149 lines
3.6 KiB
C
149 lines
3.6 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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#include <asm/insn.h>
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int arch_jump_entry_size(struct jump_entry *entry)
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{
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struct insn insn = {};
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insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
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BUG_ON(insn.length != 2 && insn.length != 5);
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return insn.length;
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}
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struct jump_label_patch {
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const void *code;
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int size;
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};
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static struct jump_label_patch
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__jump_label_patch(struct jump_entry *entry, enum jump_label_type type)
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{
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const void *expect, *code, *nop;
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const void *addr, *dest;
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int size;
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addr = (void *)jump_entry_code(entry);
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dest = (void *)jump_entry_target(entry);
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size = arch_jump_entry_size(entry);
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switch (size) {
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case JMP8_INSN_SIZE:
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code = text_gen_insn(JMP8_INSN_OPCODE, addr, dest);
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nop = x86_nops[size];
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break;
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case JMP32_INSN_SIZE:
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code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
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nop = x86_nops[size];
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break;
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default: BUG();
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}
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if (type == JUMP_LABEL_JMP)
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expect = nop;
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else
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expect = code;
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if (memcmp(addr, expect, size)) {
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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 != %5ph)) size:%d type:%d\n",
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addr, addr, addr, expect, size, type);
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BUG();
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}
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if (type == JUMP_LABEL_NOP)
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code = nop;
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return (struct jump_label_patch){.code = code, .size = size};
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}
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static __always_inline void
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__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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const struct jump_label_patch jlp = __jump_label_patch(entry, type);
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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), jlp.code, jlp.size);
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return;
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}
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text_poke_bp((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
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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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mutex_lock(&text_mutex);
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__jump_label_transform(entry, type, init);
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mutex_unlock(&text_mutex);
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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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jump_label_transform(entry, type, 0);
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}
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bool arch_jump_label_transform_queue(struct jump_entry *entry,
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enum jump_label_type type)
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{
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struct jump_label_patch jlp;
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if (system_state == SYSTEM_BOOTING) {
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/*
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* Fallback to the non-batching mode.
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*/
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arch_jump_label_transform(entry, type);
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return true;
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}
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mutex_lock(&text_mutex);
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jlp = __jump_label_patch(entry, type);
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text_poke_queue((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
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mutex_unlock(&text_mutex);
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return true;
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}
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void arch_jump_label_transform_apply(void)
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{
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mutex_lock(&text_mutex);
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text_poke_finish();
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mutex_unlock(&text_mutex);
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}
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