drivers/lguest/hypercalls.c - kernel/msm-4.9 - Gitiles

 /*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;
 	case LHCALL_BIND_DMA:
 		/* BIND_DMA really wants four arguments, but it's the only call
 		 * which does.  So the Guest packs the number of buffers and
 		 * the interrupt number into the final argument, and we decode
 		 * it here.  This can legitimately fail, since we currently
 		 * place a limit on the number of DMA pools a Guest can have.
 		 * So we return true or false from this call. */
 		args->arg0 = bind_dma(lg, args->arg1, args->arg2,
 				     args->arg3 >> 8, args->arg3 & 0xFF);
 		break;

 	/* All these calls simply pass the arguments through to the right
 	 * routines. */
 	case LHCALL_SEND_DMA:
 		send_dma(lg, args->arg1, args->arg2);
 		break;
 	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;
 	default:
 		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 we've just done a DMA to the
 		 * Launcher: it needs to service this first. */
 		if (lg->dma_is_pending)
 			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)
 	    /* We tell the Guest that it can't use the top 4MB of virtual
 	     * addresses used by the Switcher. */
 	    || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem))
 		kill_guest(lg, "bad guest page %p", lg->lguest_data);

 	/* We write the current time into the Guest's data page once now. */
 	write_timestamp(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 Guest might be referring to the old (read-only)
 	 * page. */
 	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
 	 * SEND_DMA to the Launcher, we want to return now.  Otherwise we do
 	 * the hypercall. */
 	if (!lg->dma_is_pending) {
 		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 DMA 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");
 }
	/*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;
	case LHCALL_BIND_DMA:
	/* BIND_DMA really wants four arguments, but it's the only call
	* which does. So the Guest packs the number of buffers and
	* the interrupt number into the final argument, and we decode
	* it here. This can legitimately fail, since we currently
	* place a limit on the number of DMA pools a Guest can have.
	* So we return true or false from this call. */
	args->arg0 = bind_dma(lg, args->arg1, args->arg2,
	args->arg3 >> 8, args->arg3 & 0xFF);
	break;

	/* All these calls simply pass the arguments through to the right
	* routines. */
	case LHCALL_SEND_DMA:
	send_dma(lg, args->arg1, args->arg2);
	break;
	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;
	default:
	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 we've just done a DMA to the
	* Launcher: it needs to service this first. */
	if (lg->dma_is_pending)
	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)
	/* We tell the Guest that it can't use the top 4MB of virtual
	* addresses used by the Switcher. */
	\|\| put_user(4U10241024, &lg->lguest_data->reserve_mem))
	kill_guest(lg, "bad guest page %p", lg->lguest_data);

	/* We write the current time into the Guest's data page once now. */
	write_timestamp(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 Guest might be referring to the old (read-only)
	* page. */
	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
	* SEND_DMA to the Launcher, we want to return now. Otherwise we do
	* the hypercall. */
	if (!lg->dma_is_pending) {
	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 DMA 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");
	}