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Commit | Line | Data |
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a91d74a3 | 1 | /*P:200 This contains all the /dev/lguest code, whereby the userspace launcher |
f938d2c8 | 2 | * controls and communicates with the Guest. For example, the first write will |
a91d74a3 RR |
3 | * tell us the Guest's memory layout and entry point. A read will run the |
4 | * Guest until something happens, such as a signal or the Guest doing a NOTIFY | |
5 | * out to the Launcher. | |
2e04ef76 | 6 | :*/ |
d7e28ffe RR |
7 | #include <linux/uaccess.h> |
8 | #include <linux/miscdevice.h> | |
9 | #include <linux/fs.h> | |
ca94f2bd | 10 | #include <linux/sched.h> |
df60aeef RR |
11 | #include <linux/eventfd.h> |
12 | #include <linux/file.h> | |
5a0e3ad6 | 13 | #include <linux/slab.h> |
d7e28ffe RR |
14 | #include "lg.h" |
15 | ||
a91d74a3 RR |
16 | /*L:056 |
17 | * Before we move on, let's jump ahead and look at what the kernel does when | |
18 | * it needs to look up the eventfds. That will complete our picture of how we | |
19 | * use RCU. | |
20 | * | |
21 | * The notification value is in cpu->pending_notify: we return true if it went | |
22 | * to an eventfd. | |
23 | */ | |
df60aeef RR |
24 | bool send_notify_to_eventfd(struct lg_cpu *cpu) |
25 | { | |
26 | unsigned int i; | |
27 | struct lg_eventfd_map *map; | |
28 | ||
a91d74a3 RR |
29 | /* |
30 | * This "rcu_read_lock()" helps track when someone is still looking at | |
31 | * the (RCU-using) eventfds array. It's not actually a lock at all; | |
32 | * indeed it's a noop in many configurations. (You didn't expect me to | |
33 | * explain all the RCU secrets here, did you?) | |
34 | */ | |
df60aeef | 35 | rcu_read_lock(); |
a91d74a3 RR |
36 | /* |
37 | * rcu_dereference is the counter-side of rcu_assign_pointer(); it | |
38 | * makes sure we don't access the memory pointed to by | |
39 | * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy, | |
40 | * but Alpha allows this! Paul McKenney points out that a really | |
41 | * aggressive compiler could have the same effect: | |
42 | * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html | |
43 | * | |
44 | * So play safe, use rcu_dereference to get the rcu-protected pointer: | |
45 | */ | |
df60aeef | 46 | map = rcu_dereference(cpu->lg->eventfds); |
a91d74a3 RR |
47 | /* |
48 | * Simple array search: even if they add an eventfd while we do this, | |
49 | * we'll continue to use the old array and just won't see the new one. | |
50 | */ | |
df60aeef RR |
51 | for (i = 0; i < map->num; i++) { |
52 | if (map->map[i].addr == cpu->pending_notify) { | |
53 | eventfd_signal(map->map[i].event, 1); | |
54 | cpu->pending_notify = 0; | |
55 | break; | |
56 | } | |
57 | } | |
a91d74a3 | 58 | /* We're done with the rcu-protected variable cpu->lg->eventfds. */ |
df60aeef | 59 | rcu_read_unlock(); |
a91d74a3 RR |
60 | |
61 | /* If we cleared the notification, it's because we found a match. */ | |
df60aeef RR |
62 | return cpu->pending_notify == 0; |
63 | } | |
64 | ||
a91d74a3 RR |
65 | /*L:055 |
66 | * One of the more tricksy tricks in the Linux Kernel is a technique called | |
67 | * Read Copy Update. Since one point of lguest is to teach lguest journeyers | |
68 | * about kernel coding, I use it here. (In case you're curious, other purposes | |
69 | * include learning about virtualization and instilling a deep appreciation for | |
70 | * simplicity and puppies). | |
71 | * | |
72 | * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we | |
73 | * add new eventfds without ever blocking readers from accessing the array. | |
74 | * The current Launcher only does this during boot, so that never happens. But | |
