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/*
* 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>
#ifdef HAVE_JUMP_LABEL
union jump_code_union {
char code[JUMP_LABEL_NOP_SIZE];
struct {
char jump;
int offset;
} __attribute__((packed));
};
static void bug_at(unsigned char *ip, int line)
{
/*
* 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) %d\n", ip, ip, ip, line);
BUG();
}
static void __jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
void *(*poker)(void *, const void *, size_t),
int init)
{
union jump_code_union code;
const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
if (type == JUMP_LABEL_JMP) {
if (init) {
/*
* Jump label is enabled for the first time.
* So we expect a default_nop...
*/
if (unlikely(memcmp((void *)entry->code, default_nop, 5)
!= 0))
bug_at((void *)entry->code, __LINE__);
} else {
/*
* ...otherwise expect an ideal_nop. Otherwise
* something went horribly wrong.
*/
if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
!= 0))
bug_at((void *)entry->code, __LINE__);
}
code.jump = 0xe9;
code.offset = entry->target -
(entry->code + JUMP_LABEL_NOP_SIZE);
} else {
/*
* We are disabling this jump label. If it is not what
* we think it is, then something must have gone wrong.
* If this is the first initialization call, then we
* are converting the default nop to the ideal nop.
*/
if (init) {
if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
bug_at((void *)entry->code, __LINE__);
} else {
code.jump = 0xe9;
code.offset = entry->target -
(entry->code + JUMP_LABEL_NOP_SIZE);
if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
bug_at((void *)entry->code, __LINE__);
}
memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
}
/*
* Make text_poke_bp() a default fallback poker.
*
* 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 (poker)
(*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
else
text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
(void *)entry->code + JUMP_LABEL_NOP_SIZE);
}
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, NULL, 0);
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)
{
/*
* This function is called at boot up and when modules are
* first loaded. Check if the default nop, the one that is
* inserted at compile time, is the ideal nop. If it is, then
* we do not need to update the nop, and we can leave it as is.
* If it is not, then we need to update the nop to the ideal nop.
*/
if (jlstate == JL_STATE_START) {
const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
if (memcmp(ideal_nop, default_nop, 5) != 0)
jlstate = JL_STATE_UPDATE;
else
jlstate = JL_STATE_NO_UPDATE;
}
if (jlstate == JL_STATE_UPDATE)
__jump_label_transform(entry, type, text_poke_early, 1);
}
#endif
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