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
6 * Support for Kernel relocation at boot time
8 * Copyright (C) 2015, Imagination Technologies Ltd.
9 * Authors: Matt Redfearn (matt.redfearn@mips.com)
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/sched/task.h>
22 #include <linux/start_kernel.h>
23 #include <linux/string.h>
24 #include <linux/printk.h>
26 #define RELOCATED(x) ((void *)((long)x + offset))
28 extern u32 _relocation_start[]; /* End kernel image / start relocation table */
29 extern u32 _relocation_end[]; /* End relocation table */
31 extern long __start___ex_table; /* Start exception table */
32 extern long __stop___ex_table; /* End exception table */
34 extern void __weak plat_fdt_relocated(void *new_location);
37 * This function may be defined for a platform to perform any post-relocation
39 * Return non-zero to abort relocation
41 int __weak plat_post_relocation(long offset)
46 static inline u32 __init get_synci_step(void)
50 __asm__("rdhwr %0, $1" : "=r" (res));
55 static void __init sync_icache(void *kbase, unsigned long kernel_length)
57 void *kend = kbase + kernel_length;
58 u32 step = get_synci_step();
67 } while (step && kbase < kend);
69 /* Completion barrier */
73 static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
75 *(u64 *)loc_new += offset;
80 static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
87 static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
89 unsigned long target_addr = (*loc_orig) & 0x03ffffff;
92 pr_err("Dangerous R_MIPS_26 REL relocation\n");
96 /* Original target address */
98 target_addr += (unsigned long)loc_orig & 0xf0000000;
100 /* Get the new target address */
101 target_addr += offset;
103 if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
104 pr_err("R_MIPS_26 REL relocation overflow\n");
108 target_addr -= (unsigned long)loc_new & 0xf0000000;
111 *loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
117 static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
119 unsigned long insn = *loc_orig;
120 unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
124 *loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
128 static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
129 [R_MIPS_64] = apply_r_mips_64_rel,
130 [R_MIPS_32] = apply_r_mips_32_rel,
131 [R_MIPS_26] = apply_r_mips_26_rel,
132 [R_MIPS_HI16] = apply_r_mips_hi16_rel,
135 int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
143 for (r = _relocation_start; r < _relocation_end; r++) {
144 /* Sentinel for last relocation */
148 type = (*r >> 24) & 0xff;
149 loc_orig = kbase_old + ((*r & 0x00ffffff) << 2);
150 loc_new = RELOCATED(loc_orig);
152 if (reloc_handlers_rel[type] == NULL) {
153 /* Unsupported relocation */
154 pr_err("Unhandled relocation type %d at 0x%pK\n",
159 res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
168 * The exception table is filled in by the relocs tool after vmlinux is linked.
169 * It must be relocated separately since there will not be any relocation
170 * information for it filled in by the linker.
172 static int __init relocate_exception_table(long offset)
174 unsigned long *etable_start, *etable_end, *e;
176 etable_start = RELOCATED(&__start___ex_table);
177 etable_end = RELOCATED(&__stop___ex_table);
179 for (e = etable_start; e < etable_end; e++)
185 #ifdef CONFIG_RANDOMIZE_BASE
187 static inline __init unsigned long rotate_xor(unsigned long hash,
188 const void *area, size_t size)
190 const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash));
193 diff = (void *)ptr - area;
194 if (unlikely(size < diff + sizeof(hash)))
197 size = ALIGN_DOWN(size - diff, sizeof(hash));
199 for (i = 0; i < size / sizeof(hash); i++) {
200 /* Rotate by odd number of bits and XOR. */
201 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
208 static inline __init unsigned long get_random_boot(void)
210 unsigned long entropy = random_get_entropy();
211 unsigned long hash = 0;
213 /* Attempt to create a simple but unpredictable starting entropy. */
214 hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
216 /* Add in any runtime entropy we can get */
217 hash = rotate_xor(hash, &entropy, sizeof(entropy));
219 #if defined(CONFIG_USE_OF)
220 /* Get any additional entropy passed in device tree */
221 if (initial_boot_params) {
225 node = fdt_path_offset(initial_boot_params, "/chosen");
227 prop = fdt_getprop_w(initial_boot_params, node,
229 if (prop && (len == sizeof(u64)))
230 hash = rotate_xor(hash, prop, sizeof(*prop));
233 #endif /* CONFIG_USE_OF */
238 static inline __init bool kaslr_disabled(void)
242 #if defined(CONFIG_CMDLINE_BOOL)
243 const char *builtin_cmdline = CONFIG_CMDLINE;
245 str = strstr(builtin_cmdline, "nokaslr");
246 if (str == builtin_cmdline ||
247 (str > builtin_cmdline && *(str - 1) == ' '))
250 str = strstr(arcs_cmdline, "nokaslr");
