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