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Commit | Line | Data |
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9f54288d RR |
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. | |
2e04ef76 | 8 | :*/ |
d7e28ffe RR |
9 | #include <linux/uaccess.h> |
10 | #include <linux/miscdevice.h> | |
11 | #include <linux/fs.h> | |
ca94f2bd | 12 | #include <linux/sched.h> |
df60aeef RR |
13 | #include <linux/eventfd.h> |
14 | #include <linux/file.h> | |
5a0e3ad6 | 15 | #include <linux/slab.h> |
d7e28ffe RR |
16 | #include "lg.h" |
17 | ||
a91d74a3 RR |
18 | /*L:056 |
19 | * Before we move on, let's jump ahead and look at what the kernel does when | |
20 | * it needs to look up the eventfds. That will complete our picture of how we | |
21 | * use RCU. | |
22 | * | |
23 | * The notification value is in cpu->pending_notify: we return true if it went | |
24 | * to an eventfd. | |
25 | */ | |
df60aeef RR |
26 | bool send_notify_to_eventfd(struct lg_cpu *cpu) |
27 | { | |
28 | unsigned int i; | |
29 | struct lg_eventfd_map *map; | |
30 | ||
a91d74a3 RR |
31 | /* |
32 | * This "rcu_read_lock()" helps track when someone is still looking at | |
33 | * the (RCU-using) eventfds array. It's not actually a lock at all; | |
34 | * indeed it's a noop in many configurations. (You didn't expect me to | |
35 | * explain all the RCU secrets here, did you?) | |
36 | */ | |
df60aeef | 37 | rcu_read_lock(); |
a91d74a3 RR |
38 | /* |
39 | * rcu_dereference is the counter-side of rcu_assign_pointer(); it | |
40 | * makes sure we don't access the memory pointed to by | |
41 | * cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy, | |
42 | * but Alpha allows this! Paul McKenney points out that a really | |
43 | * aggressive compiler could have the same effect: | |
44 | * http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html | |
45 | * | |
46 | * So play safe, use rcu_dereference to get the rcu-protected pointer: | |
47 | */ | |
df60aeef | 48 | map = rcu_dereference(cpu->lg->eventfds); |
a91d74a3 RR |
49 | /* |
50 | * Simple array search: even if they add an eventfd while we do this, | |
51 | * we'll continue to use the old array and just won't see the new one. | |
52 | */ | |
df60aeef RR |
53 | for (i = 0; i < map->num; i++) { |
54 | if (map->map[i].addr == cpu->pending_notify) { | |
55 | eventfd_signal(map->map[i].event, 1); | |
56 | cpu->pending_notify = 0; | |
57 | break; | |
58 | } | |
59 | } | |
a91d74a3 | 60 | /* We're done with the rcu-protected variable cpu->lg->eventfds. */ |
df60aeef | 61 | rcu_read_unlock(); |
a91d74a3 RR |
62 | |
63 | /* If we cleared the notification, it's because we found a match. */ | |
df60aeef RR |
64 | return cpu->pending_notify == 0; |
65 | } | |
66 | ||
a91d74a3 RR |
67 | /*L:055 |
68 | * One of the more tricksy tricks in the Linux Kernel is a technique called | |
69 | * Read Copy Update. Since one point of lguest is to teach lguest journeyers | |
70 | * about kernel coding, I use it here. (In case you're curious, other purposes | |
71 | * include learning about virtualization and instilling a deep appreciation for | |
72 | * simplicity and puppies). | |
73 | * | |
74 | * We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we | |
75 | * add new eventfds without ever blocking readers from accessing the array. | |
76 | * The current Launcher only does this during boot, so that never happens. But | |
77 | * Read Copy Update is cool, and adding a lock risks damaging even more puppies | |
78 | * than this code does. | |
79 | * | |
80 | * We allocate a brand new one-larger array, copy the old one and add our new | |
81 | * element. Then we make the lg eventfd pointer point to the new array. | |
