kprobes-common.c revision b4cd605ca92d9a8a2f71355cb45dd943ebcb0c97 
1/*
2 * arch/arm/kernel/kprobes-common.c
3 *
4 * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
5 *
6 * Some contents moved here from arch/arm/include/asm/kprobes-arm.c which is
7 * Copyright (C) 2006, 2007 Motorola Inc.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#include <linux/kernel.h>
15#include <linux/kprobes.h>
16
17#include "kprobes.h"
18
19
20static void __kprobes simulate_ldm1stm1(probes_opcode_t insn,
21		struct arch_probes_insn *asi,
22		struct pt_regs *regs)
23{
24	int rn = (insn >> 16) & 0xf;
25	int lbit = insn & (1 << 20);
26	int wbit = insn & (1 << 21);
27	int ubit = insn & (1 << 23);
28	int pbit = insn & (1 << 24);
29	long *addr = (long *)regs->uregs[rn];
30	int reg_bit_vector;
31	int reg_count;
32
33	reg_count = 0;
34	reg_bit_vector = insn & 0xffff;
35	while (reg_bit_vector) {
36		reg_bit_vector &= (reg_bit_vector - 1);
37		++reg_count;
38	}
39
40	if (!ubit)
41		addr -= reg_count;
42	addr += (!pbit == !ubit);
43
44	reg_bit_vector = insn & 0xffff;
45	while (reg_bit_vector) {
46		int reg = __ffs(reg_bit_vector);
47		reg_bit_vector &= (reg_bit_vector - 1);
48		if (lbit)
49			regs->uregs[reg] = *addr++;
50		else
51			*addr++ = regs->uregs[reg];
52	}
53
54	if (wbit) {
55		if (!ubit)
56			addr -= reg_count;
57		addr -= (!pbit == !ubit);
58		regs->uregs[rn] = (long)addr;
59	}
60}
61
62static void __kprobes simulate_stm1_pc(probes_opcode_t insn,
63	struct arch_probes_insn *asi,
64	struct pt_regs *regs)
65{
66	unsigned long addr = regs->ARM_pc - 4;
67
68	regs->ARM_pc = (long)addr + str_pc_offset;
69	simulate_ldm1stm1(insn, asi, regs);
70	regs->ARM_pc = (long)addr + 4;
71}
72
73static void __kprobes simulate_ldm1_pc(probes_opcode_t insn,
74	struct arch_probes_insn *asi,
75	struct pt_regs *regs)
76{
77	simulate_ldm1stm1(insn, asi, regs);
78	load_write_pc(regs->ARM_pc, regs);
79}
80
81static void __kprobes
82emulate_generic_r0_12_noflags(probes_opcode_t insn,
83	struct arch_probes_insn *asi, struct pt_regs *regs)
84{
85	register void *rregs asm("r1") = regs;
86	register void *rfn asm("lr") = asi->insn_fn;
87
88	__asm__ __volatile__ (
89		"stmdb	sp!, {%[regs], r11}	\n\t"
90		"ldmia	%[regs], {r0-r12}	\n\t"
91#if __LINUX_ARM_ARCH__ >= 6
92		"blx	%[fn]			\n\t"
93#else
94		"str	%[fn], [sp, #-4]!	\n\t"
95		"adr	lr, 1f			\n\t"
96		"ldr	pc, [sp], #4		\n\t"
97		"1:				\n\t"
98#endif
99		"ldr	lr, [sp], #4		\n\t" /* lr = regs */
100		"stmia	lr, {r0-r12}		\n\t"
101		"ldr	r11, [sp], #4		\n\t"
102		: [regs] "=r" (rregs), [fn] "=r" (rfn)
103		: "0" (rregs), "1" (rfn)
104		: "r0", "r2", "r3", "r4", "r5", "r6", "r7",
105		  "r8", "r9", "r10", "r12", "memory", "cc"
106		);
107}
108
109static void __kprobes
110emulate_generic_r2_14_noflags(probes_opcode_t insn,
111	struct arch_probes_insn *asi, struct pt_regs *regs)
112{
113	emulate_generic_r0_12_noflags(insn, asi,
114		(struct pt_regs *)(regs->uregs+2));
115}
116
117static void __kprobes
118emulate_ldm_r3_15(probes_opcode_t insn,
119	struct arch_probes_insn *asi, struct pt_regs *regs)
120{
121	emulate_generic_r0_12_noflags(insn, asi,
122		(struct pt_regs *)(regs->uregs+3));
123	load_write_pc(regs->ARM_pc, regs);
124}
125
126enum probes_insn __kprobes
127kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi,
128		const struct decode_header *h)
129{
130	probes_insn_handler_t *handler = 0;
131	unsigned reglist = insn & 0xffff;
132	int is_ldm = insn & 0x100000;
133	int rn = (insn >> 16) & 0xf;
134
135	if (rn <= 12 && (reglist & 0xe000) == 0) {
136		/* Instruction only uses registers in the range R0..R12 */
137		handler = emulate_generic_r0_12_noflags;
138
139	} else if (rn >= 2 && (reglist & 0x8003) == 0) {
140		/* Instruction only uses registers in the range R2..R14 */
141		rn -= 2;
142		reglist >>= 2;
143		handler = emulate_generic_r2_14_noflags;
144
145	} else if (rn >= 3 && (reglist & 0x0007) == 0) {
146		/* Instruction only uses registers in the range R3..R15 */
147		if (is_ldm && (reglist & 0x8000)) {
148			rn -= 3;
149			reglist >>= 3;
150			handler = emulate_ldm_r3_15;
151		}
152	}
153
154	if (handler) {
155		/* We can emulate the instruction in (possibly) modified form */
156		asi->insn[0] = (insn & 0xfff00000) | (rn << 16) | reglist;
157		asi->insn_handler = handler;
158		return INSN_GOOD;
159	}
160
161	/* Fallback to slower simulation... */
162	if (reglist & 0x8000)
163		handler = is_ldm ? simulate_ldm1_pc : simulate_stm1_pc;
164	else
165		handler = simulate_ldm1stm1;
166	asi->insn_handler = handler;
167	return INSN_GOOD_NO_SLOT;
168}
169
170