/*
 * Copyright (C) 2012,2013 - ARM Ltd
 * Author: Marc Zyngier <marc.zyngier@arm.com>
 *
 * Derived from arch/arm/kvm/handle_exit.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.h>
#include <linux/kvm_host.h>

#include <kvm/arm_psci.h>

#include <asm/esr.h>
#include <asm/exception.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_coproc.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_mmu.h>
#include <asm/debug-monitors.h>
#include <asm/traps.h>

#define CREATE_TRACE_POINTS
#include "trace.h"

typedef int (*exit_handle_fn)(struct kvm_vcpu *, struct kvm_run *);

static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u32 esr)
{
        if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(NULL, esr))
                kvm_inject_vabt(vcpu);
}

static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        int ret;

        trace_kvm_hvc_arm64(*vcpu_pc(vcpu), vcpu_get_reg(vcpu, 0),
                            kvm_vcpu_hvc_get_imm(vcpu));
        vcpu->stat.hvc_exit_stat++;

        ret = kvm_hvc_call_handler(vcpu);
        if (ret < 0) {
                vcpu_set_reg(vcpu, 0, ~0UL);
                return 1;
        }

        return ret;
}

static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        /*
         * "If an SMC instruction executed at Non-secure EL1 is
         * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a
         * Trap exception, not a Secure Monitor Call exception [...]"
         *
         * We need to advance the PC after the trap, as it would
         * otherwise return to the same address...
         */
        vcpu_set_reg(vcpu, 0, ~0UL);
        kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
        return 1;
}

/*
 * Guest access to FP/ASIMD registers are routed to this handler only
 * when the system doesn't support FP/ASIMD.
 */
static int handle_no_fpsimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        kvm_inject_undefined(vcpu);
        return 1;
}

/**
 * kvm_handle_wfx - handle a wait-for-interrupts or wait-for-event
 *                  instruction executed by a guest
 *
 * @vcpu:       the vcpu pointer
 *
 * WFE: Yield the CPU and come back to this vcpu when the scheduler
 * decides to.
 * WFI: Simply call kvm_vcpu_block(), which will halt execution of
 * world-switches and schedule other host processes until there is an
 * incoming IRQ or FIQ to the VM.
 */
static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
                trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
                vcpu->stat.wfe_exit_stat++;
                kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
        } else {
                trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
                vcpu->stat.wfi_exit_stat++;
                kvm_vcpu_block(vcpu);
                kvm_clear_request(KVM_REQ_UNHALT, vcpu);
        }

        kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));

        return 1;
}

/**
 * kvm_handle_guest_debug - handle a debug exception instruction
 *
 * @vcpu:       the vcpu pointer
 * @run:        access to the kvm_run structure for results
 *
 * We route all debug exceptions through the same handler. If both the
 * guest and host are using the same debug facilities it will be up to
 * userspace to re-inject the correct exception for guest delivery.
 *
 * @return: 0 (while setting run->exit_reason), -1 for error
 */
static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        u32 hsr = kvm_vcpu_get_hsr(vcpu);
        int ret = 0;

        run->exit_reason = KVM_EXIT_DEBUG;
        run->debug.arch.hsr = hsr;

        switch (ESR_ELx_EC(hsr)) {
        case ESR_ELx_EC_WATCHPT_LOW:
                run->debug.arch.far = vcpu->arch.fault.far_el2;
                /* fall through */
        case ESR_ELx_EC_SOFTSTP_LOW:
        case ESR_ELx_EC_BREAKPT_LOW:
        case ESR_ELx_EC_BKPT32:
        case ESR_ELx_EC_BRK64:
                break;
        default:
                kvm_err("%s: un-handled case hsr: %#08x\n",
                        __func__, (unsigned int) hsr);
                ret = -1;
                break;
        }

        return ret;
}

static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        u32 hsr = kvm_vcpu_get_hsr(vcpu);

        kvm_pr_unimpl("Unknown exception class: hsr: %#08x -- %s\n",
                      hsr, esr_get_class_string(hsr));

        kvm_inject_undefined(vcpu);
        return 1;
}

static int handle_sve(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        /* Until SVE is supported for guests: */
        kvm_inject_undefined(vcpu);
        return 1;
}

