Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
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 void *text_poke_copy(void *addr, const void *opcode, size_t len);
48extern int poke_int3_handler(struct pt_regs *regs);
49extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);
50
51extern void text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate);
52extern void text_poke_finish(void);
53
54#define INT3_INSN_SIZE 1
55#define INT3_INSN_OPCODE 0xCC
56
57#define RET_INSN_SIZE 1
58#define RET_INSN_OPCODE 0xC3
59
60#define CALL_INSN_SIZE 5
61#define CALL_INSN_OPCODE 0xE8
62
63#define JMP32_INSN_SIZE 5
64#define JMP32_INSN_OPCODE 0xE9
65
66#define JMP8_INSN_SIZE 2
67#define JMP8_INSN_OPCODE 0xEB
68
69#define DISP32_SIZE 4
70
71static __always_inline int text_opcode_size(u8 opcode)
72{
73 int size = 0;
74
75#define __CASE(insn) \
76 case insn##_INSN_OPCODE: size = insn##_INSN_SIZE; break
77
78 switch(opcode) {
79 __CASE(INT3);
80 __CASE(RET);
81 __CASE(CALL);
82 __CASE(JMP32);
83 __CASE(JMP8);
84 }
85
86#undef __CASE
87
88 return size;
89}
90
91union text_poke_insn {
92 u8 text[POKE_MAX_OPCODE_SIZE];
93 struct {
94 u8 opcode;
95 s32 disp;
96 } __attribute__((packed));
97};
98
99static __always_inline
100void __text_gen_insn(void *buf, u8 opcode, const void *addr, const void *dest, int size)
101{
102 union text_poke_insn *insn = buf;
103
104 BUG_ON(size < text_opcode_size(opcode));
105
106 /*
107 * Hide the addresses to avoid the compiler folding in constants when
108 * referencing code, these can mess up annotations like
109 * ANNOTATE_NOENDBR.
110 */
111 OPTIMIZER_HIDE_VAR(insn);
112 OPTIMIZER_HIDE_VAR(addr);
113 OPTIMIZER_HIDE_VAR(dest);
114
115 insn->opcode = opcode;
116
117 if (size > 1) {
118 insn->disp = (long)dest - (long)(addr + size);
119 if (size == 2) {
120 /*
121 * Ensure that for JMP8 the displacement
122 * actually fits the signed byte.
123 */
124 BUG_ON((insn->disp >> 31) != (insn->disp >> 7));
125 }
126 }
127}
128
129static __always_inline
130void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
131{
132 static union text_poke_insn insn; /* per instance */
133 __text_gen_insn(&insn, opcode, addr, dest, text_opcode_size(opcode));
134 return &insn.text;
135}
136
137extern int after_bootmem;
138extern __ro_after_init struct mm_struct *poking_mm;
139extern __ro_after_init unsigned long poking_addr;
140
141#ifndef CONFIG_UML_X86
142static __always_inline
143void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
144{
145 regs->ip = ip;
146}
147
148static __always_inline
149void int3_emulate_push(struct pt_regs *regs, unsigned long val)
150{
151 /*
152 * The int3 handler in entry_64.S adds a gap between the
153 * stack where the break point happened, and the saving of
154 * pt_regs. We can extend the original stack because of
155 * this gap. See the idtentry macro's create_gap option.
156 *
157 * Similarly entry_32.S will have a gap on the stack for (any) hardware
158 * exception and pt_regs; see FIXUP_FRAME.
159 */
160 regs->sp -= sizeof(unsigned long);
161 *(unsigned long *)regs->sp = val;
162}
163
164static __always_inline
165unsigned long int3_emulate_pop(struct pt_regs *regs)
166{
167 unsigned long val = *(unsigned long *)regs->sp;
168 regs->sp += sizeof(unsigned long);
169 return val;
170}
171
172static __always_inline
173void int3_emulate_call(struct pt_regs *regs, unsigned long func)
174{
175 int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
176 int3_emulate_jmp(regs, func);
177}
178
179static __always_inline
180void int3_emulate_ret(struct pt_regs *regs)
181{
182 unsigned long ip = int3_emulate_pop(regs);
183 int3_emulate_jmp(regs, ip);
184}
185#endif /* !CONFIG_UML_X86 */
186
187#endif /* _ASM_X86_TEXT_PATCHING_H */