arch/s390/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/mman.h>
  28 #include <linux/module.h>
  29 #include <linux/random.h>
  30 #include <linux/compat.h>
  31 #include <linux/security.h>
  32 #include <asm/pgalloc.h>
  33
  34 static unsigned long stack_maxrandom_size(void)
  35 {
  36         if (!(current->flags & PF_RANDOMIZE))
  37                 return 0;
  38         if (current->personality & ADDR_NO_RANDOMIZE)
  39                 return 0;
  40         return STACK_RND_MASK << PAGE_SHIFT;
  41 }
  42
  43 /*
  44  * Top of mmap area (just below the process stack).
  45  *
  46  * Leave at least a ~32 MB hole.
  47  */
  48 #define MIN_GAP (32*1024*1024)
  49 #define MAX_GAP (STACK_TOP/6*5)
  50
  51 static inline int mmap_is_legacy(void)
  52 {
  53         if (current->personality & ADDR_COMPAT_LAYOUT)
  54                 return 1;
  55         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  56                 return 1;
  57         return sysctl_legacy_va_layout;
  58 }
  59
  60 unsigned long arch_mmap_rnd(void)
  61 {
  62         return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
  63 }
  64
  65 static unsigned long mmap_base_legacy(unsigned long rnd)
  66 {
  67         return TASK_UNMAPPED_BASE + rnd;
  68 }
  69
  70 static inline unsigned long mmap_base(unsigned long rnd)
  71 {
  72         unsigned long gap = rlimit(RLIMIT_STACK);
  73
  74         if (gap < MIN_GAP)
  75                 gap = MIN_GAP;
  76         else if (gap > MAX_GAP)
  77                 gap = MAX_GAP;
  78         gap &= PAGE_MASK;
  79         return STACK_TOP - stack_maxrandom_size() - rnd - gap;
  80 }
  81
  82 unsigned long
  83 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  84                 unsigned long len, unsigned long pgoff, unsigned long flags)
  85 {
  86         struct mm_struct *mm = current->mm;
  87         struct vm_area_struct *vma;
  88         struct vm_unmapped_area_info info;
  89
  90         if (len > TASK_SIZE - mmap_min_addr)
  91                 return -ENOMEM;
  92
  93         if (flags & MAP_FIXED)
  94                 return addr;
  95
  96         if (addr) {
  97                 addr = PAGE_ALIGN(addr);
  98                 vma = find_vma(mm, addr);
  99                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 100                     (!vma || addr + len <= vma->vm_start))
 101                         return addr;
 102         }
 103
 104         info.flags = 0;
 105         info.length = len;
 106         info.low_limit = mm->mmap_base;
 107         info.high_limit = TASK_SIZE;
 108         if (filp || (flags & MAP_SHARED))
 109                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 110         else
 111                 info.align_mask = 0;
 112         info.align_offset = pgoff << PAGE_SHIFT;
 113         return vm_unmapped_area(&info);
 114 }
 115
 116 unsigned long
 117 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 118                           const unsigned long len, const unsigned long pgoff,
 119                           const unsigned long flags)
 120 {
 121         struct vm_area_struct *vma;
 122         struct mm_struct *mm = current->mm;
 123         unsigned long addr = addr0;
 124         struct vm_unmapped_area_info info;
 125
 126         /* requested length too big for entire address space */
 127         if (len > TASK_SIZE - mmap_min_addr)
 128                 return -ENOMEM;
 129
 130         if (flags & MAP_FIXED)
 131                 return addr;
 132
 133         /* requesting a specific address */
 134         if (addr) {
 135                 addr = PAGE_ALIGN(addr);
 136                 vma = find_vma(mm, addr);
 137                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 138                                 (!vma || addr + len <= vma->vm_start))
 139                         return addr;
 140         }
 141
 142         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 143         info.length = len;
 144         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 145         info.high_limit = mm->mmap_base;
 146         if (filp || (flags & MAP_SHARED))
 147                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 148         else
 149                 info.align_mask = 0;
 150         info.align_offset = pgoff << PAGE_SHIFT;
 151         addr = vm_unmapped_area(&info);
 152
 153         /*
 154          * A failed mmap() very likely causes application failure,
 155          * so fall back to the bottom-up function here. This scenario
 156          * can happen with large stack limits and large mmap()
 157          * allocations.
 158          */
 159         if (addr & ~PAGE_MASK) {
 160                 VM_BUG_ON(addr != -ENOMEM);
 161                 info.flags = 0;
 162                 info.low_limit = TASK_UNMAPPED_BASE;
 163                 info.high_limit = TASK_SIZE;
 164                 addr = vm_unmapped_area(&info);
 165         }
 166
 167         return addr;
 168 }
 169
 170 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
 171 {
 172         if (is_compat_task() || (TASK_SIZE >= (1UL << 53)))
 173                 return 0;
 174         if (!(flags & MAP_FIXED))
 175                 addr = 0;
 176         if ((addr + len) >= TASK_SIZE)
 177                 return crst_table_upgrade(current->mm, 1UL << 53);
 178         return 0;
 179 }
 180
 181 static unsigned long
 182 s390_get_unmapped_area(struct file *filp, unsigned long addr,
 183                 unsigned long len, unsigned long pgoff, unsigned long flags)
 184 {
 185         struct mm_struct *mm = current->mm;
 186         unsigned long area;
 187         int rc;
 188
 189         area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 190         if (!(area & ~PAGE_MASK))
 191                 return area;
 192         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
 193                 /* Upgrade the page table to 4 levels and retry. */
 194                 rc = crst_table_upgrade(mm, 1UL << 53);
 195                 if (rc)
 196                         return (unsigned long) rc;
 197                 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 198         }
 199         return area;
 200 }
 201
 202 static unsigned long
 203 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
 204                           const unsigned long len, const unsigned long pgoff,
 205                           const unsigned long flags)
 206 {
 207         struct mm_struct *mm = current->mm;
 208         unsigned long area;
 209         int rc;
 210
 211         area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
 212         if (!(area & ~PAGE_MASK))
 213                 return area;
 214         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < (1UL << 53)) {
 215                 /* Upgrade the page table to 4 levels and retry. */
 216                 rc = crst_table_upgrade(mm, 1UL << 53);
 217                 if (rc)
 218                         return (unsigned long) rc;
 219                 area = arch_get_unmapped_area_topdown(filp, addr, len,
 220                                                       pgoff, flags);
 221         }
 222         return area;
 223 }
 224 /*
 225  * This function, called very early during the creation of a new
 226  * process VM image, sets up which VM layout function to use:
 227  */
 228 void arch_pick_mmap_layout(struct mm_struct *mm)
 229 {
 230         unsigned long random_factor = 0UL;
 231
 232         if (current->flags & PF_RANDOMIZE)
 233                 random_factor = arch_mmap_rnd();
 234
 235         /*
 236          * Fall back to the standard layout if the personality
 237          * bit is set, or if the expected stack growth is unlimited:
 238          */
 239         if (mmap_is_legacy()) {
 240                 mm->mmap_base = mmap_base_legacy(random_factor);
 241                 mm->get_unmapped_area = s390_get_unmapped_area;
 242         } else {
 243                 mm->mmap_base = mmap_base(random_factor);
 244                 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
 245         }
 246 }