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/sched/signal.h>
  30 #include <linux/random.h>
  31 #include <linux/compat.h>
  32 #include <linux/security.h>
  33 #include <asm/pgalloc.h>
  34 #include <asm/elf.h>
  35
  36 static unsigned long stack_maxrandom_size(void)
  37 {
  38         if (!(current->flags & PF_RANDOMIZE))
  39                 return 0;
  40         if (current->personality & ADDR_NO_RANDOMIZE)
  41                 return 0;
  42         return STACK_RND_MASK << PAGE_SHIFT;
  43 }
  44
  45 /*
  46  * Top of mmap area (just below the process stack).
  47  *
  48  * Leave at least a ~32 MB hole.
  49  */
  50 #define MIN_GAP (32*1024*1024)
  51 #define MAX_GAP (STACK_TOP/6*5)
  52
  53 static inline int mmap_is_legacy(void)
  54 {
  55         if (current->personality & ADDR_COMPAT_LAYOUT)
  56                 return 1;
  57         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  58                 return 1;
  59         return sysctl_legacy_va_layout;
  60 }
  61
  62 unsigned long arch_mmap_rnd(void)
  63 {
  64         return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
  65 }
  66
  67 static unsigned long mmap_base_legacy(unsigned long rnd)
  68 {
  69         return TASK_UNMAPPED_BASE + rnd;
  70 }
  71
  72 static inline unsigned long mmap_base(unsigned long rnd)
  73 {
  74         unsigned long gap = rlimit(RLIMIT_STACK);
  75
  76         if (gap < MIN_GAP)
  77                 gap = MIN_GAP;
  78         else if (gap > MAX_GAP)
  79                 gap = MAX_GAP;
  80         gap &= PAGE_MASK;
  81         return STACK_TOP - stack_maxrandom_size() - rnd - gap;
  82 }
  83
  84 unsigned long
  85 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  86                 unsigned long len, unsigned long pgoff, unsigned long flags)
  87 {
  88         struct mm_struct *mm = current->mm;
  89         struct vm_area_struct *vma;
  90         struct vm_unmapped_area_info info;
  91
  92         if (len > TASK_SIZE - mmap_min_addr)
  93                 return -ENOMEM;
  94
  95         if (flags & MAP_FIXED)
  96                 return addr;
  97
  98         if (addr) {
  99                 addr = PAGE_ALIGN(addr);
 100                 vma = find_vma(mm, addr);
 101                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 102                     (!vma || addr + len <= vma->vm_start))
 103                         return addr;
 104         }
 105
 106         info.flags = 0;
 107         info.length = len;
 108         info.low_limit = mm->mmap_base;
 109         info.high_limit = TASK_SIZE;
 110         if (filp || (flags & MAP_SHARED))
 111                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 112         else
 113                 info.align_mask = 0;
 114         info.align_offset = pgoff << PAGE_SHIFT;
 115         return vm_unmapped_area(&info);
 116 }
 117
 118 unsigned long
 119 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 120                           const unsigned long len, const unsigned long pgoff,
 121                           const unsigned long flags)
 122 {
 123         struct vm_area_struct *vma;
 124         struct mm_struct *mm = current->mm;
 125         unsigned long addr = addr0;
 126         struct vm_unmapped_area_info info;
 127
 128         /* requested length too big for entire address space */
 129         if (len > TASK_SIZE - mmap_min_addr)
 130                 return -ENOMEM;
 131
 132         if (flags & MAP_FIXED)
 133                 return addr;
 134
 135         /* requesting a specific address */
 136         if (addr) {
 137                 addr = PAGE_ALIGN(addr);
 138                 vma = find_vma(mm, addr);
 139                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 140                                 (!vma || addr + len <= vma->vm_start))
 141                         return addr;
 142         }
 143
 144         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 145         info.length = len;
 146         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 147         info.high_limit = mm->mmap_base;
 148         if (filp || (flags & MAP_SHARED))
 149                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 150         else
 151                 info.align_mask = 0;
 152         info.align_offset = pgoff << PAGE_SHIFT;
 153         addr = vm_unmapped_area(&info);
 154
 155         /*
 156          * A failed mmap() very likely causes application failure,
 157          * so fall back to the bottom-up function here. This scenario
 158          * can happen with large stack limits and large mmap()
 159          * allocations.
