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Commit | Line | Data |
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2e04ef76 RR |
1 | /*P:400 |
2 | * This contains run_guest() which actually calls into the Host<->Guest | |
f938d2c8 | 3 | * Switcher and analyzes the return, such as determining if the Guest wants the |
2e04ef76 RR |
4 | * Host to do something. This file also contains useful helper routines. |
5 | :*/ | |
d7e28ffe RR |
6 | #include <linux/module.h> |
7 | #include <linux/stringify.h> | |
8 | #include <linux/stddef.h> | |
9 | #include <linux/io.h> | |
10 | #include <linux/mm.h> | |
174cd4b1 | 11 | #include <linux/sched/signal.h> |
d7e28ffe RR |
12 | #include <linux/vmalloc.h> |
13 | #include <linux/cpu.h> | |
14 | #include <linux/freezer.h> | |
625efab1 | 15 | #include <linux/highmem.h> |
5a0e3ad6 | 16 | #include <linux/slab.h> |
d7e28ffe | 17 | #include <asm/paravirt.h> |
d7e28ffe | 18 | #include <asm/pgtable.h> |
7c0f6ba6 | 19 | #include <linux/uaccess.h> |
d7e28ffe | 20 | #include <asm/poll.h> |
d7e28ffe | 21 | #include <asm/asm-offsets.h> |
d7e28ffe RR |
22 | #include "lg.h" |
23 | ||
406a590b | 24 | unsigned long switcher_addr; |
f1f394b1 | 25 | struct page **lg_switcher_pages; |
e27d90e8 RR |
26 | static struct vm_struct *switcher_text_vma; |
27 | static struct vm_struct *switcher_stacks_vma; | |
d7e28ffe | 28 | |
d7e28ffe RR |
29 | /* This One Big lock protects all inter-guest data structures. */ |
30 | DEFINE_MUTEX(lguest_lock); | |
d7e28ffe | 31 | |
2e04ef76 RR |
32 | /*H:010 |
33 | * We need to set up the Switcher at a high virtual address. Remember the | |
bff672e6 RR |
34 | * Switcher is a few hundred bytes of assembler code which actually changes the |
35 | * CPU to run the Guest, and then changes back to the Host when a trap or | |
36 | * interrupt happens. | |
37 | * | |
38 | * The Switcher code must be at the same virtual address in the Guest as the | |
39 | * Host since it will be running as the switchover occurs. | |
40 | * | |
41 | * Trying to map memory at a particular address is an unusual thing to do, so | |
2e04ef76 RR |
42 | * it's not a simple one-liner. |
43 | */ | |
d7e28ffe RR |
44 | static __init int map_switcher(void) |
45 | { | |
46 | int i, err; | |
d7e28ffe | 47 | |
bff672e6 RR |
48 | /* |
49 | * Map the Switcher in to high memory. | |
50 | * | |
51 | * It turns out that if we choose the address 0xFFC00000 (4MB under the | |
52 | * top virtual address), it makes setting up the page tables really | |
53 | * easy. | |
54 | */ | |
55 | ||
93a2cdff RR |
56 | /* We assume Switcher text fits into a single page. */ |
57 | if (end_switcher_text - start_switcher_text > PAGE_SIZE) { | |
58 | printk(KERN_ERR "lguest: switcher text too large (%zu)\n", | |
59 | end_switcher_text - start_switcher_text); | |
60 | return -EINVAL; | |
61 | } | |
62 | ||
2e04ef76 RR |
63 | /* |
64 | * We allocate an array of struct page pointers. map_vm_area() wants | |
65 | * this, rather than just an array of pages. | |
66 | */ | |
f1f394b1 RR |
67 | lg_switcher_pages = kmalloc(sizeof(lg_switcher_pages[0]) |
68 | * TOTAL_SWITCHER_PAGES, | |
69 | GFP_KERNEL); | |
70 | if (!lg_switcher_pages) { | |
d7e28ffe RR |
71 | err = -ENOMEM; |
72 | goto out; | |
73 | } | |
74 | ||
2e04ef76 RR |
75 | /* |
76 | * Now we actually allocate the pages. The Guest will see these pages, | |
