1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Support for Kernel relocation at boot time 4 * 5 * Copyright (C) 2023 Loongson Technology Corporation Limited 6 */ 7 8 #include <linux/elf.h> 9 #include <linux/kernel.h> 10 #include <linux/printk.h> 11 #include <linux/panic_notifier.h> 12 #include <linux/start_kernel.h> 13 #include <asm/bootinfo.h> 14 #include <asm/early_ioremap.h> 15 #include <asm/inst.h> 16 #include <asm/io.h> 17 #include <asm/sections.h> 18 #include <asm/setup.h> 19 20 #define RELOCATED(x) ((void *)((long)x + reloc_offset)) 21 #define RELOCATED_KASLR(x) ((void *)((long)x + random_offset)) 22 23 static unsigned long reloc_offset; 24 25 static inline void __init relocate_relative(void) 26 { 27 Elf64_Rela *rela, *rela_end; 28 rela = (Elf64_Rela *)&__rela_dyn_begin; 29 rela_end = (Elf64_Rela *)&__rela_dyn_end; 30 31 for ( ; rela < rela_end; rela++) { 32 Elf64_Addr addr = rela->r_offset; 33 Elf64_Addr relocated_addr = rela->r_addend; 34 35 if (rela->r_info != R_LARCH_RELATIVE) 36 continue; 37 38 relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr); 39 *(Elf64_Addr *)RELOCATED(addr) = relocated_addr; 40 } 41 42 #ifdef CONFIG_RELR 43 u64 *addr = NULL; 44 u64 *relr = (u64 *)&__relr_dyn_begin; 45 u64 *relr_end = (u64 *)&__relr_dyn_end; 46 47 for ( ; relr < relr_end; relr++) { 48 if ((*relr & 1) == 0) { 49 addr = (u64 *)(*relr + reloc_offset); 50 *addr++ += reloc_offset; 51 } else { 52 for (u64 *p = addr, r = *relr >> 1; r; p++, r >>= 1) 53 if (r & 1) 54 *p += reloc_offset; 55 addr += 63; 56 } 57 } 58 #endif 59 } 60 61 static inline void __init relocate_absolute(long random_offset) 62 { 63 void *begin, *end; 64 struct rela_la_abs *p; 65 66 begin = RELOCATED_KASLR(&__la_abs_begin); 67 end = RELOCATED_KASLR(&__la_abs_end); 68 69 for (p = begin; (void *)p < end; p++) { 70 long v = p->symvalue; 71 uint32_t lu12iw, ori, lu32id, lu52id; 72 union loongarch_instruction *insn = (void *)p->pc; 73 74 lu12iw = (v >> 12) & 0xfffff; 75 ori = v & 0xfff; 76 lu32id = (v >> 32) & 0xfffff; 77 lu52id = v >> 52; 78 79 insn[0].reg1i20_format.immediate = lu12iw; 80 insn[1].reg2i12_format.immediate = ori; 81 insn[2].reg1i20_format.immediate = lu32id; 82 insn[3].reg2i12_format.immediate = lu52id; 83 } 84 } 85 86 #ifdef CONFIG_RANDOMIZE_BASE 87 static inline __init unsigned long rotate_xor(unsigned long hash, 88 const void *area, size_t size) 89 { 90 size_t i, diff; 91 const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash)); 92 93 diff = (void *)ptr - area; 94 if (size < diff + sizeof(hash)) 95 return hash; 96 97 size = ALIGN_DOWN(size - diff, sizeof(hash)); 98 99 for (i = 0; i < size / sizeof(hash); i++) { 100 /* Rotate by odd number of bits and XOR. */ 101 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); 102 hash ^= ptr[i]; 103 } 104 105 return hash; 106 } 107 108 static inline __init unsigned long get_random_boot(void) 109 { 110 unsigned long hash = 0; 111 unsigned long entropy = random_get_entropy(); 112 113 /* Attempt to create a simple but unpredictable starting entropy. */ 114 hash = rotate_xor(hash, linux_banner, strlen(linux_banner)); 115 116 /* Add in any runtime entropy we can get */ 117 hash = rotate_xor(hash, &entropy, sizeof(entropy)); 118 119 return hash; 120 } 121 122 static int __init nokaslr(char *p) 123 { 124 pr_info("KASLR is disabled.\n"); 125 126 return 0; /* Print a notice and silence the boot warning */ 127 } 128 early_param("nokaslr", nokaslr); 129 130 static inline __init bool kaslr_disabled(void) 131 { 132 char *str; 133 const char *builtin_cmdline = CONFIG_CMDLINE; 134 135 str = strstr(builtin_cmdline, "nokaslr"); 136 if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' ')) 137 return true; 138 139 str = strstr(boot_command_line, "nokaslr"); 140 if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' ')) 141 return true; 142 143 #ifdef CONFIG_HIBERNATION 144 str = strstr(builtin_cmdline, "nohibernate"); 145 if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' ')) 146 return false; 147 148 str = strstr(boot_command_line, "nohibernate"); 149 if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' ')) 150 return false; 151 152 str = strstr(builtin_cmdline, "noresume"); 153 if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' ')) 154 return false; 155 156 str = strstr(boot_command_line, "noresume"); 157 if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' ')) 158 return false; 159 160 str = strstr(builtin_cmdline, "resume="); 161 if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' ')) 162 return true; 163 164 str = strstr(boot_command_line, "resume="); 165 if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' ')) 166 return true; 167 #endif 168 169 str = strstr(boot_command_line, "kexec_file"); 170 if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' ')) 171 return true; 172 173 return false; 174 } 175 176 /* Choose a new address for the kernel */ 177 static inline void __init *determine_relocation_address(void) 178 { 179 unsigned long kernel_length; 180 unsigned long random_offset; 181 void *destination = _text; 182 183 if (kaslr_disabled()) 184 return destination; 185 186 kernel_length = (long)_end - (long)_text; 187 188 random_offset = get_random_boot() << 16; 189 random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1); 190 if (random_offset < kernel_length) 191 random_offset += ALIGN(kernel_length, 0xffff); 192 193 return RELOCATED_KASLR(destination); 194 } 195 196 static inline int __init relocation_addr_valid(void *location_new) 197 { 198 if ((unsigned long)location_new & 0x00000ffff) 199 return 0; /* Inappropriately aligned new location */ 200 201 if ((unsigned long)location_new < (unsigned long)_end) 202 return 0; /* New location overlaps original kernel */ 203 204 return 1; 205 } 206 #endif 207 208 static inline void __init update_reloc_offset(unsigned long *addr, long random_offset) 209 { 210 unsigned long *new_addr = (unsigned long *)RELOCATED_KASLR(addr); 211 212 *new_addr = (unsigned long)reloc_offset; 213 } 214 215 unsigned long __init relocate_kernel(void) 216 { 217 unsigned long kernel_length; 218 unsigned long random_offset = 0; 219 void *location_new = _text; /* Default to original kernel start */ 220 char *cmdline = early_memremap_ro(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */ 221 222 strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE); 223 224 #ifdef CONFIG_RANDOMIZE_BASE 225 location_new = determine_relocation_address(); 226 227 /* Sanity check relocation address */ 228 if (relocation_addr_valid(location_new)) 229 random_offset = (unsigned long)location_new - (unsigned long)(_text); 230 #endif 231 reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS; 232 early_memunmap(cmdline, COMMAND_LINE_SIZE); 233 234 if (random_offset) { 235 kernel_length = (long)(_end) - (long)(_text); 236 237 /* Copy the kernel to it's new location */ 238 memcpy(location_new, _text, kernel_length); 239 240 /* Sync the caches ready for execution of new kernel */ 241 __asm__ __volatile__ ( 242 "ibar 0 \t\n" 243 "dbar 0 \t\n" 244 ::: "memory"); 245 246 reloc_offset += random_offset; 247 248 /* The current thread is now within the relocated kernel */ 249 __current_thread_info = RELOCATED_KASLR(__current_thread_info); 250 251 update_reloc_offset(&reloc_offset, random_offset); 252 } 253 254 if (reloc_offset) 255 relocate_relative(); 256 257 relocate_absolute(random_offset); 258 259 return random_offset; 260 } 261 262 /* 263 * Show relocation information on panic. 264 */ 265 static void show_kernel_relocation(const char *level) 266 { 267 if (reloc_offset > 0) { 268 printk(level); 269 pr_cont("Kernel relocated by 0x%lx\n", reloc_offset); 270 pr_cont(" .text @ 0x%px\n", _text); 271 pr_cont(" .data @ 0x%px\n", _sdata); 272 pr_cont(" .bss @ 0x%px\n", __bss_start); 273 } 274 } 275 276 static int kernel_location_notifier_fn(struct notifier_block *self, 277 unsigned long v, void *p) 278 { 279 show_kernel_relocation(KERN_EMERG); 280 return NOTIFY_DONE; 281 } 282 283 static struct notifier_block kernel_location_notifier = { 284 .notifier_call = kernel_location_notifier_fn 285 }; 286 287 static int __init register_kernel_offset_dumper(void) 288 { 289 atomic_notifier_chain_register(&panic_notifier_list, 290 &kernel_location_notifier); 291 return 0; 292 } 293 294 arch_initcall(register_kernel_offset_dumper); 295