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 #include <asm/kvm_hyp.h>
27
28 /*
29 * stolen from arch/arm/kernel/opcodes.c
30 *
31 * condition code lookup table
32 * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
33 *
34 * bit position in short is condition code: NZCV
35 */
36 static const unsigned short cc_map[16] = {
37 0xF0F0, /* EQ == Z set */
38 0x0F0F, /* NE */
39 0xCCCC, /* CS == C set */
40 0x3333, /* CC */
41 0xFF00, /* MI == N set */
42 0x00FF, /* PL */
43 0xAAAA, /* VS == V set */
44 0x5555, /* VC */
45 0x0C0C, /* HI == C set && Z clear */
46 0xF3F3, /* LS == C clear || Z set */
47 0xAA55, /* GE == (N==V) */
48 0x55AA, /* LT == (N!=V) */
49 0x0A05, /* GT == (!Z && (N==V)) */
50 0xF5FA, /* LE == (Z || (N!=V)) */
51 0xFFFF, /* AL always */
52 0 /* NV */
53 };
54
55 /*
56 * Check if a trapped instruction should have been executed or not.
57 */
kvm_condition_valid32(const struct kvm_vcpu * vcpu)58 bool __hyp_text kvm_condition_valid32(const struct kvm_vcpu *vcpu)
59 {
60 unsigned long cpsr;
61 u32 cpsr_cond;
62 int cond;
63
64 /* Top two bits non-zero? Unconditional. */
65 if (kvm_vcpu_get_hsr(vcpu) >> 30)
66 return true;
67
68 /* Is condition field valid? */
69 cond = kvm_vcpu_get_condition(vcpu);
70 if (cond == 0xE)
71 return true;
72
73 cpsr = *vcpu_cpsr(vcpu);
74
75 if (cond < 0) {
76 /* This can happen in Thumb mode: examine IT state. */
77 unsigned long it;
78
79 it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
80
81 /* it == 0 => unconditional. */
82 if (it == 0)
83 return true;
84
85 /* The cond for this insn works out as the top 4 bits. */
86 cond = (it >> 4);
87 }
88
89 cpsr_cond = cpsr >> 28;
90
91 if (!((cc_map[cond] >> cpsr_cond) & 1))
92 return false;
93
94 return true;
95 }
96
97 /**
98 * adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
99 * @vcpu: The VCPU pointer
100 *
101 * When exceptions occur while instructions are executed in Thumb IF-THEN
102 * blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have
103 * to do this little bit of work manually. The fields map like this:
104 *
105 * IT[7:0] -> CPSR[26:25],CPSR[15:10]
106 */
kvm_adjust_itstate(struct kvm_vcpu * vcpu)107 static void __hyp_text kvm_adjust_itstate(struct kvm_vcpu *vcpu)
108 {
109 unsigned long itbits, cond;
110 unsigned long cpsr = *vcpu_cpsr(vcpu);
111 bool is_arm = !(cpsr & PSR_AA32_T_BIT);
112
113 if (is_arm || !(cpsr & PSR_AA32_IT_MASK))
114 return;
115
116 cond = (cpsr & 0xe000) >> 13;
117 itbits = (cpsr & 0x1c00) >> (10 - 2);
118 itbits |= (cpsr & (0x3 << 25)) >> 25;
119
120 /* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
121 if ((itbits & 0x7) == 0)
122 itbits = cond = 0;
123 else
124 itbits = (itbits << 1) & 0x1f;
125
126 cpsr &= ~PSR_AA32_IT_MASK;
127 cpsr |= cond << 13;
128 cpsr |= (itbits & 0x1c) << (10 - 2);
129 cpsr |= (itbits & 0x3) << 25;
130 *vcpu_cpsr(vcpu) = cpsr;
131 }
132
133 /**
134 * kvm_skip_instr - skip a trapped instruction and proceed to the next
135 * @vcpu: The vcpu pointer
136 */
kvm_skip_instr32(struct kvm_vcpu * vcpu,bool is_wide_instr)137 void __hyp_text kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
138 {
139 bool is_thumb;
140
141 is_thumb = !!(*vcpu_cpsr(vcpu) & PSR_AA32_T_BIT);
142 if (is_thumb && !is_wide_instr)
143 *vcpu_pc(vcpu) += 2;
144 else
145 *vcpu_pc(vcpu) += 4;
146 kvm_adjust_itstate(vcpu);
147 }
148
149 /*
150 * Table taken from ARMv8 ARM DDI0487B-B, table G1-10.