77 | * so we make sure they're zeroed. | |
78 | */ | |
d7e28ffe | 79 | for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { |
f1f394b1 RR |
80 | lg_switcher_pages[i] = alloc_page(GFP_KERNEL|__GFP_ZERO); |
81 | if (!lg_switcher_pages[i]) { | |
d7e28ffe RR |
82 | err = -ENOMEM; |
83 | goto free_some_pages; | |
84 | } | |
d7e28ffe RR |
85 | } |
86 | ||
e27d90e8 RR |
87 | /* |
88 | * Copy in the compiled-in Switcher code (from x86/switcher_32.S). | |
89 | * It goes in the first page, which we map in momentarily. | |
90 | */ | |
91 | memcpy(kmap(lg_switcher_pages[0]), start_switcher_text, | |
92 | end_switcher_text - start_switcher_text); | |
93 | kunmap(lg_switcher_pages[0]); | |
94 | ||
2e04ef76 | 95 | /* |
6b392717 RR |
96 | * We place the Switcher underneath the fixmap area, which is the |
97 | * highest virtual address we can get. This is important, since we | |
98 | * tell the Guest it can't access this memory, so we want its ceiling | |
99 | * as high as possible. | |
2e04ef76 | 100 | */ |
e27d90e8 | 101 | switcher_addr = FIXADDR_START - TOTAL_SWITCHER_PAGES*PAGE_SIZE; |
f14ae652 | 102 | |
2e04ef76 | 103 | /* |
e27d90e8 RR |
104 | * Now we reserve the "virtual memory area"s we want. We might |
105 | * not get them in theory, but in practice it's worked so far. | |
106 | * | |
107 | * We want the switcher text to be read-only and executable, and | |
108 | * the stacks to be read-write and non-executable. | |
2e04ef76 | 109 | */ |
e27d90e8 RR |
110 | switcher_text_vma = __get_vm_area(PAGE_SIZE, VM_ALLOC|VM_NO_GUARD, |
111 | switcher_addr, | |
112 | switcher_addr + PAGE_SIZE); | |
113 | ||
114 | if (!switcher_text_vma) { | |
d7e28ffe RR |
115 | err = -ENOMEM; |
116 | printk("lguest: could not map switcher pages high\n"); | |
117 | goto free_pages; | |
118 | } | |
119 | ||
e27d90e8 RR |
120 | switcher_stacks_vma = __get_vm_area(SWITCHER_STACK_PAGES * PAGE_SIZE, |
121 | VM_ALLOC|VM_NO_GUARD, | |
122 | switcher_addr + PAGE_SIZE, | |
123 | switcher_addr + TOTAL_SWITCHER_PAGES * PAGE_SIZE); | |
124 | if (!switcher_stacks_vma) { | |
125 | err = -ENOMEM; | |
126 | printk("lguest: could not map switcher pages high\n"); | |
127 | goto free_text_vma; | |
128 | } | |
129 | ||
2e04ef76 RR |
130 | /* |
131 | * This code actually sets up the pages we've allocated to appear at | |
406a590b | 132 | * switcher_addr. map_vm_area() takes the vma we allocated above, the |
e27d90e8 RR |
133 | * kind of pages we're mapping (kernel text pages and kernel writable |
134 | * pages respectively), and a pointer to our array of struct pages. | |
2e04ef76 | 135 | */ |
e27d90e8 RR |
136 | err = map_vm_area(switcher_text_vma, PAGE_KERNEL_RX, lg_switcher_pages); |
137 | if (err) { | |
138 | printk("lguest: text map_vm_area failed: %i\n", err); | |
139 | goto free_vmas; | |
140 | } | |
141 | ||
142 | err = map_vm_area(switcher_stacks_vma, PAGE_KERNEL, | |
143 | lg_switcher_pages + SWITCHER_TEXT_PAGES); | |
d7e28ffe | 144 | if (err) { |
e27d90e8 RR |
145 | printk("lguest: stacks map_vm_area failed: %i\n", err); |
146 | goto free_vmas; | |
d7e28ffe | 147 | } |
bff672e6 | 148 | |
2e04ef76 RR |
149 | /* |
150 | * Now the Switcher is mapped at the right address, we can't fail! | |
2e04ef76 | 151 | */ |
d7e28ffe | 152 | printk(KERN_INFO "lguest: mapped switcher at %p\n", |
