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/*P:500 Just as userspace programs request kernel operations through a system

 * call, the Guest requests Host operations through a "hypercall".  You might

 * notice this nomenclature doesn't really follow any logic, but the name has

 * been around for long enough that we're stuck with it.  As you'd expect, this

 * code is basically a one big switch statement. :*/

/*  Copyright (C) 2006 Rusty Russell IBM Corporation

    This program is free software; you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation; either version 2 of the License, or

    (at your option) any later version.

    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, write to the Free Software

    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

*/

#include <linux/uaccess.h>

#include <linux/syscalls.h>

#include <linux/mm.h>

#include <asm/page.h>

#include <asm/pgtable.h>

#include "lg.h"

/*H:120 This is the core hypercall routine: where the Guest gets what it wants.

 * Or gets killed.  Or, in the case of LHCALL_CRASH, both. */

static void do_hcall(struct lguest *lg, struct hcall_args *args)

{

        switch (args->arg0) {

        case LHCALL_FLUSH_ASYNC:

                /* This call does nothing, except by breaking out of the Guest

                 * it makes us process all the asynchronous hypercalls. */

                break;

        case LHCALL_LGUEST_INIT:

                /* You can't get here unless you're already initialized.  Don't

                 * do that. */

                kill_guest(lg, "already have lguest_data");

                break;

        case LHCALL_CRASH: {

                /* Crash is such a trivial hypercall that we do it in four

                 * lines right here. */

                char msg[128];

                /* If the lgread fails, it will call kill_guest() itself; the

                 * kill_guest() with the message will be ignored. */

                __lgread(lg, msg, args->arg1, sizeof(msg));

                msg[sizeof(msg)-1] = '\0';

                kill_guest(lg, "CRASH: %s", msg);

                break;

        }

        case LHCALL_FLUSH_TLB:

                /* FLUSH_TLB comes in two flavors, depending on the

                 * argument: */

                if (args->arg1)

                        guest_pagetable_clear_all(lg);

                else

                        guest_pagetable_flush_user(lg);

                break;

        /* All these calls simply pass the arguments through to the right

         * routines. */

        case LHCALL_NEW_PGTABLE:

                guest_new_pagetable(lg, args->arg1);

                break;

        case LHCALL_SET_STACK:

                guest_set_stack(lg, args->arg1, args->arg2, args->arg3);

                break;

        case LHCALL_SET_PTE:

                guest_set_pte(lg, args->arg1, args->arg2, __pte(args->arg3));

                break;

        case LHCALL_SET_PMD:

                guest_set_pmd(lg, args->arg1, args->arg2);

                break;

        case LHCALL_SET_CLOCKEVENT:

                guest_set_clockevent(lg, args->arg1);

                break;

        case LHCALL_TS:

                /* This sets the TS flag, as we saw used in run_guest(). */

                lg->ts = args->arg1;

                break;

        case LHCALL_HALT:

                /* Similarly, this sets the halted flag for run_guest(). */

                lg->halted = 1;

                break;

        case LHCALL_NOTIFY:

                lg->pending_notify = args->arg1;

                break;

        default:

                /* It should be an architecture-specific hypercall. */

                if (lguest_arch_do_hcall(lg, args))

                        kill_guest(lg, "Bad hypercall %li\n", args->arg0);

        }

}

/*:*/

/*H:124 Asynchronous hypercalls are easy: we just look in the array in the

 * Guest's "struct lguest_data" to see if any new ones are marked "ready".

 *

 * We are careful to do these in order: obviously we respect the order the

 * Guest put them in the ring, but we also promise the Guest that they will

 * happen before any normal hypercall (which is why we check this before

 * checking for a normal hcall). */

static void do_async_hcalls(struct lguest *lg)

{

        unsigned int i;

        u8 st[LHCALL_RING_SIZE];

        /* For simplicity, we copy the entire call status array in at once. */

        if (copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st)))

                return;

        /* We process "struct lguest_data"s hcalls[] ring once. */

        for (i = 0; i < ARRAY_SIZE(st); i++) {

                struct hcall_args args;

                /* We remember where we were up to from last time.  This makes

                 * sure that the hypercalls are done in the order the Guest

                 * places them in the ring. */

                unsigned int n = lg->next_hcall;