251 if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' '))
257 static inline void __init *determine_relocation_address(void)
259 /* Choose a new address for the kernel */
260 unsigned long kernel_length;
262 unsigned long offset;
264 if (kaslr_disabled())
267 kernel_length = (long)_end - (long)(&_text);
269 offset = get_random_boot() << 16;
270 offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
271 if (offset < kernel_length)
272 offset += ALIGN(kernel_length, 0xffff);
274 return RELOCATED(dest);
279 static inline void __init *determine_relocation_address(void)
282 * Choose a new address for the kernel
283 * For now we'll hard code the destination
285 return (void *)0xffffffff81000000;
290 static inline int __init relocation_addr_valid(void *loc_new)
292 if ((unsigned long)loc_new & 0x0000ffff) {
293 /* Inappropriately aligned new location */
296 if ((unsigned long)loc_new < (unsigned long)&_end) {
297 /* New location overlaps original kernel */
303 #if defined(CONFIG_USE_OF)
304 void __weak *plat_get_fdt(void)
310 void *__init relocate_kernel(void)
313 unsigned long kernel_length;
314 unsigned long bss_length;
317 /* Default to original kernel entry point */
318 void *kernel_entry = start_kernel;
321 /* Get the command line */
323 #if defined(CONFIG_USE_OF)
324 /* Deal with the device tree */
325 fdt = plat_get_fdt();
326 early_init_dt_scan(fdt);
327 if (boot_command_line[0]) {
328 /* Boot command line was passed in device tree */
329 strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
331 #endif /* CONFIG_USE_OF */
333 kernel_length = (long)(&_relocation_start) - (long)(&_text);
334 bss_length = (long)&__bss_stop - (long)&__bss_start;
336 loc_new = determine_relocation_address();
338 /* Sanity check relocation address */
339 if (relocation_addr_valid(loc_new))
340 offset = (unsigned long)loc_new - (unsigned long)(&_text);
342 /* Reset the command line now so we don't end up with a duplicate */
343 arcs_cmdline[0] = '\0';
346 void (*fdt_relocated_)(void *) = NULL;
347 #if defined(CONFIG_USE_OF)
348 unsigned long fdt_phys = virt_to_phys(fdt);
351 * If built-in dtb is used then it will have been relocated
352 * during kernel _text relocation. If appended DTB is used
353 * then it will not be relocated, but it should remain
354 * intact in the original location. If dtb is loaded by
355 * the bootloader then it may need to be moved if it crosses
356 * the target memory area
359 if (fdt_phys >= virt_to_phys(RELOCATED(&_text)) &&
360 fdt_phys <= virt_to_phys(RELOCATED(&_end))) {
361 void *fdt_relocated =
362 RELOCATED(ALIGN((long)&_end, PAGE_SIZE));
363 memcpy(fdt_relocated, fdt, fdt_totalsize(fdt));
365 fdt_relocated_ = RELOCATED(&plat_fdt_relocated);
367 #endif /* CONFIG_USE_OF */
369 /* Copy the kernel to it's new location */
370 memcpy(loc_new, &_text, kernel_length);
372 /* Perform relocations on the new kernel */
373 res = do_relocations(&_text, loc_new, offset);
377 /* Sync the caches ready for execution of new kernel */
378 sync_icache(loc_new, kernel_length);
380 res = relocate_exception_table(offset);
385 * The original .bss has already been cleared, and
386 * some variables such as command line parameters
387 * stored to it so make a copy in the new location.
389 memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
392 * If fdt was stored outside of the kernel image and
393 * had to be moved then update platform's state data
394 * with the new fdt location
400 * Last chance for the platform to abort relocation.
401 * This may also be used by the platform to perform any
402 * initialisation required now that the new kernel is
403 * resident in memory and ready to be executed.
405 if (plat_post_relocation(offset))
408 /* The current thread is now within the relocated image */
409 __current_thread_info = RELOCATED(&init_thread_union);
411 /* Return the new kernel's entry point */
412 kernel_entry = RELOCATED(start_kernel);
419 * Show relocation information on panic.
421 void show_kernel_relocation(const char *level)
423 unsigned long offset;
425 offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
427 if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
429 pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
430 pr_cont(" .text @ 0x%pK\n", _text);
431 pr_cont(" .data @ 0x%pK\n", _sdata);
432 pr_cont(" .bss @ 0x%pK\n", __bss_start);
436 static int kernel_location_notifier_fn(struct notifier_block *self,
437 unsigned long v, void *p)
439 show_kernel_relocation(KERN_EMERG);
443 static struct notifier_block kernel_location_notifier = {
444 .notifier_call = kernel_location_notifier_fn
447 static int __init register_kernel_offset_dumper(void)
449 atomic_notifier_chain_register(&panic_notifier_list,
450 &kernel_location_notifier);
453 __initcall(register_kernel_offset_dumper);