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1/*P:200 This contains all the /dev/lguest code, whereby the userspace
2 * launcher controls and communicates with the Guest. For example,
3 * the first write will tell us the Guest's memory layout and entry
4 * point. A read will run the Guest until something happens, such as
5 * a signal or the Guest accessing a device.
6:*/
7#include <linux/uaccess.h>
8#include <linux/miscdevice.h>
9#include <linux/fs.h>
10#include <linux/sched.h>
11#include <linux/file.h>
12#include <linux/slab.h>
13#include <linux/export.h>
14#include "lg.h"
15
16/*L:052
17 The Launcher can get the registers, and also set some of them.
18*/
19static int getreg_setup(struct lg_cpu *cpu, const unsigned long __user *input)
20{
21 unsigned long which;
22
23 /* We re-use the ptrace structure to specify which register to read. */
24 if (get_user(which, input) != 0)
25 return -EFAULT;
26
27 /*
28 * We set up the cpu register pointer, and their next read will
29 * actually get the value (instead of running the guest).
30 *
31 * The last argument 'true' says we can access any register.
32 */
33 cpu->reg_read = lguest_arch_regptr(cpu, which, true);
34 if (!cpu->reg_read)
35 return -ENOENT;
36
37 /* And because this is a write() call, we return the length used. */
38 return sizeof(unsigned long) * 2;
39}
40
41static int setreg(struct lg_cpu *cpu, const unsigned long __user *input)
42{
43 unsigned long which, value, *reg;
44
45 /* We re-use the ptrace structure to specify which register to read. */
46 if (get_user(which, input) != 0)
47 return -EFAULT;
48 input++;
49 if (get_user(value, input) != 0)
50 return -EFAULT;
51
52 /* The last argument 'false' means we can't access all registers. */
53 reg = lguest_arch_regptr(cpu, which, false);
54 if (!reg)
55 return -ENOENT;
56
57 *reg = value;
58
59 /* And because this is a write() call, we return the length used. */
60 return sizeof(unsigned long) * 3;
61}
62
63/*L:050
64 * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
65 * number to /dev/lguest.
66 */
67static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
68{
69 unsigned long irq;
70
71 if (get_user(irq, input) != 0)
72 return -EFAULT;
73 if (irq >= LGUEST_IRQS)
74 return -EINVAL;
75
76 /*
77 * Next time the Guest runs, the core code will see if it can deliver
78 * this interrupt.
79 */
80 set_interrupt(cpu, irq);
81 return 0;
82}
83
84/*L:053
85 * Deliver a trap: this is used by the Launcher if it can't emulate
86 * an instruction.
87 */
88static int trap(struct lg_cpu *cpu, const unsigned long __user *input)
89{
90 unsigned long trapnum;
91
92 if (get_user(trapnum, input) != 0)
93 return -EFAULT;
94
95 if (!deliver_trap(cpu, trapnum))
96 return -EINVAL;
97
98 return 0;
99}
100
101/*L:040
102 * Once our Guest is initialized, the Launcher makes it run by reading
103 * from /dev/lguest.
104 */
105static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
106{
107 struct lguest *lg = file->private_data;
108 struct lg_cpu *cpu;
109 unsigned int cpu_id = *o;
110
111 /* You must write LHREQ_INITIALIZE first! */
112 if (!lg)
113 return -EINVAL;
114
115 /* Watch out for arbitrary vcpu indexes! */
116 if (cpu_id >= lg->nr_cpus)
117 return -EINVAL;
118
119 cpu = &lg->cpus[cpu_id];
120
121 /* If you're not the task which owns the Guest, go away. */
122 if (current != cpu->tsk)
123 return -EPERM;
124
125 /* If the Guest is already dead, we indicate why */
126 if (lg->dead) {
127 size_t len;
128
129 /* lg->dead either contains an error code, or a string. */
130 if (IS_ERR(lg->dead))
131 return PTR_ERR(lg->dead);
132
133 /* We can only return as much as the buffer they read with. */
134 len = min(size, strlen(lg->dead)+1);
135 if (copy_to_user(user, lg->dead, len) != 0)
136 return -EFAULT;
137 return len;
138 }
139
140 /*
141 * If we returned from read() last time because the Guest sent I/O,
142 * clear the flag.