75 | * Read Copy Update is cool, and adding a lock risks damaging even more puppies | |
76 | * than this code does. | |
77 | * | |
78 | * We allocate a brand new one-larger array, copy the old one and add our new | |
79 | * element. Then we make the lg eventfd pointer point to the new array. | |
80 | * That's the easy part: now we need to free the old one, but we need to make | |
81 | * sure no slow CPU somewhere is still looking at it. That's what | |
82 | * synchronize_rcu does for us: waits until every CPU has indicated that it has | |
83 | * moved on to know it's no longer using the old one. | |
84 | * | |
85 | * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update. | |
86 | */ | |
df60aeef RR |
87 | static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) |
88 | { | |
89 | struct lg_eventfd_map *new, *old = lg->eventfds; | |
90 | ||
a91d74a3 RR |
91 | /* |
92 | * We don't allow notifications on value 0 anyway (pending_notify of | |
93 | * 0 means "nothing pending"). | |
94 | */ | |
df60aeef RR |
95 | if (!addr) |
96 | return -EINVAL; | |
97 | ||
2e04ef76 RR |
98 | /* |
99 | * Replace the old array with the new one, carefully: others can | |
100 | * be accessing it at the same time. | |
101 | */ | |
df60aeef RR |
102 | new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), |
103 | GFP_KERNEL); | |
104 | if (!new) | |
105 | return -ENOMEM; | |
106 | ||
107 | /* First make identical copy. */ | |
108 | memcpy(new->map, old->map, sizeof(old->map[0]) * old->num); | |
109 | new->num = old->num; | |
110 | ||
111 | /* Now append new entry. */ | |
112 | new->map[new->num].addr = addr; | |
13389010 | 113 | new->map[new->num].event = eventfd_ctx_fdget(fd); |
df60aeef | 114 | if (IS_ERR(new->map[new->num].event)) { |
f2945262 | 115 | int err = PTR_ERR(new->map[new->num].event); |
df60aeef | 116 | kfree(new); |
f2945262 | 117 | return err; |
df60aeef RR |
118 | } |
119 | new->num++; | |
120 | ||
a91d74a3 RR |
121 | /* |
122 | * Now put new one in place: rcu_assign_pointer() is a fancy way of | |
123 | * doing "lg->eventfds = new", but it uses memory barriers to make | |
124 | * absolutely sure that the contents of "new" written above is nailed | |
125 | * down before we actually do the assignment. | |
126 | * | |
127 | * We have to think about these kinds of things when we're operating on | |
128 | * live data without locks. | |
129 | */ | |
df60aeef RR |
130 | rcu_assign_pointer(lg->eventfds, new); |
131 | ||
2e04ef76 | 132 | /* |
25985edc | 133 | * We're not in a big hurry. Wait until no one's looking at old |
a91d74a3 | 134 | * version, then free it. |
2e04ef76 | 135 | */ |
df60aeef RR |
136 | synchronize_rcu(); |
137 | kfree(old); | |
138 | ||
139 | return 0; | |
140 | } | |
141 | ||
a91d74a3 RR |
142 | /*L:052 |
143 | * Receiving notifications from the Guest is usually done by attaching a | |
144 | * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will | |
145 | * become readable when the Guest does an LHCALL_NOTIFY with that value. | |
146 | * | |
147 | * This is really convenient for processing each virtqueue in a separate | |
148 | * thread. | |
149 | */ | |
df60aeef RR |
150 | static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) |
151 | { | |
152 | unsigned long addr, fd; | |
153 | int err; | |
154 | ||
155 | if (get_user(addr, input) != 0) | |
156 | return -EFAULT; | |
157 | input++; | |
158 | if (get_user(fd, input) != 0) | |
159 | return -EFAULT; | |
160 | ||
a91d74a3 RR |
161 | /* |
162 | * Just make sure two callers don't add eventfds at once. We really | |
163 | * only need to lock against callers adding to the same Guest, so using | |
164 | * the Big Lguest Lock is overkill. But this is setup, not a fast path. | |
165 | */ | |
df60aeef RR |
166 | mutex_lock(&lguest_lock); |