/*
 * Guest usage of a ptrauth instruction (which the guest EL1 did not turn into
 * a NOP).
 */
static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        /*
         * We don't currently support ptrauth in a guest, and we mask the ID
         * registers to prevent well-behaved guests from trying to make use of
         * it.
         *
         * Inject an UNDEF, as if the feature really isn't present.
         */
        kvm_inject_undefined(vcpu);
        return 1;
}

static exit_handle_fn arm_exit_handlers[] = {
        [0 ... ESR_ELx_EC_MAX]  = kvm_handle_unknown_ec,
        [ESR_ELx_EC_WFx]        = kvm_handle_wfx,
        [ESR_ELx_EC_CP15_32]    = kvm_handle_cp15_32,
        [ESR_ELx_EC_CP15_64]    = kvm_handle_cp15_64,
        [ESR_ELx_EC_CP14_MR]    = kvm_handle_cp14_32,
        [ESR_ELx_EC_CP14_LS]    = kvm_handle_cp14_load_store,
        [ESR_ELx_EC_CP14_64]    = kvm_handle_cp14_64,
        [ESR_ELx_EC_HVC32]      = handle_hvc,
        [ESR_ELx_EC_SMC32]      = handle_smc,
        [ESR_ELx_EC_HVC64]      = handle_hvc,
        [ESR_ELx_EC_SMC64]      = handle_smc,
        [ESR_ELx_EC_SYS64]      = kvm_handle_sys_reg,
        [ESR_ELx_EC_SVE]        = handle_sve,
        [ESR_ELx_EC_IABT_LOW]   = kvm_handle_guest_abort,
        [ESR_ELx_EC_DABT_LOW]   = kvm_handle_guest_abort,
        [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
        [ESR_ELx_EC_WATCHPT_LOW]= kvm_handle_guest_debug,
        [ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
        [ESR_ELx_EC_BKPT32]     = kvm_handle_guest_debug,
        [ESR_ELx_EC_BRK64]      = kvm_handle_guest_debug,
        [ESR_ELx_EC_FP_ASIMD]   = handle_no_fpsimd,
        [ESR_ELx_EC_PAC]        = kvm_handle_ptrauth,
};

static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
{
        u32 hsr = kvm_vcpu_get_hsr(vcpu);
        u8 hsr_ec = ESR_ELx_EC(hsr);

        return arm_exit_handlers[hsr_ec];
}

/*
 * We may be single-stepping an emulated instruction. If the emulation
 * has been completed in the kernel, we can return to userspace with a
 * KVM_EXIT_DEBUG, otherwise userspace needs to complete its
 * emulation first.
 */
static int handle_trap_exceptions(struct kvm_vcpu *vcpu, struct kvm_run *run)
{
        int handled;

        /*
         * See ARM ARM B1.14.1: "Hyp traps on instructions
         * that fail their condition code check"
         */
        if (!kvm_condition_valid(vcpu)) {
                kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
                handled = 1;
        } else {
                exit_handle_fn exit_handler;

                exit_handler = kvm_get_exit_handler(vcpu);
                handled = exit_handler(vcpu, run);
        }

        return handled;
}

/*
 * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
 * proper exit to userspace.
 */
int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
                       int exception_index)
{
        if (ARM_SERROR_PENDING(exception_index)) {
                u8 hsr_ec = ESR_ELx_EC(kvm_vcpu_get_hsr(vcpu));

                /*
                 * HVC/SMC already have an adjusted PC, which we need
                 * to correct in order to return to after having
                 * injected the SError.
                 */
                if (hsr_ec == ESR_ELx_EC_HVC32 || hsr_ec == ESR_ELx_EC_HVC64 ||
                    hsr_ec == ESR_ELx_EC_SMC32 || hsr_ec == ESR_ELx_EC_SMC64) {
                        u32 adj =  kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
                        *vcpu_pc(vcpu) -= adj;
                }

                return 1;
        }

        exception_index = ARM_EXCEPTION_CODE(exception_index);

        switch (exception_index) {
        case ARM_EXCEPTION_IRQ:
                return 1;
        case ARM_EXCEPTION_EL1_SERROR:
                return 1;
        case ARM_EXCEPTION_TRAP:
                return handle_trap_exceptions(vcpu, run);
        case ARM_EXCEPTION_HYP_GONE:
                /*
                 * EL2 has been reset to the hyp-stub. This happens when a guest
                 * is pre-empted by kvm_reboot()'s shutdown call.
                 */
                run->exit_reason = KVM_EXIT_FAIL_ENTRY;
                return 0;
        case ARM_EXCEPTION_IL:
                /*
                 * We attempted an illegal exception return.  Guest state must
                 * have been corrupted somehow.  Give up.
                 */
                run->exit_reason = KVM_EXIT_FAIL_ENTRY;
                return -EINVAL;
        default:
                kvm_pr_unimpl("Unsupported exception type: %d",
                              exception_index);
                run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
                return 0;
        }
}

/* For exit types that need handling before we can be preempted */
void handle_exit_early(struct kvm_vcpu *vcpu, struct kvm_run *run,
                       int exception_index)
{
        if (ARM_SERROR_PENDING(exception_index)) {
                if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) {
                        u64 disr = kvm_vcpu_get_disr(vcpu);

                        kvm_handle_guest_serror(vcpu, disr_to_esr(disr));
                } else {
                        kvm_inject_vabt(vcpu);
                }

                return;
        }

        exception_index = ARM_EXCEPTION_CODE(exception_index);

        if (exception_index == ARM_EXCEPTION_EL1_SERROR)
                kvm_handle_guest_serror(vcpu, kvm_vcpu_get_hsr(vcpu));
}