143 */
144 if (cpu->pending.trap)
145 cpu->pending.trap = 0;
146
147 /* Run the Guest until something interesting happens. */
148 return run_guest(cpu, (unsigned long __user *)user);
149}
150
151/*L:025
152 * This actually initializes a CPU. For the moment, a Guest is only
153 * uniprocessor, so "id" is always 0.
154 */
155static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
156{
157 /* We have a limited number of CPUs in the lguest struct. */
158 if (id >= ARRAY_SIZE(cpu->lg->cpus))
159 return -EINVAL;
160
161 /* Set up this CPU's id, and pointer back to the lguest struct. */
162 cpu->id = id;
163 cpu->lg = container_of(cpu, struct lguest, cpus[id]);
164 cpu->lg->nr_cpus++;
165
166 /* Each CPU has a timer it can set. */
167 init_clockdev(cpu);
168
169 /*
170 * We need a complete page for the Guest registers: they are accessible
171 * to the Guest and we can only grant it access to whole pages.
172 */
173 cpu->regs_page = get_zeroed_page(GFP_KERNEL);
174 if (!cpu->regs_page)
175 return -ENOMEM;
176
177 /* We actually put the registers at the end of the page. */
178 cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
179
180 /*
181 * Now we initialize the Guest's registers, handing it the start
182 * address.
183 */
184 lguest_arch_setup_regs(cpu, start_ip);
185
186 /*
187 * We keep a pointer to the Launcher task (ie. current task) for when
188 * other Guests want to wake this one (eg. console input).
189 */
190 cpu->tsk = current;
191
192 /*
193 * We need to keep a pointer to the Launcher's memory map, because if
194 * the Launcher dies we need to clean it up. If we don't keep a
195 * reference, it is destroyed before close() is called.
196 */
197 cpu->mm = get_task_mm(cpu->tsk);
198
199 /*
200 * We remember which CPU's pages this Guest used last, for optimization
201 * when the same Guest runs on the same CPU twice.
202 */
203 cpu->last_pages = NULL;
204
205 /* No error == success. */
206 return 0;
207}
208
209/*L:020
210 * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
211 * addition to the LHREQ_INITIALIZE value). These are:
212 *
213 * base: The start of the Guest-physical memory inside the Launcher memory.
214 *
215 * pfnlimit: The highest (Guest-physical) page number the Guest should be
216 * allowed to access. The Guest memory lives inside the Launcher, so it sets
217 * this to ensure the Guest can only reach its own memory.
218 *
219 * start: The first instruction to execute ("eip" in x86-speak).
220 */
221static int initialize(struct file *file, const unsigned long __user *input)
222{
223 /* "struct lguest" contains all we (the Host) know about a Guest. */
224 struct lguest *lg;
225 int err;
226 unsigned long args[4];
227
228 /*
229 * We grab the Big Lguest lock, which protects against multiple
230 * simultaneous initializations.
231 */
232 mutex_lock(&lguest_lock);
233 /* You can't initialize twice! Close the device and start again... */
234 if (file->private_data) {
235 err = -EBUSY;
236 goto unlock;
237 }
238
239 if (copy_from_user(args, input, sizeof(args)) != 0) {
240 err = -EFAULT;
241 goto unlock;
242 }
243
244 lg = kzalloc(sizeof(*lg), GFP_KERNEL);
245 if (!lg) {
246 err = -ENOMEM;
247 goto unlock;
248 }
249
250 /* Populate the easy fields of our "struct lguest" */
251 lg->mem_base = (void __user *)args[0];
252 lg->pfn_limit = args[1];
253 lg->device_limit = args[3];
254
255 /* This is the first cpu (cpu 0) and it will start booting at args[2] */
256 err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
257 if (err)
258 goto free_lg;
259
260 /*
261 * Initialize the Guest's shadow page tables. This allocates
262 * memory, so can fail.
