aboutsummaryrefslogtreecommitdiff
path: root/drivers/lguest/core.c
blob: ce909ec57499729a69694b558eb0320774941105 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
/* World's simplest hypervisor, to test paravirt_ops and show
 * unbelievers that virtualization is the future.  Plus, it's fun! */
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/stddef.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/cpu.h>
#include <linux/freezer.h>
#include <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/poll.h>
#include <asm/highmem.h>
#include <asm/asm-offsets.h>
#include <asm/i387.h>
#include "lg.h"

/* Found in switcher.S */
extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
extern unsigned long default_idt_entries[];

/* Every guest maps the core switcher code. */
#define SHARED_SWITCHER_PAGES \
	DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
/* Pages for switcher itself, then two pages per cpu */
#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)

/* We map at -4M for ease of mapping into the guest (one PTE page). */
#define SWITCHER_ADDR 0xFFC00000

static struct vm_struct *switcher_vma;
static struct page **switcher_page;

static int cpu_had_pge;
static struct {
	unsigned long offset;
	unsigned short segment;
} lguest_entry;

/* This One Big lock protects all inter-guest data structures. */
DEFINE_MUTEX(lguest_lock);
static DEFINE_PER_CPU(struct lguest *, last_guest);

/* FIXME: Make dynamic. */
#define MAX_LGUEST_GUESTS 16
struct lguest lguests[MAX_LGUEST_GUESTS];

/* Offset from where switcher.S was compiled to where we've copied it */
static unsigned long switcher_offset(void)
{
	return SWITCHER_ADDR - (unsigned long)start_switcher_text;
}

/* This cpu's struct lguest_pages. */
static struct lguest_pages *lguest_pages(unsigned int cpu)
{
	return &(((struct lguest_pages *)
		  (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
}

static __init int map_switcher(void)
{
	int i, err;
	struct page **pagep;

	switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
				GFP_KERNEL);
	if (!switcher_page) {
		err = -ENOMEM;
		goto out;
	}

	for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
		unsigned long addr = get_zeroed_page(GFP_KERNEL);
		if (!addr) {
			err = -ENOMEM;
			goto free_some_pages;
		}
		switcher_page[i] = virt_to_page(addr);
	}

	switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
				       VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
	if (!switcher_vma) {
		err = -ENOMEM;
		printk("lguest: could not map switcher pages high\n");
		goto free_pages;
	}

	pagep = switcher_page;
	err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
	if (err) {
		printk("lguest: map_vm_area failed: %i\n", err);
		goto free_vma;
	}
	memcpy(switcher_vma->addr, start_switcher_text,
	       end_switcher_text - start_switcher_text);

	/* Fix up IDT entries to point into copied text. */
	for (i = 0; i < IDT_ENTRIES; i++)
		default_idt_entries[i] += switcher_offset();

	for_each_possible_cpu(i) {
		struct lguest_pages *pages = lguest_pages(i);
		struct lguest_ro_state *state = &pages->state;

		/* These fields are static: rest done in copy_in_guest_info */
		state->host_gdt_desc.size = GDT_SIZE-1;
		state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
		store_idt(&state->host_idt_desc);
		state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
		state->guest_idt_desc.address = (long)&state->guest_idt;
		state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
		state->guest_gdt_desc.address = (long)&state->guest_gdt;
		state->guest_tss.esp0 = (long)(&pages->regs + 1);
		state->guest_tss.ss0 = LGUEST_DS;
		/* No I/O for you! */
		state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
		setup_default_gdt_entries(state);
		setup_default_idt_entries(state, default_idt_entries);

		/* Setup LGUEST segments on all cpus */
		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
	}

	/* Initialize entry point into switcher. */
	lguest_entry.offset = (long)switch_to_guest + switcher_offset();
	lguest_entry.segment = LGUEST_CS;

	printk(KERN_INFO "lguest: mapped switcher at %p\n",
	       switcher_vma->addr);
	return 0;

free_vma:
	vunmap(switcher_vma->addr);
free_pages:
	i = TOTAL_SWITCHER_PAGES;
free_some_pages:
	for (--i; i >= 0; i--)
		__free_pages(switcher_page[i], 0);
	kfree(switcher_page);
out:
	return err;
}

static void unmap_switcher(void)
{
	unsigned int i;

	vunmap(switcher_vma->addr);
	for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
		__free_pages(switcher_page[i], 0);
}

/* IN/OUT insns: enough to get us past boot-time probing. */
static int emulate_insn(struct lguest *lg)
{
	u8 insn;
	unsigned int insnlen = 0, in = 0, shift = 0;
	unsigned long physaddr = guest_pa(lg, lg->regs->eip);

	/* This only works for addresses in linear mapping... */
	if (lg->regs->eip < lg->page_offset)
		return 0;
	lgread(lg, &insn, physaddr, 1);

	/* Operand size prefix means it's actually for ax. */
	if (insn == 0x66) {
		shift = 16;
		insnlen = 1;
		lgread(lg, &insn, physaddr + insnlen, 1);
	}

	switch (insn & 0xFE) {
	case 0xE4: /* in     <next byte>,%al */
		insnlen += 2;
		in = 1;
		break;
	case 0xEC: /* in     (%dx),%al */
		insnlen += 1;
		in = 1;
		break;
	case 0xE6: /* out    %al,<next byte> */
		insnlen += 2;
		break;
	case 0xEE: /* out    %al,(%dx) */
		insnlen += 1;
		break;
	default:
		return 0;
	}

	if (in) {
		/* Lower bit tells is whether it's a 16 or 32 bit access */
		if (insn & 0x1)
			lg->regs->eax = 0xFFFFFFFF;
		else
			lg->regs->eax |= (0xFFFF << shift);
	}
	lg->regs->eip += insnlen;
	return 1;
}

int lguest_address_ok(const struct lguest *lg,
		      unsigned long addr, unsigned long len)
{
	return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
}