82 | * That's the easy part: now we need to free the old one, but we need to make | |
83 | * sure no slow CPU somewhere is still looking at it. That's what | |
84 | * synchronize_rcu does for us: waits until every CPU has indicated that it has | |
85 | * moved on to know it's no longer using the old one. | |
86 | * | |
87 | * If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update. | |
88 | */ | |
df60aeef RR |
89 | static int add_eventfd(struct lguest *lg, unsigned long addr, int fd) |
90 | { | |
91 | struct lg_eventfd_map *new, *old = lg->eventfds; | |
92 | ||
a91d74a3 RR |
93 | /* |
94 | * We don't allow notifications on value 0 anyway (pending_notify of | |
95 | * 0 means "nothing pending"). | |
96 | */ | |
df60aeef RR |
97 | if (!addr) |
98 | return -EINVAL; | |
99 | ||
2e04ef76 RR |
100 | /* |
101 | * Replace the old array with the new one, carefully: others can | |
102 | * be accessing it at the same time. | |
103 | */ | |
df60aeef RR |
104 | new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1), |
105 | GFP_KERNEL); | |
106 | if (!new) | |
107 | return -ENOMEM; | |
108 | ||
109 | /* First make identical copy. */ | |
110 | memcpy(new->map, old->map, sizeof(old->map[0]) * old->num); | |
111 | new->num = old->num; | |
112 | ||
113 | /* Now append new entry. */ | |
114 | new->map[new->num].addr = addr; | |
13389010 | 115 | new->map[new->num].event = eventfd_ctx_fdget(fd); |
df60aeef | 116 | if (IS_ERR(new->map[new->num].event)) { |
f2945262 | 117 | int err = PTR_ERR(new->map[new->num].event); |
df60aeef | 118 | kfree(new); |
f2945262 | 119 | return err; |
df60aeef RR |
120 | } |
121 | new->num++; | |
122 | ||
a91d74a3 RR |
123 | /* |
124 | * Now put new one in place: rcu_assign_pointer() is a fancy way of | |
125 | * doing "lg->eventfds = new", but it uses memory barriers to make | |
126 | * absolutely sure that the contents of "new" written above is nailed | |
127 | * down before we actually do the assignment. | |
128 | * | |
129 | * We have to think about these kinds of things when we're operating on | |
130 | * live data without locks. | |
131 | */ | |
df60aeef RR |
132 | rcu_assign_pointer(lg->eventfds, new); |
133 | ||
2e04ef76 | 134 | /* |
25985edc | 135 | * We're not in a big hurry. Wait until no one's looking at old |
a91d74a3 | 136 | * version, then free it. |
2e04ef76 | 137 | */ |
df60aeef RR |
138 | synchronize_rcu(); |
139 | kfree(old); | |
140 | ||
141 | return 0; | |
142 | } | |
143 | ||
a91d74a3 RR |
144 | /*L:052 |
145 | * Receiving notifications from the Guest is usually done by attaching a | |
146 | * particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will | |
147 | * become readable when the Guest does an LHCALL_NOTIFY with that value. | |
148 | * | |
149 | * This is really convenient for processing each virtqueue in a separate | |
150 | * thread. | |
151 | */ | |
df60aeef RR |
152 | static int attach_eventfd(struct lguest *lg, const unsigned long __user *input) |
153 | { | |
154 | unsigned long addr, fd; | |
155 | int err; | |
156 | ||
157 | if (get_user(addr, input) != 0) | |
158 | return -EFAULT; | |
159 | input++; | |
160 | if (get_user(fd, input) != 0) | |
161 | return -EFAULT; | |
162 | ||
a91d74a3 RR |
163 | /* |
164 | * Just make sure two callers don't add eventfds at once. We really | |
165 | * only need to lock against callers adding to the same Guest, so using | |
166 | * the Big Lguest Lock is overkill. But this is setup, not a fast path. | |
167 | */ | |
df60aeef RR |
168 | mutex_lock(&lguest_lock); |
169 | err = add_eventfd(lg, addr, fd); | |
170 | mutex_unlock(&lguest_lock); | |
171 | ||
f2945262 | 172 | return err; |
df60aeef RR |
173 | } |
174 | ||
2e04ef76 RR |
175 | /*L:050 |
