1 /* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Copyright (C) 2011 Wind River Systems, 7 * written by Ralf Baechle <ralf@linux-mips.org> 8 */ 9 #include <linux/compiler.h> 10 #include <linux/errno.h> 11 #include <linux/mm.h> 12 #include <linux/mman.h> 13 #include <linux/module.h> 14 #include <linux/personality.h> 15 #include <linux/random.h> 16 #include <linux/sched.h> 17 18 unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */ 19 EXPORT_SYMBOL(shm_align_mask); 20 21 /* gap between mmap and stack */ 22 #define MIN_GAP (128*1024*1024UL) 23 #define MAX_GAP ((TASK_SIZE)/6*5) 24 25 static int mmap_is_legacy(void) 26 { 27 if (current->personality & ADDR_COMPAT_LAYOUT) 28 return 1; 29 30 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) 31 return 1; 32 33 return sysctl_legacy_va_layout; 34 } 35 36 static unsigned long mmap_base(unsigned long rnd) 37 { 38 unsigned long gap = rlimit(RLIMIT_STACK); 39 40 if (gap < MIN_GAP) 41 gap = MIN_GAP; 42 else if (gap > MAX_GAP) 43 gap = MAX_GAP; 44 45 return PAGE_ALIGN(TASK_SIZE - gap - rnd); 46 } 47 48 #define COLOUR_ALIGN(addr, pgoff) \ 49 ((((addr) + shm_align_mask) & ~shm_align_mask) + \ 50 (((pgoff) << PAGE_SHIFT) & shm_align_mask)) 51 52 enum mmap_allocation_direction {UP, DOWN}; 53 54 static unsigned long arch_get_unmapped_area_common(struct file *filp, 55 unsigned long addr0, unsigned long len, unsigned long pgoff, 56 unsigned long flags, enum mmap_allocation_direction dir) 57 { 58 struct mm_struct *mm = current->mm; 59 struct vm_area_struct *vma; 60 unsigned long addr = addr0; 61 int do_color_align; 62 struct vm_unmapped_area_info info; 63 64 if (unlikely(len > TASK_SIZE)) 65 return -ENOMEM; 66 67 if (flags & MAP_FIXED) { 68 /* Even MAP_FIXED mappings must reside within TASK_SIZE */ 69 if (TASK_SIZE - len < addr) 70 return -EINVAL; 71 72 /* 73 * We do not accept a shared mapping if it would violate 74 * cache aliasing constraints. 75 */ 76 if ((flags & MAP_SHARED) && 77 ((addr - (pgoff << PAGE_SHIFT)) & shm_align_mask)) 78 return -EINVAL; 79 return addr; 80 } 81 82 do_color_align = 0; 83 if (filp || (flags & MAP_SHARED)) 84 do_color_align = 1; 85 86 /* requesting a specific address */ 87 if (addr) { 88 if (do_color_align) 89 addr = COLOUR_ALIGN(addr, pgoff); 90 else 91 addr = PAGE_ALIGN(addr); 92 93 vma = find_vma(mm, addr); 94 if (TASK_SIZE - len >= addr && 95 (!vma || addr + len <= vma->vm_start)) 96 return addr; 97 } 98 99 info.length = len; 100 info.align_mask = do_color_align ? (PAGE_MASK & shm_align_mask) : 0; 101 info.align_offset = pgoff << PAGE_SHIFT; 102 103 if (dir == DOWN) { 104 info.flags = VM_UNMAPPED_AREA_TOPDOWN; 105 info.low_limit = PAGE_SIZE; 106 info.high_limit = mm->mmap_base; 107 addr = vm_unmapped_area(&info); 108 109 if (!(addr & ~PAGE_MASK)) 110 return addr; 111 112 /* 113 * A failed mmap() very likely causes application failure, 114 * so fall back to the bottom-up function here. This scenario 115 * can happen with large stack limits and large mmap() 116 * allocations. 117 */ 118 } 119 120 info.flags = 0; 121 info.low_limit = mm->mmap_base; 122 info.high_limit = TASK_SIZE; 123 return vm_unmapped_area(&info); 124 } 125 126 unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr0, 127 unsigned long len, unsigned long pgoff, unsigned long flags) 128 { 129 return arch_get_unmapped_area_common(filp, 130 addr0, len, pgoff, flags, UP); 131 } 132 133 /* 134 * There is no need to export this but sched.h declares the function as 135 * extern so making it static here results in an error. 136 */ 137 unsigned long arch_get_unmapped_area_topdown(struct file *filp, 138 unsigned long addr0, unsigned long len, unsigned long pgoff, 139 unsigned long flags) 140 { 141 return arch_get_unmapped_area_common(filp, 142 addr0, len, pgoff, flags, DOWN); 143 } 144 145 unsigned long arch_mmap_rnd(void) 146 { 147 unsigned long rnd; 148 149 rnd = (unsigned long)get_random_int(); 150 rnd <<= PAGE_SHIFT; 151 if (TASK_IS_32BIT_ADDR) 152 rnd &= 0xfffffful; 153 else 154 rnd &= 0xffffffful; 155 156 return rnd; 157 } 158 159 void arch_pick_mmap_layout(struct mm_struct *mm) 160 { 161 unsigned long random_factor = 0UL; 162 163 if (current->flags & PF_RANDOMIZE) 164 random_factor = arch_mmap_rnd(); 165 166 if (mmap_is_legacy()) { 167 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; 168 mm->get_unmapped_area = arch_get_unmapped_area; 169 } else { 170 mm->mmap_base = mmap_base(random_factor); 171 mm->get_unmapped_area = arch_get_unmapped_area_topdown; 172 } 173 } 174 175 static inline unsigned long brk_rnd(void) 176 { 177 unsigned long rnd = get_random_int(); 178 179 rnd = rnd << PAGE_SHIFT; 180 /* 8MB for 32bit, 256MB for 64bit */ 181 if (TASK_IS_32BIT_ADDR) 182 rnd = rnd & 0x7ffffful; 183 else 184 rnd = rnd & 0xffffffful; 185 186 return rnd; 187 } 188 189 unsigned long arch_randomize_brk(struct mm_struct *mm) 190 { 191 unsigned long base = mm->brk; 192 unsigned long ret; 193 194 ret = PAGE_ALIGN(base + brk_rnd()); 195 196 if (ret < mm->brk) 197 return mm->brk; 198 199 return ret; 200 } 201 202 int __virt_addr_valid(const volatile void *kaddr) 203 { 204 return pfn_valid(PFN_DOWN(virt_to_phys(kaddr))); 205 } 206 EXPORT_SYMBOL_GPL(__virt_addr_valid); 207