arch/s390/mm/mmap.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  *  flexible mmap layout support
   4  *
   5  * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
   6  * All Rights Reserved.
   7  *
   8  * Started by Ingo Molnar <mingo@elte.hu>
   9  */
  10
  11 #include <linux/elf-randomize.h>
  12 #include <linux/personality.h>
  13 #include <linux/mm.h>
  14 #include <linux/mman.h>
  15 #include <linux/sched/signal.h>
  16 #include <linux/sched/mm.h>
  17 #include <linux/random.h>
  18 #include <linux/compat.h>
  19 #include <linux/security.h>
  20 #include <asm/pgalloc.h>
  21 #include <asm/elf.h>
  22
  23 static unsigned long stack_maxrandom_size(void)
  24 {
  25         if (!(current->flags & PF_RANDOMIZE))
  26                 return 0;
  27         if (current->personality & ADDR_NO_RANDOMIZE)
  28                 return 0;
  29         return STACK_RND_MASK << PAGE_SHIFT;
  30 }
  31
  32 /*
  33  * Top of mmap area (just below the process stack).
  34  *
  35  * Leave at least a ~32 MB hole.
  36  */
  37 #define MIN_GAP (32*1024*1024)
  38 #define MAX_GAP (STACK_TOP/6*5)
  39
  40 static inline int mmap_is_legacy(void)
  41 {
  42         if (current->personality & ADDR_COMPAT_LAYOUT)
  43                 return 1;
  44         if (rlimit(RLIMIT_STACK) == RLIM_INFINITY)
  45                 return 1;
  46         return sysctl_legacy_va_layout;
  47 }
  48
  49 unsigned long arch_mmap_rnd(void)
  50 {
  51         return (get_random_int() & MMAP_RND_MASK) << PAGE_SHIFT;
  52 }
  53
  54 static unsigned long mmap_base_legacy(unsigned long rnd)
  55 {
  56         return TASK_UNMAPPED_BASE + rnd;
  57 }
  58
  59 static inline unsigned long mmap_base(unsigned long rnd)
  60 {
  61         unsigned long gap = rlimit(RLIMIT_STACK);
  62
  63         if (gap < MIN_GAP)
  64                 gap = MIN_GAP;
  65         else if (gap > MAX_GAP)
  66                 gap = MAX_GAP;
  67         gap &= PAGE_MASK;
  68         return STACK_TOP - stack_maxrandom_size() - rnd - gap;
  69 }
  70
  71 unsigned long
  72 arch_get_unmapped_area(struct file *filp, unsigned long addr,
  73                 unsigned long len, unsigned long pgoff, unsigned long flags)
  74 {
  75         struct mm_struct *mm = current->mm;
  76         struct vm_area_struct *vma;
  77         struct vm_unmapped_area_info info;
  78         int rc;
  79
  80         if (len > TASK_SIZE - mmap_min_addr)
  81                 return -ENOMEM;
  82
  83         if (flags & MAP_FIXED)
  84                 goto check_asce_limit;
  85
  86         if (addr) {
  87                 addr = PAGE_ALIGN(addr);
  88                 vma = find_vma(mm, addr);
  89                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
  90                     (!vma || addr + len <= vm_start_gap(vma)))
  91                         goto check_asce_limit;
  92         }
  93
  94         info.flags = 0;
  95         info.length = len;
  96         info.low_limit = mm->mmap_base;
  97         info.high_limit = TASK_SIZE;
  98         if (filp || (flags & MAP_SHARED))
  99                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 100         else
 101                 info.align_mask = 0;
 102         info.align_offset = pgoff << PAGE_SHIFT;
 103         addr = vm_unmapped_area(&info);
 104         if (addr & ~PAGE_MASK)
 105                 return addr;
 106
 107 check_asce_limit:
 108         if (addr + len > current->mm->context.asce_limit &&
 109             addr + len <= TASK_SIZE) {
 110                 rc = crst_table_upgrade(mm, addr + len);
 111                 if (rc)
 112                         return (unsigned long) rc;
 113         }
 114
 115         return addr;
 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         int rc;
 128
 129         /* requested length too big for entire address space */
 130         if (len > TASK_SIZE - mmap_min_addr)
 131                 return -ENOMEM;
 132
 133         if (flags & MAP_FIXED)
 134                 goto check_asce_limit;
 135
 136         /* requesting a specific address */
 137         if (addr) {
 138                 addr = PAGE_ALIGN(addr);
 139                 vma = find_vma(mm, addr);
 140                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
 141                                 (!vma || addr + len <= vm_start_gap(vma)))
 142                         goto check_asce_limit;
 143         }
 144
 145         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
 146         info.length = len;
 147         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
 148         info.high_limit = mm->mmap_base;
 149         if (filp || (flags & MAP_SHARED))
 150                 info.align_mask = MMAP_ALIGN_MASK << PAGE_SHIFT;
 151         else
 152                 info.align_mask = 0;
 153         info.align_offset = pgoff << PAGE_SHIFT;
 154         addr = vm_unmapped_area(&info);
 155
 156         /*
 157          * A failed mmap() very likely causes application failure,
 158          * so fall back to the bottom-up function here. This scenario
 159          * can happen with large stack limits and large mmap()
 160          * allocations.
 161          */
 162         if (addr & ~PAGE_MASK) {
 163                 VM_BUG_ON(addr != -ENOMEM);
 164                 info.flags = 0;
 165                 info.low_limit = TASK_UNMAPPED_BASE;
 166                 info.high_limit = TASK_SIZE;
 167                 addr = vm_unmapped_area(&info);
 168                 if (addr & ~PAGE_MASK)
 169                         return addr;
 170         }
 171
 172 check_asce_limit:
 173         if (addr + len > current->mm->context.asce_limit &&
 174             addr + len <= TASK_SIZE) {
 175                 rc = crst_table_upgrade(mm, addr + len);
 176                 if (rc)
 177                         return (unsigned long) rc;
 178         }
 179
 180         return addr;
 181 }
 182
 183 /*
 184  * This function, called very early during the creation of a new
 185  * process VM image, sets up which VM layout function to use:
 186  */
 187 void arch_pick_mmap_layout(struct mm_struct *mm)
 188 {
 189         unsigned long random_factor = 0UL;
 190
 191         if (current->flags & PF_RANDOMIZE)
 192                 random_factor = arch_mmap_rnd();
 193
 194         /*
 195          * Fall back to the standard layout if the personality
 196          * bit is set, or if the expected stack growth is unlimited:
 197          */
 198         if (mmap_is_legacy()) {
 199                 mm->mmap_base = mmap_base_legacy(random_factor);
 200                 mm->get_unmapped_area = arch_get_unmapped_area;
 201         } else {
 202                 mm->mmap_base = mmap_base(random_factor);
 203                 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 204         }
 205 }