1 /*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
2 * controls and communicates with the Guest. For example, the first write will
3 * tell us the Guest's memory layout, pagetable, entry point and kernel address
4 * offset. A read will run the Guest until something happens, such as a signal
5 * or the Guest doing a NOTIFY out to the Launcher. :*/
6 #include <linux/uaccess.h>
7 #include <linux/miscdevice.h>
9 #include <linux/sched.h>
10 #include <linux/eventfd.h>
11 #include <linux/file.h>
14 /*L:055 When something happens, the Waker process needs a way to stop the
15 * kernel running the Guest and return to the Launcher. So the Waker writes
16 * LHREQ_BREAK and the value "1" to /dev/lguest to do this. Once the Launcher
17 * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release
19 static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input)
23 /* Fetch whether they're turning break on or off. */
24 if (get_user(on, input) != 0)
29 if (!wake_up_process(cpu->tsk))
30 kick_process(cpu->tsk);
31 /* Wait for them to reset it */
32 return wait_event_interruptible(cpu->break_wq, !cpu->break_out);
35 wake_up(&cpu->break_wq);
40 bool send_notify_to_eventfd(struct lg_cpu *cpu)
43 struct lg_eventfd_map *map;
45 /* lg->eventfds is RCU-protected */
47 map = rcu_dereference(cpu->lg->eventfds);
48 for (i = 0; i < map->num; i++) {
49 if (map->map[i].addr == cpu->pending_notify) {
50 eventfd_signal(map->map[i].event, 1);
51 cpu->pending_notify = 0;
56 return cpu->pending_notify == 0;
59 static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
61 struct lg_eventfd_map *new, *old = lg->eventfds;
66 /* Replace the old array with the new one, carefully: others can
67 * be accessing it at the same time */
68 new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
73 /* First make identical copy. */
74 memcpy(new->map, old->map, sizeof(old->map[0]) * old->num);
77 /* Now append new entry. */
78 new->map[new->num].addr = addr;
79 new->map[new->num].event = eventfd_fget(fd);
80 if (IS_ERR(new->map[new->num].event)) {
82 return PTR_ERR(new->map[new->num].event);
86 /* Now put new one in place. */
87 rcu_assign_pointer(lg->eventfds, new);
89 /* We're not in a big hurry. Wait until noone's looking at old
90 * version, then delete it. */
97 static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
99 unsigned long addr, fd;
102 if (get_user(addr, input) != 0)
105 if (get_user(fd, input) != 0)
108 mutex_lock(&lguest_lock);
109 err = add_eventfd(lg, addr, fd);
110 mutex_unlock(&lguest_lock);
115 /*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
116 * number to /dev/lguest. */
117 static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
121 if (get_user(irq, input) != 0)
123 if (irq >= LGUEST_IRQS)
126 set_interrupt(cpu, irq);
130 /*L:040 Once our Guest is initialized, the Launcher makes it run by reading
131 * from /dev/lguest. */
132 static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
134 struct lguest *lg = file->private_data;
136 unsigned int cpu_id = *o;
138 /* You must write LHREQ_INITIALIZE first! */
142 /* Watch out for arbitrary vcpu indexes! */
143 if (cpu_id >= lg->nr_cpus)
146 cpu = &lg->cpus[cpu_id];
148 /* If you're not the task which owns the Guest, go away. */
149 if (current != cpu->tsk)
152 /* If the Guest is already dead, we indicate why */
156 /* lg->dead either contains an error code, or a string. */
157 if (IS_ERR(lg->dead))
158 return PTR_ERR(lg->dead);
160 /* We can only return as much as the buffer they read with. */
161 len = min(size, strlen(lg->dead)+1);
162 if (copy_to_user(user, lg->dead, len) != 0)
167 /* If we returned from read() last time because the Guest sent I/O,
169 if (cpu->pending_notify)
170 cpu->pending_notify = 0;
172 /* Run the Guest until something interesting happens. */
173 return run_guest(cpu, (unsigned long __user *)user);
176 /*L:025 This actually initializes a CPU. For the moment, a Guest is only
177 * uniprocessor, so "id" is always 0. */
178 static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
180 /* We have a limited number the number of CPUs in the lguest struct. */
181 if (id >= ARRAY_SIZE(cpu->lg->cpus))
184 /* Set up this CPU's id, and pointer back to the lguest struct. */
186 cpu->lg = container_of((cpu - id), struct lguest, cpus[0]);
189 /* Each CPU has a timer it can set. */
192 /* We need a complete page for the Guest registers: they are accessible
193 * to the Guest and we can only grant it access to whole pages. */
194 cpu->regs_page = get_zeroed_page(GFP_KERNEL);
198 /* We actually put the registers at the bottom of the page. */
199 cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
201 /* Now we initialize the Guest's registers, handing it the start
203 lguest_arch_setup_regs(cpu, start_ip);
205 /* Initialize the queue for the Waker to wait on */
206 init_waitqueue_head(&cpu->break_wq);
208 /* We keep a pointer to the Launcher task (ie. current task) for when
209 * other Guests want to wake this one (eg. console input). */
212 /* We need to keep a pointer to the Launcher's memory map, because if
213 * the Launcher dies we need to clean it up. If we don't keep a
214 * reference, it is destroyed before close() is called. */
215 cpu->mm = get_task_mm(cpu->tsk);
217 /* We remember which CPU's pages this Guest used last, for optimization
218 * when the same Guest runs on the same CPU twice. */
219 cpu->last_pages = NULL;
221 /* No error == success. */
225 /*L:020 The initialization write supplies 3 pointer sized (32 or 64 bit)
226 * values (in addition to the LHREQ_INITIALIZE value). These are:
228 * base: The start of the Guest-physical memory inside the Launcher memory.
