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f938d2c8 RR |
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 memory size, pagetable, entry point and kernel address offset. | |
4 | * A read will run the Guest until a signal is pending (-EINTR), or the Guest | |
5 | * does a DMA out to the Launcher. Writes are also used to get a DMA buffer | |
6 | * registered by the Guest and to send the Guest an interrupt. :*/ | |
d7e28ffe RR |
7 | #include <linux/uaccess.h> |
8 | #include <linux/miscdevice.h> | |
9 | #include <linux/fs.h> | |
10 | #include "lg.h" | |
11 | ||
dde79789 RR |
12 | /*L:030 setup_regs() doesn't really belong in this file, but it gives us an |
13 | * early glimpse deeper into the Host so it's worth having here. | |
14 | * | |
15 | * Most of the Guest's registers are left alone: we used get_zeroed_page() to | |
16 | * allocate the structure, so they will be 0. */ | |
d7e28ffe RR |
17 | static void setup_regs(struct lguest_regs *regs, unsigned long start) |
18 | { | |
dde79789 RR |
19 | /* There are four "segment" registers which the Guest needs to boot: |
20 | * The "code segment" register (cs) refers to the kernel code segment | |
21 | * __KERNEL_CS, and the "data", "extra" and "stack" segment registers | |
22 | * refer to the kernel data segment __KERNEL_DS. | |
23 | * | |
24 | * The privilege level is packed into the lower bits. The Guest runs | |
25 | * at privilege level 1 (GUEST_PL).*/ | |
d7e28ffe RR |
26 | regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL; |
27 | regs->cs = __KERNEL_CS|GUEST_PL; | |
dde79789 RR |
28 | |
29 | /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002) | |
30 | * is supposed to always be "1". Bit 9 (0x200) controls whether | |
31 | * interrupts are enabled. We always leave interrupts enabled while | |
32 | * running the Guest. */ | |
33 | regs->eflags = 0x202; | |
34 | ||
35 | /* The "Extended Instruction Pointer" register says where the Guest is | |
36 | * running. */ | |
d7e28ffe | 37 | regs->eip = start; |
dde79789 RR |
38 | |
39 | /* %esi points to our boot information, at physical address 0, so don't | |
40 | * touch it. */ | |
d7e28ffe RR |
41 | } |
42 | ||
dde79789 RR |
43 | /*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a |
44 | * DMA buffer. This is done by writing LHREQ_GETDMA and the key to | |
45 | * /dev/lguest. */ | |
d7e28ffe RR |
46 | static long user_get_dma(struct lguest *lg, const u32 __user *input) |
47 | { | |
48 | unsigned long key, udma, irq; | |
49 | ||
dde79789 | 50 | /* Fetch the key they wrote to us. */ |
d7e28ffe RR |
51 | if (get_user(key, input) != 0) |
52 | return -EFAULT; | |
dde79789 | 53 | /* Look for a free Guest DMA buffer bound to that key. */ |
d7e28ffe RR |
54 | udma = get_dma_buffer(lg, key, &irq); |
55 | if (!udma) | |
56 | return -ENOENT; | |
57 | ||
dde79789 RR |
58 | /* We need to tell the Launcher what interrupt the Guest expects after |
59 | * the buffer is filled. We stash it in udma->used_len. */ | |
d7e28ffe | 60 | lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq); |
dde79789 RR |
61 | |
62 | /* The (guest-physical) address of the DMA buffer is returned from | |
63 | * the write(). */ | |
d7e28ffe RR |
64 | return udma; |
65 | } | |
66 | ||
dde79789 | 67 | /*L:315 To force the Guest to stop running and return to the Launcher, the |
d7e28ffe RR |
