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240 lines
7.9 KiB
240 lines
7.9 KiB
/*P:500 Just as userspace programs request kernel operations through a system
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* call, the Guest requests Host operations through a "hypercall". You might
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* notice this nomenclature doesn't really follow any logic, but the name has
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* been around for long enough that we're stuck with it. As you'd expect, this
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* code is basically a one big switch statement. :*/
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/* Copyright (C) 2006 Rusty Russell IBM Corporation
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/uaccess.h>
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#include <linux/syscalls.h>
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#include <linux/mm.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include "lg.h"
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/*H:120 This is the core hypercall routine: where the Guest gets what it wants.
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* Or gets killed. Or, in the case of LHCALL_CRASH, both. */
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static void do_hcall(struct lguest *lg, struct hcall_args *args)
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{
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switch (args->arg0) {
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case LHCALL_FLUSH_ASYNC:
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/* This call does nothing, except by breaking out of the Guest
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* it makes us process all the asynchronous hypercalls. */
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break;
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case LHCALL_LGUEST_INIT:
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/* You can't get here unless you're already initialized. Don't
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* do that. */
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kill_guest(lg, "already have lguest_data");
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break;
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case LHCALL_CRASH: {
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/* Crash is such a trivial hypercall that we do it in four
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* lines right here. */
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char msg[128];
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/* If the lgread fails, it will call kill_guest() itself; the
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* kill_guest() with the message will be ignored. */
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__lgread(lg, msg, args->arg1, sizeof(msg));
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msg[sizeof(msg)-1] = '\0';
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kill_guest(lg, "CRASH: %s", msg);
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break;
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}
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case LHCALL_FLUSH_TLB:
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/* FLUSH_TLB comes in two flavors, depending on the
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* argument: */
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if (args->arg1)
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guest_pagetable_clear_all(lg);
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else
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guest_pagetable_flush_user(lg);
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break;
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/* All these calls simply pass the arguments through to the right
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* routines. */
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case LHCALL_NEW_PGTABLE:
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guest_new_pagetable(lg, args->arg1);
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break;
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case LHCALL_SET_STACK:
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guest_set_stack(lg, args->arg1, args->arg2, args->arg3);
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break;
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case LHCALL_SET_PTE:
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guest_set_pte(lg, args->arg1, args->arg2, __pte(args->arg3));
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break;
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case LHCALL_SET_PMD:
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guest_set_pmd(lg, args->arg1, args->arg2);
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break;
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case LHCALL_SET_CLOCKEVENT:
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guest_set_clockevent(lg, args->arg1);
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break;
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case LHCALL_TS:
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/* This sets the TS flag, as we saw used in run_guest(). */
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lg->ts = args->arg1;
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break;
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case LHCALL_HALT:
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/* Similarly, this sets the halted flag for run_guest(). */
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lg->halted = 1;
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break;
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case LHCALL_NOTIFY:
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lg->pending_notify = args->arg1;
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break;
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default:
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/* It should be an architecture-specific hypercall. */
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if (lguest_arch_do_hcall(lg, args))
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kill_guest(lg, "Bad hypercall %li\n", args->arg0);
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}
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}
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/*:*/
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/*H:124 Asynchronous hypercalls are easy: we just look in the array in the
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* Guest's "struct lguest_data" to see if any new ones are marked "ready".
