// 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 __always_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); }