130 lines
3.5 KiB
C
130 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* jump label x86 support
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*
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* Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
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*
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*/
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#include <linux/jump_label.h>
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#include <linux/memory.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/list.h>
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#include <linux/jhash.h>
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#include <linux/cpu.h>
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#include <asm/kprobes.h>
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#include <asm/alternative.h>
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#include <asm/text-patching.h>
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union jump_code_union {
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char code[JUMP_LABEL_NOP_SIZE];
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struct {
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char jump;
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int offset;
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} __attribute__((packed));
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};
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static void bug_at(unsigned char *ip, int line)
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{
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/*
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* The location is not an op that we were expecting.
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* Something went wrong. Crash the box, as something could be
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* corrupting the kernel.
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*/
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pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph) %d\n", ip, ip, ip, line);
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BUG();
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}
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static void __ref __jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type,
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int init)
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{
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union jump_code_union jmp;
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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const void *expect, *code;
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int line;
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jmp.jump = 0xe9;
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jmp.offset = jump_entry_target(entry) -
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(jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
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if (type == JUMP_LABEL_JMP) {
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if (init) {
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expect = default_nop; line = __LINE__;
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} else {
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expect = ideal_nop; line = __LINE__;
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}
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code = &jmp.code;
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} else {
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if (init) {
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expect = default_nop; line = __LINE__;
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} else {
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expect = &jmp.code; line = __LINE__;
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}
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code = ideal_nop;
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}
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if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
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bug_at((void *)jump_entry_code(entry), line);
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/*
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* As long as only a single processor is running and the code is still
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* not marked as RO, text_poke_early() can be used; Checking that
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* system_state is SYSTEM_BOOTING guarantees it. It will be set to
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* SYSTEM_SCHEDULING before other cores are awaken and before the
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* code is write-protected.
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*
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* At the time the change is being done, just ignore whether we
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* are doing nop -> jump or jump -> nop transition, and assume
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* always nop being the 'currently valid' instruction
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*/
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if (init || system_state == SYSTEM_BOOTING) {
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text_poke_early((void *)jump_entry_code(entry), code,
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JUMP_LABEL_NOP_SIZE);
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return;
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}
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text_poke_bp((void *)jump_entry_code(entry), code, JUMP_LABEL_NOP_SIZE,
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(void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
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}
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void arch_jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type)
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{
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mutex_lock(&text_mutex);
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__jump_label_transform(entry, type, 0);
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mutex_unlock(&text_mutex);
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}
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static enum {
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JL_STATE_START,
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JL_STATE_NO_UPDATE,
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JL_STATE_UPDATE,
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} jlstate __initdata_or_module = JL_STATE_START;
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__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
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enum jump_label_type type)
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{
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/*
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* This function is called at boot up and when modules are
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* first loaded. Check if the default nop, the one that is
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* inserted at compile time, is the ideal nop. If it is, then
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* we do not need to update the nop, and we can leave it as is.
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* If it is not, then we need to update the nop to the ideal nop.
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*/
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if (jlstate == JL_STATE_START) {
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const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
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const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
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if (memcmp(ideal_nop, default_nop, 5) != 0)
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jlstate = JL_STATE_UPDATE;
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else
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jlstate = JL_STATE_NO_UPDATE;
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}
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if (jlstate == JL_STATE_UPDATE)
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__jump_label_transform(entry, type, 1);
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}
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