263 */
264 err = init_guest_pagetable(lg);
265 if (err)
266 goto free_regs;
267
268 /* We keep our "struct lguest" in the file's private_data. */
269 file->private_data = lg;
270
271 mutex_unlock(&lguest_lock);
272
273 /* And because this is a write() call, we return the length used. */
274 return sizeof(args);
275
276free_regs:
277 /* FIXME: This should be in free_vcpu */
278 free_page(lg->cpus[0].regs_page);
279free_lg:
280 kfree(lg);
281unlock:
282 mutex_unlock(&lguest_lock);
283 return err;
284}
285
286/*L:010
287 * The first operation the Launcher does must be a write. All writes
288 * start with an unsigned long number: for the first write this must be
289 * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
290 * writes of other values to send interrupts or set up receipt of notifications.
291 *
292 * Note that we overload the "offset" in the /dev/lguest file to indicate what
293 * CPU number we're dealing with. Currently this is always 0 since we only
294 * support uniprocessor Guests, but you can see the beginnings of SMP support
295 * here.
296 */
297static ssize_t write(struct file *file, const char __user *in,
298 size_t size, loff_t *off)
299{
300 /*
301 * Once the Guest is initialized, we hold the "struct lguest" in the
302 * file private data.
303 */
304 struct lguest *lg = file->private_data;
305 const unsigned long __user *input = (const unsigned long __user *)in;
306 unsigned long req;
307 struct lg_cpu *uninitialized_var(cpu);
308 unsigned int cpu_id = *off;
309
310 /* The first value tells us what this request is. */
311 if (get_user(req, input) != 0)
312 return -EFAULT;
313 input++;
314
315 /* If you haven't initialized, you must do that first. */
316 if (req != LHREQ_INITIALIZE) {
317 if (!lg || (cpu_id >= lg->nr_cpus))
318 return -EINVAL;
319 cpu = &lg->cpus[cpu_id];
320
321 /* Once the Guest is dead, you can only read() why it died. */
322 if (lg->dead)
323 return -ENOENT;
324 }
325
326 switch (req) {
327 case LHREQ_INITIALIZE:
328 return initialize(file, input);
329 case LHREQ_IRQ:
330 return user_send_irq(cpu, input);
331 case LHREQ_GETREG:
332 return getreg_setup(cpu, input);
333 case LHREQ_SETREG:
334 return setreg(cpu, input);
335 case LHREQ_TRAP:
336 return trap(cpu, input);
337 default:
338 return -EINVAL;
339 }
340}
341
342static int open(struct inode *inode, struct file *file)
343{
344 file->private_data = NULL;
345
346 return 0;
347}
348
349/*L:060
350 * The final piece of interface code is the close() routine. It reverses
351 * everything done in initialize(). This is usually called because the
352 * Launcher exited.
353 *
354 * Note that the close routine returns 0 or a negative error number: it can't
355 * really fail, but it can whine. I blame Sun for this wart, and K&R C for
356 * letting them do it.
357:*/
358static int close(struct inode *inode, struct file *file)
359{
360 struct lguest *lg = file->private_data;
361 unsigned int i;
362
363 /* If we never successfully initialized, there's nothing to clean up */
364 if (!lg)
365 return 0;
366
367 /*
368 * We need the big lock, to protect from inter-guest I/O and other
369 * Launchers initializing guests.
370 */
371 mutex_lock(&lguest_lock);
372
373 /* Free up the shadow page tables for the Guest. */
374 free_guest_pagetable(lg);
375
376 for (i = 0; i < lg->nr_cpus; i++) {
377 /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
378 hrtimer_cancel(&lg->cpus[i].hrt);
379 /* We can free up the register page we allocated. */
380 free_page(lg->cpus[i].regs_page);
381 /*
382 * Now all the memory cleanups are done, it's safe to release
383 * the Launcher's memory management structure.