176 | * Sending an interrupt is done by writing LHREQ_IRQ and an interrupt | |
177 | * number to /dev/lguest. | |
178 | */ | |
177e449d | 179 | static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input) |
d7e28ffe | 180 | { |
511801dc | 181 | unsigned long irq; |
d7e28ffe RR |
182 | |
183 | if (get_user(irq, input) != 0) | |
184 | return -EFAULT; | |
185 | if (irq >= LGUEST_IRQS) | |
186 | return -EINVAL; | |
9f155a9b | 187 | |
a91d74a3 RR |
188 | /* |
189 | * Next time the Guest runs, the core code will see if it can deliver | |
190 | * this interrupt. | |
191 | */ | |
9f155a9b | 192 | set_interrupt(cpu, irq); |
d7e28ffe RR |
193 | return 0; |
194 | } | |
195 | ||
2e04ef76 RR |
196 | /*L:040 |
197 | * Once our Guest is initialized, the Launcher makes it run by reading | |
198 | * from /dev/lguest. | |
199 | */ | |
d7e28ffe RR |
200 | static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) |
201 | { | |
202 | struct lguest *lg = file->private_data; | |
d0953d42 GOC |
203 | struct lg_cpu *cpu; |
204 | unsigned int cpu_id = *o; | |
d7e28ffe | 205 | |
dde79789 | 206 | /* You must write LHREQ_INITIALIZE first! */ |
d7e28ffe RR |
207 | if (!lg) |
208 | return -EINVAL; | |
209 | ||
d0953d42 GOC |
210 | /* Watch out for arbitrary vcpu indexes! */ |
211 | if (cpu_id >= lg->nr_cpus) | |
212 | return -EINVAL; | |
213 | ||
214 | cpu = &lg->cpus[cpu_id]; | |
215 | ||
e1e72965 | 216 | /* If you're not the task which owns the Guest, go away. */ |
66686c2a | 217 | if (current != cpu->tsk) |
d7e28ffe RR |
218 | return -EPERM; |
219 | ||
a6bd8e13 | 220 | /* If the Guest is already dead, we indicate why */ |
d7e28ffe RR |
221 | if (lg->dead) { |
222 | size_t len; | |
223 | ||
dde79789 | 224 | /* lg->dead either contains an error code, or a string. */ |
d7e28ffe RR |
225 | if (IS_ERR(lg->dead)) |
226 | return PTR_ERR(lg->dead); | |
227 | ||
dde79789 | 228 | /* We can only return as much as the buffer they read with. */ |
d7e28ffe RR |
229 | len = min(size, strlen(lg->dead)+1); |
230 | if (copy_to_user(user, lg->dead, len) != 0) | |
231 | return -EFAULT; | |
232 | return len; | |
233 | } | |
234 | ||
2e04ef76 RR |
235 | /* |
236 | * If we returned from read() last time because the Guest sent I/O, | |
237 | * clear the flag. | |
238 | */ | |
5e232f4f GOC |
239 | if (cpu->pending_notify) |
240 | cpu->pending_notify = 0; | |
d7e28ffe | 241 | |
dde79789 | 242 | /* Run the Guest until something interesting happens. */ |
d0953d42 | 243 | return run_guest(cpu, (unsigned long __user *)user); |
d7e28ffe RR |
244 | } |
245 | ||
2e04ef76 RR |
246 | /*L:025 |
247 | * This actually initializes a CPU. For the moment, a Guest is only | |
248 | * uniprocessor, so "id" is always 0. | |
249 | */ | |
4dcc53da GOC |
250 | static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) |
251 | { | |
a6bd8e13 | 252 | /* We have a limited number the number of CPUs in the lguest struct. */ |
24adf127 | 253 | if (id >= ARRAY_SIZE(cpu->lg->cpus)) |
4dcc53da GOC |
254 | return -EINVAL; |
255 | ||
a6bd8e13 | 256 | /* Set up this CPU's id, and pointer back to the lguest struct. */ |
4dcc53da GOC |
257 | cpu->id = id; |
258 | cpu->lg = container_of((cpu - id), struct lguest, cpus[0]); | |
259 | cpu->lg->nr_cpus++; | |
a6bd8e13 RR |
260 | |
261 | /* Each CPU has a timer it can set. */ | |
ad8d8f3b | 262 | init_clockdev(cpu); |
4dcc53da | 263 | |
2e04ef76 RR |
264 | /* |
265 | * We need a complete page for the Guest registers: they are accessible | |
266 | * to the Guest and we can only grant it access to whole pages. | |
267 | */ | |
a53a35a8 GOC |
268 | cpu->regs_page = get_zeroed_page(GFP_KERNEL); |
269 | if (!cpu->regs_page) | |
270 | return -ENOMEM; | |
271 | ||