167 | err = add_eventfd(lg, addr, fd); | |
168 | mutex_unlock(&lguest_lock); | |
169 | ||
f2945262 | 170 | return err; |
df60aeef RR |
171 | } |
172 | ||
2e04ef76 RR |
173 | /*L:050 |
174 | * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt | |
175 | * number to /dev/lguest. | |
176 | */ | |
177e449d | 177 | static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) |
d7e28ffe | 178 | { |
511801dc | 179 | unsigned long irq; |
d7e28ffe RR |
180 | |
181 | if (get_user(irq, input) != 0) | |
182 | return -EFAULT; | |
183 | if (irq >= LGUEST_IRQS) | |
184 | return -EINVAL; | |
9f155a9b | 185 | |
a91d74a3 RR |
186 | /* |
187 | * Next time the Guest runs, the core code will see if it can deliver | |
188 | * this interrupt. | |
189 | */ | |
9f155a9b | 190 | set_interrupt(cpu, irq); |
d7e28ffe RR |
191 | return 0; |
192 | } | |
193 | ||
2e04ef76 RR |
194 | /*L:040 |
195 | * Once our Guest is initialized, the Launcher makes it run by reading | |
196 | * from /dev/lguest. | |
197 | */ | |
d7e28ffe RR |
198 | static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) |
199 | { | |
200 | struct lguest *lg = file->private_data; | |
d0953d42 GOC |
201 | struct lg_cpu *cpu; |
202 | unsigned int cpu_id = *o; | |
d7e28ffe | 203 | |
dde79789 | 204 | /* You must write LHREQ_INITIALIZE first! */ |
d7e28ffe RR |
205 | if (!lg) |
206 | return -EINVAL; | |
207 | ||
d0953d42 GOC |
208 | /* Watch out for arbitrary vcpu indexes! */ |
209 | if (cpu_id >= lg->nr_cpus) | |
210 | return -EINVAL; | |
211 | ||
212 | cpu = &lg->cpus[cpu_id]; | |
213 | ||
e1e72965 | 214 | /* If you're not the task which owns the Guest, go away. */ |
66686c2a | 215 | if (current != cpu->tsk) |
d7e28ffe RR |
216 | return -EPERM; |
217 | ||
a6bd8e13 | 218 | /* If the Guest is already dead, we indicate why */ |
d7e28ffe RR |
219 | if (lg->dead) { |
220 | size_t len; | |
221 | ||
dde79789 | 222 | /* lg->dead either contains an error code, or a string. */ |
d7e28ffe RR |
223 | if (IS_ERR(lg->dead)) |
224 | return PTR_ERR(lg->dead); | |
225 | ||
dde79789 | 226 | /* We can only return as much as the buffer they read with. */ |
d7e28ffe RR |
227 | len = min(size, strlen(lg->dead)+1); |
228 | if (copy_to_user(user, lg->dead, len) != 0) | |
229 | return -EFAULT; | |
230 | return len; | |
231 | } | |
232 | ||
2e04ef76 RR |
233 | /* |
234 | * If we returned from read() last time because the Guest sent I/O, | |
235 | * clear the flag. | |
236 | */ | |
5e232f4f GOC |
237 | if (cpu->pending_notify) |
238 | cpu->pending_notify = 0; | |
d7e28ffe | 239 | |
dde79789 | 240 | /* Run the Guest until something interesting happens. */ |
d0953d42 | 241 | return run_guest(cpu, (unsigned long __user *)user); |
d7e28ffe RR |
242 | } |
243 | ||
2e04ef76 RR |
244 | /*L:025 |
245 | * This actually initializes a CPU. For the moment, a Guest is only | |
246 | * uniprocessor, so "id" is always 0. | |
247 | */ | |
4dcc53da GOC |
248 | static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) |
249 | { | |
a6bd8e13 | 250 | /* We have a limited number the number of CPUs in the lguest struct. */ |
24adf127 | 251 | if (id >= ARRAY_SIZE(cpu->lg->cpus)) |
4dcc53da GOC |
252 | return -EINVAL; |
253 | ||
a6bd8e13 | 254 | /* Set up this CPU's id, and pointer back to the lguest struct. */ |
4dcc53da GOC |
255 | cpu->id = id; |
256 | cpu->lg = container_of((cpu - id), struct lguest, cpus[0]); | |
257 | cpu->lg->nr_cpus++; | |
a6bd8e13 RR |
258 | |
259 | /* Each CPU has a timer it can set. */ | |
ad8d8f3b | 260 | init_clockdev(cpu); |
4dcc53da | 261 | |
2e04ef76 RR |
262 | /* |
263 | * We need a complete page for the Guest registers: they are accessible | |
264 | * to the Guest and we can only grant it access to whole pages. | |
265 | */ | |
a53a35a8 GOC |