384 */
385 mmput(lg->cpus[i].mm);
386 }
387
388 /*
389 * If lg->dead doesn't contain an error code it will be NULL or a
390 * kmalloc()ed string, either of which is ok to hand to kfree().
391 */
392 if (!IS_ERR(lg->dead))
393 kfree(lg->dead);
394 /* Free the memory allocated to the lguest_struct */
395 kfree(lg);
396 /* Release lock and exit. */
397 mutex_unlock(&lguest_lock);
398
399 return 0;
400}
401
402/*L:000
403 * Welcome to our journey through the Launcher!
404 *
405 * The Launcher is the Host userspace program which sets up, runs and services
406 * the Guest. In fact, many comments in the Drivers which refer to "the Host"
407 * doing things are inaccurate: the Launcher does all the device handling for
408 * the Guest, but the Guest can't know that.
409 *
410 * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we
411 * shall see more of that later.
412 *
413 * We begin our understanding with the Host kernel interface which the Launcher
414 * uses: reading and writing a character device called /dev/lguest. All the
415 * work happens in the read(), write() and close() routines:
416 */
417static const struct file_operations lguest_fops = {
418 .owner = THIS_MODULE,
419 .open = open,
420 .release = close,
421 .write = write,
422 .read = read,
423 .llseek = default_llseek,
424};
425/*:*/
426
427/*
428 * This is a textbook example of a "misc" character device. Populate a "struct
429 * miscdevice" and register it with misc_register().
430 */
431static struct miscdevice lguest_dev = {
432 .minor = MISC_DYNAMIC_MINOR,
433 .name = "lguest",
434 .fops = &lguest_fops,
435};
436
437int __init lguest_device_init(void)
438{
439 return misc_register(&lguest_dev);
440}
441
442void __exit lguest_device_remove(void)
443{
444 misc_deregister(&lguest_dev);
445}
1/*P:200 This contains all the /dev/lguest code, whereby the userspace
2 * launcher controls and communicates with the Guest. For example,
3 * the first write will tell us the Guest's memory layout and entry
4 * point. A read will run the Guest until something happens, such as
5 * a signal or the Guest doing a NOTIFY out to the Launcher. There is
6 * also a way for the Launcher to attach eventfds to particular NOTIFY
7 * values instead of returning from the read() call.
8:*/
9#include <linux/uaccess.h>
10#include <linux/miscdevice.h>
11#include <linux/fs.h>
12#include <linux/sched.h>
13#include <linux/eventfd.h>
14#include <linux/file.h>
15#include <linux/slab.h>
16#include <linux/export.h>
17#include "lg.h"
18
19/*L:056
20 * Before we move on, let's jump ahead and look at what the kernel does when
21 * it needs to look up the eventfds. That will complete our picture of how we
22 * use RCU.
23 *
24 * The notification value is in cpu->pending_notify: we return true if it went
25 * to an eventfd.
26 */
27bool send_notify_to_eventfd(struct lg_cpu *cpu)
28{
29 unsigned int i;
30 struct lg_eventfd_map *map;
31
32 /*
33 * This "rcu_read_lock()" helps track when someone is still looking at
34 * the (RCU-using) eventfds array. It's not actually a lock at all;
35 * indeed it's a noop in many configurations. (You didn't expect me to
36 * explain all the RCU secrets here, did you?)
37 */
38 rcu_read_lock();
39 /*
40 * rcu_dereference is the counter-side of rcu_assign_pointer(); it
41 * makes sure we don't access the memory pointed to by
42 * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy,
43 * but Alpha allows this! Paul McKenney points out that a really
44 * aggressive compiler could have the same effect:
45 * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html
46 *
47 * So play safe, use rcu_dereference to get the rcu-protected pointer:
48 */
49 map = rcu_dereference(cpu->lg->eventfds);
50 /*
51 * Simple array search: even if they add an eventfd while we do this,
52 * we'll continue to use the old array and just won't see the new one.
