1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Non-emulated single-stepping support (currently limited to basic integer
* computations) used to validate the instruction emulation infrastructure.
*
* Copyright (C) 2019 IBM Corporation
*/
#include <asm/asm-offsets.h>
#include <asm/ppc_asm.h>
#include <asm/code-patching-asm.h>
#include <linux/errno.h>
/* int exec_instr(struct pt_regs *regs) */
_GLOBAL(exec_instr)
/*
* Stack frame layout (INT_FRAME_SIZE bytes)
* In-memory pt_regs (SP + STACK_INT_FRAME_REGS)
* Scratch space (SP + 8)
* Back chain (SP + 0)
*/
/*
* Allocate a new stack frame with enough space to hold the register
* states in an in-memory pt_regs and also create the back chain to
* the caller's stack frame.
*/
stdu r1, -INT_FRAME_SIZE(r1)
/*
* Save non-volatile GPRs on stack. This includes TOC pointer (GPR2)
* and local variables (GPR14 to GPR31). The register for the pt_regs
* parameter (GPR3) is saved additionally to ensure that the resulting
* register state can still be saved even if GPR3 gets overwritten
* when loading the initial register state for the test instruction.
* The stack pointer (GPR1) and the thread pointer (GPR13) are not
* saved as these should not be modified anyway.
*/
SAVE_GPRS(2, 3, r1)
SAVE_NVGPRS(r1)
/*
* Save LR on stack to ensure that the return address is available
* even if it gets overwritten by the test instruction.
*/
mflr r0
std r0, _LINK(r1)
/*
* Save CR on stack. For simplicity, the entire register is saved
* even though only fields 2 to 4 are non-volatile.
*/
mfcr r0
std r0, _CCR(r1)
/*
* Load register state for the test instruction without touching the
* critical non-volatile registers. The register state is passed as a
* pointer to a pt_regs instance.
*/
subi r31, r3, GPR0
/* Load LR from pt_regs */
ld r0, _LINK(r31)
mtlr r0
/* Load CR from pt_regs */
ld r0, _CCR(r31)
mtcr r0
/* Load XER from pt_regs */
ld r0, _XER(r31)
mtxer r0
/* Load GPRs from pt_regs */
REST_GPR(0, r31)
REST_GPRS(2, 12, r31)
REST_NVGPRS(r31)
/* Placeholder for the test instruction */
.balign 64
1: nop
nop
patch_site 1b patch__exec_instr
/*
* Since GPR3 is overwritten, temporarily restore it back to its
* original state, i.e. the pointer to pt_regs, to ensure that the
* resulting register state can be saved. Before doing this, a copy
* of it is created in the scratch space which is used later on to
* save it to pt_regs.
*/
std r3, 8(r1)
REST_GPR(3, r1)
/* Save resulting GPR state to pt_regs */
subi r3, r3, GPR0
SAVE_GPR(0, r3)
SAVE_GPR(2, r3)
SAVE_GPRS(4, 12, r3)
SAVE_NVGPRS(r3)
/* Save resulting LR to pt_regs */
mflr r0
std r0, _LINK(r3)
/* Save resulting CR to pt_regs */
mfcr r0
std r0, _CCR(r3)
/* Save resulting XER to pt_regs */
mfxer r0
std r0, _XER(r3)
/* Restore resulting GPR3 from scratch space and save it to pt_regs */
ld r0, 8(r1)
std r0, GPR3(r3)
/* Set return value to denote execution success */
li r3, 0
/* Continue */
b 3f
/* Set return value to denote execution failure */
2: li r3, -EFAULT
/* Restore the non-volatile GPRs from stack */
3: REST_GPR(2, r1)
REST_NVGPRS(r1)
/* Restore LR from stack to be able to return */
ld r0, _LINK(r1)
mtlr r0
/* Restore CR from stack */
ld r0, _CCR(r1)
mtcr r0
/* Tear down stack frame */
addi r1, r1, INT_FRAME_SIZE
/* Return */
blr
/* Setup exception table */
EX_TABLE(1b, 2b)
_ASM_NOKPROBE_SYMBOL(exec_instr)
|
