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(struct rlimit *rlim_stack)
  43 {
  44         if (current->personality & ADDR_COMPAT_LAYOUT)
  45                 return 1;
  46
  47         if (rlim_stack->rlim_cur == 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                                       struct rlimit *rlim_stack)
  81 {
  82         unsigned long gap = rlim_stack->rlim_cur;
  83         unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
  84
  85         /* Values close to RLIM_INFINITY can overflow. */
  86         if (gap + pad > gap)
  87                 gap += pad;
  88
  89         if (gap < MIN_GAP)
  90                 gap = MIN_GAP;
  91         else if (gap > MAX_GAP)
  92                 gap = MAX_GAP;
  93
  94         return PAGE_ALIGN(DEFAULT_MAP_WINDOW - gap - rnd);
  95 }
  96
  97 #ifdef CONFIG_PPC_RADIX_MMU
  98 /*
  99  * Same function as generic code used only for radix, because we don't need to overload
 100  * the generic one. But we will have to duplicate, because hash select
 101  * HAVE_ARCH_UNMAPPED_AREA
 102  */
 103 static unsigned long
 104 radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
 105                              unsigned long len, unsigned long pgoff,
 106                              unsigned long flags)
 107 {
 108         struct mm_struct *mm = current->mm;
 109         struct vm_area_struct *vma;
 110         int fixed = (flags & MAP_FIXED);
 111         unsigned long high_limit;
 112         struct vm_unmapped_area_info info;
 113
 114         high_limit = DEFAULT_MAP_WINDOW;
 115         if (addr >= high_limit || (fixed && (addr + len > high_limit)))
 116                 high_limit = TASK_SIZE;
 117
 118         if (len > high_limit)
 119                 return -ENOMEM;
 120
 121         if (fixed) {
 122                 if (addr > high_limit - len)
 123                         return -ENOMEM;
 124                 return addr;
 125         }
 126
 127         if (addr) {
 128                 addr = PAGE_ALIGN(addr);
 129                 vma = find_vma(mm, addr);
 130                 if (high_limit - len >= addr && addr >= mmap_min_addr &&
 131                     (!vma || addr + len <= vm_start_gap(vma)))
 132                         return addr;
 133         }
 134
 135         info.flags = 0;
 136         info.length = len;
 137         info.low_limit = mm->mmap_base;
 138         info.high_limit = high_limit;
 139         info.align_mask = 0;
 140
 141         return vm_unmapped_area(&info);
 142 }
 143
 144 static unsigned long
 145 radix__arch_get_unmapped_area_topdown(struct file *filp,
 146                                      const unsigned long addr0,
 147                                      const unsigned long len,
 148                                      const unsigned long pgoff,
 149                                      const unsigned long flags)
 150 {
 151         struct vm_area_struct *vma;
 152         struct mm_struct *mm = current->mm;
 153         unsigned long addr = addr0;
 154         int fixed = (flags & MAP_FIXED);
 155         unsigned long high_limit;
 156         struct vm_unmapped_area_info info;
 157
 158         high_limit = DEFAULT_MAP_WINDOW;
 159         if (addr >= high_limit || (fixed && (addr + len > high_limit)))
 160                 high_limit = TASK_SIZE;
 161
 162         if (len > high_limit)
 163                 return -ENOMEM;
 164
 165         if (fixed) {
 166                 if (addr > high_limit - len)
 167                         return -ENOMEM;
 168                 return addr;
 169         }
 170
 171         if (addr) {
 172                 addr = PAGE_ALIGN(addr);
 173                 vma = find_vma(mm, addr);
 174                 if (high_limit - len >= addr && addr >= mmap_min_addr &&
 175                     (!vma || addr + len <= vm_start_gap(vma)))
 176                         return addr;
 177         }
 178
 179         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 180         info.length = len;
 181         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 182         info.high_limit = mm->mmap_base + (high_limit - DEFAULT_MAP_WINDOW);
 183         info.align_mask = 0;
 184
 185         addr = vm_unmapped_area(&info);
 186         if (!(addr & ~PAGE_MASK))
 187                 return addr;
 188         VM_BUG_ON(addr != -ENOMEM);
 189
 190         /*
 191          * A failed mmap() very likely causes application failure,
 192          * so fall back to the bottom-up function here. This scenario
 193          * can happen with large stack limits and large mmap()
 194          * allocations.
 195          */
 196         return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 197 }
 198
 199 static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 200                                         unsigned long random_factor,
 201                                         struct rlimit *rlim_stack)
 202 {
 203         if (mmap_is_legacy(rlim_stack)) {
 204                 mm->mmap_base = TASK_UNMAPPED_BASE;
 205                 mm->get_unmapped_area = radix__arch_get_unmapped_area;
 206         } else {
 207                 mm->mmap_base = mmap_base(random_factor, rlim_stack);
 208                 mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
 209         }
 210 }
 211 #else
 212 /* dummy */
 213 extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 214                                         unsigned long random_factor,
 215                                         struct rlimit *rlim_stack);
 216 #endif
 217 /*
 218  * This function, called very early during the creation of a new
 219  * process VM image, sets up which VM layout function to use:
 220  */
 221 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 222 {
 223         unsigned long random_factor = 0UL;
 224
 225         if (current->flags & PF_RANDOMIZE)
 226                 random_factor = arch_mmap_rnd();
 227
 228         if (radix_enabled())
 229                 return radix__arch_pick_mmap_layout(mm, random_factor,
 230                                                     rlim_stack);
 231         /*
 232          * Fall back to the standard layout if the personality
 233          * bit is set, or if the expected stack growth is unlimited:
 234          */
 235         if (mmap_is_legacy(rlim_stack)) {
 236                 mm->mmap_base = TASK_UNMAPPED_BASE;
 237                 mm->get_unmapped_area = arch_get_unmapped_area;
 238         } else {
 239                 mm->mmap_base = mmap_base(random_factor, rlim_stack);
 240                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 241         }
 242 }