68 | * Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest. The |
69 | * Launcher then writes LHREQ_BREAK and "0" to release the Waker. */ | |
70 | static int break_guest_out(struct lguest *lg, const u32 __user *input) | |
71 | { | |
72 | unsigned long on; | |
73 | ||
74 | /* Fetch whether they're turning break on or off.. */ | |
75 | if (get_user(on, input) != 0) | |
76 | return -EFAULT; | |
77 | ||
78 | if (on) { | |
79 | lg->break_out = 1; | |
80 | /* Pop it out (may be running on different CPU) */ | |
81 | wake_up_process(lg->tsk); | |
82 | /* Wait for them to reset it */ | |
83 | return wait_event_interruptible(lg->break_wq, !lg->break_out); | |
84 | } else { | |
85 | lg->break_out = 0; | |
86 | wake_up(&lg->break_wq); | |
87 | return 0; | |
88 | } | |
89 | } | |
90 | ||
dde79789 RR |
91 | /*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt |
92 | * number to /dev/lguest. */ | |
d7e28ffe RR |
93 | static int user_send_irq(struct lguest *lg, const u32 __user *input) |
94 | { | |
95 | u32 irq; | |
96 | ||
97 | if (get_user(irq, input) != 0) | |
98 | return -EFAULT; | |
99 | if (irq >= LGUEST_IRQS) | |
100 | return -EINVAL; | |
dde79789 RR |
101 | /* Next time the Guest runs, the core code will see if it can deliver |
102 | * this interrupt. */ | |
d7e28ffe RR |
103 | set_bit(irq, lg->irqs_pending); |
104 | return 0; | |
105 | } | |
106 | ||
dde79789 RR |
107 | /*L:040 Once our Guest is initialized, the Launcher makes it run by reading |
108 | * from /dev/lguest. */ | |
d7e28ffe RR |
109 | static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) |
110 | { | |
111 | struct lguest *lg = file->private_data; | |
112 | ||
dde79789 | 113 | /* You must write LHREQ_INITIALIZE first! */ |
d7e28ffe RR |
114 | if (!lg) |
115 | return -EINVAL; | |
116 | ||
117 | /* If you're not the task which owns the guest, go away. */ | |
118 | if (current != lg->tsk) | |
119 | return -EPERM; | |
120 | ||
dde79789 | 121 | /* If the guest is already dead, we indicate why */ |
d7e28ffe RR |
122 | if (lg->dead) { |
123 | size_t len; | |
124 | ||
dde79789 | 125 | /* lg->dead either contains an error code, or a string. */ |
d7e28ffe RR |
126 | if (IS_ERR(lg->dead)) |
127 | return PTR_ERR(lg->dead); | |
128 | ||
dde79789 | 129 | /* We can only return as much as the buffer they read with. */ |
d7e28ffe RR |
130 | len = min(size, strlen(lg->dead)+1); |
131 | if (copy_to_user(user, lg->dead, len) != 0) | |
132 | return -EFAULT; | |
133 | return len; | |
134 | } | |
135 | ||
dde79789 RR |
136 | /* If we returned from read() last time because the Guest sent DMA, |
137 | * clear the flag. */ | |
d7e28ffe RR |
138 | if (lg->dma_is_pending) |
139 | lg->dma_is_pending = 0; | |
140 | ||
dde79789 | 141 | /* Run the Guest until something interesting happens. */ |
d7e28ffe RR |
142 | return run_guest(lg, (unsigned long __user *)user); |
143 | } | |
144 | ||
dde79789 RR |
145 | /*L:020 The initialization write supplies 4 32-bit values (in addition to the |
146 | * 32-bit LHREQ_INITIALIZE value). These are: | |
147 | * | |
148 | * pfnlimit: The highest (Guest-physical) page number the Guest should be | |
149 | * allowed to access. The Launcher has to live in Guest memory, so it sets | |
150 | * this to ensure the Guest can't reach it. | |
151 | * | |
152 | * pgdir: The (Guest-physical) address of the top of the initial Guest | |
153 | * pagetables (which are set up by the Launcher). | |