272 | /* We actually put the registers at the bottom of the page. */ | |
273 | cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs); | |
274 | ||
2e04ef76 RR |
275 | /* |
276 | * Now we initialize the Guest's registers, handing it the start | |
277 | * address. | |
278 | */ | |
a53a35a8 GOC |
279 | lguest_arch_setup_regs(cpu, start_ip); |
280 | ||
2e04ef76 RR |
281 | /* |
282 | * We keep a pointer to the Launcher task (ie. current task) for when | |
283 | * other Guests want to wake this one (eg. console input). | |
284 | */ | |
66686c2a GOC |
285 | cpu->tsk = current; |
286 | ||
2e04ef76 RR |
287 | /* |
288 | * We need to keep a pointer to the Launcher's memory map, because if | |
66686c2a | 289 | * the Launcher dies we need to clean it up. If we don't keep a |
2e04ef76 RR |
290 | * reference, it is destroyed before close() is called. |
291 | */ | |
66686c2a GOC |
292 | cpu->mm = get_task_mm(cpu->tsk); |
293 | ||
2e04ef76 RR |
294 | /* |
295 | * We remember which CPU's pages this Guest used last, for optimization | |
296 | * when the same Guest runs on the same CPU twice. | |
297 | */ | |
f34f8c5f GOC |
298 | cpu->last_pages = NULL; |
299 | ||
a6bd8e13 | 300 | /* No error == success. */ |
4dcc53da GOC |
301 | return 0; |
302 | } | |
303 | ||
2e04ef76 RR |
304 | /*L:020 |
305 | * The initialization write supplies 3 pointer sized (32 or 64 bit) values (in | |
306 | * addition to the LHREQ_INITIALIZE value). These are: | |
dde79789 | 307 | * |
3c6b5bfa RR |
308 | * base: The start of the Guest-physical memory inside the Launcher memory. |
309 | * | |
dde79789 | 310 | * pfnlimit: The highest (Guest-physical) page number the Guest should be |
e1e72965 RR |
311 | * allowed to access. The Guest memory lives inside the Launcher, so it sets |
312 | * this to ensure the Guest can only reach its own memory. | |
dde79789 | 313 | * |
dde79789 | 314 | * start: The first instruction to execute ("eip" in x86-speak). |
dde79789 | 315 | */ |
511801dc | 316 | static int initialize(struct file *file, const unsigned long __user *input) |
d7e28ffe | 317 | { |
2e04ef76 | 318 | /* "struct lguest" contains all we (the Host) know about a Guest. */ |
d7e28ffe | 319 | struct lguest *lg; |
48245cc0 | 320 | int err; |
58a24566 | 321 | unsigned long args[3]; |
d7e28ffe | 322 | |
2e04ef76 RR |
323 | /* |
324 | * We grab the Big Lguest lock, which protects against multiple | |
325 | * simultaneous initializations. | |
326 | */ | |
d7e28ffe | 327 | mutex_lock(&lguest_lock); |
dde79789 | 328 | /* You can't initialize twice! Close the device and start again... */ |
d7e28ffe RR |
329 | if (file->private_data) { |
330 | err = -EBUSY; | |
331 | goto unlock; | |
332 | } | |
333 | ||
334 | if (copy_from_user(args, input, sizeof(args)) != 0) { | |
335 | err = -EFAULT; | |
336 | goto unlock; | |
337 | } | |
338 | ||
48245cc0 RR |
339 | lg = kzalloc(sizeof(*lg), GFP_KERNEL); |
340 | if (!lg) { | |
341 | err = -ENOMEM; | |
d7e28ffe RR |
342 | goto unlock; |
343 | } | |
dde79789 | 344 | |
df60aeef RR |
345 | lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL); |
346 | if (!lg->eventfds) { | |
347 | err = -ENOMEM; | |
348 | goto free_lg; | |
349 | } | |
350 | lg->eventfds->num = 0; | |
351 | ||
dde79789 | 352 | /* Populate the easy fields of our "struct lguest" */ |
74dbf719 | 353 | lg->mem_base = (void __user *)args[0]; |
3c6b5bfa | 354 | lg->pfn_limit = args[1]; |
dde79789 | 355 | |
58a24566 MZ |
356 | /* This is the first cpu (cpu 0) and it will start booting at args[2] */ |
357 | err = lg_cpu_start(&lg->cpus[0], 0, args[2]); | |
4dcc53da | 358 | if (err) |
df60aeef | 359 | goto free_eventfds; |
4dcc53da | 360 | |
2e04ef76 | 361 | /* |
9f54288d RR |
