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@imgtec.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.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 static inline u32 __init get_synci_step(void)
38 __asm__("rdhwr %0, $1" : "=r" (res));
43 static void __init sync_icache(void *kbase, unsigned long kernel_length)
45 void *kend = kbase + kernel_length;
46 u32 step = get_synci_step();
55 } while (kbase < kend);
57 /* Completion barrier */
61 static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
63 *(u64 *)loc_new += offset;
68 static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
75 static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
77 unsigned long target_addr = (*loc_orig) & 0x03ffffff;
80 pr_err("Dangerous R_MIPS_26 REL relocation\n");
84 /* Original target address */
86 target_addr += (unsigned long)loc_orig & ~0x03ffffff;
88 /* Get the new target address */
89 target_addr += offset;
91 if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
92 pr_err("R_MIPS_26 REL relocation overflow\n");
96 target_addr -= (unsigned long)loc_new & ~0x03ffffff;
99 *loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
105 static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
107 unsigned long insn = *loc_orig;
108 unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
112 *loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
116 static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
117 [R_MIPS_64] = apply_r_mips_64_rel,
118 [R_MIPS_32] = apply_r_mips_32_rel,
119 [R_MIPS_26] = apply_r_mips_26_rel,
120 [R_MIPS_HI16] = apply_r_mips_hi16_rel,
123 int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
131 for (r = _relocation_start; r < _relocation_end; r++) {
132 /* Sentinel for last relocation */
136 type = (*r >> 24) & 0xff;
137 loc_orig = (void *)(kbase_old + ((*r & 0x00ffffff) << 2));
138 loc_new = RELOCATED(loc_orig);
140 if (reloc_handlers_rel[type] == NULL) {
141 /* Unsupported relocation */
142 pr_err("Unhandled relocation type %d at 0x%pK\n",
147 res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
156 * The exception table is filled in by the relocs tool after vmlinux is linked.
157 * It must be relocated separately since there will not be any relocation
158 * information for it filled in by the linker.
160 static int __init relocate_exception_table(long offset)
162 unsigned long *etable_start, *etable_end, *e;
164 etable_start = RELOCATED(&__start___ex_table);
165 etable_end = RELOCATED(&__stop___ex_table);
167 for (e = etable_start; e < etable_end; e++)
173 #ifdef CONFIG_RANDOMIZE_BASE
175 static inline __init unsigned long rotate_xor(unsigned long hash,
176 const void *area, size_t size)
179 unsigned long *ptr = (unsigned long *)area;
181 for (i = 0; i < size / sizeof(hash); i++) {
182 /* Rotate by odd number of bits and XOR. */
183 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
190 static inline __init unsigned long get_random_boot(void)
192 unsigned long entropy = random_get_entropy();
193 unsigned long hash = 0;
195 /* Attempt to create a simple but unpredictable starting entropy. */
196 hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
198 /* Add in any runtime entropy we can get */
199 hash = rotate_xor(hash, &entropy, sizeof(entropy));
201 #if defined(CONFIG_USE_OF)
202 /* Get any additional entropy passed in device tree */
207 node = fdt_path_offset(initial_boot_params, "/chosen");
209 prop = fdt_getprop_w(initial_boot_params, node,
211 if (prop && (len == sizeof(u64)))
212 hash = rotate_xor(hash, prop, sizeof(*prop));
215 #endif /* CONFIG_USE_OF */
220 static inline __init bool kaslr_disabled(void)
224 #if defined(CONFIG_CMDLINE_BOOL)
225 const char *builtin_cmdline = CONFIG_CMDLINE;
227 str = strstr(builtin_cmdline, "nokaslr");
228 if (str == builtin_cmdline ||
229 (str > builtin_cmdline && *(str - 1) == ' '))
232 str = strstr(arcs_cmdline, "nokaslr");
233 if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' '))
239 static inline void __init *determine_relocation_address(void)
241 /* Choose a new address for the kernel */
242 unsigned long kernel_length;
244 unsigned long offset;
246 if (kaslr_disabled())
249 kernel_length = (long)_end - (long)(&_text);
251 offset = get_random_boot() << 16;
252 offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
253 if (offset < kernel_length)
254 offset += ALIGN(kernel_length, 0xffff);
256 return RELOCATED(dest);
261 static inline void __init *determine_relocation_address(void)
264 * Choose a new address for the kernel
265 * For now we'll hard code the destination
267 return (void *)0xffffffff81000000;
272 static inline int __init relocation_addr_valid(void *loc_new)
274 if ((unsigned long)loc_new & 0x0000ffff) {
275 /* Inappropriately aligned new location */
278 if ((unsigned long)loc_new < (unsigned long)&_end) {
279 /* New location overlaps original kernel */
285 void *__init relocate_kernel(void)
288 unsigned long kernel_length;
289 unsigned long bss_length;
292 /* Default to original kernel entry point */
293 void *kernel_entry = start_kernel;
295 /* Get the command line */
297 #if defined(CONFIG_USE_OF)
298 /* Deal with the device tree */
299 early_init_dt_scan(plat_get_fdt());
300 if (boot_command_line[0]) {
301 /* Boot command line was passed in device tree */
302 strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
304 #endif /* CONFIG_USE_OF */
306 kernel_length = (long)(&_relocation_start) - (long)(&_text);
307 bss_length = (long)&__bss_stop - (long)&__bss_start;
309 loc_new = determine_relocation_address();
311 /* Sanity check relocation address */
312 if (relocation_addr_valid(loc_new))
313 offset = (unsigned long)loc_new - (unsigned long)(&_text);
315 /* Reset the command line now so we don't end up with a duplicate */
316 arcs_cmdline[0] = '\0';
319 /* Copy the kernel to it's new location */
320 memcpy(loc_new, &_text, kernel_length);
322 /* Perform relocations on the new kernel */
323 res = do_relocations(&_text, loc_new, offset);
327 /* Sync the caches ready for execution of new kernel */
328 sync_icache(loc_new, kernel_length);
330 res = relocate_exception_table(offset);
335 * The original .bss has already been cleared, and
336 * some variables such as command line parameters
337 * stored to it so make a copy in the new location.
339 memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
341 /* The current thread is now within the relocated image */
342 __current_thread_info = RELOCATED(&init_thread_union);
344 /* Return the new kernel's entry point */
345 kernel_entry = RELOCATED(start_kernel);
352 * Show relocation information on panic.
354 void show_kernel_relocation(const char *level)
356 unsigned long offset;
358 offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
360 if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
362 pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
363 pr_cont(" .text @ 0x%pK\n", _text);
364 pr_cont(" .data @ 0x%pK\n", _sdata);
365 pr_cont(" .bss @ 0x%pK\n", __bss_start);
369 static int kernel_location_notifier_fn(struct notifier_block *self,
370 unsigned long v, void *p)
372 show_kernel_relocation(KERN_EMERG);
376 static struct notifier_block kernel_location_notifier = {
377 .notifier_call = kernel_location_notifier_fn
380 static int __init register_kernel_offset_dumper(void)
382 atomic_notifier_chain_register(&panic_notifier_list,
383 &kernel_location_notifier);
386 __initcall(register_kernel_offset_dumper);