1 /*
2 * xen/arch/arm/decode.c
3 *
4 * Instruction decoder
5 *
6 * Julien Grall <julien.grall@linaro.org>
7 * Copyright (C) 2013 Linaro Limited.
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 as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
18 */
19
20 #include <xen/types.h>
21 #include <xen/sched.h>
22 #include <asm/current.h>
23 #include <asm/guest_access.h>
24 #include <xen/lib.h>
25
26 #include "decode.h"
27
update_dabt(struct hsr_dabt * dabt,int reg,uint8_t size,bool sign)28 static void update_dabt(struct hsr_dabt *dabt, int reg,
29 uint8_t size, bool sign)
30 {
31 dabt->reg = reg;
32 dabt->size = size;
33 dabt->sign = sign;
34 }
35
decode_thumb2(register_t pc,struct hsr_dabt * dabt,uint16_t hw1)36 static int decode_thumb2(register_t pc, struct hsr_dabt *dabt, uint16_t hw1)
37 {
38 uint16_t hw2;
39 uint16_t rt;
40
41 if ( raw_copy_from_guest(&hw2, (void *__user)(pc + 2), sizeof (hw2)) )
42 return -EFAULT;
43
44 rt = (hw2 >> 12) & 0xf;
45
46 switch ( (hw1 >> 9) & 0xf )
47 {
48 case 12:
49 {
50 bool sign = (hw1 & (1u << 8));
51 bool load = (hw1 & (1u << 4));
52
53 if ( (hw1 & 0x0110) == 0x0100 )
54 /* NEON instruction */
55 goto bad_thumb2;
56
57 if ( (hw1 & 0x0070) == 0x0070 )
58 /* Undefined opcodes */
59 goto bad_thumb2;
60
61 /* Store/Load single data item */
62 if ( rt == 15 )
63 /* XXX: Rt == 15 is only invalid for store instruction */
64 goto bad_thumb2;
65
66 if ( !load && sign )
67 /* Store instruction doesn't support sign extension */
68 goto bad_thumb2;
69
70 update_dabt(dabt, rt, (hw1 >> 5) & 3, sign);
71
72 break;
73 }
74 default:
75 goto bad_thumb2;
76 }
77
78 return 0;
79
80 bad_thumb2:
81 gprintk(XENLOG_ERR, "unhandled THUMB2 instruction 0x%x%x\n", hw1, hw2);
82
83 return 1;
84 }
85
decode_thumb(register_t pc,struct hsr_dabt * dabt)86 static int decode_thumb(register_t pc, struct hsr_dabt *dabt)
87 {
88 uint16_t instr;
89
90 if ( raw_copy_from_guest(&instr, (void * __user)pc, sizeof (instr)) )
91 return -EFAULT;
92
93 switch ( instr >> 12 )
94 {
95 case 5:
96 {
97 /* Load/Store register */
98 uint16_t opB = (instr >> 9) & 0x7;
99 int reg = instr & 7;
100
101 switch ( opB & 0x3 )
102 {
103 case 0: /* Non-signed word */
104 update_dabt(dabt, reg, 2, false);
105 break;
106 case 1: /* Non-signed halfword */
107 update_dabt(dabt, reg, 1, false);
108 break;
109 case 2: /* Non-signed byte */
110 update_dabt(dabt, reg, 0, false);
111 break;
112 case 3: /* Signed byte */
113 update_dabt(dabt, reg, 0, true);
114 break;
115 }
116
117 break;
118 }
119 case 6:
120 /* Load/Store word immediate offset */
121 update_dabt(dabt, instr & 7, 2, false);
122 break;
123 case 7:
124 /* Load/Store byte immediate offset */
125 update_dabt(dabt, instr & 7, 0, false);
126 break;
127 case 8:
128 /* Load/Store halfword immediate offset */
129 update_dabt(dabt, instr & 7, 1, false);
130 break;
131 case 9:
132 /* Load/Store word sp offset */
133 update_dabt(dabt, (instr >> 8) & 7, 2, false);
134 break;
135 case 14:
136 if ( instr & (1 << 11) )
137 return decode_thumb2(pc, dabt, instr);
138 goto bad_thumb;
139 case 15:
140 return decode_thumb2(pc, dabt, instr);
141 default:
142 goto bad_thumb;
143 }
144
145 return 0;
146
147 bad_thumb:
148 gprintk(XENLOG_ERR, "unhandled THUMB instruction 0x%x\n", instr);
149 return 1;
150 }
151
decode_instruction(const struct cpu_user_regs * regs,struct hsr_dabt * dabt)152 int decode_instruction(const struct cpu_user_regs *regs, struct hsr_dabt *dabt)
153 {
154 if ( is_32bit_domain(current->domain) && regs->cpsr & PSR_THUMB )
155 return decode_thumb(regs->pc, dabt);
156
157 /* TODO: Handle ARM instruction */
158 gprintk(XENLOG_ERR, "unhandled ARM instruction\n");
159
160 return 1;
161 }
162
163 /*
164 * Local variables:
165 * mode: C
166 * c-file-style: "BSD"
167 * c-basic-offset: 4
168 * tab-width: 4
169 * indent-tabs-mode: nil
170 * End:
171 */
172