[mirror_ubuntu-zesty-kernel.git] / arch / arm64 / kvm / emulate.c

/*
 * (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                     */
};

/*
 * 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);
}
Commit	Line	Data
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
	112	BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
	113
	114	if (!(cpsr & COMPAT_PSR_IT_MASK))
	115	return;
	116
	117	cond = (cpsr & 0xe000) >> 13;
118	itbits = (cpsr & 0x1c00) >> (10 - 2);
119	itbits \|= (cpsr & (0x3 << 25)) >> 25;
120
121	/* Perform ITAdvance (see page A2-52 in ARM DDI 0406C) */
122	if ((itbits & 0x7) == 0)
123	itbits = cond = 0;
124	else
125	itbits = (itbits << 1) & 0x1f;
126
127	cpsr &= ~COMPAT_PSR_IT_MASK;
128	cpsr \|= cond << 13;
129	cpsr \|= (itbits & 0x1c) << (10 - 2);
130	cpsr \|= (itbits & 0x3) << 25;
131	*vcpu_cpsr(vcpu) = cpsr;
132	}
133
134	/**
135	* kvm_skip_instr - skip a trapped instruction and proceed to the next
136	* @vcpu: The vcpu pointer
137	*/
138	void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
139	{
140	bool is_thumb;
141
142	is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT);
143	if (is_thumb && !is_wide_instr)
144	*vcpu_pc(vcpu) += 2;
145	else
146	*vcpu_pc(vcpu) += 4;
147	kvm_adjust_itstate(vcpu);
148	}