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 #include <linux/sched/mm.h>
  18
  19 unsigned long shm_align_mask = PAGE_SIZE - 1;   /* Sane caches */
  20 EXPORT_SYMBOL(shm_align_mask);
  21
  22 /* gap between mmap and stack */
  23 #define MIN_GAP (128*1024*1024UL)
  24 #define MAX_GAP ((TASK_SIZE)/6*5)
  25
  26 static int mmap_is_legacy(void)
  27 {
  28         if (current->personality & ADDR_COMPAT_LAYOUT)
  29                 return 1;
  30
  31         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  32                 return 1;
  33
  34         return sysctl_legacy_va_layout;
  35 }
  36
  37 static unsigned long mmap_base(unsigned long rnd)
  38 {
  39         unsigned long gap = rlimit(RLIMIT_STACK);
  40
  41         if (gap < MIN_GAP)
  42                 gap = MIN_GAP;
  43         else if (gap > MAX_GAP)
  44                 gap = MAX_GAP;
  45
  46         return PAGE_ALIGN(TASK_SIZE - gap - rnd);
  47 }
  48
  49 #define COLOUR_ALIGN(addr, pgoff)                               \
  50         ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
  51          (((pgoff) << PAGE_SHIFT) & shm_align_mask))
  52
  53 enum mmap_allocation_direction {UP, DOWN};
  54
  55 static unsigned long arch_get_unmapped_area_common(struct file *filp,
  56         unsigned long addr0, unsigned long len, unsigned long pgoff,
  57         unsigned long flags, enum mmap_allocation_direction dir)
  58 {
  59         struct mm_struct *mm = current->mm;
  60         struct vm_area_struct *vma;
  61         unsigned long addr = addr0;
  62         int do_color_align;
  63         struct vm_unmapped_area_info info;
  64
  65         if (unlikely(len > TASK_SIZE))
  66                 return -ENOMEM;
  67
  68         if (flags & MAP_FIXED) {
  69                 /* Even MAP_FIXED mappings must reside within TASK_SIZE */
  70                 if (TASK_SIZE - len < addr)
  71                         return -EINVAL;
  72
  73                 /*
  74                  * We do not accept a shared mapping if it would violate
  75                  * cache aliasing constraints.
  76                  */
  77                 if ((flags & MAP_SHARED) &&
  78                     ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
  79                         return -EINVAL;
  80                 return addr;
  81         }
  82
  83         do_color_align = 0;
  84         if (filp || (flags & MAP_SHARED))
  85                 do_color_align = 1;
  86
  87         /* requesting a specific address */
  88         if (addr) {
  89                 if (do_color_align)
  90                         addr = COLOUR_ALIGN(addr, pgoff);
  91                 else
  92                         addr = PAGE_ALIGN(addr);
  93
  94                 vma = find_vma(mm, addr);
  95                 if (TASK_SIZE - len >= addr &&
  96                     (!vma || addr + len <= vm_start_gap(vma)))
  97                         return addr;
  98         }
  99
 100         info.length = len;
 101         info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0;
 102         info.align_offset = pgoff << PAGE_SHIFT;
 103
 104         if (dir == DOWN) {
 105                 info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 106                 info.low_limit = PAGE_SIZE;
 107                 info.high_limit = mm->mmap_base;
 108                 addr = vm_unmapped_area(&info);
 109
 110                 if (!(addr & ~PAGE_MASK))
 111                         return addr;
 112
 113                 /*
 114                  * A failed mmap() very likely causes application failure,
 115                  * so fall back to the bottom-up function here. This scenario
 116                  * can happen with large stack limits and large mmap()
 117                  * allocations.
 118                  */
 119         }
 120
 121         info.flags = 0;
 122         info.low_limit = mm->mmap_base;
 123         info.high_limit = TASK_SIZE;
 124         return vm_unmapped_area(&info);
 125 }
 126
 127 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0,
 128         unsigned long len, unsigned long pgoff, unsigned long flags)
 129 {
 130         return arch_get_unmapped_area_common(filp,
 131                         addr0, len, pgoff, flags, UP);
 132 }
 133
 134 /*
 135  * There is no need to export this but sched.h declares the function as
 136  * extern so making it static here results in an error.
 137  */
 138 unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 139         unsigned long addr0, unsigned long len, unsigned long pgoff,
 140         unsigned long flags)
 141 {
 142         return arch_get_unmapped_area_common(filp,
 143                         addr0, len, pgoff, flags, DOWN);
 144 }
 145
 146 unsigned long arch_mmap_rnd(void)
 147 {
 148         unsigned long rnd;
 149
 150 #ifdef CONFIG_COMPAT
 151         if (TASK_IS_32BIT_ADDR)
 152                 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
 153         else
 154 #endif /* CONFIG_COMPAT */
 155                 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
 156
 157         return rnd << PAGE_SHIFT;
 158 }
 159
 160 void arch_pick_mmap_layout(struct mm_struct *mm)
 161 {
 162         unsigned long random_factor = 0UL;
 163
 164         if (current->flags & PF_RANDOMIZE)
 165                 random_factor = arch_mmap_rnd();
 166
 167         if (mmap_is_legacy()) {
 168                 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
 169                 mm->get_unmapped_area = arch_get_unmapped_area;
 170         } else {
 171                 mm->mmap_base = mmap_base(random_factor);
 172                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 173         }
 174 }
 175
 176 static inline unsigned long brk_rnd(void)
 177 {
 178         unsigned long rnd = get_random_long();
 179
 180         rnd = rnd << PAGE_SHIFT;
 181         /* 8MB for 32bit, 256MB for 64bit */
 182         if (TASK_IS_32BIT_ADDR)
 183                 rnd = rnd & 0x7ffffful;
 184         else
 185                 rnd = rnd & 0xffffffful;
 186
 187         return rnd;
 188 }
 189
 190 unsigned long arch_randomize_brk(struct mm_struct *mm)
 191 {
 192         unsigned long base = mm->brk;
 193         unsigned long ret;
 194
 195         ret = PAGE_ALIGN(base + brk_rnd());
 196
 197         if (ret < mm->brk)
 198                 return mm->brk;
 199
 200         return ret;
 201 }
 202
 203 int __virt_addr_valid(const volatile void *kaddr)
 204 {
 205         return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
 206 }
 207 EXPORT_SYMBOL_GPL(__virt_addr_valid);