arch/powerpc/mm/mmap.c

   1 /*
   2  *  flexible mmap layout support
   3  *
   4  * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
   5  * All Rights Reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  *
  21  *
  22  * Started by Ingo Molnar <mingo@elte.hu>
  23  */
  24
  25 #include <linux/personality.h>
  26 #include <linux/mm.h>
  27 #include <linux/random.h>
  28 #include <linux/sched/signal.h>
  29 #include <linux/sched/mm.h>
  30 #include <linux/elf-randomize.h>
  31 #include <linux/security.h>
  32 #include <linux/mman.h>
  33
  34 /*
  35  * Top of mmap area (just below the process stack).
  36  *
  37  * Leave at least a ~128 MB hole.
  38  */
  39 #define MIN_GAP (128*1024*1024)
  40 #define MAX_GAP (TASK_SIZE/6*5)
  41
  42 static inline int mmap_is_legacy(void)
  43 {
  44         if (current->personality & ADDR_COMPAT_LAYOUT)
  45                 return 1;
  46
  47         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  48                 return 1;
  49
  50         return sysctl_legacy_va_layout;
  51 }
  52
  53 unsigned long arch_mmap_rnd(void)
  54 {
  55         unsigned long shift, rnd;
  56
  57         shift = mmap_rnd_bits;
  58 #ifdef CONFIG_COMPAT
  59         if (is_32bit_task())
  60                 shift = mmap_rnd_compat_bits;
  61 #endif
  62         rnd = get_random_long() % (1ul << shift);
  63
  64         return rnd << PAGE_SHIFT;
  65 }
  66
  67 static inline unsigned long stack_maxrandom_size(void)
  68 {
  69         if (!(current->flags & PF_RANDOMIZE))
  70                 return 0;
  71
  72         /* 8MB for 32bit, 1GB for 64bit */
  73         if (is_32bit_task())
  74                 return (1<<23);
  75         else
  76                 return (1<<30);
  77 }
  78
  79 static inline unsigned long mmap_base(unsigned long rnd)
  80 {
  81         unsigned long gap = rlimit(RLIMIT_STACK);
  82         unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
  83
  84         /* Values close to RLIM_INFINITY can overflow. */
  85         if (gap + pad > gap)
  86                 gap += pad;
  87
  88         if (gap < MIN_GAP)
  89                 gap = MIN_GAP;
  90         else if (gap > MAX_GAP)
  91                 gap = MAX_GAP;
  92
  93         return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd);
  94 }
  95
  96 #ifdef CONFIG_PPC_RADIX_MMU
  97 /*
  98  * Same function as generic code used only for radix, because we don't need to overload
  99  * the generic one. But we will have to duplicate, because hash select
 100  * HAVE_ARCH_UNMAPPED_AREA
 101  */
 102 static unsigned long
 103 radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
 104                              unsigned long len, unsigned long pgoff,
 105                              unsigned long flags)
 106 {
 107         struct mm_struct *mm = current->mm;
 108         struct vm_area_struct *vma;
 109         int fixed = (flags & MAP_FIXED);
 110         unsigned long high_limit;
 111         struct vm_unmapped_area_info info;
 112
 113         high_limit = DEFAULT_MAP_WINDOW;
 114         if (addr >= high_limit || (fixed && (addr + len > high_limit)))
 115                 high_limit = TASK_SIZE;
 116
 117         if (len > high_limit)
 118                 return -ENOMEM;
 119
 120         if (fixed) {
 121                 if (addr > high_limit - len)
 122                         return -ENOMEM;
 123                 return addr;
 124         }
 125
 126         if (addr) {
 127                 addr = PAGE_ALIGN(addr);
 128                 vma = find_vma(mm, addr);
 129                 if (high_limit - len >= addr && addr >= mmap_min_addr &&
 130                     (!vma || addr + len <= vm_start_gap(vma)))
 131                         return addr;
 132         }
 133
 134         info.flags = 0;
 135         info.length = len;
 136         info.low_limit = mm->mmap_base;
 137         info.high_limit = high_limit;
 138         info.align_mask = 0;
 139
 140         return vm_unmapped_area(&info);
 141 }
 142
 143 static unsigned long
 144 radix__arch_get_unmapped_area_topdown(struct file *filp,
 145                                      const unsigned long addr0,
 146                                      const unsigned long len,
 147                                      const unsigned long pgoff,
 148                                      const unsigned long flags)
 149 {
 150         struct vm_area_struct *vma;
 151         struct mm_struct *mm = current->mm;
 152         unsigned long addr = addr0;
 153         int fixed = (flags & MAP_FIXED);
 154         unsigned long high_limit;
 155         struct vm_unmapped_area_info info;
 156
 157         high_limit = DEFAULT_MAP_WINDOW;
 158         if (addr >= high_limit || (fixed && (addr + len > high_limit)))
 159                 high_limit = TASK_SIZE;
 160
 161         if (len > high_limit)
 162                 return -ENOMEM;
 163
 164         if (fixed) {
 165                 if (addr > high_limit - len)
 166                         return -ENOMEM;
 167                 return addr;
 168         }
 169
 170         if (addr) {
 171                 addr = PAGE_ALIGN(addr);
 172                 vma = find_vma(mm, addr);
 173                 if (high_limit - len >= addr && addr >= mmap_min_addr &&
 174                     (!vma || addr + len <= vm_start_gap(vma)))
 175                         return addr;
 176         }
 177
 178         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 179         info.length = len;
 180         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 181         info.high_limit = mm->mmap_base + (high_limit - DEFAULT_MAP_WINDOW);
 182         info.align_mask = 0;
 183
 184         addr = vm_unmapped_area(&info);
 185         if (!(addr & ~PAGE_MASK))
 186                 return addr;
 187         VM_BUG_ON(addr != -ENOMEM);
 188
 189         /*
 190          * A failed mmap() very likely causes application failure,
 191          * so fall back to the bottom-up function here. This scenario
 192          * can happen with large stack limits and large mmap()
 193          * allocations.
 194          */
 195         return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 196 }
 197
 198 static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 199                                         unsigned long random_factor)
 200 {
 201         if (mmap_is_legacy()) {
 202                 mm->mmap_base = TASK_UNMAPPED_BASE;
 203                 mm->get_unmapped_area = radix__arch_get_unmapped_area;
 204         } else {
 205                 mm->mmap_base = mmap_base(random_factor);
 206                 mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
 207         }
 208 }
 209 #else
 210 /* dummy */
 211 extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 212                                         unsigned long random_factor);
 213 #endif
 214 /*
 215  * This function, called very early during the creation of a new
 216  * process VM image, sets up which VM layout function to use:
 217  */
 218 void arch_pick_mmap_layout(struct mm_struct *mm)
 219 {
 220         unsigned long random_factor = 0UL;
 221
 222         if (current->flags & PF_RANDOMIZE)
 223                 random_factor = arch_mmap_rnd();
 224
 225         if (radix_enabled())
 226                 return radix__arch_pick_mmap_layout(mm, random_factor);
 227         /*
 228          * Fall back to the standard layout if the personality
 229          * bit is set, or if the expected stack growth is unlimited:
 230          */
 231         if (mmap_is_legacy()) {
 232                 mm->mmap_base = TASK_UNMAPPED_BASE;
 233                 mm->get_unmapped_area = arch_get_unmapped_area;
 234         } else {
 235                 mm->mmap_base = mmap_base(random_factor);
 236                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 237         }
 238 }