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 | * Support for Kernel relocation at boot time |
7 | * |
8 | * Copyright (C) 2015, Imagination Technologies Ltd. |
9 | * Authors: Matt Redfearn (matt.redfearn@mips.com) |
10 | */ |
11 | #include <asm/bootinfo.h> |
12 | #include <asm/cacheflush.h> |
13 | #include <asm/fw/fw.h> |
14 | #include <asm/sections.h> |
15 | #include <asm/setup.h> |
16 | #include <asm/timex.h> |
17 | #include <linux/elf.h> |
18 | #include <linux/kernel.h> |
19 | #include <linux/libfdt.h> |
20 | #include <linux/of_fdt.h> |
21 | #include <linux/panic_notifier.h> |
22 | #include <linux/sched/task.h> |
23 | #include <linux/start_kernel.h> |
24 | #include <linux/string.h> |
25 | #include <linux/printk.h> |
26 | |
27 | #define RELOCATED(x) ((void *)((long)x + offset)) |
28 | |
29 | extern u32 _relocation_start[]; /* End kernel image / start relocation table */ |
30 | extern u32 _relocation_end[]; /* End relocation table */ |
31 | |
32 | extern long __start___ex_table; /* Start exception table */ |
33 | extern long __stop___ex_table; /* End exception table */ |
34 | |
35 | extern void __weak plat_fdt_relocated(void *new_location); |
36 | |
37 | /* |
38 | * This function may be defined for a platform to perform any post-relocation |
39 | * fixup necessary. |
40 | * Return non-zero to abort relocation |
41 | */ |
42 | int __weak plat_post_relocation(long offset) |
43 | { |
44 | return 0; |
45 | } |
46 | |
47 | static inline u32 __init get_synci_step(void) |
48 | { |
49 | u32 res; |
50 | |
51 | __asm__("rdhwr %0, $1" : "=r" (res)); |
52 | |
53 | return res; |
54 | } |
55 | |
56 | static void __init sync_icache(void *kbase, unsigned long kernel_length) |
57 | { |
58 | void *kend = kbase + kernel_length; |
59 | u32 step = get_synci_step(); |
60 | |
61 | do { |
62 | __asm__ __volatile__( |
63 | "synci 0(%0)" |
64 | : /* no output */ |
65 | : "r" (kbase)); |
66 | |
67 | kbase += step; |
68 | } while (step && kbase < kend); |
69 | |
70 | /* Completion barrier */ |
71 | __sync(); |
72 | } |
73 | |
74 | static void __init apply_r_mips_64_rel(u32 *loc_new, long offset) |
75 | { |
76 | *(u64 *)loc_new += offset; |
77 | } |
78 | |
79 | static void __init apply_r_mips_32_rel(u32 *loc_new, long offset) |
80 | { |
81 | *loc_new += offset; |
82 | } |
83 | |
84 | static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset) |
85 | { |
86 | unsigned long target_addr = (*loc_orig) & 0x03ffffff; |
87 | |
88 | if (offset % 4) { |
89 | pr_err("Dangerous R_MIPS_26 REL relocation\n" ); |
90 | return -ENOEXEC; |
91 | } |
92 | |
93 | /* Original target address */ |
94 | target_addr <<= 2; |
95 | target_addr += (unsigned long)loc_orig & 0xf0000000; |
96 | |
97 | /* Get the new target address */ |
98 | target_addr += offset; |
99 | |
100 | if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) { |
101 | pr_err("R_MIPS_26 REL relocation overflow\n" ); |
102 | return -ENOEXEC; |
103 | } |
104 | |
105 | target_addr -= (unsigned long)loc_new & 0xf0000000; |
106 | target_addr >>= 2; |
107 | |
108 | *loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff); |
109 | |
110 | return 0; |
111 | } |
112 | |
113 | |
114 | static void __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, |
115 | long offset) |
116 | { |
117 | unsigned long insn = *loc_orig; |
118 | unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */ |
119 | |
120 | target += offset; |
121 | |
122 | *loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff); |
123 | } |
124 | |
125 | static int __init reloc_handler(u32 type, u32 *loc_orig, u32 *loc_new, |
126 | long offset) |
