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/elf-randomize.h>
  26 #include <linux/personality.h>
  27 #include <linux/mm.h>
  28 #include <linux/mman.h>
  29 #include <linux/random.h>
  30 #include <linux/compat.h>
  31 #include <linux/security.h>
  32 #include <asm/pgalloc.h>
  33 #include <asm/elf.h>
  34
  35 static unsigned long stack_maxrandom_size(void)
  36 {
  37         if (!(current->flags & PF_RANDOMIZE))
  38                 return 0;
  39         if (current->personality & ADDR_NO_RANDOMIZE)
  40                 return 0;
  41         return STACK_RND_MASK << PAGE_SHIFT;
  42 }
  43
  44 /*
  45  * Top of mmap area (just below the process stack).
  46  *
  47  * Leave at least a ~32 MB hole.
  48  */
  49 #define MIN_GAP (32*1024*1024)
  50 #define MAX_GAP (STACK_TOP/6*5)
  51
  52 static inline int mmap_is_legacy(void)
  53 {
  54         if (current->personality & ADDR_COMPAT_LAYOUT)
  55                 return 1;
  56         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  57                 return 1;
  58         return sysctl_legacy_va_layout;
  59 }
  60
  61 unsigned long arch_mmap_rnd(void)
  62 {
  63         return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
  64 }
  65
  66 static unsigned long mmap_base_legacy(unsigned long rnd)
  67 {
  68         return TASK_UNMAPPED_BASE + rnd;
  69 }
  70
  71 static inline unsigned long mmap_base(unsigned long rnd)
  72 {
  73         unsigned long gap = rlimit(RLIMIT_STACK);
  74
  75         if (gap < MIN_GAP)
  76                 gap = MIN_GAP;
  77         else if (gap > MAX_GAP)
  78                 gap = MAX_GAP;
  79         gap &= PAGE_MASK;
  80         return STACK_TOP - stack_maxrandom_size() - rnd - gap;
  81 }
  82
  83 unsigned long
  84 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  85                 unsigned long len, unsigned long pgoff, unsigned long flags)
  86 {
  87         struct mm_struct *mm = current->mm;
  88         struct vm_area_struct *vma;
  89         struct vm_unmapped_area_info info;
  90
  91         if (len > TASK_SIZE - mmap_min_addr)
  92                 return -ENOMEM;
  93
  94         if (flags & MAP_FIXED)
  95                 return addr;
  96
  97         if (addr) {
  98                 addr = PAGE_ALIGN(addr);
  99                 vma = find_vma(mm, addr);
 100                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 101                     (!vma || addr + len <= vma->vm_start))
 102                         return addr;
 103         }
 104
 105         info.flags = 0;
 106         info.length = len;
 107         info.low_limit = mm->mmap_base;
 108         info.high_limit = TASK_SIZE;
 109         if (filp || (flags & MAP_SHARED))
 110                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 111         else
 112                 info.align_mask = 0;
 113         info.align_offset = pgoff << PAGE_SHIFT;
 114         return vm_unmapped_area(&info);
 115 }
 116
 117 unsigned long
 118 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 119                           const unsigned long len, const unsigned long pgoff,
 120                           const unsigned long flags)
 121 {
 122         struct vm_area_struct *vma;
 123         struct mm_struct *mm = current->mm;
 124         unsigned long addr = addr0;
 125         struct vm_unmapped_area_info info;
 126
 127         /* requested length too big for entire address space */
 128         if (len > TASK_SIZE - mmap_min_addr)
 129                 return -ENOMEM;
 130
 131         if (flags & MAP_FIXED)
 132                 return addr;
 133
 134         /* requesting a specific address */
 135         if (addr) {
 136                 addr = PAGE_ALIGN(addr);
 137                 vma = find_vma(mm, addr);
 138                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 139                                 (!vma || addr + len <= vma->vm_start))
 140                         return addr;
 141         }
 142
 143         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 144         info.length = len;
 145         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 146         info.high_limit = mm->mmap_base;
 147         if (filp || (flags & MAP_SHARED))
 148                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 149         else
 150                 info.align_mask = 0;
 151         info.align_offset = pgoff << PAGE_SHIFT;
 152         addr = vm_unmapped_area(&info);
 153
 154         /*
 155          * A failed mmap() very likely causes application failure,
 156          * so fall back to the bottom-up function here. This scenario
 157          * can happen with large stack limits and large mmap()
 158          * allocations.
 159          */
 160         if (addr & ~PAGE_MASK) {
 161                 VM_BUG_ON(addr != -ENOMEM);
 162                 info.flags = 0;
 163                 info.low_limit = TASK_UNMAPPED_BASE;
 164                 info.high_limit = TASK_SIZE;
 165                 addr = vm_unmapped_area(&info);
 166         }
 167
 168         return addr;
 169 }
 170
 171 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
 172 {
 173         if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
 174                 return 0;
 175         if (!(flags & MAP_FIXED))
 176                 addr = 0;
 177         if ((addr + len) >= TASK_SIZE)
 178                 return crst_table_upgrade(current->mm);
 179         return 0;
 180 }
 181
 182 static unsigned long
 183 s390_get_unmapped_area(struct file *filp, unsigned long addr,
 184                 unsigned long len, unsigned long pgoff, unsigned long flags)
 185 {
 186         struct mm_struct *mm = current->mm;
 187         unsigned long area;
 188         int rc;
 189
 190         area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 191         if (!(area & ~PAGE_MASK))
 192                 return area;
 193         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
 194                 /* Upgrade the page table to 4 levels and retry. */
 195                 rc = crst_table_upgrade(mm);
 196                 if (rc)
 197                         return (unsigned long) rc;
 198                 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 199         }
 200         return area;
 201 }
 202
 203 static unsigned long
 204 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
 205                           const unsigned long len, const unsigned long pgoff,
 206                           const unsigned long flags)
 207 {
 208         struct mm_struct *mm = current->mm;
 209         unsigned long area;
 210         int rc;
 211
 212         area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
 213         if (!(area & ~PAGE_MASK))
 214                 return area;
 215         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
 216                 /* Upgrade the page table to 4 levels and retry. */
 217                 rc = crst_table_upgrade(mm);
 218                 if (rc)
 219                         return (unsigned long) rc;
 220                 area = arch_get_unmapped_area_topdown(filp, addr, len,
 221                                                       pgoff, flags);
 222         }
 223         return area;
 224 }
 225 /*
 226  * This function, called very early during the creation of a new
 227  * process VM image, sets up which VM layout function to use:
 228  */
 229 void arch_pick_mmap_layout(struct mm_struct *mm)
 230 {
 231         unsigned long random_factor = 0UL;
 232
 233         if (current->flags & PF_RANDOMIZE)
 234                 random_factor = arch_mmap_rnd();
 235
 236         /*
 237          * Fall back to the standard layout if the personality
 238          * bit is set, or if the expected stack growth is unlimited:
 239          */
 240         if (mmap_is_legacy()) {
 241                 mm->mmap_base = mmap_base_legacy(random_factor);
 242                 mm->get_unmapped_area = s390_get_unmapped_area;
 243         } else {
 244                 mm->mmap_base = mmap_base(random_factor);
 245                 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
 246         }
 247 }