154 | * | |
155 | * start: The first instruction to execute ("eip" in x86-speak). | |
156 | * | |
157 | * page_offset: The PAGE_OFFSET constant in the Guest kernel. We should | |
158 | * probably wean the code off this, but it's a very useful constant! Any | |
159 | * address above this is within the Guest kernel, and any kernel address can | |
160 | * quickly converted from physical to virtual by adding PAGE_OFFSET. It's | |
161 | * 0xC0000000 (3G) by default, but it's configurable at kernel build time. | |
162 | */ | |
d7e28ffe RR |
163 | static int initialize(struct file *file, const u32 __user *input) |
164 | { | |
dde79789 RR |
165 | /* "struct lguest" contains everything we (the Host) know about a |
166 | * Guest. */ | |
d7e28ffe RR |
167 | struct lguest *lg; |
168 | int err, i; | |
169 | u32 args[4]; | |
170 | ||
171 | /* We grab the Big Lguest lock, which protects the global array | |
172 | * "lguests" and multiple simultaneous initializations. */ | |
173 | mutex_lock(&lguest_lock); | |
dde79789 | 174 | /* You can't initialize twice! Close the device and start again... */ |
d7e28ffe RR |
175 | if (file->private_data) { |
176 | err = -EBUSY; | |
177 | goto unlock; | |
178 | } | |
179 | ||
180 | if (copy_from_user(args, input, sizeof(args)) != 0) { | |
181 | err = -EFAULT; | |
182 | goto unlock; | |
183 | } | |
184 | ||
dde79789 | 185 | /* Find an unused guest. */ |
d7e28ffe RR |
186 | i = find_free_guest(); |
187 | if (i < 0) { | |
188 | err = -ENOSPC; | |
189 | goto unlock; | |
190 | } | |
dde79789 RR |
191 | /* OK, we have an index into the "lguest" array: "lg" is a convenient |
192 | * pointer. */ | |
d7e28ffe | 193 | lg = &lguests[i]; |
dde79789 RR |
194 | |
195 | /* Populate the easy fields of our "struct lguest" */ | |
d7e28ffe RR |
196 | lg->guestid = i; |
197 | lg->pfn_limit = args[0]; | |
198 | lg->page_offset = args[3]; | |
dde79789 RR |
199 | |
200 | /* We need a complete page for the Guest registers: they are accessible | |
201 | * to the Guest and we can only grant it access to whole pages. */ | |
d7e28ffe RR |
202 | lg->regs_page = get_zeroed_page(GFP_KERNEL); |
203 | if (!lg->regs_page) { | |
204 | err = -ENOMEM; | |
205 | goto release_guest; | |
206 | } | |
dde79789 | 207 | /* We actually put the registers at the bottom of the page. */ |
d7e28ffe RR |
208 | lg->regs = (void *)lg->regs_page + PAGE_SIZE - sizeof(*lg->regs); |
209 | ||
dde79789 RR |
210 | /* Initialize the Guest's shadow page tables, using the toplevel |
211 | * address the Launcher gave us. This allocates memory, so can | |
212 | * fail. */ | |
d7e28ffe RR |
213 | err = init_guest_pagetable(lg, args[1]); |
214 | if (err) | |
215 | goto free_regs; | |
216 | ||
dde79789 RR |
217 | /* Now we initialize the Guest's registers, handing it the start |
218 | * address. */ | |
d7e28ffe | 219 | setup_regs(lg->regs, args[2]); |
dde79789 RR |
220 | |
221 | /* There are a couple of GDT entries the Guest expects when first | |
222 | * booting. */ | |
d7e28ffe | 223 | setup_guest_gdt(lg); |
dde79789 RR |
224 | |
225 | /* The timer for lguest's clock needs initialization. */ | |
d7e28ffe | 226 | init_clockdev(lg); |
dde79789 RR |
227 | |
228 | /* We keep a pointer to the Launcher task (ie. current task) for when | |
229 | * other Guests want to wake this one (inter-Guest I/O). */ | |
