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>
12 /*L:055 When something happens, the Waker process needs a way to stop the
13 * kernel running the Guest and return to the Launcher. So the Waker writes
14 * LHREQ_BREAK and the value "1" to /dev/lguest to do this. Once the Launcher
15 * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release
17 static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input)
21 /* Fetch whether they're turning break on or off. */
22 if (get_user(on, input) != 0)
27 /* Pop it out of the Guest (may be running on different CPU) */
28 wake_up_process(cpu->tsk);
29 /* Wait for them to reset it */
30 return wait_event_interruptible(cpu->break_wq, !cpu->break_out);
33 wake_up(&cpu->break_wq);
38 /*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
39 * number to /dev/lguest. */
40 static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
44 if (get_user(irq, input) != 0)
46 if (irq >= LGUEST_IRQS)
48 /* Next time the Guest runs, the core code will see if it can deliver
50 set_bit(irq, cpu->irqs_pending);
54 /*L:040 Once our Guest is initialized, the Launcher makes it run by reading
55 * from /dev/lguest. */
56 static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
58 struct lguest *lg = file->private_data;
60 unsigned int cpu_id = *o;
62 /* You must write LHREQ_INITIALIZE first! */
66 /* Watch out for arbitrary vcpu indexes! */
67 if (cpu_id >= lg->nr_cpus)
70 cpu = &lg->cpus[cpu_id];
72 /* If you're not the task which owns the Guest, go away. */
73 if (current != cpu->tsk)
76 /* If the Guest is already dead, we indicate why */
80 /* lg->dead either contains an error code, or a string. */
82 return PTR_ERR(lg->dead);
84 /* We can only return as much as the buffer they read with. */
85 len = min(size, strlen(lg->dead)+1);
86 if (copy_to_user(user, lg->dead, len) != 0)
91 /* If we returned from read() last time because the Guest sent I/O,
93 if (cpu->pending_notify)
94 cpu->pending_notify = 0;
96 /* Run the Guest until something interesting happens. */
97 return run_guest(cpu, (unsigned long __user *)user);
100 /*L:025 This actually initializes a CPU. For the moment, a Guest is only
101 * uniprocessor, so "id" is always 0. */
102 static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
104 /* We have a limited number the number of CPUs in the lguest struct. */
105 if (id >= ARRAY_SIZE(cpu->lg->cpus))
108 /* Set up this CPU's id, and pointer back to the lguest struct. */
110 cpu->lg = container_of((cpu - id), struct lguest, cpus[0]);
113 /* Each CPU has a timer it can set. */
116 /* We need a complete page for the Guest registers: they are accessible
117 * to the Guest and we can only grant it access to whole pages. */
118 cpu->regs_page = get_zeroed_page(GFP_KERNEL);
122 /* We actually put the registers at the bottom of the page. */
123 cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
125 /* Now we initialize the Guest's registers, handing it the start
127 lguest_arch_setup_regs(cpu, start_ip);
129 /* Initialize the queue for the Waker to wait on */
130 init_waitqueue_head(&cpu->break_wq);
132 /* We keep a pointer to the Launcher task (ie. current task) for when
133 * other Guests want to wake this one (eg. console input). */
136 /* We need to keep a pointer to the Launcher's memory map, because if
137 * the Launcher dies we need to clean it up. If we don't keep a
138 * reference, it is destroyed before close() is called. */
139 cpu->mm = get_task_mm(cpu->tsk);
141 /* We remember which CPU's pages this Guest used last, for optimization
142 * when the same Guest runs on the same CPU twice. */
143 cpu->last_pages = NULL;
145 /* No error == success. */
149 /*L:020 The initialization write supplies 3 pointer sized (32 or 64 bit)
150 * values (in addition to the LHREQ_INITIALIZE value). These are:
152 * base: The start of the Guest-physical memory inside the Launcher memory.
154 * pfnlimit: The highest (Guest-physical) page number the Guest should be
155 * allowed to access. The Guest memory lives inside the Launcher, so it sets
156 * this to ensure the Guest can only reach its own memory.
158 * start: The first instruction to execute ("eip" in x86-speak).
