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#include <asm/opcodes.h>
17
18#include "kprobes.h"
19
20
21static void __kprobes simulate_ldm1stm1(probes_opcode_t insn,
22		struct arch_probes_insn *asi,
23		struct pt_regs *regs)
24{
25	int rn = (insn >> 16) & 0xf;
26	int lbit = insn & (1 << 20);
27	int wbit = insn & (1 << 21);
28	int ubit = insn & (1 << 23);
29	int pbit = insn & (1 << 24);
30	long *addr = (long *)regs->uregs[rn];
31	int reg_bit_vector;
32	int reg_count;
33
34	reg_count = 0;
35	reg_bit_vector = insn & 0xffff;
36	while (reg_bit_vector) {
37		reg_bit_vector &= (reg_bit_vector - 1);
38		++reg_count;
39	}
40
41	if (!ubit)
42		addr -= reg_count;
43	addr += (!pbit == !ubit);
44
45	reg_bit_vector = insn & 0xffff;
46	while (reg_bit_vector) {
47		int reg = __ffs(reg_bit_vector);
48		reg_bit_vector &= (reg_bit_vector - 1);
49		if (lbit)
50			regs->uregs[reg] = *addr++;
51		else
52			*addr++ = regs->uregs[reg];
53	}
54
55	if (wbit) {
56		if (!ubit)
57			addr -= reg_count;
58		addr -= (!pbit == !ubit);
59		regs->uregs[rn] = (long)addr;
60	}
61}
62
63static void __kprobes simulate_stm1_pc(probes_opcode_t insn,
64	struct arch_probes_insn *asi,
65	struct pt_regs *regs)
66{
67	unsigned long addr = regs->ARM_pc - 4;
68
69	regs->ARM_pc = (long)addr + str_pc_offset;
70	simulate_ldm1stm1(insn, asi, regs);
71	regs->ARM_pc = (long)addr + 4;
72}
73
74static void __kprobes simulate_ldm1_pc(probes_opcode_t insn,
75	struct arch_probes_insn *asi,
76	struct pt_regs *regs)
77{
78	simulate_ldm1stm1(insn, asi, regs);
79	load_write_pc(regs->ARM_pc, regs);
80}
81
82static void __kprobes
83emulate_generic_r0_12_noflags(probes_opcode_t insn,
84	struct arch_probes_insn *asi, struct pt_regs *regs)
85{
86	register void *rregs asm("r1") = regs;
87	register void *rfn asm("lr") = asi->insn_fn;
88
89	__asm__ __volatile__ (
90		"stmdb	sp!, {%[regs], r11}	\n\t"
91		"ldmia	%[regs], {r0-r12}	\n\t"
92#if __LINUX_ARM_ARCH__ >= 6
93		"blx	%[fn]			\n\t"
94#else
95		"str	%[fn], [sp, #-4]!	\n\t"
96		"adr	lr, 1f			\n\t"
97		"ldr	pc, [sp], #4		\n\t"
98		"1:				\n\t"
99#endif
100		"ldr	lr, [sp], #4		\n\t" /* lr = regs */
101		"stmia	lr, {r0-r12}		\n\t"
102		"ldr	r11, [sp], #4		\n\t"
103		: [regs] "=r" (rregs), [fn] "=r" (rfn)
104		: "0" (rregs), "1" (rfn)
105		: "r0", "r2", "r3", "r4", "r5", "r6", "r7",
106		  "r8", "r9", "r10", "r12", "memory", "cc"
107		);
108}
109
110static void __kprobes
111emulate_generic_r2_14_noflags(probes_opcode_t insn,
112	struct arch_probes_insn *asi, struct pt_regs *regs)
113{
114	emulate_generic_r0_12_noflags(insn, asi,
115		(struct pt_regs *)(regs->uregs+2));
116}
117
118static void __kprobes
119emulate_ldm_r3_15(probes_opcode_t insn,
120	struct arch_probes_insn *asi, struct pt_regs *regs)
121{
122	emulate_generic_r0_12_noflags(insn, asi,
123		(struct pt_regs *)(regs->uregs+3));
124	load_write_pc(regs->ARM_pc, regs);
125}
126
127enum probes_insn __kprobes
128kprobe_decode_ldmstm(probes_opcode_t insn, struct arch_probes_insn *asi,
129		const struct decode_header *h)
130{
131	probes_insn_handler_t *handler = 0;
132	unsigned reglist = insn & 0xffff;
133	int is_ldm = insn & 0x100000;
134	int rn = (insn >> 16) & 0xf;
135
136	if (rn <= 12 && (reglist & 0xe000) == 0) {
137		/* Instruction only uses registers in the range R0..R12 */
138		handler = emulate_generic_r0_12_noflags;
139
140	} else if (rn >= 2 && (reglist & 0x8003) == 0) {
141		/* Instruction only uses registers in the range R2..R14 */
142		rn -= 2;
143		reglist >>= 2;
144		handler = emulate_generic_r2_14_noflags;
145
146	} else if (rn >= 3 && (reglist & 0x0007) == 0) {
147		/* Instruction only uses registers in the range R3..R15 */
148		if (is_ldm && (reglist & 0x8000)) {
149			rn -= 3;
150			reglist >>= 3;
151			handler = emulate_ldm_r3_15;
152		}
153	}
154
155	if (handler) {
156		/* We can emulate the instruction in (possibly) modified form */
157		asi->insn[0] = __opcode_to_mem_arm((insn & 0xfff00000) |
158						   (rn << 16) | reglist);
159		asi->insn_handler = handler;
160		return INSN_GOOD;
161	}
162
163	/* Fallback to slower simulation... */
164	if (reglist & 0x8000)
165		handler = is_ldm ? simulate_ldm1_pc : simulate_stm1_pc;
166	else
167		handler = simulate_ldm1stm1;
168	asi->insn_handler = handler;
169	return INSN_GOOD_NO_SLOT;
170}
171
172