Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_TEXT_PATCHING_H
3#define _ASM_X86_TEXT_PATCHING_H
4
5#include <linux/types.h>
6#include <linux/stddef.h>
7#include <asm/ptrace.h>
8
9struct paravirt_patch_site;
10#ifdef CONFIG_PARAVIRT
11void apply_paravirt(struct paravirt_patch_site *start,
12 struct paravirt_patch_site *end);
13#else
14static inline void apply_paravirt(struct paravirt_patch_site *start,
15 struct paravirt_patch_site *end)
16{}
17#define __parainstructions NULL
18#define __parainstructions_end NULL
19#endif
20
21/*
22 * Currently, the max observed size in the kernel code is
23 * JUMP_LABEL_NOP_SIZE/RELATIVEJUMP_SIZE, which are 5.
24 * Raise it if needed.
25 */
26#define POKE_MAX_OPCODE_SIZE 5
27
28extern void text_poke_early(void *addr, const void *opcode, size_t len);
29
30/*
31 * Clear and restore the kernel write-protection flag on the local CPU.
32 * Allows the kernel to edit read-only pages.
33 * Side-effect: any interrupt handler running between save and restore will have
34 * the ability to write to read-only pages.
35 *
36 * Warning:
37 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
38 * no thread can be preempted in the instructions being modified (no iret to an
39 * invalid instruction possible) or if the instructions are changed from a
40 * consistent state to another consistent state atomically.
41 * On the local CPU you need to be protected against NMI or MCE handlers seeing
42 * an inconsistent instruction while you patch.
43 */
44extern void *text_poke(void *addr, const void *opcode, size_t len);
45extern void text_poke_sync(void);
46extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);
47extern int poke_int3_handler(struct pt_regs *regs);
48extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);
49
50extern void text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate);
51extern void text_poke_finish(void);
52
53#define INT3_INSN_SIZE 1
54#define INT3_INSN_OPCODE 0xCC
55
56#define CALL_INSN_SIZE 5
57#define CALL_INSN_OPCODE 0xE8
58
59#define JMP32_INSN_SIZE 5
60#define JMP32_INSN_OPCODE 0xE9
61
62#define JMP8_INSN_SIZE 2
63#define JMP8_INSN_OPCODE 0xEB
64
65#define DISP32_SIZE 4
66
67static __always_inline int text_opcode_size(u8 opcode)
68{
69 int size = 0;
70
71#define __CASE(insn) \
72 case insn##_INSN_OPCODE: size = insn##_INSN_SIZE; break
73
74 switch(opcode) {
75 __CASE(INT3);
76 __CASE(CALL);
77 __CASE(JMP32);
78 __CASE(JMP8);
79 }
80
81#undef __CASE
82
83 return size;
84}
85
86union text_poke_insn {
87 u8 text[POKE_MAX_OPCODE_SIZE];
88 struct {
89 u8 opcode;
90 s32 disp;
91 } __attribute__((packed));
92};
93
94static __always_inline
95void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
96{
97 static union text_poke_insn insn; /* per instance */
98 int size = text_opcode_size(opcode);
99
100 insn.opcode = opcode;
101
102 if (size > 1) {
103 insn.disp = (long)dest - (long)(addr + size);
104 if (size == 2) {
105 /*
106 * Ensure that for JMP9 the displacement
107 * actually fits the signed byte.
108 */
109 BUG_ON((insn.disp >> 31) != (insn.disp >> 7));
110 }
111 }
112
113 return &insn.text;
114}
115
116extern int after_bootmem;
117extern __ro_after_init struct mm_struct *poking_mm;
118extern __ro_after_init unsigned long poking_addr;
119
120#ifndef CONFIG_UML_X86
121static __always_inline
122void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
123{
124 regs->ip = ip;
125}
126
127static __always_inline
128void int3_emulate_push(struct pt_regs *regs, unsigned long val)
129{
130 /*
131 * The int3 handler in entry_64.S adds a gap between the
132 * stack where the break point happened, and the saving of
133 * pt_regs. We can extend the original stack because of
134 * this gap. See the idtentry macro's create_gap option.
135 *
136 * Similarly entry_32.S will have a gap on the stack for (any) hardware
137 * exception and pt_regs; see FIXUP_FRAME.
138 */
139 regs->sp -= sizeof(unsigned long);
140 *(unsigned long *)regs->sp = val;
141}
142
143static __always_inline
144void int3_emulate_call(struct pt_regs *regs, unsigned long func)
145{
146 int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
147 int3_emulate_jmp(regs, func);
148}
149#endif /* !CONFIG_UML_X86 */
150
151#endif /* _ASM_X86_TEXT_PATCHING_H */