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