 160          */
 161         if (addr & ~PAGE_MASK) {
 162                 VM_BUG_ON(addr != -ENOMEM);
 163                 info.flags = 0;
 164                 info.low_limit = TASK_UNMAPPED_BASE;
 165                 info.high_limit = TASK_SIZE;
 166                 addr = vm_unmapped_area(&info);
 167         }
 168
 169         return addr;
 170 }
 171
 172 int s390_mmap_check(unsigned long addr, unsigned long len, unsigned long flags)
 173 {
 174         if (is_compat_task() || TASK_SIZE >= TASK_MAX_SIZE)
 175                 return 0;
 176         if (!(flags & MAP_FIXED))
 177                 addr = 0;
 178         if ((addr + len) >= TASK_SIZE)
 179                 return crst_table_upgrade(current->mm);
 180         return 0;
 181 }
 182
 183 static unsigned long
 184 s390_get_unmapped_area(struct file *filp, unsigned long addr,
 185                 unsigned long len, unsigned long pgoff, unsigned long flags)
 186 {
 187         struct mm_struct *mm = current->mm;
 188         unsigned long area;
 189         int rc;
 190
 191         area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 192         if (!(area & ~PAGE_MASK))
 193                 return area;
 194         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
 195                 /* Upgrade the page table to 4 levels and retry. */
 196                 rc = crst_table_upgrade(mm);
 197                 if (rc)
 198                         return (unsigned long) rc;
 199                 area = arch_get_unmapped_area(filp, addr, len, pgoff, flags);
 200         }
 201         return area;
 202 }
 203
 204 static unsigned long
 205 s390_get_unmapped_area_topdown(struct file *filp, const unsigned long addr,
 206                           const unsigned long len, const unsigned long pgoff,
 207                           const unsigned long flags)
 208 {
 209         struct mm_struct *mm = current->mm;
 210         unsigned long area;
 211         int rc;
 212
 213         area = arch_get_unmapped_area_topdown(filp, addr, len, pgoff, flags);
 214         if (!(area & ~PAGE_MASK))
 215                 return area;
 216         if (area == -ENOMEM && !is_compat_task() && TASK_SIZE < TASK_MAX_SIZE) {
 217                 /* Upgrade the page table to 4 levels and retry. */
 218                 rc = crst_table_upgrade(mm);
 219                 if (rc)
 220                         return (unsigned long) rc;
 221                 area = arch_get_unmapped_area_topdown(filp, addr, len,
 222                                                       pgoff, flags);
 223         }
 224         return area;
 225 }
 226 /*
 227  * This function, called very early during the creation of a new
 228  * process VM image, sets up which VM layout function to use:
 229  */
 230 void arch_pick_mmap_layout(struct mm_struct *mm)
 231 {
 232         unsigned long random_factor = 0UL;
 233
 234         if (current->flags & PF_RANDOMIZE)
 235                 random_factor = arch_mmap_rnd();
 236
 237         /*
 238          * Fall back to the standard layout if the personality
 239          * bit is set, or if the expected stack growth is unlimited:
 240          */
 241         if (mmap_is_legacy()) {
 242                 mm->mmap_base = mmap_base_legacy(random_factor);
 243                 mm->get_unmapped_area = s390_get_unmapped_area;
 244         } else {
 245                 mm->mmap_base = mmap_base(random_factor);
 246                 mm->get_unmapped_area = s390_get_unmapped_area_topdown;
 247         }
 248 }