266 | cpu->regs_page = get_zeroed_page(GFP_KERNEL); |
267 | if (!cpu->regs_page) | |
268 | return -ENOMEM; | |
269 | ||
270 | /* We actually put the registers at the bottom of the page. */ | |
271 | cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs); | |
272 | ||
2e04ef76 RR |
273 | /* |
274 | * Now we initialize the Guest's registers, handing it the start | |
275 | * address. | |
276 | */ | |
a53a35a8 GOC |
277 | lguest_arch_setup_regs(cpu, start_ip); |
278 | ||
2e04ef76 RR |
279 | /* |
280 | * We keep a pointer to the Launcher task (ie. current task) for when | |
281 | * other Guests want to wake this one (eg. console input). | |
282 | */ | |
66686c2a GOC |
283 | cpu->tsk = current; |
284 | ||
2e04ef76 RR |
285 | /* |
286 | * We need to keep a pointer to the Launcher's memory map, because if | |
66686c2a | 287 | * the Launcher dies we need to clean it up. If we don't keep a |
2e04ef76 RR |
288 | * reference, it is destroyed before close() is called. |
289 | */ | |
66686c2a GOC |
290 | cpu->mm = get_task_mm(cpu->tsk); |
291 | ||
2e04ef76 RR |
292 | /* |
293 | * We remember which CPU's pages this Guest used last, for optimization | |
294 | * when the same Guest runs on the same CPU twice. | |
295 | */ | |
f34f8c5f GOC |
296 | cpu->last_pages = NULL; |
297 | ||
a6bd8e13 | 298 | /* No error == success. */ |
4dcc53da GOC |
299 | return 0; |
300 | } | |
301 | ||
2e04ef76 RR |
302 | /*L:020 |
303 | * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in | |
304 | * addition to the LHREQ_INITIALIZE value). These are: | |
dde79789 | 305 | * |
3c6b5bfa RR |
306 | * base: The start of the Guest-physical memory inside the Launcher memory. |
307 | * | |
dde79789 | 308 | * pfnlimit: The highest (Guest-physical) page number the Guest should be |
e1e72965 RR |
309 | * allowed to access. The Guest memory lives inside the Launcher, so it sets |
310 | * this to ensure the Guest can only reach its own memory. | |
dde79789 | 311 | * |
dde79789 | 312 | * start: The first instruction to execute ("eip" in x86-speak). |
dde79789 | 313 | */ |
511801dc | 314 | static int initialize(struct file *file, const unsigned long __user *input) |
d7e28ffe | 315 | { |
2e04ef76 | 316 | /* "struct lguest" contains all we (the Host) know about a Guest. */ |
d7e28ffe | 317 | struct lguest *lg; |
48245cc0 | 318 | int err; |
58a24566 | 319 | unsigned long args[3]; |
d7e28ffe | 320 | |
2e04ef76 RR |
321 | /* |
322 | * We grab the Big Lguest lock, which protects against multiple | |
323 | * simultaneous initializations. | |
324 | */ | |
d7e28ffe | 325 | mutex_lock(&lguest_lock); |
dde79789 | 326 | /* You can't initialize twice! Close the device and start again... */ |
d7e28ffe RR |
327 | if (file->private_data) { |
328 | err = -EBUSY; | |
329 | goto unlock; | |
330 | } | |
331 | ||
332 | if (copy_from_user(args, input, sizeof(args)) != 0) { | |
333 | err = -EFAULT; | |
334 | goto unlock; | |
335 | } | |
336 | ||
48245cc0 RR |
337 | lg = kzalloc(sizeof(*lg), GFP_KERNEL); |
338 | if (!lg) { | |
339 | err = -ENOMEM; | |
d7e28ffe RR |
340 | goto unlock; |
341 | } | |
dde79789 | 342 | |
df60aeef RR |
343 | lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL); |
344 | if (!lg->eventfds) { | |
345 | err = -ENOMEM; | |
346 | goto free_lg; | |
347 | } | |
348 | lg->eventfds->num = 0; | |
349 | ||
dde79789 | 350 | /* Populate the easy fields of our "struct lguest" */ |
74dbf719 | 351 | lg->mem_base = (void __user *)args[0]; |
3c6b5bfa | 352 | lg->pfn_limit = args[1]; |
dde79789 | 353 | |
58a24566 MZ |
354 | /* This is the first cpu (cpu 0) and it will start booting at args[2] */ |
355 | err = lg_cpu_start(&lg->cpus[0], 0, args[2]); | |
4dcc53da | 356 | if (err) |
df60aeef | 357 | goto free_eventfds; |