e27d90e8 | 153 | switcher_text_vma->addr); |
bff672e6 | 154 | /* And we succeeded... */ |
d7e28ffe RR |
155 | return 0; |
156 | ||
e27d90e8 RR |
157 | free_vmas: |
158 | /* Undoes map_vm_area and __get_vm_area */ | |
159 | vunmap(switcher_stacks_vma->addr); | |
160 | free_text_vma: | |
161 | vunmap(switcher_text_vma->addr); | |
d7e28ffe RR |
162 | free_pages: |
163 | i = TOTAL_SWITCHER_PAGES; | |
164 | free_some_pages: | |
165 | for (--i; i >= 0; i--) | |
f1f394b1 RR |
166 | __free_pages(lg_switcher_pages[i], 0); |
167 | kfree(lg_switcher_pages); | |
d7e28ffe RR |
168 | out: |
169 | return err; | |
170 | } | |
bff672e6 | 171 | /*:*/ |
d7e28ffe | 172 | |
2e04ef76 | 173 | /* Cleaning up the mapping when the module is unloaded is almost... too easy. */ |
d7e28ffe RR |
174 | static void unmap_switcher(void) |
175 | { | |
176 | unsigned int i; | |
177 | ||
bff672e6 | 178 | /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */ |
e27d90e8 RR |
179 | vunmap(switcher_text_vma->addr); |
180 | vunmap(switcher_stacks_vma->addr); | |
bff672e6 | 181 | /* Now we just need to free the pages we copied the switcher into */ |
d7e28ffe | 182 | for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) |
f1f394b1 RR |
183 | __free_pages(lg_switcher_pages[i], 0); |
184 | kfree(lg_switcher_pages); | |
d7e28ffe RR |
185 | } |
186 | ||
e1e72965 | 187 | /*H:032 |
dde79789 RR |
188 | * Dealing With Guest Memory. |
189 | * | |
e1e72965 RR |
190 | * Before we go too much further into the Host, we need to grok the routines |
191 | * we use to deal with Guest memory. | |
192 | * | |
dde79789 | 193 | * When the Guest gives us (what it thinks is) a physical address, we can use |
3c6b5bfa RR |
194 | * the normal copy_from_user() & copy_to_user() on the corresponding place in |
195 | * the memory region allocated by the Launcher. | |
dde79789 RR |
196 | * |
197 | * But we can't trust the Guest: it might be trying to access the Launcher | |
198 | * code. We have to check that the range is below the pfn_limit the Launcher | |
199 | * gave us. We have to make sure that addr + len doesn't give us a false | |
2e04ef76 RR |
200 | * positive by overflowing, too. |
201 | */ | |
df1693ab MZ |
202 | bool lguest_address_ok(const struct lguest *lg, |
203 | unsigned long addr, unsigned long len) | |
d7e28ffe | 204 | { |
83a35114 | 205 | return addr+len <= lg->pfn_limit * PAGE_SIZE && (addr+len >= addr); |
d7e28ffe RR |
206 | } |
207 | ||
2e04ef76 RR |
208 | /* |
209 | * This routine copies memory from the Guest. Here we can see how useful the | |
2d37f94a | 210 | * kill_lguest() routine we met in the Launcher can be: we return a random |
2e04ef76 RR |
211 | * value (all zeroes) instead of needing to return an error. |
212 | */ | |
382ac6b3 | 213 | void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes) |
d7e28ffe | 214 | { |
382ac6b3 GOC |
215 | if (!lguest_address_ok(cpu->lg, addr, bytes) |
216 | || copy_from_user(b, cpu->lg->mem_base + addr, bytes) != 0) { | |
d7e28ffe RR |
217 | /* copy_from_user should do this, but as we rely on it... */ |
218 | memset(b, 0, bytes); | |
382ac6b3 | 219 | kill_guest(cpu, "bad read address %#lx len %u", addr, bytes); |
d7e28ffe RR |
220 | } |
221 | } | |
222 | ||
a6bd8e13 | 223 | /* This is the write (copy into Guest) version. */ |
382ac6b3 | 224 | void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b, |