127 | { |
128 | switch (type) { |
129 | case R_MIPS_64: |
130 | apply_r_mips_64_rel(loc_new, offset); |
131 | break; |
132 | case R_MIPS_32: |
133 | apply_r_mips_32_rel(loc_new, offset); |
134 | break; |
135 | case R_MIPS_26: |
136 | return apply_r_mips_26_rel(loc_orig, loc_new, offset); |
137 | case R_MIPS_HI16: |
138 | apply_r_mips_hi16_rel(loc_orig, loc_new, offset); |
139 | break; |
140 | default: |
141 | pr_err("Unhandled relocation type %d at 0x%pK\n" , type, |
142 | loc_orig); |
143 | return -ENOEXEC; |
144 | } |
145 | |
146 | return 0; |
147 | } |
148 | |
149 | static int __init do_relocations(void *kbase_old, void *kbase_new, long offset) |
150 | { |
151 | u32 *r; |
152 | u32 *loc_orig; |
153 | u32 *loc_new; |
154 | int type; |
155 | int res; |
156 | |
157 | for (r = _relocation_start; r < _relocation_end; r++) { |
158 | /* Sentinel for last relocation */ |
159 | if (*r == 0) |
160 | break; |
161 | |
162 | type = (*r >> 24) & 0xff; |
163 | loc_orig = kbase_old + ((*r & 0x00ffffff) << 2); |
164 | loc_new = RELOCATED(loc_orig); |
165 | |
166 | res = reloc_handler(type, loc_orig, loc_new, offset); |
167 | if (res) |
168 | return res; |
169 | } |
170 | |
171 | return 0; |
172 | } |
173 | |
174 | /* |
175 | * The exception table is filled in by the relocs tool after vmlinux is linked. |
176 | * It must be relocated separately since there will not be any relocation |
177 | * information for it filled in by the linker. |
178 | */ |
179 | static int __init relocate_exception_table(long offset) |
180 | { |
181 | unsigned long *etable_start, *etable_end, *e; |
182 | |
183 | etable_start = RELOCATED(&__start___ex_table); |
184 | etable_end = RELOCATED(&__stop___ex_table); |
185 | |
186 | for (e = etable_start; e < etable_end; e++) |
187 | *e += offset; |
188 | |
189 | return 0; |
190 | } |
191 | |
192 | #ifdef CONFIG_RANDOMIZE_BASE |
193 | |
194 | static inline __init unsigned long rotate_xor(unsigned long hash, |
195 | const void *area, size_t size) |
196 | { |
197 | const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash)); |
198 | size_t diff, i; |
199 | |
200 | diff = (void *)ptr - area; |
201 | if (unlikely(size < diff + sizeof(hash))) |
202 | return hash; |
203 | |
204 | size = ALIGN_DOWN(size - diff, sizeof(hash)); |
205 | |
206 | for (i = 0; i < size / sizeof(hash); i++) { |
207 | /* Rotate by odd number of bits and XOR. */ |
208 | hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); |
209 | hash ^= ptr[i]; |
210 | } |
211 | |
212 | return hash; |
213 | } |
214 | |
215 | static inline __init unsigned long get_random_boot(void) |
216 | { |
217 | unsigned long entropy = random_get_entropy(); |
218 | unsigned long hash = 0; |
219 | |
220 | /* Attempt to create a simple but unpredictable starting entropy. */ |
221 | hash = rotate_xor(hash, area: linux_banner, strlen(linux_banner)); |
222 | |
223 | /* Add in any runtime entropy we can get */ |
224 | hash = rotate_xor(hash, area: &entropy, size: sizeof(entropy)); |
225 | |
226 | #if defined(CONFIG_USE_OF) |
227 | /* Get any additional entropy passed in device tree */ |
228 | if (initial_boot_params) { |
229 | int node, len; |
230 | u64 *prop; |
231 | |
232 | node = fdt_path_offset(initial_boot_params, "/chosen" ); |
233 | if (node >= 0) { |
234 | prop = fdt_getprop_w(initial_boot_params, node, |
235 | "kaslr-seed" , &len); |
236 | if (prop && (len == sizeof(u64))) |
237 | hash = rotate_xor(hash, prop, sizeof(*prop)); |
238 | } |
239 | } |
240 | #endif /* CONFIG_USE_OF */ |
241 | |
242 | return hash; |
243 | } |
244 | |
245 | static inline __init bool kaslr_disabled(void) |
