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/errno.h>
  10 #include <linux/mm.h>
  11 #include <linux/mman.h>
  12 #include <linux/module.h>
  13 #include <linux/random.h>
  14 #include <linux/sched.h>
  15
  16 unsigned long shm_align_mask = PAGE_SIZE - 1;   /* Sane caches */
  17
  18 EXPORT_SYMBOL(shm_align_mask);
  19
  20 #define COLOUR_ALIGN(addr,pgoff)                                \
  21         ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
  22          (((pgoff) << PAGE_SHIFT) & shm_align_mask))
  23
  24 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
  25         unsigned long len, unsigned long pgoff, unsigned long flags)
  26 {
  27         struct vm_area_struct * vmm;
  28         int do_color_align;
  29
  30         if (len > TASK_SIZE)
  31                 return -ENOMEM;
  32
  33         if (flags & MAP_FIXED) {
  34                 /* Even MAP_FIXED mappings must reside within TASK_SIZE.  */
  35                 if (TASK_SIZE - len < addr)
  36                         return -EINVAL;
  37
  38                 /*
  39                  * We do not accept a shared mapping if it would violate
  40                  * cache aliasing constraints.
  41                  */
  42                 if ((flags & MAP_SHARED) &&
  43                     ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask))
  44                         return -EINVAL;
  45                 return addr;
  46         }
  47
  48         do_color_align = 0;
  49         if (filp || (flags & MAP_SHARED))
  50                 do_color_align = 1;
  51         if (addr) {
  52                 if (do_color_align)
  53                         addr = COLOUR_ALIGN(addr, pgoff);
  54                 else
  55                         addr = PAGE_ALIGN(addr);
  56                 vmm = find_vma(current->mm, addr);
  57                 if (TASK_SIZE - len >= addr &&
  58                     (!vmm || addr + len <= vmm->vm_start))
  59                         return addr;
  60         }
  61         addr = current->mm->mmap_base;
  62         if (do_color_align)
  63                 addr = COLOUR_ALIGN(addr, pgoff);
  64         else
  65                 addr = PAGE_ALIGN(addr);
  66
  67         for (vmm = find_vma(current->mm, addr); ; vmm = vmm->vm_next) {
  68                 /* At this point:  (!vmm || addr < vmm->vm_end). */
  69                 if (TASK_SIZE - len < addr)
  70                         return -ENOMEM;
  71                 if (!vmm || addr + len <= vmm->vm_start)
  72                         return addr;
  73                 addr = vmm->vm_end;
  74                 if (do_color_align)
  75                         addr = COLOUR_ALIGN(addr, pgoff);
  76         }
  77 }
  78
  79 void arch_pick_mmap_layout(struct mm_struct *mm)
  80 {
  81         unsigned long random_factor = 0UL;
  82
  83         if (current->flags & PF_RANDOMIZE) {
  84                 random_factor = get_random_int();
  85                 random_factor = random_factor << PAGE_SHIFT;
  86                 if (TASK_IS_32BIT_ADDR)
  87                         random_factor &= 0xfffffful;
  88                 else
  89                         random_factor &= 0xffffffful;
  90         }
  91
  92         mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
  93         mm->get_unmapped_area = arch_get_unmapped_area;
  94         mm->unmap_area = arch_unmap_area;
  95 }
  96
  97 static inline unsigned long brk_rnd(void)
  98 {
  99         unsigned long rnd = get_random_int();
 100
 101         rnd = rnd << PAGE_SHIFT;
 102         /* 8MB for 32bit, 256MB for 64bit */
 103         if (TASK_IS_32BIT_ADDR)
 104                 rnd = rnd & 0x7ffffful;
 105         else
 106                 rnd = rnd & 0xffffffful;
 107
 108         return rnd;
 109 }
 110
 111 unsigned long arch_randomize_brk(struct mm_struct *mm)
 112 {
 113         unsigned long base = mm->brk;
 114         unsigned long ret;
 115
 116         ret = PAGE_ALIGN(base + brk_rnd());
 117
 118         if (ret < mm->brk)
 119                 return mm->brk;
 120
 121         return ret;
 122 }