151 */
152 static const u8 return_offsets[8][2] = {
153 [0] = { 0, 0 }, /* Reset, unused */
154 [1] = { 4, 2 }, /* Undefined */
155 [2] = { 0, 0 }, /* SVC, unused */
156 [3] = { 4, 4 }, /* Prefetch abort */
157 [4] = { 8, 8 }, /* Data abort */
158 [5] = { 0, 0 }, /* HVC, unused */
159 [6] = { 4, 4 }, /* IRQ, unused */
160 [7] = { 4, 4 }, /* FIQ, unused */
161 };
162
prepare_fault32(struct kvm_vcpu * vcpu,u32 mode,u32 vect_offset)163 static void prepare_fault32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset)
164 {
165 unsigned long cpsr;
166 unsigned long new_spsr_value = *vcpu_cpsr(vcpu);
167 bool is_thumb = (new_spsr_value & PSR_AA32_T_BIT);
168 u32 return_offset = return_offsets[vect_offset >> 2][is_thumb];
169 u32 sctlr = vcpu_cp15(vcpu, c1_SCTLR);
170
171 cpsr = mode | PSR_AA32_I_BIT;
172
173 if (sctlr & (1 << 30))
174 cpsr |= PSR_AA32_T_BIT;
175 if (sctlr & (1 << 25))
176 cpsr |= PSR_AA32_E_BIT;
177
178 *vcpu_cpsr(vcpu) = cpsr;
179
180 /* Note: These now point to the banked copies */
181 vcpu_write_spsr(vcpu, new_spsr_value);
182 *vcpu_reg32(vcpu, 14) = *vcpu_pc(vcpu) + return_offset;
183
184 /* Branch to exception vector */
185 if (sctlr & (1 << 13))
186 vect_offset += 0xffff0000;
187 else /* always have security exceptions */
188 vect_offset += vcpu_cp15(vcpu, c12_VBAR);
189
190 *vcpu_pc(vcpu) = vect_offset;
191 }
192
kvm_inject_undef32(struct kvm_vcpu * vcpu)193 void kvm_inject_undef32(struct kvm_vcpu *vcpu)
194 {
195 prepare_fault32(vcpu, PSR_AA32_MODE_UND, 4);
196 }
197
198 /*
199 * Modelled after TakeDataAbortException() and TakePrefetchAbortException
200 * pseudocode.
201 */
inject_abt32(struct kvm_vcpu * vcpu,bool is_pabt,unsigned long addr)202 static void inject_abt32(struct kvm_vcpu *vcpu, bool is_pabt,
203 unsigned long addr)
204 {
205 u32 vect_offset;
206 u32 *far, *fsr;
207 bool is_lpae;
208
209 if (is_pabt) {
210 vect_offset = 12;
211 far = &vcpu_cp15(vcpu, c6_IFAR);
212 fsr = &vcpu_cp15(vcpu, c5_IFSR);
213 } else { /* !iabt */
214 vect_offset = 16;
215 far = &vcpu_cp15(vcpu, c6_DFAR);
216 fsr = &vcpu_cp15(vcpu, c5_DFSR);
217 }
218
219 prepare_fault32(vcpu, PSR_AA32_MODE_ABT | PSR_AA32_A_BIT, vect_offset);
220
221 *far = addr;
222
223 /* Give the guest an IMPLEMENTATION DEFINED exception */
224 is_lpae = (vcpu_cp15(vcpu, c2_TTBCR) >> 31);
225 if (is_lpae)
226 *fsr = 1 << 9 | 0x34;
227 else
228 *fsr = 0x14;
229 }
230
kvm_inject_dabt32(struct kvm_vcpu * vcpu,unsigned long addr)231 void kvm_inject_dabt32(struct kvm_vcpu *vcpu, unsigned long addr)
232 {
233 inject_abt32(vcpu, false, addr);
234 }
235
kvm_inject_pabt32(struct kvm_vcpu * vcpu,unsigned long addr)236 void kvm_inject_pabt32(struct kvm_vcpu *vcpu, unsigned long addr)
237 {
238 inject_abt32(vcpu, true, addr);
239 }
240
