1 /*P:500
2 * Just as userspace programs request kernel operations through a system
3 * call, the Guest requests Host operations through a "hypercall". You might
4 * notice this nomenclature doesn't really follow any logic, but the name has
5 * been around for long enough that we're stuck with it. As you'd expect, this
6 * code is basically a one big switch statement.
7 :*/
8
9 /* Copyright (C) 2006 Rusty Russell IBM Corporation
10
11 This program is free software; you can redistribute it and/or modify
12 it under the terms of the GNU General Public License as published by
13 the Free Software Foundation; either version 2 of the License, or
14 (at your option) any later version.
15
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License for more details.
20
21 You should have received a copy of the GNU General Public License
22 along with this program; if not, write to the Free Software
23 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25 #include <linux/uaccess.h>
26 #include <linux/syscalls.h>
27 #include <linux/mm.h>
28 #include <linux/ktime.h>
29 #include <asm/page.h>
30 #include <asm/pgtable.h>
31 #include "lg.h"
32
33 /*H:120
34 * This is the core hypercall routine: where the Guest gets what it wants.
35 * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
36 */
do_hcall(struct lg_cpu * cpu,struct hcall_args * args)37 static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
38 {
39 switch (args->arg0) {
40 case LHCALL_FLUSH_ASYNC:
41 /*
42 * This call does nothing, except by breaking out of the Guest
43 * it makes us process all the asynchronous hypercalls.
44 */
45 break;
46 case LHCALL_SEND_INTERRUPTS:
47 /*
48 * This call does nothing too, but by breaking out of the Guest
49 * it makes us process any pending interrupts.
50 */
51 break;
52 case LHCALL_LGUEST_INIT:
53 /*
54 * You can't get here unless you're already initialized. Don't
55 * do that.
56 */
57 kill_guest(cpu, "already have lguest_data");
58 break;
59 case LHCALL_SHUTDOWN: {
60 char msg[128];
61 /*
62 * Shutdown is such a trivial hypercall that we do it in five
63 * lines right here.
64 *
65 * If the lgread fails, it will call kill_guest() itself; the
66 * kill_guest() with the message will be ignored.
67 */
68 __lgread(cpu, msg, args->arg1, sizeof(msg));
69 msg[sizeof(msg)-1] = '\0';
70 kill_guest(cpu, "CRASH: %s", msg);
71 if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
72 cpu->lg->dead = ERR_PTR(-ERESTART);
73 break;
74 }
75 case LHCALL_FLUSH_TLB:
76 /* FLUSH_TLB comes in two flavors, depending on the argument: */
77 if (args->arg1)
78 guest_pagetable_clear_all(cpu);
79 else
80 guest_pagetable_flush_user(cpu);
81 break;
82
83 /*
84 * All these calls simply pass the arguments through to the right
85 * routines.
86 */
87 case LHCALL_NEW_PGTABLE:
88 guest_new_pagetable(cpu, args->arg1);
89 break;
90 case LHCALL_SET_STACK:
91 guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
92 break;
93 case LHCALL_SET_PTE:
94 #ifdef CONFIG_X86_PAE
95 guest_set_pte(cpu, args->arg1, args->arg2,
96 __pte(args->arg3 | (u64)args->arg4 << 32));
97 #else
98 guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
99 #endif
100 break;
101 case LHCALL_SET_PGD:
102 guest_set_pgd(cpu->lg, args->arg1, args->arg2);
103 break;
104 #ifdef CONFIG_X86_PAE
105 case LHCALL_SET_PMD:
106 guest_set_pmd(cpu->lg, args->arg1, args->arg2);
107 break;
108 #endif
109 case LHCALL_SET_CLOCKEVENT:
110 guest_set_clockevent(cpu, args->arg1);
111 break;
112 case LHCALL_TS:
113 /* This sets the TS flag, as we saw used in run_guest(). */
114 cpu->ts = args->arg1;
115 break;
116 case LHCALL_HALT:
117 /* Similarly, this sets the halted flag for run_guest(). */
118 cpu->halted = 1;
119 break;
120 default:
121 /* It should be an architecture-specific hypercall. */
122 if (lguest_arch_do_hcall(cpu, args))
123 kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
124 }
125 }
126
127 /*H:124
128 * Asynchronous hypercalls are easy: we just look in the array in the
129 * Guest's "struct lguest_data" to see if any new ones are marked "ready".
130 *
131 * We are careful to do these in order: obviously we respect the order the
132 * Guest put them in the ring, but we also promise the Guest that they will
133 * happen before any normal hypercall (which is why we check this before
134 * checking for a normal hcall).
135 */
do_async_hcalls(struct lg_cpu * cpu)136 static void do_async_hcalls(struct lg_cpu *cpu)
137 {
138 unsigned int i;
139 u8 st[LHCALL_RING_SIZE];
140
141 /* For simplicity, we copy the entire call status array in at once. */
142 if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
143 return;
144
145 /* We process "struct lguest_data"s hcalls[] ring once. */
146 for (i = 0; i < ARRAY_SIZE(st); i++) {
147 struct hcall_args args;
148 /*
149 * We remember where we were up to from last time. This makes
150 * sure that the hypercalls are done in the order the Guest
151 * places them in the ring.
