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157 lines
4.2 KiB
157 lines
4.2 KiB
// 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 <[email protected]> |
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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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static void bug_at(const void *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 const void * |
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__jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, 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, *code; |
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const void *addr, *dest; |
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int line; |
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addr = (void *)jump_entry_code(entry); |
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dest = (void *)jump_entry_target(entry); |
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code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest); |
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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; line = __LINE__; |
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} |
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if (memcmp(addr, expect, JUMP_LABEL_NOP_SIZE)) |
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bug_at(addr, line); |
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if (type == JUMP_LABEL_NOP) |
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code = ideal_nop; |
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return code; |
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} |
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static inline void __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 void *opcode = __jump_label_set_jump_code(entry, type, 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), opcode, |
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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), opcode, JUMP_LABEL_NOP_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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const void *opcode; |
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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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opcode = __jump_label_set_jump_code(entry, type, 0); |
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text_poke_queue((void *)jump_entry_code(entry), |
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opcode, JUMP_LABEL_NOP_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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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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