1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Hyp portion of the (not much of an) Emulation layer for 32bit guests.
4 *
5 * Copyright (C) 2012,2013 - ARM Ltd
6 * Author: Marc Zyngier <marc.zyngier@arm.com>
7 *
8 * based on arch/arm/kvm/emulate.c
9 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
10 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
11 */
12
13 #include <linux/kvm_host.h>
14 #include <asm/kvm_emulate.h>
15 #include <asm/kvm_hyp.h>
16
17 /*
18 * stolen from arch/arm/kernel/opcodes.c
19 *
20 * condition code lookup table
21 * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
22 *
23 * bit position in short is condition code: NZCV
24 */
25 static const unsigned short cc_map[16] = {
26 0xF0F0, /* EQ == Z set */
27 0x0F0F, /* NE */
28 0xCCCC, /* CS == C set */
29 0x3333, /* CC */
30 0xFF00, /* MI == N set */
31 0x00FF, /* PL */
32 0xAAAA, /* VS == V set */
33 0x5555, /* VC */
34 0x0C0C, /* HI == C set && Z clear */
35 0xF3F3, /* LS == C clear || Z set */
36 0xAA55, /* GE == (N==V) */
37 0x55AA, /* LT == (N!=V) */
38 0x0A05, /* GT == (!Z && (N==V)) */
39 0xF5FA, /* LE == (Z || (N!=V)) */
40 0xFFFF, /* AL always */
41 0 /* NV */
42 };
43
44 /*
45 * Check if a trapped instruction should have been executed or not.
46 */
kvm_condition_valid32(const struct kvm_vcpu * vcpu)47 bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
48 {
49 unsigned long cpsr;
50 u32 cpsr_cond;
51 int cond;
52
53 /* Top two bits non-zero? Unconditional. */
54 if (kvm_vcpu_get_esr(vcpu) >> 30)
55 return true;
56
57 /* Is condition field valid? */
58 cond = kvm_vcpu_get_condition(vcpu);
59 if (cond == 0xE)
60 return true;
61
62 cpsr = *vcpu_cpsr(vcpu);
63
64 if (cond < 0) {
65 /* This can happen in Thumb mode: examine IT state. */
66 unsigned long it;
67
68 it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
69
70 /* it == 0 => unconditional. */
71 if (it == 0)
72 return true;
73
74 /* The cond for this insn works out as the top 4 bits. */
75 cond = (it >> 4);
76 }
77
78 cpsr_cond = cpsr >> 28;
79
80 if (!((cc_map[cond] >> cpsr_cond) & 1))
81 return false;
82
83 return true;
84 }
85
86 /**
87 * adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
88 * @vcpu: The VCPU pointer
89 *
90 * When exceptions occur while instructions are executed in Thumb IF-THEN
91 * blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have
92 * to do this little bit of work manually. The fields map like this:
93 *
94 * IT[7:0] -> CPSR[26:25],CPSR[15:10]
95 */
kvm_adjust_itstate(struct kvm_vcpu * vcpu)96 static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
97 {
98 unsigned long itbits, cond;
99 unsigned long cpsr = *vcpu_cpsr(vcpu);
100 bool is_arm = !(cpsr & PSR_AA32_T_BIT);
101
102 if (is_arm || !(cpsr & PSR_AA32_IT_MASK))
103 return;
104
105 cond = (cpsr & 0xe000) >> 13;
106 itbits = (cpsr & 0x1c00) >> (10 - 2);
107 itbits |= (cpsr & (0x3 << 25)) >> 25;
108
109 /* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
110 if ((itbits & 0x7) == 0)
111 itbits = cond = 0;
112 else
113 itbits = (itbits << 1) & 0x1f;
114
115 cpsr &= ~PSR_AA32_IT_MASK;
116 cpsr |= cond << 13;
117 cpsr |= (itbits & 0x1c) << (10 - 2);
118 cpsr |= (itbits & 0x3) << 25;
119 *vcpu_cpsr(vcpu) = cpsr;
120 }
121
122 /**
123 * kvm_skip_instr - skip a trapped instruction and proceed to the next
124 * @vcpu: The vcpu pointer
125 */
kvm_skip_instr32(struct kvm_vcpu * vcpu)126 void kvm_skip_instr32(struct kvm_vcpu *vcpu)
127 {
128 u32 pc = *vcpu_pc(vcpu);
129 bool is_thumb;
130
131 is_thumb = !!(*vcpu_cpsr(vcpu) & PSR_AA32_T_BIT);
132 if (is_thumb && !kvm_vcpu_trap_il_is32bit(vcpu))
133 pc += 2;
134 else
135 pc += 4;
136
137 *vcpu_pc(vcpu) = pc;
138
139 kvm_adjust_itstate(vcpu);
140 }
141