152 */
153 unsigned int n = cpu->next_hcall;
154
155 /* 0xFF means there's no call here (yet). */
156 if (st[n] == 0xFF)
157 break;
158
159 /*
160 * OK, we have hypercall. Increment the "next_hcall" cursor,
161 * and wrap back to 0 if we reach the end.
162 */
163 if (++cpu->next_hcall == LHCALL_RING_SIZE)
164 cpu->next_hcall = 0;
165
166 /*
167 * Copy the hypercall arguments into a local copy of the
168 * hcall_args struct.
169 */
170 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
171 sizeof(struct hcall_args))) {
172 kill_guest(cpu, "Fetching async hypercalls");
173 break;
174 }
175
176 /* Do the hypercall, same as a normal one. */
177 do_hcall(cpu, &args);
178
179 /* Mark the hypercall done. */
180 if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
181 kill_guest(cpu, "Writing result for async hypercall");
182 break;
183 }
184
185 /*
186 * Stop doing hypercalls if they want to notify the Launcher:
187 * it needs to service this first.
188 */
189 if (cpu->pending.trap)
190 break;
191 }
192 }
193
194 /*
195 * Last of all, we look at what happens first of all. The very first time the
196 * Guest makes a hypercall, we end up here to set things up:
197 */
initialize(struct lg_cpu * cpu)198 static void initialize(struct lg_cpu *cpu)
199 {
200 /*
201 * You can't do anything until you're initialized. The Guest knows the
202 * rules, so we're unforgiving here.
203 */
204 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
205 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
206 return;
207 }
208
209 if (lguest_arch_init_hypercalls(cpu))
210 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
211
212 /*
213 * The Guest tells us where we're not to deliver interrupts by putting
214 * the instruction address into "struct lguest_data".
215 */
216 if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret))
217 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
218
219 /*
220 * We write the current time into the Guest's data page once so it can
221 * set its clock.
222 */
223 write_timestamp(cpu);
224
225 /* page_tables.c will also do some setup. */
226 page_table_guest_data_init(cpu);
227
228 /*
229 * This is the one case where the above accesses might have been the
230 * first write to a Guest page. This may have caused a copy-on-write
231 * fault, but the old page might be (read-only) in the Guest
232 * pagetable.
233 */
234 guest_pagetable_clear_all(cpu);
235 }
236 /*:*/
237
238 /*M:013
239 * If a Guest reads from a page (so creates a mapping) that it has never
240 * written to, and then the Launcher writes to it (ie. the output of a virtual
241 * device), the Guest will still see the old page. In practice, this never
242 * happens: why would the Guest read a page which it has never written to? But
243 * a similar scenario might one day bite us, so it's worth mentioning.
244 *
245 * Note that if we used a shared anonymous mapping in the Launcher instead of
246 * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
247 * need that to switch the Launcher to processes (away from threads) anyway.
248 :*/
249
250 /*H:100
251 * Hypercalls
252 *
253 * Remember from the Guest, hypercalls come in two flavors: normal and
254 * asynchronous. This file handles both of types.
255 */
do_hypercalls(struct lg_cpu * cpu)256 void do_hypercalls(struct lg_cpu *cpu)
257 {
258 /* Not initialized yet? This hypercall must do it. */
259 if (unlikely(!cpu->lg->lguest_data)) {
260 /* Set up the "struct lguest_data" */
261 initialize(cpu);
262 /* Hcall is done. */
263 cpu->hcall = NULL;
264 return;
265 }
266
267 /*
268 * The Guest has initialized.
269 *
270 * Look in the hypercall ring for the async hypercalls:
271 */
272 do_async_hcalls(cpu);
273
274 /*
275 * If we stopped reading the hypercall ring because the Guest did a
276 * NOTIFY to the Launcher, we want to return now. Otherwise we do
277 * the hypercall.
278 */
279 if (!cpu->pending.trap) {
280 do_hcall(cpu, cpu->hcall);
281 /*
282 * Tricky point: we reset the hcall pointer to mark the
283 * hypercall as "done". We use the hcall pointer rather than
284 * the trap number to indicate a hypercall is pending.
285 * Normally it doesn't matter: the Guest will run again and
286 * update the trap number before we come back here.
287 *
288 * However, if we are signalled or the Guest sends I/O to the
289 * Launcher, the run_guest() loop will exit without running the
290 * Guest. When it comes back it would try to re-run the
291 * hypercall. Finding that bug sucked.
292 */
293 cpu->hcall = NULL;
294 }
295 }
296
297 /*
298 * This routine supplies the Guest with time: it's used for wallclock time at
299 * initial boot and as a rough time source if the TSC isn't available.
300 */
write_timestamp(struct lg_cpu * cpu)301 void write_timestamp(struct lg_cpu *cpu)
302 {
303 struct timespec now;
304 ktime_get_real_ts(&now);
305 if (copy_to_user(&cpu->lg->lguest_data->time,
306 &now, sizeof(struct timespec)))
307 kill_guest(cpu, "Writing timestamp");
308 }
309