                /* 0xFF means there's no call here (yet). */

                if (st[n] == 0xFF)

                        break;

                /* OK, we have hypercall.  Increment the "next_hcall" cursor,

                 * and wrap back to 0 if we reach the end. */

                if (++lg->next_hcall == LHCALL_RING_SIZE)

                        lg->next_hcall = 0;

                /* Copy the hypercall arguments into a local copy of

                 * the hcall_args struct. */

                if (copy_from_user(&args, &lg->lguest_data->hcalls[n],

                                   sizeof(struct hcall_args))) {

                        kill_guest(lg, "Fetching async hypercalls");

                        break;

                }

                /* Do the hypercall, same as a normal one. */

                do_hcall(lg, &args);

                /* Mark the hypercall done. */

                if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) {

                        kill_guest(lg, "Writing result for async hypercall");

                        break;

                }

                /* Stop doing hypercalls if they want to notify the Launcher:

                 * it needs to service this first. */

                if (lg->pending_notify)

                        break;

        }

}

/* Last of all, we look at what happens first of all.  The very first time the

 * Guest makes a hypercall, we end up here to set things up: */

static void initialize(struct lguest *lg)

{

        /* You can't do anything until you're initialized.  The Guest knows the

         * rules, so we're unforgiving here. */

        if (lg->hcall->arg0 != LHCALL_LGUEST_INIT) {

                kill_guest(lg, "hypercall %li before INIT", lg->hcall->arg0);

                return;

        }

        if (lguest_arch_init_hypercalls(lg))

                kill_guest(lg, "bad guest page %p", lg->lguest_data);

        /* The Guest tells us where we're not to deliver interrupts by putting

         * the range of addresses into "struct lguest_data". */

        if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start)

            || get_user(lg->noirq_end, &lg->lguest_data->noirq_end))

                kill_guest(lg, "bad guest page %p", lg->lguest_data);

        /* We write the current time into the Guest's data page once so it can

         * set its clock. */

        write_timestamp(lg);

        /* page_tables.c will also do some setup. */

        page_table_guest_data_init(lg);

        /* This is the one case where the above accesses might have been the

         * first write to a Guest page.  This may have caused a copy-on-write

         * fault, but the old page might be (read-only) in the Guest

         * pagetable. */

        guest_pagetable_clear_all(lg);

}

/*H:100

 * Hypercalls

 *

 * Remember from the Guest, hypercalls come in two flavors: normal and

 * asynchronous.  This file handles both of types.

 */

void do_hypercalls(struct lguest *lg)

{

        /* Not initialized yet?  This hypercall must do it. */

        if (unlikely(!lg->lguest_data)) {

                /* Set up the "struct lguest_data" */

                initialize(lg);

                /* Hcall is done. */

                lg->hcall = NULL;

                return;

        }

        /* The Guest has initialized.

         *

         * Look in the hypercall ring for the async hypercalls: */

        do_async_hcalls(lg);

        /* If we stopped reading the hypercall ring because the Guest did a

         * NOTIFY to the Launcher, we want to return now.  Otherwise we do

         * the hypercall. */

        if (!lg->pending_notify) {

                do_hcall(lg, lg->hcall);

                /* Tricky point: we reset the hcall pointer to mark the

                 * hypercall as "done".  We use the hcall pointer rather than

                 * the trap number to indicate a hypercall is pending.

                 * Normally it doesn't matter: the Guest will run again and

                 * update the trap number before we come back here.

                 *

                 * However, if we are signalled or the Guest sends I/O to the

                 * Launcher, the run_guest() loop will exit without running the

                 * Guest.  When it comes back it would try to re-run the

                 * hypercall. */

                lg->hcall = NULL;

        }

}

/* This routine supplies the Guest with time: it's used for wallclock time at

 * initial boot and as a rough time source if the TSC isn't available. */

void write_timestamp(struct lguest *lg)

{

        struct timespec now;

        ktime_get_real_ts(&now);

        if (copy_to_user(&lg->lguest_data->time, &now, sizeof(struct timespec)))

                kill_guest(lg, "Writing timestamp");

}