4dcc53da | 358 | |
2e04ef76 RR |
359 | /* |
360 | * Initialize the Guest's shadow page tables, using the toplevel | |
361 | * address the Launcher gave us. This allocates memory, so can fail. | |
362 | */ | |
58a24566 | 363 | err = init_guest_pagetable(lg); |
d7e28ffe RR |
364 | if (err) |
365 | goto free_regs; | |
366 | ||
dde79789 | 367 | /* We keep our "struct lguest" in the file's private_data. */ |
d7e28ffe RR |
368 | file->private_data = lg; |
369 | ||
370 | mutex_unlock(&lguest_lock); | |
371 | ||
dde79789 | 372 | /* And because this is a write() call, we return the length used. */ |
d7e28ffe RR |
373 | return sizeof(args); |
374 | ||
375 | free_regs: | |
a53a35a8 GOC |
376 | /* FIXME: This should be in free_vcpu */ |
377 | free_page(lg->cpus[0].regs_page); | |
df60aeef RR |
378 | free_eventfds: |
379 | kfree(lg->eventfds); | |
380 | free_lg: | |
43054412 | 381 | kfree(lg); |
d7e28ffe RR |
382 | unlock: |
383 | mutex_unlock(&lguest_lock); | |
384 | return err; | |
385 | } | |
386 | ||
2e04ef76 RR |
387 | /*L:010 |
388 | * The first operation the Launcher does must be a write. All writes | |
e1e72965 | 389 | * start with an unsigned long number: for the first write this must be |
dde79789 | 390 | * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use |
a91d74a3 | 391 | * writes of other values to send interrupts or set up receipt of notifications. |
a6bd8e13 RR |
392 | * |
393 | * Note that we overload the "offset" in the /dev/lguest file to indicate what | |
a91d74a3 | 394 | * CPU number we're dealing with. Currently this is always 0 since we only |
a6bd8e13 | 395 | * support uniprocessor Guests, but you can see the beginnings of SMP support |
2e04ef76 RR |
396 | * here. |
397 | */ | |
511801dc | 398 | static ssize_t write(struct file *file, const char __user *in, |
d7e28ffe RR |
399 | size_t size, loff_t *off) |
400 | { | |
2e04ef76 RR |
401 | /* |
402 | * Once the Guest is initialized, we hold the "struct lguest" in the | |
403 | * file private data. | |
404 | */ | |
d7e28ffe | 405 | struct lguest *lg = file->private_data; |
511801dc JS |
406 | const unsigned long __user *input = (const unsigned long __user *)in; |
407 | unsigned long req; | |
177e449d | 408 | struct lg_cpu *uninitialized_var(cpu); |
7ea07a15 | 409 | unsigned int cpu_id = *off; |
d7e28ffe | 410 | |
a6bd8e13 | 411 | /* The first value tells us what this request is. */ |
d7e28ffe RR |
412 | if (get_user(req, input) != 0) |
413 | return -EFAULT; | |
511801dc | 414 | input++; |
d7e28ffe | 415 | |
dde79789 | 416 | /* If you haven't initialized, you must do that first. */ |
7ea07a15 GOC |
417 | if (req != LHREQ_INITIALIZE) { |
418 | if (!lg || (cpu_id >= lg->nr_cpus)) | |
419 | return -EINVAL; | |
420 | cpu = &lg->cpus[cpu_id]; | |
dde79789 | 421 | |
f73d1e6c ET |
422 | /* Once the Guest is dead, you can only read() why it died. */ |
423 | if (lg->dead) | |
424 | return -ENOENT; | |
f73d1e6c | 425 | } |
d7e28ffe RR |
426 | |
427 | switch (req) { | |
428 | case LHREQ_INITIALIZE: | |
511801dc | 429 | return initialize(file, input); |
d7e28ffe | 430 | case LHREQ_IRQ: |
177e449d | 431 | return user_send_irq(cpu, input); |
df60aeef RR |
432 | case LHREQ_EVENTFD: |
433 | return attach_eventfd(lg, input); | |
d7e28ffe RR |
434 | default: |
435 | return -EINVAL; | |
436 | } | |
437 | } | |
438 | ||
2e04ef76 RR |
439 | /*L:060 |
440 | * The final piece of interface code is the close() routine. It reverses | |
dde79789 RR |
441 | * everything done in initialize(). This is usually called because the |
442 | * Launcher exited. | |
443 | * | |
444 | * Note that the close routine returns 0 or a negative error number: it can't | |
445 | * really fail, but it can whine. I blame Sun for this wart, and K&R C for | |
2e04ef76 RR |
