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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 | */ | |
19 | static 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 | ||
41 | static 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 | */ | |
67 | static 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 | */ | |
88 | static 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 | */ | |
105 | static 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 | */ | |
155 | static 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 | */ | |
221 | static 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 | ||
276 | free_regs: | |
277 | /* FIXME: This should be in free_vcpu */ | |
278 | free_page(lg->cpus[0].regs_page); | |
279 | free_lg: | |
280 | kfree(lg); | |
281 | unlock: | |
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 | */ | |
297 | static 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 | ||
342 | /*L:060 | |
343 | * The final piece of interface code is the close() routine. It reverses | |
344 | * everything done in initialize(). This is usually called because the | |
345 | * Launcher exited. | |
346 | * | |
347 | * Note that the close routine returns 0 or a negative error number: it can't | |
348 | * really fail, but it can whine. I blame Sun for this wart, and K&R C for | |
349 | * letting them do it. | |
350 | :*/ | |
351 | static int close(struct inode *inode, struct file *file) | |
352 | { | |
353 | struct lguest *lg = file->private_data; | |
354 | unsigned int i; | |
355 | ||
356 | /* If we never successfully initialized, there's nothing to clean up */ | |
357 | if (!lg) | |
358 | return 0; | |
359 | ||
360 | /* | |
361 | * We need the big lock, to protect from inter-guest I/O and other | |
362 | * Launchers initializing guests. | |
363 | */ | |
364 | mutex_lock(&lguest_lock); | |
365 | ||
366 | /* Free up the shadow page tables for the Guest. */ | |
367 | free_guest_pagetable(lg); | |
368 | ||
369 | for (i = 0; i < lg->nr_cpus; i++) { | |
370 | /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ | |
371 | hrtimer_cancel(&lg->cpus[i].hrt); | |
372 | /* We can free up the register page we allocated. */ | |
373 | free_page(lg->cpus[i].regs_page); | |
374 | /* | |
375 | * Now all the memory cleanups are done, it's safe to release | |
376 | * the Launcher's memory management structure. | |
377 | */ | |
378 | mmput(lg->cpus[i].mm); | |
379 | } | |
380 | ||
381 | /* | |
382 | * If lg->dead doesn't contain an error code it will be NULL or a | |
383 | * kmalloc()ed string, either of which is ok to hand to kfree(). | |
384 | */ | |
385 | if (!IS_ERR(lg->dead)) | |
386 | kfree(lg->dead); | |
387 | /* Free the memory allocated to the lguest_struct */ | |
388 | kfree(lg); | |
389 | /* Release lock and exit. */ | |
390 | mutex_unlock(&lguest_lock); | |
391 | ||
392 | return 0; | |
393 | } | |
394 | ||
395 | /*L:000 | |
396 | * Welcome to our journey through the Launcher! | |
397 | * | |
398 | * The Launcher is the Host userspace program which sets up, runs and services | |
399 | * the Guest. In fact, many comments in the Drivers which refer to "the Host" | |
400 | * doing things are inaccurate: the Launcher does all the device handling for | |
401 | * the Guest, but the Guest can't know that. | |
402 | * | |
403 | * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we | |
404 | * shall see more of that later. | |
405 | * | |
406 | * We begin our understanding with the Host kernel interface which the Launcher | |
407 | * uses: reading and writing a character device called /dev/lguest. All the | |
408 | * work happens in the read(), write() and close() routines: | |
409 | */ | |
410 | static const struct file_operations lguest_fops = { | |
411 | .owner = THIS_MODULE, | |
412 | .release = close, | |
413 | .write = write, | |
414 | .read = read, | |
415 | .llseek = default_llseek, | |
416 | }; | |
417 | /*:*/ | |
418 | ||
419 | /* | |
420 | * This is a textbook example of a "misc" character device. Populate a "struct | |
421 | * miscdevice" and register it with misc_register(). | |
422 | */ | |
423 | static struct miscdevice lguest_dev = { | |
424 | .minor = MISC_DYNAMIC_MINOR, | |
425 | .name = "lguest", | |
426 | .fops = &lguest_fops, | |
427 | }; | |
428 | ||
429 | int __init lguest_device_init(void) | |
430 | { | |
431 | return misc_register(&lguest_dev); | |
432 | } | |
433 | ||
434 | void __exit lguest_device_remove(void) | |
435 | { | |
436 | misc_deregister(&lguest_dev); | |
437 | } |