1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/compat.h> 3 #include <linux/errno.h> 4 #include <linux/sched.h> 5 #include <linux/sched/mm.h> 6 #include <linux/syscalls.h> 7 #include <linux/mm.h> 8 #include <linux/fs.h> 9 #include <linux/smp.h> 10 #include <linux/sem.h> 11 #include <linux/msg.h> 12 #include <linux/shm.h> 13 #include <linux/stat.h> 14 #include <linux/mman.h> 15 #include <linux/file.h> 16 #include <linux/utsname.h> 17 #include <linux/personality.h> 18 #include <linux/random.h> 19 #include <linux/uaccess.h> 20 #include <linux/elf.h> 21 22 #include <asm/elf.h> 23 #include <asm/ia32.h> 24 25 /* 26 * Align a virtual address to avoid aliasing in the I$ on AMD F15h. 27 */ 28 static unsigned long get_align_mask(void) 29 { 30 /* handle 32- and 64-bit case with a single conditional */ 31 if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32()))) 32 return 0; 33 34 if (!(current->flags & PF_RANDOMIZE)) 35 return 0; 36 37 return va_align.mask; 38 } 39 40 /* 41 * To avoid aliasing in the I$ on AMD F15h, the bits defined by the 42 * va_align.bits, [12:upper_bit), are set to a random value instead of 43 * zeroing them. This random value is computed once per boot. This form 44 * of ASLR is known as "per-boot ASLR". 45 * 46 * To achieve this, the random value is added to the info.align_offset 47 * value before calling vm_unmapped_area() or ORed directly to the 48 * address. 49 */ 50 static unsigned long get_align_bits(void) 51 { 52 return va_align.bits & get_align_mask(); 53 } 54 55 static int __init control_va_addr_alignment(char *str) 56 { 57 /* guard against enabling this on other CPU families */ 58 if (va_align.flags < 0) 59 return 1; 60 61 if (*str == 0) 62 return 1; 63 64 if (!strcmp(str, "32")) 65 va_align.flags = ALIGN_VA_32; 66 else if (!strcmp(str, "64")) 67 va_align.flags = ALIGN_VA_64; 68 else if (!strcmp(str, "off")) 69 va_align.flags = 0; 70 else if (!strcmp(str, "on")) 71 va_align.flags = ALIGN_VA_32 | ALIGN_VA_64; 72 else 73 pr_warn("invalid option value: 'align_va_addr=%s'\n", str); 74 75 return 1; 76 } 77 __setup("align_va_addr=", control_va_addr_alignment); 78 79 SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, 80 unsigned long, prot, unsigned long, flags, 81 unsigned long, fd, unsigned long, off) 82 { 83 if (off & ~PAGE_MASK) 84 return -EINVAL; 85 86 return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT); 87 } 88 89 static void find_start_end(unsigned long addr, unsigned long flags, 90 unsigned long *begin, unsigned long *end) 91 { 92 if (!in_32bit_syscall() && (flags & MAP_32BIT)) { 93 /* This is usually used needed to map code in small 94 model, so it needs to be in the first 31bit. Limit 95 it to that. This means we need to move the 96 unmapped base down for this case. This can give 97 conflicts with the heap, but we assume that glibc 98 malloc knows how to fall back to mmap. Give it 1GB 99 of playground for now. -AK */ 100 *begin = 0x40000000; 101 *end = 0x80000000; 102 if (current->flags & PF_RANDOMIZE) { 103 *begin = randomize_page(*begin, 0x02000000); 104 } 105 return; 106 } 107 108 *begin = get_mmap_base(1); 109 if (in_32bit_syscall()) 110 *end = task_size_32bit(); 111 else 112 *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW); 113 } 114 115 static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) 116 { 117 if (vm_flags & VM_SHADOW_STACK) 118 return PAGE_SIZE; 119 120 return 0; 121 } 122 123 unsigned long 124 arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, 125 unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags) 126 { 127 struct mm_struct *mm = current->mm; 128 struct vm_area_struct *vma; 129 struct vm_unmapped_area_info info = {}; 130 unsigned long begin, end; 131 132 if (flags & MAP_FIXED) 133 return addr; 134 135 find_start_end(addr, flags, &begin, &end); 136 137 if (len > end) 138 return -ENOMEM; 139 140 if (addr) { 141 addr = PAGE_ALIGN(addr); 142 vma = find_vma(mm, addr); 143 if (end - len >= addr && 144 (!vma || addr + len <= vm_start_gap(vma))) 145 return addr; 146 } 147 148 info.length = len; 149 info.low_limit = begin; 150 info.high_limit = end; 151 info.align_offset = pgoff << PAGE_SHIFT; 152 info.start_gap = stack_guard_placement(vm_flags); 153 if (filp) { 154 info.align_mask = get_align_mask(); 155 info.align_offset += get_align_bits(); 156 } 157 return vm_unmapped_area(&info); 158 } 159 160 unsigned long 161 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr0, 162 unsigned long len, unsigned long pgoff, 163 unsigned long flags, vm_flags_t vm_flags) 164 { 165 struct vm_area_struct *vma; 166 struct mm_struct *mm = current->mm; 167 unsigned long addr = addr0; 168 struct vm_unmapped_area_info info = {}; 169 170 /* requested length too big for entire address space */ 171 if (len > TASK_SIZE) 172 return -ENOMEM; 173 174 /* No address checking. See comment at mmap_address_hint_valid() */ 175 if (flags & MAP_FIXED) 176 return addr; 177 178 /* for MAP_32BIT mappings we force the legacy mmap base */ 179 if (!in_32bit_syscall() && (flags & MAP_32BIT)) 180 goto bottomup; 181 182 /* requesting a specific address */ 183 if (addr) { 184 addr &= PAGE_MASK; 185 if (!mmap_address_hint_valid(addr, len)) 186 goto get_unmapped_area; 187 188 vma = find_vma(mm, addr); 189 if (!vma || addr + len <= vm_start_gap(vma)) 190 return addr; 191 } 192 get_unmapped_area: 193 194 info.flags = VM_UNMAPPED_AREA_TOPDOWN; 195 info.length = len; 196 if (!in_32bit_syscall() && (flags & MAP_ABOVE4G)) 197 info.low_limit = SZ_4G; 198 else 199 info.low_limit = PAGE_SIZE; 200 201 info.high_limit = get_mmap_base(0); 202 info.start_gap = stack_guard_placement(vm_flags); 203 204 /* 205 * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area 206 * in the full address space. 207 * 208 * !in_32bit_syscall() check to avoid high addresses for x32 209 * (and make it no op on native i386). 210 */ 211 if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall()) 212 info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW; 213 214 info.align_offset = pgoff << PAGE_SHIFT; 215 if (filp) { 216 info.align_mask = get_align_mask(); 217 info.align_offset += get_align_bits(); 218 } 219 addr = vm_unmapped_area(&info); 220 if (!(addr & ~PAGE_MASK)) 221 return addr; 222 VM_BUG_ON(addr != -ENOMEM); 223 224 bottomup: 225 /* 226 * A failed mmap() very likely causes application failure, 227 * so fall back to the bottom-up function here. This scenario 228 * can happen with large stack limits and large mmap() 229 * allocations. 230 */ 231 return arch_get_unmapped_area(filp, addr0, len, pgoff, flags, 0); 232 } 233