2d37f94a | 225 | unsigned bytes) |
d7e28ffe | 226 | { |
382ac6b3 GOC |
227 | if (!lguest_address_ok(cpu->lg, addr, bytes) |
228 | || copy_to_user(cpu->lg->mem_base + addr, b, bytes) != 0) | |
229 | kill_guest(cpu, "bad write address %#lx len %u", addr, bytes); | |
d7e28ffe | 230 | } |
2d37f94a | 231 | /*:*/ |
d7e28ffe | 232 | |
2e04ef76 RR |
233 | /*H:030 |
234 | * Let's jump straight to the the main loop which runs the Guest. | |
bff672e6 | 235 | * Remember, this is called by the Launcher reading /dev/lguest, and we keep |
2e04ef76 RR |
236 | * going around and around until something interesting happens. |
237 | */ | |
d0953d42 | 238 | int run_guest(struct lg_cpu *cpu, unsigned long __user *user) |
d7e28ffe | 239 | { |
18c13737 RR |
240 | /* If the launcher asked for a register with LHREQ_GETREG */ |
241 | if (cpu->reg_read) { | |
242 | if (put_user(*cpu->reg_read, user)) | |
243 | return -EFAULT; | |
244 | cpu->reg_read = NULL; | |
245 | return sizeof(*cpu->reg_read); | |
246 | } | |
247 | ||
bff672e6 | 248 | /* We stop running once the Guest is dead. */ |
382ac6b3 | 249 | while (!cpu->lg->dead) { |
abd41f03 | 250 | unsigned int irq; |
a32a8813 | 251 | bool more; |
abd41f03 | 252 | |
cc6d4fbc | 253 | /* First we run any hypercalls the Guest wants done. */ |
73044f05 GOC |
254 | if (cpu->hcall) |
255 | do_hypercalls(cpu); | |
cc6d4fbc | 256 | |
d9bab50a | 257 | /* Do we have to tell the Launcher about a trap? */ |
69a09dc1 | 258 | if (cpu->pending.trap) { |
d9bab50a RR |
259 | if (copy_to_user(user, &cpu->pending, |
260 | sizeof(cpu->pending))) | |
261 | return -EFAULT; | |
262 | return sizeof(cpu->pending); | |
d7e28ffe RR |
263 | } |
264 | ||
0acf0001 MH |
265 | /* |
266 | * All long-lived kernel loops need to check with this horrible | |
267 | * thing called the freezer. If the Host is trying to suspend, | |
268 | * it stops us. | |
269 | */ | |
270 | try_to_freeze(); | |
271 | ||
bff672e6 | 272 | /* Check for signals */ |
d7e28ffe RR |
273 | if (signal_pending(current)) |
274 | return -ERESTARTSYS; | |
275 | ||
2e04ef76 RR |
276 | /* |
277 | * Check if there are any interrupts which can be delivered now: | |
a6bd8e13 | 278 | * if so, this sets up the hander to be executed when we next |
2e04ef76 RR |
279 | * run the Guest. |
280 | */ | |
a32a8813 | 281 | irq = interrupt_pending(cpu, &more); |
abd41f03 | 282 | if (irq < LGUEST_IRQS) |
a32a8813 | 283 | try_deliver_interrupt(cpu, irq, more); |
d7e28ffe | 284 | |
2e04ef76 RR |
285 | /* |
286 | * Just make absolutely sure the Guest is still alive. One of | |
287 | * those hypercalls could have been fatal, for example. | |
288 | */ | |
382ac6b3 | 289 | if (cpu->lg->dead) |
d7e28ffe RR |
290 | break; |
291 | ||
2e04ef76 RR |
292 | /* |
293 | * If the Guest asked to be stopped, we sleep. The Guest's | |
294 | * clock timer will wake us. | |
295 | */ | |
66686c2a | 296 | if (cpu->halted) { |
d7e28ffe | 297 | set_current_state(TASK_INTERRUPTIBLE); |
2e04ef76 RR |
298 | /* |
299 | * Just before we sleep, make sure no interrupt snuck in | |
300 | * which we should be doing. | |
301 | */ | |
5dac051b | 302 | if (interrupt_pending(cpu, &more) < LGUEST_IRQS) |
abd41f03 RR |
303 | set_current_state(TASK_RUNNING); |
304 | else | |
305 | schedule(); | |
d7e28ffe RR |
306 | continue; |
307 | } | |
308 | ||