230 * pfnlimit: The highest (Guest-physical) page number the Guest should be
231 * allowed to access. The Guest memory lives inside the Launcher, so it sets
232 * this to ensure the Guest can only reach its own memory.
234 * start: The first instruction to execute ("eip" in x86-speak).
236 static int initialize(struct file *file, const unsigned long __user *input)
238 /* "struct lguest" contains everything we (the Host) know about a
242 unsigned long args[3];
244 /* We grab the Big Lguest lock, which protects against multiple
245 * simultaneous initializations. */
246 mutex_lock(&lguest_lock);
247 /* You can't initialize twice! Close the device and start again... */
248 if (file->private_data) {
253 if (copy_from_user(args, input, sizeof(args)) != 0) {
258 lg = kzalloc(sizeof(*lg), GFP_KERNEL);
264 lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL);
269 lg->eventfds->num = 0;
271 /* Populate the easy fields of our "struct lguest" */
272 lg->mem_base = (void __user *)args[0];
273 lg->pfn_limit = args[1];
275 /* This is the first cpu (cpu 0) and it will start booting at args[2] */
276 err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
280 /* Initialize the Guest's shadow page tables, using the toplevel
281 * address the Launcher gave us. This allocates memory, so can fail. */
282 err = init_guest_pagetable(lg);
286 /* We keep our "struct lguest" in the file's private_data. */
287 file->private_data = lg;
289 mutex_unlock(&lguest_lock);
291 /* And because this is a write() call, we return the length used. */
295 /* FIXME: This should be in free_vcpu */
296 free_page(lg->cpus[0].regs_page);
302 mutex_unlock(&lguest_lock);
306 /*L:010 The first operation the Launcher does must be a write. All writes
307 * start with an unsigned long number: for the first write this must be
308 * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
309 * writes of other values to send interrupts.
311 * Note that we overload the "offset" in the /dev/lguest file to indicate what
312 * CPU number we're dealing with. Currently this is always 0, since we only
313 * support uniprocessor Guests, but you can see the beginnings of SMP support
315 static ssize_t write(struct file *file, const char __user *in,
316 size_t size, loff_t *off)
318 /* Once the Guest is initialized, we hold the "struct lguest" in the
319 * file private data. */
320 struct lguest *lg = file->private_data;
321 const unsigned long __user *input = (const unsigned long __user *)in;
323 struct lg_cpu *uninitialized_var(cpu);
324 unsigned int cpu_id = *off;
326 /* The first value tells us what this request is. */
327 if (get_user(req, input) != 0)
331 /* If you haven't initialized, you must do that first. */
332 if (req != LHREQ_INITIALIZE) {
333 if (!lg || (cpu_id >= lg->nr_cpus))
335 cpu = &lg->cpus[cpu_id];
337 /* Once the Guest is dead, you can only read() why it died. */
343 case LHREQ_INITIALIZE:
344 return initialize(file, input);
346 return user_send_irq(cpu, input);
348 return break_guest_out(cpu, input);
350 return attach_eventfd(lg, input);
356 /*L:060 The final piece of interface code is the close() routine. It reverses
357 * everything done in initialize(). This is usually called because the
360 * Note that the close routine returns 0 or a negative error number: it can't
361 * really fail, but it can whine. I blame Sun for this wart, and K&R C for
362 * letting them do it. :*/
363 static int close(struct inode *inode, struct file *file)
365 struct lguest *lg = file->private_data;
368 /* If we never successfully initialized, there's nothing to clean up */
372 /* We need the big lock, to protect from inter-guest I/O and other
373 * Launchers initializing guests. */
374 mutex_lock(&lguest_lock);
376 /* Free up the shadow page tables for the Guest. */
377 free_guest_pagetable(lg);
379 for (i = 0; i < lg->nr_cpus; i++) {
380 /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
381 hrtimer_cancel(&lg->cpus[i].hrt);
382 /* We can free up the register page we allocated. */
383 free_page(lg->cpus[i].regs_page);
384 /* Now all the memory cleanups are done, it's safe to release
385 * the Launcher's memory management structure. */
386 mmput(lg->cpus[i].mm);
389 /* Release any eventfds they registered. */
390 for (i = 0; i < lg->eventfds->num; i++)
391 fput(lg->eventfds->map[i].event);
394 /* If lg->dead doesn't contain an error code it will be NULL or a
395 * kmalloc()ed string, either of which is ok to hand to kfree(). */
396 if (!IS_ERR(lg->dead))
398 /* Free the memory allocated to the lguest_struct */
400 /* Release lock and exit. */
401 mutex_unlock(&lguest_lock);
407 * Welcome to our journey through the Launcher!
409 * The Launcher is the Host userspace program which sets up, runs and services
410 * the Guest. In fact, many comments in the Drivers which refer to "the Host"
411 * doing things are inaccurate: the Launcher does all the device handling for
412 * the Guest, but the Guest can't know that.
414 * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we
415 * shall see more of that later.
417 * We begin our understanding with the Host kernel interface which the Launcher
418 * uses: reading and writing a character device called /dev/lguest. All the
419 * work happens in the read(), write() and close() routines: */
420 static struct file_operations lguest_fops = {
421 .owner = THIS_MODULE,
427 /* This is a textbook example of a "misc" character device. Populate a "struct
428 * miscdevice" and register it with misc_register(). */
429 static struct miscdevice lguest_dev = {
430 .minor = MISC_DYNAMIC_MINOR,
432 .fops = &lguest_fops,
435 int __init lguest_device_init(void)
437 return misc_register(&lguest_dev);
440 void __exit lguest_device_remove(void)
442 misc_deregister(&lguest_dev);