53 */
54 for (i = 0; i < map->num; i++) {
55 if (map->map[i].addr == cpu->pending_notify) {
56 eventfd_signal(map->map[i].event, 1);
57 cpu->pending_notify = 0;
58 break;
59 }
60 }
61 /* We're done with the rcu-protected variable cpu->lg->eventfds. */
62 rcu_read_unlock();
63
64 /* If we cleared the notification, it's because we found a match. */
65 return cpu->pending_notify == 0;
66}
67
68/*L:055
69 * One of the more tricksy tricks in the Linux Kernel is a technique called
70 * Read Copy Update. Since one point of lguest is to teach lguest journeyers
71 * about kernel coding, I use it here. (In case you're curious, other purposes
72 * include learning about virtualization and instilling a deep appreciation for
73 * simplicity and puppies).
74 *
75 * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we
76 * add new eventfds without ever blocking readers from accessing the array.
77 * The current Launcher only does this during boot, so that never happens. But
78 * Read Copy Update is cool, and adding a lock risks damaging even more puppies
79 * than this code does.
80 *
81 * We allocate a brand new one-larger array, copy the old one and add our new
82 * element. Then we make the lg eventfd pointer point to the new array.
83 * That's the easy part: now we need to free the old one, but we need to make
84 * sure no slow CPU somewhere is still looking at it. That's what
85 * synchronize_rcu does for us: waits until every CPU has indicated that it has
86 * moved on to know it's no longer using the old one.
87 *
88 * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update.
89 */
90static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
91{
92 struct lg_eventfd_map *new, *old = lg->eventfds;
93
94 /*
95 * We don't allow notifications on value 0 anyway (pending_notify of
96 * 0 means "nothing pending").
97 */
98 if (!addr)
99 return -EINVAL;
100
101 /*
102 * Replace the old array with the new one, carefully: others can
103 * be accessing it at the same time.
104 */
105 new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
106 GFP_KERNEL);
107 if (!new)
108 return -ENOMEM;
109
110 /* First make identical copy. */
111 memcpy(new->map, old->map, sizeof(old->map[0]) * old->num);
112 new->num = old->num;
113
114 /* Now append new entry. */
115 new->map[new->num].addr = addr;
116 new->map[new->num].event = eventfd_ctx_fdget(fd);
117 if (IS_ERR(new->map[new->num].event)) {
118 int err = PTR_ERR(new->map[new->num].event);
119 kfree(new);
120 return err;
121 }
122 new->num++;
123
124 /*
125 * Now put new one in place: rcu_assign_pointer() is a fancy way of
126 * doing "lg->eventfds = new", but it uses memory barriers to make
127 * absolutely sure that the contents of "new" written above is nailed
128 * down before we actually do the assignment.
129 *
130 * We have to think about these kinds of things when we're operating on
131 * live data without locks.
132 */
133 rcu_assign_pointer(lg->eventfds, new);
134
135 /*
136 * We're not in a big hurry. Wait until no one's looking at old
137 * version, then free it.
138 */
139 synchronize_rcu();
140 kfree(old);
141
142 return 0;
143}
144
145/*L:052
146 * Receiving notifications from the Guest is usually done by attaching a
147 * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will
148 * become readable when the Guest does an LHCALL_NOTIFY with that value.
149 *
150 * This is really convenient for processing each virtqueue in a separate
151 * thread.
152 */
153static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
154{
155 unsigned long addr, fd;
156 int err;
157
158 if (get_user(addr, input) != 0)
159 return -EFAULT;
160 input++;
161 if (get_user(fd, input) != 0)
162 return -EFAULT;
163
164 /*
165 * Just make sure two callers don't add eventfds at once. We really
166 * only need to lock against callers adding to the same Guest, so using
167 * the Big Lguest Lock is overkill. But this is setup, not a fast path.