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*
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* We are careful to do these in order: obviously we respect the order the
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* Guest put them in the ring, but we also promise the Guest that they will
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* happen before any normal hypercall (which is why we check this before
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* checking for a normal hcall). */
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static void do_async_hcalls(struct lguest *lg)
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{
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unsigned int i;
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u8 st[LHCALL_RING_SIZE];
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/* For simplicity, we copy the entire call status array in at once. */
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if (copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st)))
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return;
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/* We process "struct lguest_data"s hcalls[] ring once. */
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for (i = 0; i < ARRAY_SIZE(st); i++) {
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struct hcall_args args;
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/* We remember where we were up to from last time. This makes
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* sure that the hypercalls are done in the order the Guest
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* places them in the ring. */
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unsigned int n = lg->next_hcall;
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/* 0xFF means there's no call here (yet). */
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if (st[n] == 0xFF)
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break;
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/* OK, we have hypercall. Increment the "next_hcall" cursor,
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* and wrap back to 0 if we reach the end. */
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if (++lg->next_hcall == LHCALL_RING_SIZE)
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lg->next_hcall = 0;
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/* Copy the hypercall arguments into a local copy of
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* the hcall_args struct. */
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if (copy_from_user(&args, &lg->lguest_data->hcalls[n],
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sizeof(struct hcall_args))) {
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kill_guest(lg, "Fetching async hypercalls");
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break;
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}
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/* Do the hypercall, same as a normal one. */
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do_hcall(lg, &args);
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/* Mark the hypercall done. */
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if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) {
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kill_guest(lg, "Writing result for async hypercall");
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break;
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}
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/* Stop doing hypercalls if they want to notify the Launcher:
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* it needs to service this first. */
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if (lg->pending_notify)
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break;
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}
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}
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/* Last of all, we look at what happens first of all. The very first time the
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* Guest makes a hypercall, we end up here to set things up: */
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static void initialize(struct lguest *lg)
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{
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/* You can't do anything until you're initialized. The Guest knows the
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* rules, so we're unforgiving here. */
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if (lg->hcall->arg0 != LHCALL_LGUEST_INIT) {
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kill_guest(lg, "hypercall %li before INIT", lg->hcall->arg0);
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return;
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}
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if (lguest_arch_init_hypercalls(lg))
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kill_guest(lg, "bad guest page %p", lg->lguest_data);
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/* The Guest tells us where we're not to deliver interrupts by putting
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* the range of addresses into "struct lguest_data". */
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if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start)
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|| get_user(lg->noirq_end, &lg->lguest_data->noirq_end))
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kill_guest(lg, "bad guest page %p", lg->lguest_data);
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/* We write the current time into the Guest's data page once so it can
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* set its clock. */
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write_timestamp(lg);
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/* page_tables.c will also do some setup. */
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page_table_guest_data_init(lg);
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/* This is the one case where the above accesses might have been the
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* first write to a Guest page. This may have caused a copy-on-write
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* fault, but the old page might be (read-only) in the Guest
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* pagetable. */
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guest_pagetable_clear_all(lg);
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}
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/*H:100
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* Hypercalls
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*
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* Remember from the Guest, hypercalls come in two flavors: normal and
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* asynchronous. This file handles both of types.
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*/
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void do_hypercalls(struct lguest *lg)
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{
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/* Not initialized yet? This hypercall must do it. */
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if (unlikely(!lg->lguest_data)) {
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/* Set up the "struct lguest_data" */
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initialize(lg);
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/* Hcall is done. */
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lg->hcall = NULL;
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return;
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}
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/* The Guest has initialized.
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*
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* Look in the hypercall ring for the async hypercalls: */
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do_async_hcalls(lg);
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/* If we stopped reading the hypercall ring because the Guest did a
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* NOTIFY to the Launcher, we want to return now. Otherwise we do
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* the hypercall. */
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if (!lg->pending_notify) {
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do_hcall(lg, lg->hcall);
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/* Tricky point: we reset the hcall pointer to mark the
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* hypercall as "done". We use the hcall pointer rather than
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* the trap number to indicate a hypercall is pending.
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* Normally it doesn't matter: the Guest will run again and
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* update the trap number before we come back here.
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*
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* However, if we are signalled or the Guest sends I/O to the
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* Launcher, the run_guest() loop will exit without running the
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* Guest. When it comes back it would try to re-run the
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* hypercall. */
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lg->hcall = NULL;
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}
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}
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/* This routine supplies the Guest with time: it's used for wallclock time at
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* initial boot and as a rough time source if the TSC isn't available. */
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void write_timestamp(struct lguest *lg)
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{
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struct timespec now;
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ktime_get_real_ts(&now);
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if (copy_to_user(&lg->lguest_data->time, &now, sizeof(struct timespec)))
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kill_guest(lg, "Writing timestamp");
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}
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