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
relocate_relative(void)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
relocate_absolute(long random_offset)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
rotate_xor(unsigned long hash,const void * area,size_t size)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
get_random_boot(void)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
nokaslr(char * p)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
kaslr_disabled(void)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 */
determine_relocation_address(void)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
relocation_addr_valid(void * location_new)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
update_reloc_offset(unsigned long * addr,long random_offset)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
relocate_kernel(void)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 */
show_kernel_relocation(const char * level)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
kernel_location_notifier_fn(struct notifier_block * self,unsigned long v,void * p)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
register_kernel_offset_dumper(void)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