168 */
169 mutex_lock(&lguest_lock);
170 err = add_eventfd(lg, addr, fd);
171 mutex_unlock(&lguest_lock);
172
173 return err;
174}
175
176/*L:050
177 * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
178 * number to /dev/lguest.
179 */
180static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
181{
182 unsigned long irq;
183
184 if (get_user(irq, input) != 0)
185 return -EFAULT;
186 if (irq >= LGUEST_IRQS)
187 return -EINVAL;
188
189 /*
190 * Next time the Guest runs, the core code will see if it can deliver
191 * this interrupt.
192 */
193 set_interrupt(cpu, irq);
194 return 0;
195}
196
197/*L:040
198 * Once our Guest is initialized, the Launcher makes it run by reading
199 * from /dev/lguest.
200 */
201static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
202{
203 struct lguest *lg = file->private_data;
204 struct lg_cpu *cpu;
205 unsigned int cpu_id = *o;
206
207 /* You must write LHREQ_INITIALIZE first! */
208 if (!lg)
209 return -EINVAL;
210
211 /* Watch out for arbitrary vcpu indexes! */
212 if (cpu_id >= lg->nr_cpus)
213 return -EINVAL;
214
215 cpu = &lg->cpus[cpu_id];
216
217 /* If you're not the task which owns the Guest, go away. */
218 if (current != cpu->tsk)
219 return -EPERM;
220
221 /* If the Guest is already dead, we indicate why */
222 if (lg->dead) {
223 size_t len;
224
225 /* lg->dead either contains an error code, or a string. */
226 if (IS_ERR(lg->dead))
227 return PTR_ERR(lg->dead);
228
229 /* We can only return as much as the buffer they read with. */
230 len = min(size, strlen(lg->dead)+1);
231 if (copy_to_user(user, lg->dead, len) != 0)
232 return -EFAULT;
233 return len;
234 }
235
236 /*
237 * If we returned from read() last time because the Guest sent I/O,
238 * clear the flag.
239 */
240 if (cpu->pending_notify)
241 cpu->pending_notify = 0;
242
243 /* Run the Guest until something interesting happens. */
244 return run_guest(cpu, (unsigned long __user *)user);
245}
246
247/*L:025
248 * This actually initializes a CPU. For the moment, a Guest is only
249 * uniprocessor, so "id" is always 0.
250 */
251static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
252{
253 /* We have a limited number the number of CPUs in the lguest struct. */
254 if (id >= ARRAY_SIZE(cpu->lg->cpus))
255 return -EINVAL;
256
257 /* Set up this CPU's id, and pointer back to the lguest struct. */
258 cpu->id = id;
259 cpu->lg = container_of((cpu - id), struct lguest, cpus[0]);
260 cpu->lg->nr_cpus++;
261
262 /* Each CPU has a timer it can set. */
263 init_clockdev(cpu);
264
265 /*
266 * We need a complete page for the Guest registers: they are accessible
267 * to the Guest and we can only grant it access to whole pages.
268 */
269 cpu->regs_page = get_zeroed_page(GFP_KERNEL);
270 if (!cpu->regs_page)
271 return -ENOMEM;
272
273 /* We actually put the registers at the bottom of the page. */
274 cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
275
276 /*
277 * Now we initialize the Guest's registers, handing it the start
278 * address.
279 */
280 lguest_arch_setup_regs(cpu, start_ip);
281
282 /*
283 * We keep a pointer to the Launcher task (ie. current task) for when
284 * other Guests want to wake this one (eg. console input).
285 */
286 cpu->tsk = current;
287
288 /*
289 * We need to keep a pointer to the Launcher's memory map, because if
290 * the Launcher dies we need to clean it up. If we don't keep a
291 * reference, it is destroyed before close() is called.
