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