summaryrefslogtreecommitdiff
path: root/arch/arm/probes/kprobes/actions-common.c
blob: bd20a71cd34a0f1f4887b72788f47fcb85f6c42e (plain)
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
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
/*
 * arch/arm/probes/kprobes/actions-common.c
 *
 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
 *
 * Some contents moved here from arch/arm/include/asm/kprobes-arm.c which is
 * Copyright (C) 2006, 2007 Motorola Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <asm/opcodes.h>

#include "core.h"


static void __kprobes simulate_ldm1stm1(probes_opcode_t insn,
		struct arch_probes_insn *asi,
		struct pt_regs *regs)
{
	int rn = (insn >> 16) & 0xf;
	int lbit = insn & (1 << 20);
	int wbit = insn & (1 << 21);
	int ubit = insn & (1 << 23);
	int pbit = insn & (1 << 24);
	long *addr = (long *)regs->uregs[rn];
	int reg_bit_vector;
	int reg_count;

	reg_count = 0;
	reg_bit_vector = insn & 0xffff;
	while (reg_bit_vector) {
		reg_bit_vector &= (reg_bit_vector - 1);
		++reg_count;
	}

	if (!ubit)
		addr -= reg_count;
	addr += (!pbit == !ubit);

	reg_bit_vector = insn & 0xffff;
	while (reg_bit_vector) {
		int reg = __ffs(reg_bit_vector);
		reg_bit_vector &= (reg_bit_vector - 1);
		if (lbit)
			regs->uregs[reg] = *addr++;
		else
			*addr++ = regs->uregs[reg];
	}

	if (wbit) {
		if (!ubit)
			addr -= reg_count;
		addr -= (!pbit == !ubit);
		regs->uregs[rn] = (long)addr;
	}
}

static void __kprobes simulate_stm1_pc(probes_opcode_t insn,
	struct arch_probes_insn *asi,
	struct pt_regs *regs)
{
	unsigned long addr = regs->ARM_pc - 4;

	regs->ARM_pc = (long)addr + str_pc_offset;
	simulate_ldm1stm1(insn, asi, regs);
	regs->ARM_pc = (long)addr + 4;
}

static void __kprobes simulate_ldm1_pc(probes_opcode_t insn,
	struct arch_probes_insn *asi,
	struct pt_regs *regs)
{
	simulate_ldm1stm1(insn, asi, regs);
	load_write_pc(regs->ARM_pc, regs);
}

static void __kprobes
emulate_generic_r0_12_noflags(probes_opcode_t insn,
	struct arch_probes_insn *asi, struct pt_regs *regs)
{
	register void *rregs asm("r1") = regs;
	register void *rfn asm("lr") = asi->insn_fn;

	__asm__ __volatile__ (
		"stmdb	sp!, {%[regs], r11}	\n\t"
		"ldmia	%[regs], {r0-r12}	\n\t"
#if __LINUX_ARM_ARCH__ >= 6
		"blx	%[fn]			\n\t"
#else
		"str	%[fn], [sp, #-4]!	\n\t"
		"adr	lr, 1f			\n\t"
		"ldr	pc, [sp], #4		\n\t"
		"1:				\n\t"
#endif
		"ldr	lr, [sp], #4		\n\t" /* lr = regs */
		"stmia	lr, {r0-r12}		\n\t"
		"ldr	r11, [sp], #4		\n\t"
		: [regs] "=r" (rregs), [fn] "=r" (rfn)
		: "0" (rregs), "1" (rfn)
		: "r0", "r2", "r3", "r4", "r5", "r6", "r7",
		  "r8", "r9", "r10", "r12", "memory", "cc"
		);
}

static void __kprobes
emulate_generic_r2_14_noflags(probes_opcode_t insn,
	struct arch_probes_insn *asi, struct pt_regs *regs)
{
	emulate_generic_r0_12_noflags(insn, asi,
		(struct pt_regs *)(regs->uregs+2));
}

static void __kprobes
emulate_ldm_r3_15(probes_opcode_t insn,
	struct arch_probes_insn *asi, struct pt_regs *regs)
{
	emulate_generic_r0_12_noflags(insn, asi,
		(struct pt_regs *)(regs->uregs+3));
	load_write_pc(regs->ARM_pc, regs);
}

enum probes_insn __kprobes
kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi,
		const struct decode_header *h)
{
	probes_insn_handler_t *handler = 0;
	unsigned reglist = insn & 0xffff;
	int is_ldm = insn & 0x100000;
	int rn = (insn >> 16) & 0xf;

	if (rn <= 12 && (reglist & 0xe000) == 0) {
		/* Instruction only uses registers in the range R0..R12 */
		handler = emulate_generic_r0_12_noflags;

	} else if (rn >= 2 && (reglist & 0x8003) == 0) {
		/* Instruction only uses registers in the range R2..R14 */
		rn -= 2;
		reglist >>= 2;
		handler = emulate_generic_r2_14_noflags;

	} else if (rn >= 3 && (reglist & 0x0007) == 0) {
		/* Instruction only uses registers in the range R3..R15 */
		if (is_ldm && (reglist & 0x8000)) {
			rn -= 3;
			reglist >>= 3;
			handler = emulate_ldm_r3_15;
		}
	}

	if (handler) {
		/* We can emulate the instruction in (possibly) modified form */
		asi->insn[0] = __opcode_to_mem_arm((insn & 0xfff00000) |
						   (rn << 16) | reglist);
		asi->insn_handler = handler;
		return INSN_GOOD;
	}

	/* Fallback to slower simulation... */
	if (reglist & 0x8000)
		handler = is_ldm ? simulate_ldm1_pc : simulate_stm1_pc;
	else
		handler = simulate_ldm1stm1;
	asi->insn_handler = handler;
	return INSN_GOOD_NO_SLOT;
}