292 */
293 cpu->mm = get_task_mm(cpu->tsk);
294
295 /*
296 * We remember which CPU's pages this Guest used last, for optimization
297 * when the same Guest runs on the same CPU twice.
298 */
299 cpu->last_pages = NULL;
300
301 /* No error == success. */
302 return 0;
303}
304
305/*L:020
306 * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
307 * addition to the LHREQ_INITIALIZE value). These are:
308 *
309 * base: The start of the Guest-physical memory inside the Launcher memory.
310 *
311 * pfnlimit: The highest (Guest-physical) page number the Guest should be
312 * allowed to access. The Guest memory lives inside the Launcher, so it sets
313 * this to ensure the Guest can only reach its own memory.
314 *
315 * start: The first instruction to execute ("eip" in x86-speak).
316 */
317static int initialize(struct file *file, const unsigned long __user *input)
318{
319 /* "struct lguest" contains all we (the Host) know about a Guest. */
320 struct lguest *lg;
321 int err;
322 unsigned long args[3];
323
324 /*
325 * We grab the Big Lguest lock, which protects against multiple
326 * simultaneous initializations.
327 */
328 mutex_lock(&lguest_lock);
329 /* You can't initialize twice! Close the device and start again... */
330 if (file->private_data) {
331 err = -EBUSY;
332 goto unlock;
333 }
334
335 if (copy_from_user(args, input, sizeof(args)) != 0) {
336 err = -EFAULT;
337 goto unlock;
338 }
339
340 lg = kzalloc(sizeof(*lg), GFP_KERNEL);
341 if (!lg) {
342 err = -ENOMEM;
343 goto unlock;
344 }
345
346 lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL);
347 if (!lg->eventfds) {
348 err = -ENOMEM;
349 goto free_lg;
350 }
351 lg->eventfds->num = 0;
352
353 /* Populate the easy fields of our "struct lguest" */
354 lg->mem_base = (void __user *)args[0];
355 lg->pfn_limit = args[1];
356
357 /* This is the first cpu (cpu 0) and it will start booting at args[2] */
358 err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
359 if (err)
360 goto free_eventfds;
361
362 /*
363 * Initialize the Guest's shadow page tables. This allocates
364 * memory, so can fail.
365 */
366 err = init_guest_pagetable(lg);
367 if (err)
368 goto free_regs;
369
370 /* We keep our "struct lguest" in the file's private_data. */
371 file->private_data = lg;
372
373 mutex_unlock(&lguest_lock);
374
375 /* And because this is a write() call, we return the length used. */
376 return sizeof(args);
377
378free_regs:
379 /* FIXME: This should be in free_vcpu */
380 free_page(lg->cpus[0].regs_page);
381free_eventfds:
382 kfree(lg->eventfds);
383free_lg:
384 kfree(lg);
385unlock:
386 mutex_unlock(&lguest_lock);
387 return err;
388}
389
390/*L:010
391 * The first operation the Launcher does must be a write. All writes
392 * start with an unsigned long number: for the first write this must be
393 * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
394 * writes of other values to send interrupts or set up receipt of notifications.
395 *
396 * Note that we overload the "offset" in the /dev/lguest file to indicate what
397 * CPU number we're dealing with. Currently this is always 0 since we only
398 * support uniprocessor Guests, but you can see the beginnings of SMP support
399 * here.
400 */
401static ssize_t write(struct file *file, const char __user *in,
402 size_t size, loff_t *off)
403{
404 /*
405 * Once the Guest is initialized, we hold the "struct lguest" in the
406 * file private data.