246 | { |
247 | char *str; |
248 | |
249 | #if defined(CONFIG_CMDLINE_BOOL) |
250 | const char *builtin_cmdline = CONFIG_CMDLINE; |
251 | |
252 | str = strstr(builtin_cmdline, "nokaslr" ); |
253 | if (str == builtin_cmdline || |
254 | (str > builtin_cmdline && *(str - 1) == ' ')) |
255 | return true; |
256 | #endif |
257 | str = strstr(arcs_cmdline, "nokaslr" ); |
258 | if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' ')) |
259 | return true; |
260 | |
261 | return false; |
262 | } |
263 | |
264 | static inline void __init *determine_relocation_address(void) |
265 | { |
266 | /* Choose a new address for the kernel */ |
267 | unsigned long kernel_length; |
268 | void *dest = &_text; |
269 | unsigned long offset; |
270 | |
271 | if (kaslr_disabled()) |
272 | return dest; |
273 | |
274 | kernel_length = (long)_end - (long)(&_text); |
275 | |
276 | offset = get_random_boot() << 16; |
277 | offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1); |
278 | if (offset < kernel_length) |
279 | offset += ALIGN(kernel_length, 0xffff); |
280 | |
281 | return RELOCATED(dest); |
282 | } |
283 | |
284 | #else |
285 | |
286 | static inline void __init *determine_relocation_address(void) |
287 | { |
288 | /* |
289 | * Choose a new address for the kernel |
290 | * For now we'll hard code the destination |
291 | */ |
292 | return (void *)0xffffffff81000000; |
293 | } |
294 | |
295 | #endif |
296 | |
297 | static inline int __init relocation_addr_valid(void *loc_new) |
298 | { |
299 | if ((unsigned long)loc_new & 0x0000ffff) { |
300 | /* Inappropriately aligned new location */ |
301 | return 0; |
302 | } |
303 | if ((unsigned long)loc_new < (unsigned long)&_end) { |
304 | /* New location overlaps original kernel */ |
305 | return 0; |
306 | } |
307 | return 1; |
308 | } |
309 | |
310 | static inline void __init update_kaslr_offset(unsigned long *addr, long offset) |
311 | { |
312 | unsigned long *new_addr = (unsigned long *)RELOCATED(addr); |
313 | |
314 | *new_addr = (unsigned long)offset; |
315 | } |
316 | |
317 | #if defined(CONFIG_USE_OF) |
318 | void __weak *plat_get_fdt(void) |
319 | { |
320 | return NULL; |
321 | } |
322 | #endif |
323 | |
324 | void *__init relocate_kernel(void) |
325 | { |
326 | void *loc_new; |
327 | unsigned long kernel_length; |
328 | unsigned long bss_length; |
329 | long offset = 0; |
330 | int res = 1; |
331 | /* Default to original kernel entry point */ |
332 | void *kernel_entry = start_kernel; |
333 | void *fdt = NULL; |
334 | |
335 | /* Get the command line */ |
336 | fw_init_cmdline(); |
337 | #if defined(CONFIG_USE_OF) |
338 | /* Deal with the device tree */ |
339 | fdt = plat_get_fdt(); |
340 | early_init_dt_scan(fdt); |
341 | if (boot_command_line[0]) { |
342 | /* Boot command line was passed in device tree */ |
343 | strscpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE); |
344 | } |
345 | #endif /* CONFIG_USE_OF */ |
346 | |
347 | kernel_length = (long)(&_relocation_start) - (long)(&_text); |
348 | bss_length = (long)&__bss_stop - (long)&__bss_start; |
349 | |
350 | loc_new = determine_relocation_address(); |
351 | |
352 | /* Sanity check relocation address */ |
353 | if (relocation_addr_valid(loc_new)) |
354 | offset = (unsigned long)loc_new - (unsigned long)(&_text); |
355 | |
356 | /* Reset the command line now so we don't end up with a duplicate */ |
357 | arcs_cmdline[0] = '\0'; |
358 | |
359 | if (offset) { |
360 | void (*fdt_relocated_)(void *) = NULL; |
361 | #if defined(CONFIG_USE_OF) |
362 | unsigned long fdt_phys = virt_to_phys(fdt); |
363 | |
364 | /* |
