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