d7e28ffe | 230 | lg->tsk = current; |
dde79789 RR |
231 | /* We need to keep a pointer to the Launcher's memory map, because if |
232 | * the Launcher dies we need to clean it up. If we don't keep a | |
233 | * reference, it is destroyed before close() is called. */ | |
d7e28ffe | 234 | lg->mm = get_task_mm(lg->tsk); |
dde79789 RR |
235 | |
236 | /* Initialize the queue for the waker to wait on */ | |
d7e28ffe | 237 | init_waitqueue_head(&lg->break_wq); |
dde79789 RR |
238 | |
239 | /* We remember which CPU's pages this Guest used last, for optimization | |
240 | * when the same Guest runs on the same CPU twice. */ | |
d7e28ffe | 241 | lg->last_pages = NULL; |
dde79789 RR |
242 | |
243 | /* We keep our "struct lguest" in the file's private_data. */ | |
d7e28ffe RR |
244 | file->private_data = lg; |
245 | ||
246 | mutex_unlock(&lguest_lock); | |
247 | ||
dde79789 | 248 | /* And because this is a write() call, we return the length used. */ |
d7e28ffe RR |
249 | return sizeof(args); |
250 | ||
251 | free_regs: | |
252 | free_page(lg->regs_page); | |
253 | release_guest: | |
254 | memset(lg, 0, sizeof(*lg)); | |
255 | unlock: | |
256 | mutex_unlock(&lguest_lock); | |
257 | return err; | |
258 | } | |
259 | ||
dde79789 RR |
260 | /*L:010 The first operation the Launcher does must be a write. All writes |
261 | * start with a 32 bit number: for the first write this must be | |
262 | * LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use | |
263 | * writes of other values to get DMA buffers and send interrupts. */ | |
d7e28ffe RR |
264 | static ssize_t write(struct file *file, const char __user *input, |
265 | size_t size, loff_t *off) | |
266 | { | |
dde79789 RR |
267 | /* Once the guest is initialized, we hold the "struct lguest" in the |
268 | * file private data. */ | |
d7e28ffe RR |
269 | struct lguest *lg = file->private_data; |
270 | u32 req; | |
271 | ||
272 | if (get_user(req, input) != 0) | |
273 | return -EFAULT; | |
274 | input += sizeof(req); | |
275 | ||
dde79789 | 276 | /* If you haven't initialized, you must do that first. */ |
d7e28ffe RR |
277 | if (req != LHREQ_INITIALIZE && !lg) |
278 | return -EINVAL; | |
dde79789 RR |
279 | |
280 | /* Once the Guest is dead, all you can do is read() why it died. */ | |
d7e28ffe RR |
281 | if (lg && lg->dead) |
282 | return -ENOENT; | |
283 | ||
284 | /* If you're not the task which owns the Guest, you can only break */ | |
285 | if (lg && current != lg->tsk && req != LHREQ_BREAK) | |
286 | return -EPERM; | |
287 | ||
288 | switch (req) { | |
289 | case LHREQ_INITIALIZE: | |
290 | return initialize(file, (const u32 __user *)input); | |
291 | case LHREQ_GETDMA: | |
292 | return user_get_dma(lg, (const u32 __user *)input); | |
293 | case LHREQ_IRQ: | |
294 | return user_send_irq(lg, (const u32 __user *)input); | |
295 | case LHREQ_BREAK: | |
296 | return break_guest_out(lg, (const u32 __user *)input); | |
297 | default: | |
298 | return -EINVAL; | |
299 | } | |
300 | } | |
301 | ||
dde79789 RR |
302 | /*L:060 The final piece of interface code is the close() routine. It reverses |
303 | * everything done in initialize(). This is usually called because the | |
304 | * Launcher exited. | |
305 | * | |
306 | * Note that the close routine returns 0 or a negative error number: it can't | |
307 | * really fail, but it can whine. I blame Sun for this wart, and K&R C for | |
