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         struct vm_unmapped_area_info info;
 110
 111         if (unlikely(addr > mm->context.addr_limit &&
 112                      mm->context.addr_limit != TASK_SIZE))
 113                 mm->context.addr_limit = TASK_SIZE;
 114
 115         if (len > mm->task_size - mmap_min_addr)
 116                 return -ENOMEM;
 117
 118         if (flags & MAP_FIXED)
 119                 return addr;
 120
 121         if (addr) {
 122                 addr = PAGE_ALIGN(addr);
 123                 vma = find_vma(mm, addr);
 124                 if (mm->task_size - len >= addr && addr >= mmap_min_addr &&
 125                     (!vma || addr + len <= vm_start_gap(vma)))
 126                         return addr;
 127         }
 128
 129         info.flags = 0;
 130         info.length = len;
 131         info.low_limit = mm->mmap_base;
 132         info.align_mask = 0;
 133
 134         if (unlikely(addr > DEFAULT_MAP_WINDOW))
 135                 info.high_limit = mm->context.addr_limit;
 136         else
 137                 info.high_limit = DEFAULT_MAP_WINDOW;
 138
 139         return vm_unmapped_area(&info);
 140 }
 141
 142 static unsigned long
 143 radix__arch_get_unmapped_area_topdown(struct file *filp,
 144                                      const unsigned long addr0,
 145                                      const unsigned long len,
 146                                      const unsigned long pgoff,
 147                                      const unsigned long flags)
 148 {
 149         struct vm_area_struct *vma;
 150         struct mm_struct *mm = current->mm;
 151         unsigned long addr = addr0;
 152         struct vm_unmapped_area_info info;
 153
 154         if (unlikely(addr > mm->context.addr_limit &&
 155                      mm->context.addr_limit != TASK_SIZE))
 156                 mm->context.addr_limit = TASK_SIZE;
 157
 158         /* requested length too big for entire address space */
 159         if (len > mm->task_size - mmap_min_addr)
 160                 return -ENOMEM;
 161
 162         if (flags & MAP_FIXED)
 163                 return addr;
 164
 165         /* requesting a specific address */
 166         if (addr) {
 167                 addr = PAGE_ALIGN(addr);
 168                 vma = find_vma(mm, addr);
 169                 if (mm->task_size - len >= addr && addr >= mmap_min_addr &&
 170                                 (!vma || addr + len <= vm_start_gap(vma)))
 171                         return addr;
 172         }
 173
 174         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 175         info.length = len;
 176         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 177         info.high_limit = mm->mmap_base;
 178         info.align_mask = 0;
 179
 180         if (addr > DEFAULT_MAP_WINDOW)
 181                 info.high_limit += mm->context.addr_limit - DEFAULT_MAP_WINDOW;
 182
 183         addr = vm_unmapped_area(&info);
 184         if (!(addr & ~PAGE_MASK))
 185                 return addr;
 186         VM_BUG_ON(addr != -ENOMEM);
 187
 188         /*
 189          * A failed mmap() very likely causes application failure,
 190          * so fall back to the bottom-up function here. This scenario
 191          * can happen with large stack limits and large mmap()
 192          * allocations.
 193          */
 194         return radix__arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 195 }
 196
 197 static void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 198                                         unsigned long random_factor)
 199 {
 200         if (mmap_is_legacy()) {
 201                 mm->mmap_base = TASK_UNMAPPED_BASE;
 202                 mm->get_unmapped_area = radix__arch_get_unmapped_area;
 203         } else {
 204                 mm->mmap_base = mmap_base(random_factor);
 205                 mm->get_unmapped_area = radix__arch_get_unmapped_area_topdown;
 206         }
 207 }
 208 #else
 209 /* dummy */
 210 extern void radix__arch_pick_mmap_layout(struct mm_struct *mm,
 211                                         unsigned long random_factor);
 212 #endif
 213 /*
 214  * This function, called very early during the creation of a new
 215  * process VM image, sets up which VM layout function to use:
 216  */
 217 void arch_pick_mmap_layout(struct mm_struct *mm)
 218 {
 219         unsigned long random_factor = 0UL;
 220
 221         if (current->flags & PF_RANDOMIZE)
 222                 random_factor = arch_mmap_rnd();
 223
 224         if (radix_enabled())
 225                 return radix__arch_pick_mmap_layout(mm, random_factor);
 226         /*
 227          * Fall back to the standard layout if the personality
 228          * bit is set, or if the expected stack growth is unlimited:
 229          */
 230         if (mmap_is_legacy()) {
 231                 mm->mmap_base = TASK_UNMAPPED_BASE;
 232                 mm->get_unmapped_area = arch_get_unmapped_area;
 233         } else {
 234                 mm->mmap_base = mmap_base(random_factor);
 235                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 236         }
 237 }