1 /*
2 * (not much of an) Emulation layer for 32bit guests.
3 *
4 * Copyright (C) 2012,2013 - ARM Ltd
5 * Author: Marc Zyngier <marc.zyngier@arm.com>
6 *
7 * based on arch/arm/kvm/emulate.c
8 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
9 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
10 *
11 * This program is free software: you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program. If not, see <http://www.gnu.org/licenses/>.
22 */
23
24 #include <linux/kvm_host.h>
25 #include <asm/kvm_emulate.h>
26
27 /*
28 * stolen from arch/arm/kernel/opcodes.c
29 *
30 * condition code lookup table
31 * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
32 *
33 * bit position in short is condition code: NZCV
34 */
35 static const unsigned short cc_map[16] = {
36 0xF0F0, /* EQ == Z set */
37 0x0F0F, /* NE */
38 0xCCCC, /* CS == C set */
39 0x3333, /* CC */
40 0xFF00, /* MI == N set */
41 0x00FF, /* PL */
42 0xAAAA, /* VS == V set */
43 0x5555, /* VC */
44 0x0C0C, /* HI == C set && Z clear */
45 0xF3F3, /* LS == C clear || Z set */
46 0xAA55, /* GE == (N==V) */
47 0x55AA, /* LT == (N!=V) */
48 0x0A05, /* GT == (!Z && (N==V)) */
49 0xF5FA, /* LE == (Z || (N!=V)) */
50 0xFFFF, /* AL always */
51 0 /* NV */
52 };
53
kvm_vcpu_get_condition(const struct kvm_vcpu * vcpu)54 static int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
55 {
56 u32 esr = kvm_vcpu_get_hsr(vcpu);
57
58 if (esr & ESR_EL2_CV)
59 return (esr & ESR_EL2_COND) >> ESR_EL2_COND_SHIFT;
60
61 return -1;
62 }
63
64 /*
65 * Check if a trapped instruction should have been executed or not.
66 */
kvm_condition_valid32(const struct kvm_vcpu * vcpu)67 bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
68 {
69 unsigned long cpsr;
70 u32 cpsr_cond;
71 int cond;
72
73 /* Top two bits non-zero? Unconditional. */
74 if (kvm_vcpu_get_hsr(vcpu) >> 30)
75 return true;
76
77 /* Is condition field valid? */
78 cond = kvm_vcpu_get_condition(vcpu);
79 if (cond == 0xE)
80 return true;
81
82 cpsr = *vcpu_cpsr(vcpu);
83
84 if (cond < 0) {
85 /* This can happen in Thumb mode: examine IT state. */
86 unsigned long it;
87
88 it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
89
90 /* it == 0 => unconditional. */
91 if (it == 0)
92 return true;
93
94 /* The cond for this insn works out as the top 4 bits. */
95 cond = (it >> 4);
96 }
97
98 cpsr_cond = cpsr >> 28;
99
100 if (!((cc_map[cond] >> cpsr_cond) & 1))
101 return false;
102
103 return true;
104 }
105
106 /**
107 * adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
108 * @vcpu: The VCPU pointer
109 *
110 * When exceptions occur while instructions are executed in Thumb IF-THEN
111 * blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have
112 * to do this little bit of work manually. The fields map like this:
113 *
114 * IT[7:0] -> CPSR[26:25],CPSR[15:10]
115 */
kvm_adjust_itstate(struct kvm_vcpu * vcpu)116 static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
117 {
118 unsigned long itbits, cond;
119 unsigned long cpsr = *vcpu_cpsr(vcpu);
120 bool is_arm = !(cpsr & COMPAT_PSR_T_BIT);
121
122 BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
123
124 if (!(cpsr & COMPAT_PSR_IT_MASK))
125 return;
126
127 cond = (cpsr & 0xe000) >> 13;
128 itbits = (cpsr & 0x1c00) >> (10 - 2);
129 itbits |= (cpsr & (0x3 << 25)) >> 25;
130
131 /* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
132 if ((itbits & 0x7) == 0)
133 itbits = cond = 0;
134 else
135 itbits = (itbits << 1) & 0x1f;
136
137 cpsr &= ~COMPAT_PSR_IT_MASK;
138 cpsr |= cond << 13;
139 cpsr |= (itbits & 0x1c) << (10 - 2);
140 cpsr |= (itbits & 0x3) << 25;
141 *vcpu_cpsr(vcpu) = cpsr;
142 }
143
144 /**
145 * kvm_skip_instr - skip a trapped instruction and proceed to the next
146 * @vcpu: The vcpu pointer
147 */
kvm_skip_instr32(struct kvm_vcpu * vcpu,bool is_wide_instr)148 void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
149 {
150 bool is_thumb;
151
152 is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT);
153 if (is_thumb && !is_wide_instr)
154 *vcpu_pc(vcpu) += 2;
155 else
156 *vcpu_pc(vcpu) += 4;
157 kvm_adjust_itstate(vcpu);
158 }
159