// SPDX-License-Identifier: GPL-2.0-only
#include "test_util.h"
#include "kvm_util.h"
#include "processor.h"

#include <signal.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/time.h>

#include "kselftest.h"

static void guest_ud_handler(struct ex_regs *regs)
{
        /* Loop on the ud2 until guest state is made invalid. */
}

static void guest_code(void)
{
        asm volatile("ud2");
}

static void __run_vcpu_with_invalid_state(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;

        vcpu_run(vcpu);

        TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_INTERNAL_ERROR);
        TEST_ASSERT(run->emulation_failure.suberror == KVM_INTERNAL_ERROR_EMULATION,
                    "Expected emulation failure, got %d",
                    run->emulation_failure.suberror);
}

static void run_vcpu_with_invalid_state(struct kvm_vcpu *vcpu)
{
        /*
         * Always run twice to verify KVM handles the case where _KVM_ queues
         * an exception with invalid state and then exits to userspace, i.e.
         * that KVM doesn't explode if userspace ignores the initial error.
         */
        __run_vcpu_with_invalid_state(vcpu);
        __run_vcpu_with_invalid_state(vcpu);
}

static void set_timer(void)
{
        struct itimerval timer;

        timer.it_value.tv_sec  = 0;
        timer.it_value.tv_usec = 200;
        timer.it_interval = timer.it_value;
        TEST_ASSERT_EQ(setitimer(ITIMER_REAL, &timer, NULL), 0);
}

static void set_or_clear_invalid_guest_state(struct kvm_vcpu *vcpu, bool set)
{
        static struct kvm_sregs sregs;

        if (!sregs.cr0)
                vcpu_sregs_get(vcpu, &sregs);
        sregs.tr.unusable = !!set;
        vcpu_sregs_set(vcpu, &sregs);
}

static void set_invalid_guest_state(struct kvm_vcpu *vcpu)
{
        set_or_clear_invalid_guest_state(vcpu, true);
}

static void clear_invalid_guest_state(struct kvm_vcpu *vcpu)
{
        set_or_clear_invalid_guest_state(vcpu, false);
}

static struct kvm_vcpu *get_set_sigalrm_vcpu(struct kvm_vcpu *__vcpu)
{
        static struct kvm_vcpu *vcpu = NULL;

        if (__vcpu)
                vcpu = __vcpu;
        return vcpu;
}

static void sigalrm_handler(int sig)
{
        struct kvm_vcpu *vcpu = get_set_sigalrm_vcpu(NULL);
        struct kvm_vcpu_events events;

        TEST_ASSERT(sig == SIGALRM, "Unexpected signal = %d", sig);

        vcpu_events_get(vcpu, &events);

        /*
         * If an exception is pending, attempt KVM_RUN with invalid guest,
         * otherwise rearm the timer and keep doing so until the timer fires
         * between KVM queueing an exception and re-entering the guest.
         */
        if (events.exception.pending) {
                set_invalid_guest_state(vcpu);
                run_vcpu_with_invalid_state(vcpu);
        } else {
                set_timer();
        }
}

int main(int argc, char *argv[])
{
        struct kvm_vcpu *vcpu;
        struct kvm_vm *vm;

        TEST_REQUIRE(host_cpu_is_intel);
        TEST_REQUIRE(!kvm_is_unrestricted_guest_enabled());

        vm = vm_create_with_one_vcpu(&vcpu, guest_code);
        get_set_sigalrm_vcpu(vcpu);

        vm_install_exception_handler(vm, UD_VECTOR, guest_ud_handler);

        /*
         * Stuff invalid guest state for L2 by making TR unusuable.  The next
         * KVM_RUN should induce a TRIPLE_FAULT in L2 as KVM doesn't support
         * emulating invalid guest state for L2.
         */
        set_invalid_guest_state(vcpu);
        run_vcpu_with_invalid_state(vcpu);

        /*
         * Verify KVM also handles the case where userspace gains control while
         * an exception is pending and stuffs invalid state.  Run with valid
         * guest state and a timer firing every 200us, and attempt to enter the
         * guest with invalid state when the handler interrupts KVM with an
         * exception pending.
         */
        clear_invalid_guest_state(vcpu);
        TEST_ASSERT(signal(SIGALRM, sigalrm_handler) != SIG_ERR,
                    "Failed to register SIGALRM handler, errno = %d (%s)",
                    errno, strerror(errno));

        set_timer();
        run_vcpu_with_invalid_state(vcpu);
}