362 | * Initialize the Guest's shadow page tables. This allocates |
363 | * memory, so can fail. | |
2e04ef76 | 364 | */ |
58a24566 | 365 | err = init_guest_pagetable(lg); |
d7e28ffe RR |
366 | if (err) |
367 | goto free_regs; | |
368 | ||
dde79789 | 369 | /* We keep our "struct lguest" in the file's private_data. */ |
d7e28ffe RR |
370 | file->private_data = lg; |
371 | ||
372 | mutex_unlock(&lguest_lock); | |
373 | ||
dde79789 | 374 | /* And because this is a write() call, we return the length used. */ |
d7e28ffe RR |
375 | return sizeof(args); |
376 | ||
377 | free_regs: | |
a53a35a8 GOC |
378 | /* FIXME: This should be in free_vcpu */ |
379 | free_page(lg->cpus[0].regs_page); | |
df60aeef RR |
380 | free_eventfds: |
381 | kfree(lg->eventfds); | |
382 | free_lg: | |
43054412 | 383 | kfree(lg); |
d7e28ffe RR |
384 | unlock: |
385 | mutex_unlock(&lguest_lock); | |
386 | return err; | |
387 | } | |
388 | ||
2e04ef76 RR |
389 | /*L:010 |
390 | * The first operation the Launcher does must be a write. All writes | |
e1e72965 | 391 | * start with an unsigned long number: for the first write this must be |
dde79789 | 392 | * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use |
a91d74a3 | 393 | * writes of other values to send interrupts or set up receipt of notifications. |
a6bd8e13 RR |
394 | * |
395 | * Note that we overload the "offset" in the /dev/lguest file to indicate what | |
a91d74a3 | 396 | * CPU number we're dealing with. Currently this is always 0 since we only |
a6bd8e13 | 397 | * support uniprocessor Guests, but you can see the beginnings of SMP support |
2e04ef76 RR |
398 | * here. |
399 | */ | |
511801dc | 400 | static ssize_t write(struct file *file, const char __user *in, |
d7e28ffe RR |
401 | size_t size, loff_t *off) |
402 | { | |
2e04ef76 RR |
403 | /* |
404 | * Once the Guest is initialized, we hold the "struct lguest" in the | |
405 | * file private data. | |
406 | */ | |
d7e28ffe | 407 | struct lguest *lg = file->private_data; |
511801dc JS |
408 | const unsigned long __user *input = (const unsigned long __user *)in; |
409 | unsigned long req; | |
177e449d | 410 | struct lg_cpu *uninitialized_var(cpu); |
7ea07a15 | 411 | unsigned int cpu_id = *off; |
d7e28ffe | 412 | |
a6bd8e13 | 413 | /* The first value tells us what this request is. */ |
d7e28ffe RR |
414 | if (get_user(req, input) != 0) |
415 | return -EFAULT; | |
511801dc | 416 | input++; |
d7e28ffe | 417 | |
dde79789 | 418 | /* If you haven't initialized, you must do that first. */ |
7ea07a15 GOC |
419 | if (req != LHREQ_INITIALIZE) { |
420 | if (!lg || (cpu_id >= lg->nr_cpus)) | |
421 | return -EINVAL; | |
422 | cpu = &lg->cpus[cpu_id]; | |
dde79789 | 423 | |
f73d1e6c ET |
424 | /* Once the Guest is dead, you can only read() why it died. */ |
425 | if (lg->dead) | |
426 | return -ENOENT; | |
f73d1e6c | 427 | } |
d7e28ffe RR |
428 | |
429 | switch (req) { | |
430 | case LHREQ_INITIALIZE: | |
511801dc | 431 | return initialize(file, input); |
d7e28ffe | 432 | case LHREQ_IRQ: |
177e449d | 433 | return user_send_irq(cpu, input); |
df60aeef RR |
434 | case LHREQ_EVENTFD: |
435 | return attach_eventfd(lg, input); | |
d7e28ffe RR |
436 | default: |
437 | return -EINVAL; | |
438 | } | |
439 | } | |
440 | ||
2e04ef76 RR |
441 | /*L:060 |
442 | * The final piece of interface code is the close() routine. It reverses | |
dde79789 RR |
443 | * everything done in initialize(). This is usually called because the |
444 | * Launcher exited. | |
445 | * | |
446 | * Note that the close routine returns 0 or a negative error number: it can't | |
447 | * really fail, but it can whine. I blame Sun for this wart, and K&R C for | |
2e04ef76 RR |
448 | * letting them do it. |
449 | :*/ | |
d7e28ffe RR |
