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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Support for Kernel relocation at boot time
*
* Copyright (C) 2015, Imagination Technologies Ltd.
* Authors: Matt Redfearn (matt.redfearn@imgtec.com)
*/
#include <asm/cacheflush.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/timex.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/start_kernel.h>
#include <linux/string.h>
#define RELOCATED(x) ((void *)((long)x + offset))
extern u32 _relocation_start[]; /* End kernel image / start relocation table */
extern u32 _relocation_end[]; /* End relocation table */
extern long __start___ex_table; /* Start exception table */
extern long __stop___ex_table; /* End exception table */
static inline u32 __init get_synci_step(void)
{
u32 res;
__asm__("rdhwr %0, $1" : "=r" (res));
return res;
}
static void __init sync_icache(void *kbase, unsigned long kernel_length)
{
void *kend = kbase + kernel_length;
u32 step = get_synci_step();
do {
__asm__ __volatile__(
"synci 0(%0)"
: /* no output */
: "r" (kbase));
kbase += step;
} while (kbase < kend);
/* Completion barrier */
__sync();
}
static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
{
*(u64 *)loc_new += offset;
return 0;
}
static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
{
*loc_new += offset;
return 0;
}
static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
{
unsigned long target_addr = (*loc_orig) & 0x03ffffff;
if (offset % 4) {
pr_err("Dangerous R_MIPS_26 REL relocation\n");
return -ENOEXEC;
}
/* Original target address */
target_addr <<= 2;
target_addr += (unsigned long)loc_orig & ~0x03ffffff;
/* Get the new target address */
target_addr += offset;
if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
pr_err("R_MIPS_26 REL relocation overflow\n");
return -ENOEXEC;
}
target_addr -= (unsigned long)loc_new & ~0x03ffffff;
target_addr >>= 2;
*loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
return 0;
}
static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
{
unsigned long insn = *loc_orig;
unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
target += offset;
*loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
return 0;
}
static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
[R_MIPS_64] = apply_r_mips_64_rel,
[R_MIPS_32] = apply_r_mips_32_rel,
[R_MIPS_26] = apply_r_mips_26_rel,
[R_MIPS_HI16] = apply_r_mips_hi16_rel,
};
int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
{
u32 *r;
u32 *loc_orig;
u32 *loc_new;
int type;
int res;
for (r = _relocation_start; r < _relocation_end; r++) {
/* Sentinel for last relocation */
if (*r == 0)
break;
type = (*r >> 24) & 0xff;
loc_orig = (void *)(kbase_old + ((*r & 0x00ffffff) << 2));
loc_new = RELOCATED(loc_orig);
if (reloc_handlers_rel[type] == NULL) {
/* Unsupported relocation */
pr_err("Unhandled relocation type %d at 0x%pK\n",
type, loc_orig);
return -ENOEXEC;
}
res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
if (res)
return res;
}
return 0;
}
/*
* The exception table is filled in by the relocs tool after vmlinux is linked.
* It must be relocated separately since there will not be any relocation
* information for it filled in by the linker.
*/
static int __init relocate_exception_table(long offset)
{
unsigned long *etable_start, *etable_end, *e;
etable_start = RELOCATED(&__start___ex_table);
etable_end = RELOCATED(&__stop___ex_table);
for (e = etable_start; e < etable_end; e++)
*e += offset;
return 0;
}
static inline void __init *determine_relocation_address(void)
{
/*
* Choose a new address for the kernel
* For now we'll hard code the destination
*/
return (void *)0xffffffff81000000;
}
static inline int __init relocation_addr_valid(void *loc_new)
{
if ((unsigned long)loc_new & 0x0000ffff) {
/* Inappropriately aligned new location */
return 0;
}
if ((unsigned long)loc_new < (unsigned long)&_end) {
/* New location overlaps original kernel */
return 0;
}
return 1;
}
void *__init relocate_kernel(void)
{
void *loc_new;
unsigned long kernel_length;
unsigned long bss_length;
long offset = 0;
int res = 1;
/* Default to original kernel entry point */
void *kernel_entry = start_kernel;
kernel_length = (long)(&_relocation_start) - (long)(&_text);
bss_length = (long)&__bss_stop - (long)&__bss_start;
loc_new = determine_relocation_address();
/* Sanity check relocation address */
if (relocation_addr_valid(loc_new))
offset = (unsigned long)loc_new - (unsigned long)(&_text);
if (offset) {
/* Copy the kernel to it's new location */
memcpy(loc_new, &_text, kernel_length);
/* Perform relocations on the new kernel */
res = do_relocations(&_text, loc_new, offset);
if (res < 0)
goto out;
/* Sync the caches ready for execution of new kernel */
sync_icache(loc_new, kernel_length);
res = relocate_exception_table(offset);
if (res < 0)
goto out;
/*
* The original .bss has already been cleared, and
* some variables such as command line parameters
* stored to it so make a copy in the new location.
*/
memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
/* The current thread is now within the relocated image */
__current_thread_info = RELOCATED(&init_thread_union);
/* Return the new kernel's entry point */
kernel_entry = RELOCATED(start_kernel);
}
out:
return kernel_entry;
}
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