arch/arm64/kvm/inject_fault.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Fault injection for both 32 and 64bit 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>
 */

#include <linux/kvm_host.h>
#include <asm/kvm_emulate.h>
#include <asm/esr.h>

#define CURRENT_EL_SP_EL0_VECTOR	0x0
#define CURRENT_EL_SP_ELx_VECTOR	0x200
#define LOWER_EL_AArch64_VECTOR		0x400
#define LOWER_EL_AArch32_VECTOR		0x600

enum exception_type {
	except_type_sync	= 0,
	except_type_irq		= 0x80,
	except_type_fiq		= 0x100,
	except_type_serror	= 0x180,
};

/*
 * This performs the exception entry at a given EL (@target_mode), stashing PC
 * and PSTATE into ELR and SPSR respectively, and compute the new PC/PSTATE.
 * The EL passed to this function *must* be a non-secure, privileged mode with
 * bit 0 being set (PSTATE.SP == 1).
 *
 * When an exception is taken, most PSTATE fields are left unchanged in the
 * handler. However, some are explicitly overridden (e.g. M[4:0]). Luckily all
 * of the inherited bits have the same position in the AArch64/AArch32 SPSR_ELx
 * layouts, so we don't need to shuffle these for exceptions from AArch32 EL0.
 *
 * For the SPSR_ELx layout for AArch64, see ARM DDI 0487E.a page C5-429.
 * For the SPSR_ELx layout for AArch32, see ARM DDI 0487E.a page C5-426.
 *
 * Here we manipulate the fields in order of the AArch64 SPSR_ELx layout, from
 * MSB to LSB.
 */
static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
			      enum exception_type type)
{
	unsigned long sctlr, vbar, old, new, mode;
	u64 exc_offset;

	mode = *vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT);

	if      (mode == target_mode)
		exc_offset = CURRENT_EL_SP_ELx_VECTOR;
	else if ((mode | PSR_MODE_THREAD_BIT) == target_mode)
		exc_offset = CURRENT_EL_SP_EL0_VECTOR;
	else if (!(mode & PSR_MODE32_BIT))
		exc_offset = LOWER_EL_AArch64_VECTOR;
	else
		exc_offset = LOWER_EL_AArch32_VECTOR;

	switch (target_mode) {
	case PSR_MODE_EL1h:
		vbar = vcpu_read_sys_reg(vcpu, VBAR_EL1);
		sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
		vcpu_write_elr_el1(vcpu, *vcpu_pc(vcpu));
		break;
	default:
		/* Don't do that */
		BUG();
	}

	*vcpu_pc(vcpu) = vbar + exc_offset + type;

	old = *vcpu_cpsr(vcpu);
	new = 0;

	new |= (old & PSR_N_BIT);
	new |= (old & PSR_Z_BIT);
	new |= (old & PSR_C_BIT);
	new |= (old & PSR_V_BIT);

	// TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)

	new |= (old & PSR_DIT_BIT);

	// PSTATE.UAO is set to zero upon any exception to AArch64
	// See ARM DDI 0487E.a, page D5-2579.

	// PSTATE.PAN is unchanged unless SCTLR_ELx.SPAN == 0b0
	// SCTLR_ELx.SPAN is RES1 when ARMv8.1-PAN is not implemented
	// See ARM DDI 0487E.a, page D5-2578.
	new |= (old & PSR_PAN_BIT);
	if (!(sctlr & SCTLR_EL1_SPAN))
		new |= PSR_PAN_BIT;

	// PSTATE.SS is set to zero upon any exception to AArch64
	// See ARM DDI 0487E.a, page D2-2452.

	// PSTATE.IL is set to zero upon any exception to AArch64
	// See ARM DDI 0487E.a, page D1-2306.

