch_get_unmapped_area;
 169         } else {
 170                 mm->mmap_base = mmap_base(random_factor);
 171                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 172         }
 173 }
 174
 175 static inline unsigned long brk_rnd(void)
 176 {
 177         unsigned long rnd = get_random_long();
 178
 179         rnd = rnd << PAGE_SHIFT;
 180         /* 8MB for 32bit, 256MB for 64bit */
 181         if (TASK_IS_32BIT_ADDR)
 182                 rnd = rnd & 0x7ffffful;
 183         else
 184                 rnd = rnd & 0xffffffful;
 185
 186         return rnd;
 187 }
 188
 189 unsigned long arch_randomize_brk(struct mm_struct *mm)
 190 {
 191         unsigned long base = mm->brk;
 192         unsigned long ret;
 193
 194         ret = PAGE_ALIGN(base + brk_rnd());
 195
 196         if (ret < mm->brk)
 197                 return mm->brk;
 198
 199         return ret;
 200 }
 201
 202 int __virt_addr_valid(const volatile void *kaddr)
 203 {
 204         return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
 205 }
 206 EXPORT_SYMBOL_GPL(__virt_addr_valid);