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// SPDX-License-Identifier: GPL-2.0
/*
* Support for Kernel relocation at boot time
*
* Copyright (C) 2023 Loongson Technology Corporation Limited
*/
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/printk.h>
#include <linux/panic_notifier.h>
#include <linux/start_kernel.h>
#include <asm/bootinfo.h>
#include <asm/early_ioremap.h>
#include <asm/inst.h>
#include <asm/sections.h>
#include <asm/setup.h>
#define RELOCATED(x) ((void *)((long)x + reloc_offset))
#define RELOCATED_KASLR(x) ((void *)((long)x + random_offset))
static unsigned long reloc_offset;
static inline void __init relocate_relative(void)
{
Elf64_Rela *rela, *rela_end;
rela = (Elf64_Rela *)&__rela_dyn_begin;
rela_end = (Elf64_Rela *)&__rela_dyn_end;
for ( ; rela < rela_end; rela++) {
Elf64_Addr addr = rela->r_offset;
Elf64_Addr relocated_addr = rela->r_addend;
if (rela->r_info != R_LARCH_RELATIVE)
continue;
if (relocated_addr >= VMLINUX_LOAD_ADDRESS)
relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);
*(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
}
}
static inline void __init relocate_absolute(long random_offset)
{
void *begin, *end;
struct rela_la_abs *p;
begin = RELOCATED_KASLR(&__la_abs_begin);
end = RELOCATED_KASLR(&__la_abs_end);
for (p = begin; (void *)p < end; p++) {
long v = p->symvalue;
uint32_t lu12iw, ori, lu32id, lu52id;
union loongarch_instruction *insn = (void *)p->pc;
lu12iw = (v >> 12) & 0xfffff;
ori = v & 0xfff;
lu32id = (v >> 32) & 0xfffff;
lu52id = v >> 52;
insn[0].reg1i20_format.immediate = lu12iw;
insn[1].reg2i12_format.immediate = ori;
insn[2].reg1i20_format.immediate = lu32id;
insn[3].reg2i12_format.immediate = lu52id;
}
}
#ifdef CONFIG_RANDOMIZE_BASE
static inline __init unsigned long rotate_xor(unsigned long hash,
const void *area, size_t size)
{
size_t i, diff;
const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash));
diff = (void *)ptr - area;
if (size < diff + sizeof(hash))
return hash;
size = ALIGN_DOWN(size - diff, sizeof(hash));
for (i = 0; i < size / sizeof(hash); i++) {
/* Rotate by odd number of bits and XOR. */
hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
hash ^= ptr[i];
}
return hash;
}
static inline __init unsigned long get_random_boot(void)
{
unsigned long hash = 0;
unsigned long entropy = random_get_entropy();
/* Attempt to create a simple but unpredictable starting entropy. */
hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
/* Add in any runtime entropy we can get */
hash = rotate_xor(hash, &entropy, sizeof(entropy));
return hash;
}
static inline __init bool kaslr_disabled(void)
{
char *str;
const char *builtin_cmdline = CONFIG_CMDLINE;
str = strstr(builtin_cmdline, "nokaslr");
if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' '))
return true;
str = strstr(boot_command_line, "nokaslr");
if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
return true;
return false;
}
/* Choose a new address for the kernel */
static inline void __init *determine_relocation_address(void)
{
unsigned long kernel_length;
unsigned long random_offset;
void *destination = _text;
if (kaslr_disabled())
return destination;
kernel_length = (long)_end - (long)_text;
random_offset = get_random_boot() << 16;
random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
if (random_offset < kernel_length)
random_offset += ALIGN(kernel_length, 0xffff);
return RELOCATED_KASLR(destination);
}
static inline int __init relocation_addr_valid(void *location_new)
{
if ((unsigned long)location_new & 0x00000ffff)
return 0; /* Inappropriately aligned new location */
if ((unsigned long)location_new < (unsigned long)_end)
return 0; /* New location overlaps original kernel */
return 1;
}
#endif
static inline void __init update_reloc_offset(unsigned long *addr, long random_offset)
{
unsigned long *new_addr = (unsigned long *)RELOCATED_KASLR(addr);
*new_addr = (unsigned long)reloc_offset;
}
unsigned long __init relocate_kernel(void)
{
unsigned long kernel_length;
unsigned long random_offset = 0;
void *location_new = _text; /* Default to original kernel start */
char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */
strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
#ifdef CONFIG_RANDOMIZE_BASE
location_new = determine_relocation_address();
/* Sanity check relocation address */
if (relocation_addr_valid(location_new))
random_offset = (unsigned long)location_new - (unsigned long)(_text);
#endif
reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS;
if (random_offset) {
kernel_length = (long)(_end) - (long)(_text);
/* Copy the kernel to it's new location */
memcpy(location_new, _text, kernel_length);
/* Sync the caches ready for execution of new kernel */
__asm__ __volatile__ (
"ibar 0 \t\n"
"dbar 0 \t\n"
::: "memory");
reloc_offset += random_offset;
/* The current thread is now within the relocated kernel */
__current_thread_info = RELOCATED_KASLR(__current_thread_info);
update_reloc_offset(&reloc_offset, random_offset);
}
if (reloc_offset)
relocate_relative();
relocate_absolute(random_offset);
return random_offset;
}
/*
* Show relocation information on panic.
*/
static void show_kernel_relocation(const char *level)
{
if (reloc_offset > 0) {
printk(level);
pr_cont("Kernel relocated by 0x%lx\n", reloc_offset);
pr_cont(" .text @ 0x%px\n", _text);
pr_cont(" .data @ 0x%px\n", _sdata);
pr_cont(" .bss @ 0x%px\n", __bss_start);
}
}
static int kernel_location_notifier_fn(struct notifier_block *self,
unsigned long v, void *p)
{
show_kernel_relocation(KERN_EMERG);
return NOTIFY_DONE;
}
static struct notifier_block kernel_location_notifier = {
.notifier_call = kernel_location_notifier_fn
};
static int __init register_kernel_offset_dumper(void)
{
atomic_notifier_chain_register(&panic_notifier_list,
&kernel_location_notifier);
return 0;
}
arch_initcall(register_kernel_offset_dumper);
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