2e04ef76 RR |
309 | /* |
310 | * OK, now we're ready to jump into the Guest. First we put up | |
311 | * the "Do Not Disturb" sign: | |
312 | */ | |
d7e28ffe RR |
313 | local_irq_disable(); |
314 | ||
625efab1 | 315 | /* Actually run the Guest until something happens. */ |
d0953d42 | 316 | lguest_arch_run_guest(cpu); |
bff672e6 RR |
317 | |
318 | /* Now we're ready to be interrupted or moved to other CPUs */ | |
d7e28ffe RR |
319 | local_irq_enable(); |
320 | ||
625efab1 | 321 | /* Now we deal with whatever happened to the Guest. */ |
73044f05 | 322 | lguest_arch_handle_trap(cpu); |
d7e28ffe | 323 | } |
625efab1 | 324 | |
a6bd8e13 | 325 | /* Special case: Guest is 'dead' but wants a reboot. */ |
382ac6b3 | 326 | if (cpu->lg->dead == ERR_PTR(-ERESTART)) |
ec04b13f | 327 | return -ERESTART; |
a6bd8e13 | 328 | |
bff672e6 | 329 | /* The Guest is dead => "No such file or directory" */ |
d7e28ffe RR |
330 | return -ENOENT; |
331 | } | |
332 | ||
bff672e6 RR |
333 | /*H:000 |
334 | * Welcome to the Host! | |
335 | * | |
336 | * By this point your brain has been tickled by the Guest code and numbed by | |
337 | * the Launcher code; prepare for it to be stretched by the Host code. This is | |
338 | * the heart. Let's begin at the initialization routine for the Host's lg | |
339 | * module. | |
340 | */ | |
d7e28ffe RR |
341 | static int __init init(void) |
342 | { | |
343 | int err; | |
344 | ||
bff672e6 | 345 | /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */ |
b56e3215 | 346 | if (get_kernel_rpl() != 0) { |
5c55841d | 347 | printk("lguest is afraid of being a guest\n"); |
d7e28ffe RR |
348 | return -EPERM; |
349 | } | |
350 | ||
bff672e6 | 351 | /* First we put the Switcher up in very high virtual memory. */ |
d7e28ffe RR |
352 | err = map_switcher(); |
353 | if (err) | |
c18acd73 | 354 | goto out; |
d7e28ffe | 355 | |
c18acd73 RR |
356 | /* We might need to reserve an interrupt vector. */ |
357 | err = init_interrupts(); | |
358 | if (err) | |
3412b6ae | 359 | goto unmap; |
c18acd73 | 360 | |
bff672e6 | 361 | /* /dev/lguest needs to be registered. */ |
d7e28ffe | 362 | err = lguest_device_init(); |
c18acd73 RR |
363 | if (err) |
364 | goto free_interrupts; | |
bff672e6 | 365 | |
625efab1 JS |
366 | /* Finally we do some architecture-specific setup. */ |
367 | lguest_arch_host_init(); | |
bff672e6 RR |
368 | |
369 | /* All good! */ | |
d7e28ffe | 370 | return 0; |
c18acd73 RR |
371 | |
372 | free_interrupts: | |
373 | free_interrupts(); | |
c18acd73 RR |
374 | unmap: |
375 | unmap_switcher(); | |
376 | out: | |
377 | return err; | |
d7e28ffe RR |
378 | } |
379 | ||
bff672e6 | 380 | /* Cleaning up is just the same code, backwards. With a little French. */ |
d7e28ffe RR |
381 | static void __exit fini(void) |
382 | { | |
383 | lguest_device_remove(); | |
c18acd73 | 384 | free_interrupts(); |
d7e28ffe | 385 | unmap_switcher(); |
bff672e6 | 386 | |
625efab1 | 387 | lguest_arch_host_fini(); |
d7e28ffe | 388 | } |
625efab1 | 389 | /*:*/ |
d7e28ffe | 390 | |
2e04ef76 RR |
391 | /* |
392 | * The Host side of lguest can be a module. This is a nice way for people to | |
393 | * play with it. | |
394 | */ | |
d7e28ffe RR |
395 | module_init(init); |
396 | module_exit(fini); | |
397 | MODULE_LICENSE("GPL"); | |
398 | MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>"); |