446 | * letting them do it. |
447 | :*/ | |
d7e28ffe RR |
448 | static int close(struct inode *inode, struct file *file) |
449 | { | |
450 | struct lguest *lg = file->private_data; | |
ad8d8f3b | 451 | unsigned int i; |
d7e28ffe | 452 | |
dde79789 | 453 | /* If we never successfully initialized, there's nothing to clean up */ |
d7e28ffe RR |
454 | if (!lg) |
455 | return 0; | |
456 | ||
2e04ef76 RR |
457 | /* |
458 | * We need the big lock, to protect from inter-guest I/O and other | |
459 | * Launchers initializing guests. | |
460 | */ | |
d7e28ffe | 461 | mutex_lock(&lguest_lock); |
66686c2a GOC |
462 | |
463 | /* Free up the shadow page tables for the Guest. */ | |
464 | free_guest_pagetable(lg); | |
465 | ||
a53a35a8 | 466 | for (i = 0; i < lg->nr_cpus; i++) { |
ad8d8f3b GOC |
467 | /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ |
468 | hrtimer_cancel(&lg->cpus[i].hrt); | |
a53a35a8 GOC |
469 | /* We can free up the register page we allocated. */ |
470 | free_page(lg->cpus[i].regs_page); | |
2e04ef76 RR |
471 | /* |
472 | * Now all the memory cleanups are done, it's safe to release | |
473 | * the Launcher's memory management structure. | |
474 | */ | |
66686c2a | 475 | mmput(lg->cpus[i].mm); |
a53a35a8 | 476 | } |
df60aeef RR |
477 | |
478 | /* Release any eventfds they registered. */ | |
479 | for (i = 0; i < lg->eventfds->num; i++) | |
13389010 | 480 | eventfd_ctx_put(lg->eventfds->map[i].event); |
df60aeef RR |
481 | kfree(lg->eventfds); |
482 | ||
2e04ef76 RR |
483 | /* |
484 | * If lg->dead doesn't contain an error code it will be NULL or a | |
485 | * kmalloc()ed string, either of which is ok to hand to kfree(). | |
486 | */ | |
d7e28ffe RR |
487 | if (!IS_ERR(lg->dead)) |
488 | kfree(lg->dead); | |
05dfdbbd MW |
489 | /* Free the memory allocated to the lguest_struct */ |
490 | kfree(lg); | |
dde79789 | 491 | /* Release lock and exit. */ |
d7e28ffe | 492 | mutex_unlock(&lguest_lock); |
dde79789 | 493 | |
d7e28ffe RR |
494 | return 0; |
495 | } | |
496 | ||
dde79789 RR |
497 | /*L:000 |
498 | * Welcome to our journey through the Launcher! | |
499 | * | |
500 | * The Launcher is the Host userspace program which sets up, runs and services | |
501 | * the Guest. In fact, many comments in the Drivers which refer to "the Host" | |
502 | * doing things are inaccurate: the Launcher does all the device handling for | |
e1e72965 | 503 | * the Guest, but the Guest can't know that. |
dde79789 RR |
504 | * |
505 | * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we | |
506 | * shall see more of that later. | |
507 | * | |
508 | * We begin our understanding with the Host kernel interface which the Launcher | |
509 | * uses: reading and writing a character device called /dev/lguest. All the | |
2e04ef76 RR |
510 | * work happens in the read(), write() and close() routines: |
511 | */ | |
828c0950 | 512 | static const struct file_operations lguest_fops = { |
d7e28ffe RR |
513 | .owner = THIS_MODULE, |
514 | .release = close, | |
515 | .write = write, | |
516 | .read = read, | |
6038f373 | 517 | .llseek = default_llseek, |
d7e28ffe | 518 | }; |
dde79789 | 519 | |
2e04ef76 RR |
520 | /* |
521 | * This is a textbook example of a "misc" character device. Populate a "struct | |
522 | * miscdevice" and register it with misc_register(). | |
523 | */ | |
d7e28ffe RR |
524 | static struct miscdevice lguest_dev = { |
525 | .minor = MISC_DYNAMIC_MINOR, | |
526 | .name = "lguest", | |
527 | .fops = &lguest_fops, | |
528 | }; | |
529 | ||
530 | int __init lguest_device_init(void) | |
531 | { | |
532 | return misc_register(&lguest_dev); | |
533 | } | |
534 | ||
535 | void __exit lguest_device_remove(void) | |
536 | { | |
537 | misc_deregister(&lguest_dev); | |
538 | } |