450 | static int close(struct inode *inode, struct file *file) |
451 | { | |
452 | struct lguest *lg = file->private_data; | |
ad8d8f3b | 453 | unsigned int i; |
d7e28ffe | 454 | |
dde79789 | 455 | /* If we never successfully initialized, there's nothing to clean up */ |
d7e28ffe RR |
456 | if (!lg) |
457 | return 0; | |
458 | ||
2e04ef76 RR |
459 | /* |
460 | * We need the big lock, to protect from inter-guest I/O and other | |
461 | * Launchers initializing guests. | |
462 | */ | |
d7e28ffe | 463 | mutex_lock(&lguest_lock); |
66686c2a GOC |
464 | |
465 | /* Free up the shadow page tables for the Guest. */ | |
466 | free_guest_pagetable(lg); | |
467 | ||
a53a35a8 | 468 | for (i = 0; i < lg->nr_cpus; i++) { |
ad8d8f3b GOC |
469 | /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ |
470 | hrtimer_cancel(&lg->cpus[i].hrt); | |
a53a35a8 GOC |
471 | /* We can free up the register page we allocated. */ |
472 | free_page(lg->cpus[i].regs_page); | |
2e04ef76 RR |
473 | /* |
474 | * Now all the memory cleanups are done, it's safe to release | |
475 | * the Launcher's memory management structure. | |
476 | */ | |
66686c2a | 477 | mmput(lg->cpus[i].mm); |
a53a35a8 | 478 | } |
df60aeef RR |
479 | |
480 | /* Release any eventfds they registered. */ | |
481 | for (i = 0; i < lg->eventfds->num; i++) | |
13389010 | 482 | eventfd_ctx_put(lg->eventfds->map[i].event); |
df60aeef RR |
483 | kfree(lg->eventfds); |
484 | ||
2e04ef76 RR |
485 | /* |
486 | * If lg->dead doesn't contain an error code it will be NULL or a | |
487 | * kmalloc()ed string, either of which is ok to hand to kfree(). | |
488 | */ | |
d7e28ffe RR |
489 | if (!IS_ERR(lg->dead)) |
490 | kfree(lg->dead); | |
05dfdbbd MW |
491 | /* Free the memory allocated to the lguest_struct */ |
492 | kfree(lg); | |
dde79789 | 493 | /* Release lock and exit. */ |
d7e28ffe | 494 | mutex_unlock(&lguest_lock); |
dde79789 | 495 | |
d7e28ffe RR |
496 | return 0; |
497 | } | |
498 | ||
dde79789 RR |
499 | /*L:000 |
500 | * Welcome to our journey through the Launcher! | |
501 | * | |
502 | * The Launcher is the Host userspace program which sets up, runs and services | |
503 | * the Guest. In fact, many comments in the Drivers which refer to "the Host" | |
504 | * doing things are inaccurate: the Launcher does all the device handling for | |
e1e72965 | 505 | * the Guest, but the Guest can't know that. |
dde79789 RR |
506 | * |
507 | * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we | |
508 | * shall see more of that later. | |
509 | * | |
510 | * We begin our understanding with the Host kernel interface which the Launcher | |
511 | * uses: reading and writing a character device called /dev/lguest. All the | |
2e04ef76 RR |
512 | * work happens in the read(), write() and close() routines: |
513 | */ | |
828c0950 | 514 | static const struct file_operations lguest_fops = { |
d7e28ffe RR |
515 | .owner = THIS_MODULE, |
516 | .release = close, | |
517 | .write = write, | |
518 | .read = read, | |
6038f373 | 519 | .llseek = default_llseek, |
d7e28ffe | 520 | }; |
9f54288d | 521 | /*:*/ |
dde79789 | 522 | |
2e04ef76 RR |
523 | /* |
524 | * This is a textbook example of a "misc" character device. Populate a "struct | |
525 | * miscdevice" and register it with misc_register(). | |
526 | */ | |
d7e28ffe RR |
527 | static struct miscdevice lguest_dev = { |
528 | .minor = MISC_DYNAMIC_MINOR, | |
529 | .name = "lguest", | |
530 | .fops = &lguest_fops, | |
531 | }; | |
532 | ||
533 | int __init lguest_device_init(void) | |
534 | { | |
535 | return misc_register(&lguest_dev); | |
536 | } | |
537 | ||
538 | void __exit lguest_device_remove(void) | |
539 | { | |
540 | misc_deregister(&lguest_dev); | |
541 | } |