160 static int initialize(struct file *file, const unsigned long __user *input)
162 /* "struct lguest" contains everything we (the Host) know about a
166 unsigned long args[3];
168 /* We grab the Big Lguest lock, which protects against multiple
169 * simultaneous initializations. */
170 mutex_lock(&lguest_lock);
171 /* You can't initialize twice! Close the device and start again... */
172 if (file->private_data) {
177 if (copy_from_user(args, input, sizeof(args)) != 0) {
182 lg = kzalloc(sizeof(*lg), GFP_KERNEL);
188 /* Populate the easy fields of our "struct lguest" */
189 lg->mem_base = (void __user *)args[0];
190 lg->pfn_limit = args[1];
192 /* This is the first cpu (cpu 0) and it will start booting at args[2] */
193 err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
197 /* Initialize the Guest's shadow page tables, using the toplevel
198 * address the Launcher gave us. This allocates memory, so can fail. */
199 err = init_guest_pagetable(lg);
203 /* We keep our "struct lguest" in the file's private_data. */
204 file->private_data = lg;
206 mutex_unlock(&lguest_lock);
208 /* And because this is a write() call, we return the length used. */
212 /* FIXME: This should be in free_vcpu */
213 free_page(lg->cpus[0].regs_page);
217 mutex_unlock(&lguest_lock);
221 /*L:010 The first operation the Launcher does must be a write. All writes
222 * start with an unsigned long number: for the first write this must be
223 * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
224 * writes of other values to send interrupts.
226 * Note that we overload the "offset" in the /dev/lguest file to indicate what
227 * CPU number we're dealing with. Currently this is always 0, since we only
228 * support uniprocessor Guests, but you can see the beginnings of SMP support
230 static ssize_t write(struct file *file, const char __user *in,
231 size_t size, loff_t *off)
233 /* Once the Guest is initialized, we hold the "struct lguest" in the
234 * file private data. */
235 struct lguest *lg = file->private_data;
236 const unsigned long __user *input = (const unsigned long __user *)in;
238 struct lg_cpu *uninitialized_var(cpu);
239 unsigned int cpu_id = *off;
241 /* The first value tells us what this request is. */
242 if (get_user(req, input) != 0)
246 /* If you haven't initialized, you must do that first. */
247 if (req != LHREQ_INITIALIZE) {
248 if (!lg || (cpu_id >= lg->nr_cpus))
250 cpu = &lg->cpus[cpu_id];
252 /* Once the Guest is dead, you can only read() why it died. */
256 /* If you're not the task which owns the Guest, all you can do
257 * is break the Launcher out of running the Guest. */
258 if (current != cpu->tsk && req != LHREQ_BREAK)
263 case LHREQ_INITIALIZE:
264 return initialize(file, input);
266 return user_send_irq(cpu, input);
268 return break_guest_out(cpu, input);
274 /*L:060 The final piece of interface code is the close() routine. It reverses
275 * everything done in initialize(). This is usually called because the
278 * Note that the close routine returns 0 or a negative error number: it can't
279 * really fail, but it can whine. I blame Sun for this wart, and K&R C for
280 * letting them do it. :*/
281 static int close(struct inode *inode, struct file *file)
283 struct lguest *lg = file->private_data;
286 /* If we never successfully initialized, there's nothing to clean up */
290 /* We need the big lock, to protect from inter-guest I/O and other
291 * Launchers initializing guests. */
292 mutex_lock(&lguest_lock);
294 /* Free up the shadow page tables for the Guest. */
295 free_guest_pagetable(lg);
297 for (i = 0; i < lg->nr_cpus; i++) {
298 /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
299 hrtimer_cancel(&lg->cpus[i].hrt);
300 /* We can free up the register page we allocated. */
301 free_page(lg->cpus[i].regs_page);
302 /* Now all the memory cleanups are done, it's safe to release
303 * the Launcher's memory management structure. */
304 mmput(lg->cpus[i].mm);
306 /* If lg->dead doesn't contain an error code it will be NULL or a
307 * kmalloc()ed string, either of which is ok to hand to kfree(). */
308 if (!IS_ERR(lg->dead))
310 /* Free the memory allocated to the lguest_struct */
312 /* Release lock and exit. */
313 mutex_unlock(&lguest_lock);
319 * Welcome to our journey through the Launcher!
321 * The Launcher is the Host userspace program which sets up, runs and services
322 * the Guest. In fact, many comments in the Drivers which refer to "the Host"
323 * doing things are inaccurate: the Launcher does all the device handling for
324 * the Guest, but the Guest can't know that.
326 * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we
327 * shall see more of that later.
329 * We begin our understanding with the Host kernel interface which the Launcher
330 * uses: reading and writing a character device called /dev/lguest. All the
331 * work happens in the read(), write() and close() routines: */
332 static struct file_operations lguest_fops = {
333 .owner = THIS_MODULE,
339 /* This is a textbook example of a "misc" character device. Populate a "struct
340 * miscdevice" and register it with misc_register(). */
341 static struct miscdevice lguest_dev = {
342 .minor = MISC_DYNAMIC_MINOR,
344 .fops = &lguest_fops,
347 int __init lguest_device_init(void)
349 return misc_register(&lguest_dev);
352 void __exit lguest_device_remove(void)
354 misc_deregister(&lguest_dev);