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27b190bd MZ |
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 | ||
27b190bd MZ |
54 | /* |
55 | * Check if a trapped instruction should have been executed or not. | |
56 | */ | |
57 | bool kvm_condition_valid32(const struct kvm_vcpu *vcpu) | |
58 | { | |
59 | unsigned long cpsr; | |
60 | u32 cpsr_cond; | |
61 | int cond; | |
62 | ||
63 | /* Top two bits non-zero? Unconditional. */ | |
64 | if (kvm_vcpu_get_hsr(vcpu) >> 30) | |
65 | return true; | |
66 | ||
67 | /* Is condition field valid? */ | |
68 | cond = kvm_vcpu_get_condition(vcpu); | |
69 | if (cond == 0xE) | |
70 | return true; | |
71 | ||
72 | cpsr = *vcpu_cpsr(vcpu); | |
73 | ||
74 | if (cond < 0) { | |
75 | /* This can happen in Thumb mode: examine IT state. */ | |
76 | unsigned long it; | |
77 | ||
78 | it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3); | |
79 | ||
80 | /* it == 0 => unconditional. */ | |
81 | if (it == 0) | |
82 | return true; | |
83 | ||
84 | /* The cond for this insn works out as the top 4 bits. */ | |
85 | cond = (it >> 4); | |
86 | } | |
87 | ||
88 | cpsr_cond = cpsr >> 28; | |
89 | ||
90 | if (!((cc_map[cond] >> cpsr_cond) & 1)) | |
91 | return false; | |
92 | ||
93 | return true; | |
94 | } | |
95 | ||
96 | /** | |
97 | * adjust_itstate - adjust ITSTATE when emulating instructions in IT-block | |
98 | * @vcpu: The VCPU pointer | |
99 | * | |
100 | * When exceptions occur while instructions are executed in Thumb IF-THEN | |
101 | * blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have | |
102 | * to do this little bit of work manually. The fields map like this: | |
103 | * | |
104 | * IT[7:0] -> CPSR[26:25],CPSR[15:10] | |
105 | */ | |
106 | static void kvm_adjust_itstate(struct kvm_vcpu *vcpu) | |
107 | { | |
108 | unsigned long itbits, cond; | |
109 | unsigned long cpsr = *vcpu_cpsr(vcpu); | |
110 | bool is_arm = !(cpsr & COMPAT_PSR_T_BIT); | |
111 | ||
427d7cac | 112 | if (is_arm || !(cpsr & COMPAT_PSR_IT_MASK)) |
27b190bd MZ |
113 | return; |
114 | ||
115 | cond = (cpsr & 0xe000) >> 13; | |
116 | itbits = (cpsr & 0x1c00) >> (10 - 2); | |
117 | itbits |= (cpsr & (0x3 << 25)) >> 25; | |
118 | ||
119 | /* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */ | |
120 | if ((itbits & 0x7) == 0) | |
121 | itbits = cond = 0; | |
122 | else | |
123 | itbits = (itbits << 1) & 0x1f; | |
124 | ||
125 | cpsr &= ~COMPAT_PSR_IT_MASK; | |
126 | cpsr |= cond << 13; | |
127 | cpsr |= (itbits & 0x1c) << (10 - 2); | |
128 | cpsr |= (itbits & 0x3) << 25; | |
129 | *vcpu_cpsr(vcpu) = cpsr; | |
130 | } | |
131 | ||
132 | /** | |
133 | * kvm_skip_instr - skip a trapped instruction and proceed to the next | |
134 | * @vcpu: The vcpu pointer | |
135 | */ | |
136 | void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr) | |
137 | { | |
138 | bool is_thumb; | |
139 | ||
140 | is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT); | |
141 | if (is_thumb && !is_wide_instr) | |
142 | *vcpu_pc(vcpu) += 2; | |
143 | else | |
144 | *vcpu_pc(vcpu) += 4; | |
145 | kvm_adjust_itstate(vcpu); | |
146 | } |