/*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 <linux/ktime.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_SHUTDOWN, both.
   */
  static void do_hcall(struct lg_cpu *cpu, 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_SEND_INTERRUPTS:
  		/*
  		 * This call does nothing too, but by breaking out of the Guest
  		 * it makes us process any pending interrupts.
  		 */
  		break;
  	case LHCALL_LGUEST_INIT:
  		/*
  		 * You can't get here unless you're already initialized.  Don't
  		 * do that.
  		 */
  		kill_guest(cpu, "already have lguest_data");
  		break;
  	case LHCALL_SHUTDOWN: {
  		char msg[128];
  		/*
  		 * Shutdown is such a trivial hypercall that we do it in five
  		 * lines right here.
  		 *
  		 * If the lgread fails, it will call kill_guest() itself; the
  		 * kill_guest() with the message will be ignored.
  		 */
  		__lgread(cpu, msg, args->arg1, sizeof(msg));
  		msg[sizeof(msg)-1] = '\0';
  		kill_guest(cpu, "CRASH: %s", msg);
  		if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
  			cpu->lg->dead = ERR_PTR(-ERESTART);
  		break;
  	}
  	case LHCALL_FLUSH_TLB:
  		/* FLUSH_TLB comes in two flavors, depending on the argument: */
  		if (args->arg1)
  			guest_pagetable_clear_all(cpu);
  		else
  			guest_pagetable_flush_user(cpu);
  		break;
  
  	/*
  	 * All these calls simply pass the arguments through to the right
  	 * routines.
  	 */
  	case LHCALL_NEW_PGTABLE:
  		guest_new_pagetable(cpu, args->arg1);
  		break;
  	case LHCALL_SET_STACK:
  		guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
  		break;
  	case LHCALL_SET_PTE:
  #ifdef CONFIG_X86_PAE
  		guest_set_pte(cpu, args->arg1, args->arg2,
  				__pte(args->arg3 | (u64)args->arg4 << 32));
  #else
  		guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
  #endif
  		break;
  	case LHCALL_SET_PGD:
  		guest_set_pgd(cpu->lg, args->arg1, args->arg2);
  		break;
  #ifdef CONFIG_X86_PAE
  	case LHCALL_SET_PMD:
  		guest_set_pmd(cpu->lg, args->arg1, args->arg2);
  		break;
  #endif
  	case LHCALL_SET_CLOCKEVENT:
  		guest_set_clockevent(cpu, args->arg1);
  		break;
  	case LHCALL_TS:
  		/* This sets the TS flag, as we saw used in run_guest(). */
  		cpu->ts = args->arg1;
  		break;
  	case LHCALL_HALT:
  		/* Similarly, this sets the halted flag for run_guest(). */
  		cpu->halted = 1;
  		break;
  	case LHCALL_NOTIFY:
  		cpu->pending_notify = args->arg1;
  		break;
  	default:
  		/* It should be an architecture-specific hypercall. */
  		if (lguest_arch_do_hcall(cpu, args))
  			kill_guest(cpu, "Bad hypercall %li
  ", 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 lg_cpu *cpu)
  {
  	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, &cpu->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 = cpu->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 (++cpu->next_hcall == LHCALL_RING_SIZE)
  			cpu->next_hcall = 0;
  
  		/*
  		 * Copy the hypercall arguments into a local copy of the
  		 * hcall_args struct.
  		 */
  		if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
  				   sizeof(struct hcall_args))) {
  			kill_guest(cpu, "Fetching async hypercalls");
  			break;
  		}
  
  		/* Do the hypercall, same as a normal one. */
  		do_hcall(cpu, &args);
  
  		/* Mark the hypercall done. */
  		if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
  			kill_guest(cpu, "Writing result for async hypercall");
  			break;
  		}
  
  		/*
  		 * Stop doing hypercalls if they want to notify the Launcher:
  		 * it needs to service this first.
  		 */
  		if (cpu->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 lg_cpu *cpu)
  {
  	/*
  	 * You can't do anything until you're initialized.  The Guest knows the
  	 * rules, so we're unforgiving here.
  	 */
  	if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
  		kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
  		return;
  	}
  
  	if (lguest_arch_init_hypercalls(cpu))
  		kill_guest(cpu, "bad guest page %p", cpu->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(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
  	    || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
  		kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
  
  	/*
  	 * We write the current time into the Guest's data page once so it can
  	 * set its clock.
  	 */
  	write_timestamp(cpu);
  
  	/* page_tables.c will also do some setup. */
  	page_table_guest_data_init(cpu);
  
  	/*
  	 * 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(cpu);
  }
  /*:*/
  
  /*M:013
   * If a Guest reads from a page (so creates a mapping) that it has never
   * written to, and then the Launcher writes to it (ie. the output of a virtual
   * device), the Guest will still see the old page.  In practice, this never
   * happens: why would the Guest read a page which it has never written to?  But
   * a similar scenario might one day bite us, so it's worth mentioning.
   *
   * Note that if we used a shared anonymous mapping in the Launcher instead of
   * mapping /dev/zero private, we wouldn't worry about cop-on-write.  And we
   * need that to switch the Launcher to processes (away from threads) anyway.
  :*/
  
  /*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 lg_cpu *cpu)
  {
  	/* Not initialized yet?  This hypercall must do it. */
  	if (unlikely(!cpu->lg->lguest_data)) {
  		/* Set up the "struct lguest_data" */
  		initialize(cpu);
  		/* Hcall is done. */
  		cpu->hcall = NULL;
  		return;
  	}
  
  	/*
  	 * The Guest has initialized.
  	 *
  	 * Look in the hypercall ring for the async hypercalls:
  	 */
  	do_async_hcalls(cpu);
  
  	/*
  	 * 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 (!cpu->pending_notify) {
  		do_hcall(cpu, cpu->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.  Finding that bug sucked.
  		 */
  		cpu->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 lg_cpu *cpu)
  {
  	struct timespec now;
  	ktime_get_real_ts(&now);
  	if (copy_to_user(&cpu->lg->lguest_data->time,
  			 &now, sizeof(struct timespec)))
  		kill_guest(cpu, "Writing timestamp");
  }