407 */
408 struct lguest *lg = file->private_data;
409 const unsigned long __user *input = (const unsigned long __user *)in;
410 unsigned long req;
411 struct lg_cpu *uninitialized_var(cpu);
412 unsigned int cpu_id = *off;
413
414 /* The first value tells us what this request is. */
415 if (get_user(req, input) != 0)
416 return -EFAULT;
417 input++;
418
419 /* If you haven't initialized, you must do that first. */
420 if (req != LHREQ_INITIALIZE) {
421 if (!lg || (cpu_id >= lg->nr_cpus))
422 return -EINVAL;
423 cpu = &lg->cpus[cpu_id];
424
425 /* Once the Guest is dead, you can only read() why it died. */
426 if (lg->dead)
427 return -ENOENT;
428 }
429
430 switch (req) {
431 case LHREQ_INITIALIZE:
432 return initialize(file, input);
433 case LHREQ_IRQ:
434 return user_send_irq(cpu, input);
435 case LHREQ_EVENTFD:
436 return attach_eventfd(lg, input);
437 default:
438 return -EINVAL;
439 }
440}
441
442/*L:060
443 * The final piece of interface code is the close() routine. It reverses
444 * everything done in initialize(). This is usually called because the
445 * Launcher exited.
446 *
447 * Note that the close routine returns 0 or a negative error number: it can't
448 * really fail, but it can whine. I blame Sun for this wart, and K&R C for
449 * letting them do it.
450:*/
451static int close(struct inode *inode, struct file *file)
452{
453 struct lguest *lg = file->private_data;
454 unsigned int i;
455
456 /* If we never successfully initialized, there's nothing to clean up */
457 if (!lg)
458 return 0;
459
460 /*
461 * We need the big lock, to protect from inter-guest I/O and other
462 * Launchers initializing guests.
463 */
464 mutex_lock(&lguest_lock);
465
466 /* Free up the shadow page tables for the Guest. */
467 free_guest_pagetable(lg);
468
469 for (i = 0; i < lg->nr_cpus; i++) {
470 /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
471 hrtimer_cancel(&lg->cpus[i].hrt);
472 /* We can free up the register page we allocated. */
473 free_page(lg->cpus[i].regs_page);
474 /*
475 * Now all the memory cleanups are done, it's safe to release
476 * the Launcher's memory management structure.
477 */
478 mmput(lg->cpus[i].mm);
479 }
480
481 /* Release any eventfds they registered. */
482 for (i = 0; i < lg->eventfds->num; i++)
483 eventfd_ctx_put(lg->eventfds->map[i].event);
484 kfree(lg->eventfds);
485
486 /*
487 * If lg->dead doesn't contain an error code it will be NULL or a
488 * kmalloc()ed string, either of which is ok to hand to kfree().
489 */
490 if (!IS_ERR(lg->dead))
491 kfree(lg->dead);
492 /* Free the memory allocated to the lguest_struct */
493 kfree(lg);
494 /* Release lock and exit. */
495 mutex_unlock(&lguest_lock);
496
497 return 0;
498}
499
500/*L:000
501 * Welcome to our journey through the Launcher!
502 *
503 * The Launcher is the Host userspace program which sets up, runs and services
504 * the Guest. In fact, many comments in the Drivers which refer to "the Host"
505 * doing things are inaccurate: the Launcher does all the device handling for
506 * the Guest, but the Guest can't know that.
507 *
508 * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we
509 * shall see more of that later.
510 *
511 * We begin our understanding with the Host kernel interface which the Launcher
512 * uses: reading and writing a character device called /dev/lguest. All the
513 * work happens in the read(), write() and close() routines:
514 */
515static const struct file_operations lguest_fops = {
516 .owner = THIS_MODULE,
517 .release = close,
518 .write = write,
519 .read = read,
520 .llseek = default_llseek,
521};
522/*:*/
523
524/*
525 * This is a textbook example of a "misc" character device. Populate a "struct
526 * miscdevice" and register it with misc_register().
527 */
528static struct miscdevice lguest_dev = {
529 .minor = MISC_DYNAMIC_MINOR,
530 .name = "lguest",
531 .fops = &lguest_fops,
532};
533
534int __init lguest_device_init(void)
535{
536 return misc_register(&lguest_dev);
537}
538
539void __exit lguest_device_remove(void)
540{
541 misc_deregister(&lguest_dev);
542}