1 /* 2 * Flexible mmap layout support 3 * 4 * Based on code by Ingo Molnar and Andi Kleen, copyrighted 5 * as follows: 6 * 7 * Copyright 2003-2009 Red Hat Inc. 8 * All Rights Reserved. 9 * Copyright 2005 Andi Kleen, SUSE Labs. 10 * Copyright 2007 Jiri Kosina, SUSE Labs. 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License as published by 14 * the Free Software Foundation; either version 2 of the License, or 15 * (at your option) any later version. 16 * 17 * This program is distributed in the hope that it will be useful, 18 * but WITHOUT ANY WARRANTY; without even the implied warranty of 19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20 * GNU General Public License for more details. 21 * 22 * You should have received a copy of the GNU General Public License 23 * along with this program; if not, write to the Free Software 24 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 25 */ 26 27 #include <linux/personality.h> 28 #include <linux/mm.h> 29 #include <linux/random.h> 30 #include <linux/limits.h> 31 #include <linux/sched/signal.h> 32 #include <linux/sched/mm.h> 33 #include <linux/compat.h> 34 #include <asm/elf.h> 35 36 struct va_alignment __read_mostly va_align = { 37 .flags = -1, 38 }; 39 40 unsigned long task_size_32bit(void) 41 { 42 return IA32_PAGE_OFFSET; 43 } 44 45 unsigned long task_size_64bit(int full_addr_space) 46 { 47 return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW; 48 } 49 50 static unsigned long stack_maxrandom_size(unsigned long task_size) 51 { 52 unsigned long max = 0; 53 if (current->flags & PF_RANDOMIZE) { 54 max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit()); 55 max <<= PAGE_SHIFT; 56 } 57 58 return max; 59 } 60 61 #ifdef CONFIG_COMPAT 62 # define mmap32_rnd_bits mmap_rnd_compat_bits 63 # define mmap64_rnd_bits mmap_rnd_bits 64 #else 65 # define mmap32_rnd_bits mmap_rnd_bits 66 # define mmap64_rnd_bits mmap_rnd_bits 67 #endif 68 69 #define SIZE_128M (128 * 1024 * 1024UL) 70 71 static int mmap_is_legacy(void) 72 { 73 if (current->personality & ADDR_COMPAT_LAYOUT) 74 return 1; 75 76 return sysctl_legacy_va_layout; 77 } 78 79 static unsigned long arch_rnd(unsigned int rndbits) 80 { 81 if (!(current->flags & PF_RANDOMIZE)) 82 return 0; 83 return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; 84 } 85 86 unsigned long arch_mmap_rnd(void) 87 { 88 return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits); 89 } 90 91 static unsigned long mmap_base(unsigned long rnd, unsigned long task_size) 92 { 93 unsigned long gap = rlimit(RLIMIT_STACK); 94 unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap; 95 unsigned long gap_min, gap_max; 96 97 /* Values close to RLIM_INFINITY can overflow. */ 98 if (gap + pad > gap) 99 gap += pad; 100 101 /* 102 * Top of mmap area (just below the process stack). 103 * Leave an at least ~128 MB hole with possible stack randomization. 104 */ 105 gap_min = SIZE_128M; 106 gap_max = (task_size / 6) * 5; 107 108 if (gap < gap_min) 109 gap = gap_min; 110 else if (gap > gap_max) 111 gap = gap_max; 112 113 return PAGE_ALIGN(task_size - gap - rnd); 114 } 115 116 static unsigned long mmap_legacy_base(unsigned long rnd, 117 unsigned long task_size) 118 { 119 return __TASK_UNMAPPED_BASE(task_size) + rnd; 120 } 121 122 /* 123 * This function, called very early during the creation of a new 124 * process VM image, sets up which VM layout function to use: 125 */ 126 static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base, 127 unsigned long random_factor, unsigned long task_size) 128 { 129 *legacy_base = mmap_legacy_base(random_factor, task_size); 130 if (mmap_is_legacy()) 131 *base = *legacy_base; 132 else 133 *base = mmap_base(random_factor, task_size); 134 } 135 136 void arch_pick_mmap_layout(struct mm_struct *mm) 137 { 138 if (mmap_is_legacy()) 139 mm->get_unmapped_area = arch_get_unmapped_area; 140 else 141 mm->get_unmapped_area = arch_get_unmapped_area_topdown; 142 143 arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base, 144 arch_rnd(mmap64_rnd_bits), task_size_64bit(0)); 145 146 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES 147 /* 148 * The mmap syscall mapping base decision depends solely on the 149 * syscall type (64-bit or compat). This applies for 64bit 150 * applications and 32bit applications. The 64bit syscall uses 151 * mmap_base, the compat syscall uses mmap_compat_base. 152 */ 153 arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base, 154 arch_rnd(mmap32_rnd_bits), task_size_32bit()); 155 #endif 156 } 157 158 unsigned long get_mmap_base(int is_legacy) 159 { 160 struct mm_struct *mm = current->mm; 161 162 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES 163 if (in_compat_syscall()) { 164 return is_legacy ? mm->mmap_compat_legacy_base 165 : mm->mmap_compat_base; 166 } 167 #endif 168 return is_legacy ? mm->mmap_legacy_base : mm->mmap_base; 169 } 170 171 const char *arch_vma_name(struct vm_area_struct *vma) 172 { 173 if (vma->vm_flags & VM_MPX) 174 return "[mpx]"; 175 return NULL; 176 } 177 178 int valid_phys_addr_range(phys_addr_t addr, size_t count) 179 { 180 return addr + count <= __pa(high_memory); 181 } 182 183 int valid_mmap_phys_addr_range(unsigned long pfn, size_t count) 184 { 185 phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT; 186 187 return valid_phys_addr_range(addr, count); 188 } 189