308 | * letting them do it. :*/ | |
d7e28ffe RR |
309 | static int close(struct inode *inode, struct file *file) |
310 | { | |
311 | struct lguest *lg = file->private_data; | |
312 | ||
dde79789 | 313 | /* If we never successfully initialized, there's nothing to clean up */ |
d7e28ffe RR |
314 | if (!lg) |
315 | return 0; | |
316 | ||
dde79789 RR |
317 | /* We need the big lock, to protect from inter-guest I/O and other |
318 | * Launchers initializing guests. */ | |
d7e28ffe RR |
319 | mutex_lock(&lguest_lock); |
320 | /* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */ | |
321 | hrtimer_cancel(&lg->hrt); | |
dde79789 | 322 | /* Free any DMA buffers the Guest had bound. */ |
d7e28ffe | 323 | release_all_dma(lg); |
dde79789 | 324 | /* Free up the shadow page tables for the Guest. */ |
d7e28ffe | 325 | free_guest_pagetable(lg); |
dde79789 RR |
326 | /* Now all the memory cleanups are done, it's safe to release the |
327 | * Launcher's memory management structure. */ | |
d7e28ffe | 328 | mmput(lg->mm); |
dde79789 RR |
329 | /* If lg->dead doesn't contain an error code it will be NULL or a |
330 | * kmalloc()ed string, either of which is ok to hand to kfree(). */ | |
d7e28ffe RR |
331 | if (!IS_ERR(lg->dead)) |
332 | kfree(lg->dead); | |
dde79789 | 333 | /* We can free up the register page we allocated. */ |
d7e28ffe | 334 | free_page(lg->regs_page); |
dde79789 RR |
335 | /* We clear the entire structure, which also marks it as free for the |
336 | * next user. */ | |
d7e28ffe | 337 | memset(lg, 0, sizeof(*lg)); |
dde79789 | 338 | /* Release lock and exit. */ |
d7e28ffe | 339 | mutex_unlock(&lguest_lock); |
dde79789 | 340 | |
d7e28ffe RR |
341 | return 0; |
342 | } | |
343 | ||
dde79789 RR |
344 | /*L:000 |
345 | * Welcome to our journey through the Launcher! | |
346 | * | |
347 | * The Launcher is the Host userspace program which sets up, runs and services | |
348 | * the Guest. In fact, many comments in the Drivers which refer to "the Host" | |
349 | * doing things are inaccurate: the Launcher does all the device handling for | |
350 | * the Guest. The Guest can't tell what's done by the the Launcher and what by | |
351 | * the Host. | |
352 | * | |
353 | * Just to confuse you: to the Host kernel, the Launcher *is* the Guest and we | |
354 | * shall see more of that later. | |
355 | * | |
356 | * We begin our understanding with the Host kernel interface which the Launcher | |
357 | * uses: reading and writing a character device called /dev/lguest. All the | |
358 | * work happens in the read(), write() and close() routines: */ | |
d7e28ffe RR |
359 | static struct file_operations lguest_fops = { |
360 | .owner = THIS_MODULE, | |
361 | .release = close, | |
362 | .write = write, | |
363 | .read = read, | |
364 | }; | |
dde79789 RR |
365 | |
366 | /* This is a textbook example of a "misc" character device. Populate a "struct | |
367 | * miscdevice" and register it with misc_register(). */ | |
d7e28ffe RR |
368 | static struct miscdevice lguest_dev = { |
369 | .minor = MISC_DYNAMIC_MINOR, | |
370 | .name = "lguest", | |
371 | .fops = &lguest_fops, | |
372 | }; | |
373 | ||
374 | int __init lguest_device_init(void) | |
375 | { | |
376 | return misc_register(&lguest_dev); | |
377 | } | |
378 | ||
379 | void __exit lguest_device_remove(void) | |
380 | { | |
381 | misc_deregister(&lguest_dev); | |
382 | } |