	// PSTATE.SSBS is set to SCTLR_ELx.DSSBS upon any exception to AArch64
	// See ARM DDI 0487E.a, page D13-3258
	if (sctlr & SCTLR_ELx_DSSBS)
		new |= PSR_SSBS_BIT;

	// PSTATE.BTYPE is set to zero upon any exception to AArch64
	// See ARM DDI 0487E.a, pages D1-2293 to D1-2294.

	new |= PSR_D_BIT;
	new |= PSR_A_BIT;
	new |= PSR_I_BIT;
	new |= PSR_F_BIT;

	new |= target_mode;

	*vcpu_cpsr(vcpu) = new;
	vcpu_write_spsr(vcpu, old);
}

static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr)
{
	unsigned long cpsr = *vcpu_cpsr(vcpu);
	bool is_aarch32 = vcpu_mode_is_32bit(vcpu);
	u32 esr = 0;

	enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);

	vcpu_write_sys_reg(vcpu, addr, FAR_EL1);

	/*
	 * Build an {i,d}abort, depending on the level and the
	 * instruction set. Report an external synchronous abort.
	 */
	if (kvm_vcpu_trap_il_is32bit(vcpu))
		esr |= ESR_ELx_IL;

	/*
	 * Here, the guest runs in AArch64 mode when in EL1. If we get
	 * an AArch32 fault, it means we managed to trap an EL0 fault.
	 */
	if (is_aarch32 || (cpsr & PSR_MODE_MASK) == PSR_MODE_EL0t)
		esr |= (ESR_ELx_EC_IABT_LOW << ESR_ELx_EC_SHIFT);
	else
		esr |= (ESR_ELx_EC_IABT_CUR << ESR_ELx_EC_SHIFT);

	if (!is_iabt)
		esr |= ESR_ELx_EC_DABT_LOW << ESR_ELx_EC_SHIFT;

	vcpu_write_sys_reg(vcpu, esr | ESR_ELx_FSC_EXTABT, ESR_EL1);
}

static void inject_undef64(struct kvm_vcpu *vcpu)
{
	u32 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);

	enter_exception64(vcpu, PSR_MODE_EL1h, except_type_sync);

	/*
	 * Build an unknown exception, depending on the instruction
	 * set.
	 */
	if (kvm_vcpu_trap_il_is32bit(vcpu))
		esr |= ESR_ELx_IL;

	vcpu_write_sys_reg(vcpu, esr, ESR_EL1);
}

/**
 * kvm_inject_dabt - inject a data abort into the guest
 * @vcpu: The VCPU to receive the data abort
 * @addr: The address to report in the DFAR
 *
 * It is assumed that this code is called from the VCPU thread and that the
 * VCPU therefore is not currently executing guest code.
 */
void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
	if (vcpu_el1_is_32bit(vcpu))
		kvm_inject_dabt32(vcpu, addr);
	else
		inject_abt64(vcpu, false, addr);
}

/**
 * kvm_inject_pabt - inject a prefetch abort into the guest
 * @vcpu: The VCPU to receive the prefetch abort
 * @addr: The address to report in the DFAR
 *
 * It is assumed that this code is called from the VCPU thread and that the
 * VCPU therefore is not currently executing guest code.
 */
void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr)
{
	if (vcpu_el1_is_32bit(vcpu))
		kvm_inject_pabt32(vcpu, addr);
	else
		inject_abt64(vcpu, true, addr);
}

/**
 * kvm_inject_undefined - inject an undefined instruction into the guest
 *
 * It is assumed that this code is called from the VCPU thread and that the
 * VCPU therefore is not currently executing guest code.
 */
void kvm_inject_undefined(struct kvm_vcpu *vcpu)
{
	if (vcpu_el1_is_32bit(vcpu))
		kvm_inject_undef32(vcpu);
	else
		inject_undef64(vcpu);
}

void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 esr)
{
	vcpu_set_vsesr(vcpu, esr & ESR_ELx_ISS_MASK);
	*vcpu_hcr(vcpu) |= HCR_VSE;
}

/**
 * kvm_inject_vabt - inject an async abort / SError into the guest
 * @vcpu: The VCPU to receive the exception
 *
 * It is assumed that this code is called from the VCPU thread and that the
 * VCPU therefore is not currently executing guest code.
 *
 * Systems with the RAS Extensions specify an imp-def ESR (ISV/IDS = 1) with
 * the remaining ISS all-zeros so that this error is not interpreted as an
 * uncategorized RAS error. Without the RAS Extensions we can't specify an ESR
 * value, so the CPU generates an imp-def value.
 */
void kvm_inject_vabt(struct kvm_vcpu *vcpu)
{
	kvm_set_sei_esr(vcpu, ESR_ELx_ISV);
}