mirror of https://gitee.com/openkylin/linux.git
198 lines
5.2 KiB
C
198 lines
5.2 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 __jump_label_set_jump_code(struct jump_entry *entry,
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enum jump_label_type type,
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union jump_code_union *code,
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int init)
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{
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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;
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int line;
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code->jump = 0xe9;
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code->offset = jump_entry_target(entry) -
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(jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
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if (init) {
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expect = default_nop; line = __LINE__;
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} else if (type == JUMP_LABEL_JMP) {
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expect = ideal_nop; line = __LINE__;
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} else {
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expect = code->code; line = __LINE__;
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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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if (type == JUMP_LABEL_NOP)
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memcpy(code, ideal_nop, JUMP_LABEL_NOP_SIZE);
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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 code;
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__jump_label_set_jump_code(entry, type, &code, init);
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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, NULL);
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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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#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
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static struct text_poke_loc tp_vec[TP_VEC_MAX];
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static int tp_vec_nr;
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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 text_poke_loc *tp;
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void *entry_code;
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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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/*
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* No more space in the vector, tell upper layer to apply
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* the queue before continuing.
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*/
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if (tp_vec_nr == TP_VEC_MAX)
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return false;
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tp = &tp_vec[tp_vec_nr];
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entry_code = (void *)jump_entry_code(entry);
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/*
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* The INT3 handler will do a bsearch in the queue, so we need entries
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* to be sorted. We can survive an unsorted list by rejecting the entry,
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* forcing the generic jump_label code to apply the queue. Warning once,
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* to raise the attention to the case of an unsorted entry that is
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* better not happen, because, in the worst case we will perform in the
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* same way as we do without batching - with some more overhead.
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*/
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if (tp_vec_nr > 0) {
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int prev = tp_vec_nr - 1;
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struct text_poke_loc *prev_tp = &tp_vec[prev];
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if (WARN_ON_ONCE(prev_tp->addr > entry_code))
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return false;
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}
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__jump_label_set_jump_code(entry, type,
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(union jump_code_union *)&tp->text, 0);
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text_poke_loc_init(tp, entry_code, NULL, JUMP_LABEL_NOP_SIZE, NULL);
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tp_vec_nr++;
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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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if (!tp_vec_nr)
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return;
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mutex_lock(&text_mutex);
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text_poke_bp_batch(tp_vec, tp_vec_nr);
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mutex_unlock(&text_mutex);
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tp_vec_nr = 0;
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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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