Logo Search packages:      
Sourcecode: linux version File versions  Download package

hypercalls.c

/*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");
}

Generated by  Doxygen 1.6.0   Back to index