365 | * If built-in dtb is used then it will have been relocated |
366 | * during kernel _text relocation. If appended DTB is used |
367 | * then it will not be relocated, but it should remain |
368 | * intact in the original location. If dtb is loaded by |
369 | * the bootloader then it may need to be moved if it crosses |
370 | * the target memory area |
371 | */ |
372 | |
373 | if (fdt_phys >= virt_to_phys(RELOCATED(&_text)) && |
374 | fdt_phys <= virt_to_phys(RELOCATED(&_end))) { |
375 | void *fdt_relocated = |
376 | RELOCATED(ALIGN((long)&_end, PAGE_SIZE)); |
377 | memcpy(fdt_relocated, fdt, fdt_totalsize(fdt)); |
378 | fdt = fdt_relocated; |
379 | fdt_relocated_ = RELOCATED(&plat_fdt_relocated); |
380 | } |
381 | #endif /* CONFIG_USE_OF */ |
382 | |
383 | /* Copy the kernel to it's new location */ |
384 | memcpy(loc_new, &_text, kernel_length); |
385 | |
386 | /* Perform relocations on the new kernel */ |
387 | res = do_relocations(kbase_old: &_text, kbase_new: loc_new, offset); |
388 | if (res < 0) |
389 | goto out; |
390 | |
391 | /* Sync the caches ready for execution of new kernel */ |
392 | sync_icache(kbase: loc_new, kernel_length); |
393 | |
394 | res = relocate_exception_table(offset); |
395 | if (res < 0) |
396 | goto out; |
397 | |
398 | /* |
399 | * The original .bss has already been cleared, and |
400 | * some variables such as command line parameters |
401 | * stored to it so make a copy in the new location. |
402 | */ |
403 | memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length); |
404 | |
405 | /* |
406 | * If fdt was stored outside of the kernel image and |
407 | * had to be moved then update platform's state data |
408 | * with the new fdt location |
409 | */ |
410 | if (fdt_relocated_) |
411 | fdt_relocated_(fdt); |
412 | |
413 | /* |
414 | * Last chance for the platform to abort relocation. |
415 | * This may also be used by the platform to perform any |
416 | * initialisation required now that the new kernel is |
417 | * resident in memory and ready to be executed. |
418 | */ |
419 | if (plat_post_relocation(offset)) |
420 | goto out; |
421 | |
422 | /* The current thread is now within the relocated image */ |
423 | __current_thread_info = RELOCATED(&init_thread_union); |
424 | |
425 | /* Return the new kernel's entry point */ |
426 | kernel_entry = RELOCATED(start_kernel); |
427 | |
428 | /* Error may occur before, so keep it at last */ |
429 | update_kaslr_offset(addr: &__kaslr_offset, offset); |
430 | } |
431 | out: |
432 | return kernel_entry; |
433 | } |
434 | |
435 | /* |
436 | * Show relocation information on panic. |
437 | */ |
438 | static void show_kernel_relocation(const char *level) |
439 | { |
440 | if (__kaslr_offset > 0) { |
441 | printk(level); |
442 | pr_cont("Kernel relocated by 0x%pK\n" , (void *)__kaslr_offset); |
443 | pr_cont(" .text @ 0x%pK\n" , _text); |
444 | pr_cont(" .data @ 0x%pK\n" , _sdata); |
445 | pr_cont(" .bss @ 0x%pK\n" , __bss_start); |
446 | } |
447 | } |
448 | |
449 | static int kernel_location_notifier_fn(struct notifier_block *self, |
450 | unsigned long v, void *p) |
451 | { |
452 | show_kernel_relocation(KERN_EMERG); |
453 | return NOTIFY_DONE; |
454 | } |
455 | |
456 | static struct notifier_block kernel_location_notifier = { |
457 | .notifier_call = kernel_location_notifier_fn |
458 | }; |
459 | |
460 | static int __init register_kernel_offset_dumper(void) |
461 | { |
462 | atomic_notifier_chain_register(nh: &panic_notifier_list, |
463 | nb: &kernel_location_notifier); |
464 | return 0; |
465 | } |
466 | __initcall(register_kernel_offset_dumper); |
467 | |