emulate.c
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/*
* (not much of an) Emulation layer for 32bit guests.
*
* Copyright (C) 2012,2013 - ARM Ltd
* Author: Marc Zyngier <marc.zyngier@arm.com>
*
* based on arch/arm/kvm/emulate.c
* Copyright (C) 2012 - Virtual Open Systems and Columbia University
* Author: Christoffer Dall <c.dall@virtualopensystems.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/kvm_host.h>
#include <asm/kvm_emulate.h>
/*
* stolen from arch/arm/kernel/opcodes.c
*
* condition code lookup table
* index into the table is test code: EQ, NE, ... LT, GT, AL, NV
*
* bit position in short is condition code: NZCV
*/
static const unsigned short cc_map[16] = {
0xF0F0, /* EQ == Z set */
0x0F0F, /* NE */
0xCCCC, /* CS == C set */
0x3333, /* CC */
0xFF00, /* MI == N set */
0x00FF, /* PL */
0xAAAA, /* VS == V set */
0x5555, /* VC */
0x0C0C, /* HI == C set && Z clear */
0xF3F3, /* LS == C clear || Z set */
0xAA55, /* GE == (N==V) */
0x55AA, /* LT == (N!=V) */
0x0A05, /* GT == (!Z && (N==V)) */
0xF5FA, /* LE == (Z || (N!=V)) */
0xFFFF, /* AL always */
0 /* NV */
};
static int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
{
u32 esr = kvm_vcpu_get_hsr(vcpu);
if (esr & ESR_EL2_CV)
return (esr & ESR_EL2_COND) >> ESR_EL2_COND_SHIFT;
return -1;
}
/*
* Check if a trapped instruction should have been executed or not.
*/
bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
{
unsigned long cpsr;
u32 cpsr_cond;
int cond;
/* Top two bits non-zero? Unconditional. */
if (kvm_vcpu_get_hsr(vcpu) >> 30)
return true;
/* Is condition field valid? */
cond = kvm_vcpu_get_condition(vcpu);
if (cond == 0xE)
return true;
cpsr = *vcpu_cpsr(vcpu);
if (cond < 0) {
/* This can happen in Thumb mode: examine IT state. */
unsigned long it;
it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
/* it == 0 => unconditional. */
if (it == 0)
return true;
/* The cond for this insn works out as the top 4 bits. */
cond = (it >> 4);
}
cpsr_cond = cpsr >> 28;
if (!((cc_map[cond] >> cpsr_cond) & 1))
return false;
return true;
}
/**
* adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
* @vcpu: The VCPU pointer
*
* When exceptions occur while instructions are executed in Thumb IF-THEN
* blocks, the ITSTATE field of the CPSR is not advanced (updated), so we have
* to do this little bit of work manually. The fields map like this:
*
* IT[7:0] -> CPSR[26:25],CPSR[15:10]
*/
static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
{
unsigned long itbits, cond;
unsigned long cpsr = *vcpu_cpsr(vcpu);
bool is_arm = !(cpsr & COMPAT_PSR_T_BIT);
BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
if (!(cpsr & COMPAT_PSR_IT_MASK))
return;
cond = (cpsr & 0xe000) >> 13;
itbits = (cpsr & 0x1c00) >> (10 - 2);
itbits |= (cpsr & (0x3 << 25)) >> 25;
/* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
if ((itbits & 0x7) == 0)
itbits = cond = 0;
else
itbits = (itbits << 1) & 0x1f;
cpsr &= ~COMPAT_PSR_IT_MASK;
cpsr |= cond << 13;
cpsr |= (itbits & 0x1c) << (10 - 2);
cpsr |= (itbits & 0x3) << 25;
*vcpu_cpsr(vcpu) = cpsr;
}
/**
* kvm_skip_instr - skip a trapped instruction and proceed to the next
* @vcpu: The vcpu pointer
*/
void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
{
bool is_thumb;
is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT);
if (is_thumb && !is_wide_instr)
*vcpu_pc(vcpu) += 2;
else
*vcpu_pc(vcpu) += 4;
kvm_adjust_itstate(vcpu);
}