MIPS: Kernel: Add relocate.c
arch/mips/kernel/relocate.c contains the functions necessary to relocate the kernel elsewhere in memory The kernel makes a copy of itself at the new address. It uses the relocation table inserted by the relocs tool to fix symbol references within the new image. If copy/relocation is sucessful then the entry point of the new kernel is returned, otherwise fall back to starting the kernel in place. Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: James Hogan <james.hogan@imgtec.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Cc: kernel-hardening@lists.openwall.com Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/12985/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Matt Redfearn
Ralf Baechle
parent
e818fac595
commit
279b991b24
@ -83,6 +83,8 @@ obj-$(CONFIG_I8253) += i8253.o
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obj-$(CONFIG_GPIO_TXX9) += gpio_txx9.o
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obj-$(CONFIG_RELOCATABLE) += relocate.o
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obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
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obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
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obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
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240
arch/mips/kernel/relocate.c
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240
arch/mips/kernel/relocate.c
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@ -0,0 +1,240 @@
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/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Support for Kernel relocation at boot time
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*
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* Copyright (C) 2015, Imagination Technologies Ltd.
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* Authors: Matt Redfearn (matt.redfearn@imgtec.com)
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*/
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#include <asm/cacheflush.h>
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#include <asm/sections.h>
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#include <asm/setup.h>
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#include <asm/timex.h>
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#include <linux/elf.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/start_kernel.h>
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#include <linux/string.h>
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#define RELOCATED(x) ((void *)((long)x + offset))
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extern u32 _relocation_start[]; /* End kernel image / start relocation table */
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extern u32 _relocation_end[]; /* End relocation table */
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extern long __start___ex_table; /* Start exception table */
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extern long __stop___ex_table; /* End exception table */
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static inline u32 __init get_synci_step(void)
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{
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u32 res;
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__asm__("rdhwr %0, $1" : "=r" (res));
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return res;
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}
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static void __init sync_icache(void *kbase, unsigned long kernel_length)
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{
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void *kend = kbase + kernel_length;
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u32 step = get_synci_step();
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do {
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__asm__ __volatile__(
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"synci 0(%0)"
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: /* no output */
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: "r" (kbase));
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kbase += step;
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} while (kbase < kend);
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/* Completion barrier */
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__sync();
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}
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static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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*(u64 *)loc_new += offset;
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return 0;
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}
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static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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*loc_new += offset;
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return 0;
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}
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static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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unsigned long target_addr = (*loc_orig) & 0x03ffffff;
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if (offset % 4) {
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pr_err("Dangerous R_MIPS_26 REL relocation\n");
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return -ENOEXEC;
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}
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/* Original target address */
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target_addr <<= 2;
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target_addr += (unsigned long)loc_orig & ~0x03ffffff;
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/* Get the new target address */
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target_addr += offset;
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if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
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pr_err("R_MIPS_26 REL relocation overflow\n");
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return -ENOEXEC;
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}
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target_addr -= (unsigned long)loc_new & ~0x03ffffff;
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target_addr >>= 2;
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*loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
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return 0;
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}
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static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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unsigned long insn = *loc_orig;
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unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
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target += offset;
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*loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
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return 0;
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}
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static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
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[R_MIPS_64] = apply_r_mips_64_rel,
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[R_MIPS_32] = apply_r_mips_32_rel,
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[R_MIPS_26] = apply_r_mips_26_rel,
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[R_MIPS_HI16] = apply_r_mips_hi16_rel,
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};
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int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
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{
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u32 *r;
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u32 *loc_orig;
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u32 *loc_new;
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int type;
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int res;
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for (r = _relocation_start; r < _relocation_end; r++) {
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/* Sentinel for last relocation */
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if (*r == 0)
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break;
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type = (*r >> 24) & 0xff;
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loc_orig = (void *)(kbase_old + ((*r & 0x00ffffff) << 2));
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loc_new = RELOCATED(loc_orig);
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if (reloc_handlers_rel[type] == NULL) {
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/* Unsupported relocation */
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pr_err("Unhandled relocation type %d at 0x%pK\n",
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type, loc_orig);
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return -ENOEXEC;
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}
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res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
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if (res)
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return res;
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}
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return 0;
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}
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/*
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* The exception table is filled in by the relocs tool after vmlinux is linked.
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* It must be relocated separately since there will not be any relocation
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* information for it filled in by the linker.
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*/
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static int __init relocate_exception_table(long offset)
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{
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unsigned long *etable_start, *etable_end, *e;
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etable_start = RELOCATED(&__start___ex_table);
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etable_end = RELOCATED(&__stop___ex_table);
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for (e = etable_start; e < etable_end; e++)
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*e += offset;
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return 0;
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}
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static inline void __init *determine_relocation_address(void)
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{
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/*
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* Choose a new address for the kernel
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* For now we'll hard code the destination
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*/
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return (void *)0xffffffff81000000;
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}
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static inline int __init relocation_addr_valid(void *loc_new)
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{
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if ((unsigned long)loc_new & 0x0000ffff) {
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/* Inappropriately aligned new location */
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return 0;
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}
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if ((unsigned long)loc_new < (unsigned long)&_end) {
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/* New location overlaps original kernel */
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return 0;
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}
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return 1;
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}
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void *__init relocate_kernel(void)
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{
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void *loc_new;
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unsigned long kernel_length;
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unsigned long bss_length;
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long offset = 0;
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int res = 1;
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/* Default to original kernel entry point */
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void *kernel_entry = start_kernel;
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kernel_length = (long)(&_relocation_start) - (long)(&_text);
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bss_length = (long)&__bss_stop - (long)&__bss_start;
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loc_new = determine_relocation_address();
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/* Sanity check relocation address */
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if (relocation_addr_valid(loc_new))
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offset = (unsigned long)loc_new - (unsigned long)(&_text);
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if (offset) {
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/* Copy the kernel to it's new location */
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memcpy(loc_new, &_text, kernel_length);
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/* Perform relocations on the new kernel */
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res = do_relocations(&_text, loc_new, offset);
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if (res < 0)
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goto out;
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/* Sync the caches ready for execution of new kernel */
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sync_icache(loc_new, kernel_length);
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res = relocate_exception_table(offset);
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if (res < 0)
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goto out;
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/*
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* The original .bss has already been cleared, and
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* some variables such as command line parameters
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* stored to it so make a copy in the new location.
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*/
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memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
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/* The current thread is now within the relocated image */
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__current_thread_info = RELOCATED(&init_thread_union);
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/* Return the new kernel's entry point */
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kernel_entry = RELOCATED(start_kernel);
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}
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out:
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return kernel_entry;
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}
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