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// SPDX-License-Identifier: GPL-2.0
/*
* jump label x86 support
*
* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
*
*/
#include <linux/jump_label.h>
#include <linux/memory.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/cpu.h>
#include <asm/kprobes.h>
#include <asm/alternative.h>
#include <asm/text-patching.h>
#include <asm/insn.h>
int arch_jump_entry_size(struct jump_entry *entry)
{
struct insn insn = {};
insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
BUG_ON(insn.length != 2 && insn.length != 5);
return insn.length;
}
struct jump_label_patch {
const void *code;
int size;
};
static struct jump_label_patch
__jump_label_patch(struct jump_entry *entry, enum jump_label_type type)
{
const void *expect, *code, *nop;
const void *addr, *dest;
int size;
addr = (void *)jump_entry_code(entry);
dest = (void *)jump_entry_target(entry);
size = arch_jump_entry_size(entry);
switch (size) {
case JMP8_INSN_SIZE:
code = text_gen_insn(JMP8_INSN_OPCODE, addr, dest);
nop = x86_nops[size];
break;
case JMP32_INSN_SIZE:
code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
nop = x86_nops[size];
break;
default: BUG();
}
if (type == JUMP_LABEL_JMP)
expect = nop;
else
expect = code;
if (memcmp(addr, expect, size)) {
/*
* The location is not an op that we were expecting.
* Something went wrong. Crash the box, as something could be
* corrupting the kernel.
*/
pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n",
addr, addr, addr, expect, size, type);
BUG();
}
if (type == JUMP_LABEL_NOP)
code = nop;
return (struct jump_label_patch){.code = code, .size = size};
}
static inline void __jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
int init)
{
const struct jump_label_patch jlp = __jump_label_patch(entry, type);
/*
* As long as only a single processor is running and the code is still
* not marked as RO, text_poke_early() can be used; Checking that
* system_state is SYSTEM_BOOTING guarantees it. It will be set to
* SYSTEM_SCHEDULING before other cores are awaken and before the
* code is write-protected.
*
* At the time the change is being done, just ignore whether we
* are doing nop -> jump or jump -> nop transition, and assume
* always nop being the 'currently valid' instruction
*/
if (init || system_state == SYSTEM_BOOTING) {
text_poke_early((void *)jump_entry_code(entry), jlp.code, jlp.size);
return;
}
text_poke_bp((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
}
static void __ref jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
int init)
{
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, init);
mutex_unlock(&text_mutex);
}
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
jump_label_transform(entry, type, 0);
}
bool arch_jump_label_transform_queue(struct jump_entry *entry,
enum jump_label_type type)
{
struct jump_label_patch jlp;
if (system_state == SYSTEM_BOOTING) {
/*
* Fallback to the non-batching mode.
*/
arch_jump_label_transform(entry, type);
return true;
}
mutex_lock(&text_mutex);
jlp = __jump_label_patch(entry, type);
text_poke_queue((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
mutex_unlock(&text_mutex);
return true;
}
void arch_jump_label_transform_apply(void)
{
mutex_lock(&text_mutex);
text_poke_finish();
mutex_unlock(&text_mutex);
}
static enum {
JL_STATE_START,
JL_STATE_NO_UPDATE,
JL_STATE_UPDATE,
} jlstate __initdata_or_module = JL_STATE_START;
__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
if (jlstate == JL_STATE_UPDATE)
jump_label_transform(entry, type, 1);
}
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