160 lines
4.2 KiB
C
160 lines
4.2 KiB
C
/*
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* (not much of an) Emulation layer for 32bit guests.
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*
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* Copyright (C) 2012,2013 - ARM Ltd
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* Author: Marc Zyngier <marc.zyngier@arm.com>
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*
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* based on arch/arm/kvm/emulate.c
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* Copyright (C) 2012 - Virtual Open Systems and Columbia University
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* Author: Christoffer Dall <c.dall@virtualopensystems.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/kvm_host.h>
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#include <asm/esr.h>
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#include <asm/kvm_emulate.h>
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/*
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* stolen from arch/arm/kernel/opcodes.c
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*
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* condition code lookup table
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* index into the table is test code: EQ, NE, ... LT, GT, AL, NV
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*
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* bit position in short is condition code: NZCV
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*/
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static const unsigned short cc_map[16] = {
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0xF0F0, /* EQ == Z set */
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0x0F0F, /* NE */
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0xCCCC, /* CS == C set */
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0x3333, /* CC */
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0xFF00, /* MI == N set */
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0x00FF, /* PL */
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0xAAAA, /* VS == V set */
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0x5555, /* VC */
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0x0C0C, /* HI == C set && Z clear */
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0xF3F3, /* LS == C clear || Z set */
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0xAA55, /* GE == (N==V) */
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0x55AA, /* LT == (N!=V) */
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0x0A05, /* GT == (!Z && (N==V)) */
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0xF5FA, /* LE == (Z || (N!=V)) */
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0xFFFF, /* AL always */
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0 /* NV */
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};
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static int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
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{
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u32 esr = kvm_vcpu_get_hsr(vcpu);
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if (esr & ESR_ELx_CV)
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return (esr & ESR_ELx_COND_MASK) >> ESR_ELx_COND_SHIFT;
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return -1;
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}
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/*
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* Check if a trapped instruction should have been executed or not.
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*/
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bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
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{
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unsigned long cpsr;
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u32 cpsr_cond;
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int cond;
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/* Top two bits non-zero? Unconditional. */
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if (kvm_vcpu_get_hsr(vcpu) >> 30)
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return true;
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/* Is condition field valid? */
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cond = kvm_vcpu_get_condition(vcpu);
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if (cond == 0xE)
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return true;
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cpsr = *vcpu_cpsr(vcpu);
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if (cond < 0) {
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/* This can happen in Thumb mode: examine IT state. */
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unsigned long it;
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it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
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/* it == 0 => unconditional. */
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if (it == 0)
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return true;
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/* The cond for this insn works out as the top 4 bits. */
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cond = (it >> 4);
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}
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cpsr_cond = cpsr >> 28;
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if (!((cc_map[cond] >> cpsr_cond) & 1))
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return false;
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return true;
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}
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/**
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* adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
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* @vcpu: The VCPU pointer
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*
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* When exceptions occur while instructions are executed in Thumb IF-THEN
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* blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have
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* to do this little bit of work manually. The fields map like this:
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*
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* IT[7:0] -> CPSR[26:25],CPSR[15:10]
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*/
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static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
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{
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unsigned long itbits, cond;
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unsigned long cpsr = *vcpu_cpsr(vcpu);
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bool is_arm = !(cpsr & COMPAT_PSR_T_BIT);
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BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
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if (!(cpsr & COMPAT_PSR_IT_MASK))
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return;
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cond = (cpsr & 0xe000) >> 13;
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itbits = (cpsr & 0x1c00) >> (10 - 2);
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itbits |= (cpsr & (0x3 << 25)) >> 25;
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/* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
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if ((itbits & 0x7) == 0)
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itbits = cond = 0;
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else
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itbits = (itbits << 1) & 0x1f;
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cpsr &= ~COMPAT_PSR_IT_MASK;
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cpsr |= cond << 13;
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cpsr |= (itbits & 0x1c) << (10 - 2);
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cpsr |= (itbits & 0x3) << 25;
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*vcpu_cpsr(vcpu) = cpsr;
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}
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/**
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* kvm_skip_instr - skip a trapped instruction and proceed to the next
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* @vcpu: The vcpu pointer
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*/
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void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
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{
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bool is_thumb;
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is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT);
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if (is_thumb && !is_wide_instr)
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*vcpu_pc(vcpu) += 2;
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else
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*vcpu_pc(vcpu) += 4;
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kvm_adjust_itstate(vcpu);
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}
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