/* Just like get_user, but don't let guest access lguest binary. */
u32 lgread_u32(struct lguest *lg, unsigned long addr)
{
	u32 val = 0;

	/* Don't let them access lguest binary */
	if (!lguest_address_ok(lg, addr, sizeof(val))
	    || get_user(val, (u32 __user *)addr) != 0)
		kill_guest(lg, "bad read address %#lx", addr);
	return val;
}

void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
{
	if (!lguest_address_ok(lg, addr, sizeof(val))
	    || put_user(val, (u32 __user *)addr) != 0)
		kill_guest(lg, "bad write address %#lx", addr);
}

void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
{
	if (!lguest_address_ok(lg, addr, bytes)
	    || copy_from_user(b, (void __user *)addr, bytes) != 0) {
		/* copy_from_user should do this, but as we rely on it... */
		memset(b, 0, bytes);
		kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
	}
}

void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
	     unsigned bytes)
{
	if (!lguest_address_ok(lg, addr, bytes)
	    || copy_to_user((void __user *)addr, b, bytes) != 0)
		kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
}

static void set_ts(void)
{
	u32 cr0;

	cr0 = read_cr0();
	if (!(cr0 & 8))
		write_cr0(cr0|8);
}

static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
{
	if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
		__get_cpu_var(last_guest) = lg;
		lg->last_pages = pages;
		lg->changed = CHANGED_ALL;
	}

	/* These are pretty cheap, so we do them unconditionally. */
	pages->state.host_cr3 = __pa(current->mm->pgd);
	map_switcher_in_guest(lg, pages);
	pages->state.guest_tss.esp1 = lg->esp1;
	pages->state.guest_tss.ss1 = lg->ss1;

	/* Copy direct trap entries. */
	if (lg->changed & CHANGED_IDT)
		copy_traps(lg, pages->state.guest_idt, default_idt_entries);

	/* Copy all GDT entries but the TSS. */
	if (lg->changed & CHANGED_GDT)
		copy_gdt(lg, pages->state.guest_gdt);
	/* If only the TLS entries have changed, copy them. */
	else if (lg->changed & CHANGED_GDT_TLS)
		copy_gdt_tls(lg, pages->state.guest_gdt);

	lg->changed = 0;
}

static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
{
	unsigned int clobber;

	copy_in_guest_info(lg, pages);

	/* Put eflags on stack, lcall does rest: suitable for iret return. */
	asm volatile("pushf; lcall *lguest_entry"
		     : "=a"(clobber), "=b"(clobber)
		     : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
		     : "memory", "%edx", "%ecx", "%edi", "%esi");
}

int run_guest(struct lguest *lg, unsigned long __user *user)
{
	while (!lg->dead) {
		unsigned int cr2 = 0; /* Damn gcc */

		/* Hypercalls first: we might have been out to userspace */
		do_hypercalls(lg);
		if (lg->dma_is_pending) {
			if (put_user(lg->pending_dma, user) ||
			    put_user(lg->pending_key, user+1))
				return -EFAULT;
			return sizeof(unsigned long)*2;
		}

		if (signal_pending(current))
			return -ERESTARTSYS;

		/* If Waker set break_out, return to Launcher. */
		if (lg->break_out)
			return -EAGAIN;

		maybe_do_interrupt(lg);

		try_to_freeze();

		if (lg->dead)
			break;

		if (lg->halted) {
			set_current_state(TASK_INTERRUPTIBLE);
			schedule();
			continue;
		}

		local_irq_disable();

		/* Even if *we* don't want FPU trap, guest might... */
		if (lg->ts)
			set_ts();

		/* Don't let Guest do SYSENTER: we can't handle it. */
		if (boot_cpu_has(X86_FEATURE_SEP))
			wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);

		run_guest_once(lg, lguest_pages(raw_smp_processor_id()));

		/* Save cr2 now if we page-faulted. */
		if (lg->regs->trapnum == 14)
			cr2 = read_cr2();
		else if (lg->regs->trapnum == 7)
			math_state_restore();

		if (boot_cpu_has(X86_FEATURE_SEP))
			wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
		local_irq_enable();

		switch (lg->regs->trapnum) {
		case 13: /* We've intercepted a GPF. */
			if (lg->regs->errcode == 0) {
				if (emulate_insn(lg))
					continue;
			}
			break;
		case 14: /* We've intercepted a page fault. */
			if (demand_page(lg, cr2, lg->regs->errcode))
				continue;

			/* If lguest_data is NULL, this won't hurt. */
			if (put_user(cr2, &lg->lguest_data->cr2))
				kill_guest(lg, "Writing cr2");
			break;
		case 7: /* We've intercepted a Device Not Available fault. */
			/* If they don't want to know, just absorb it. */
			if (!lg->ts)
				continue;
			break;
		case 32 ... 255: /* Real interrupt, fall thru */
			cond_resched();
		case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
			continue;
		}

		if (deliver_trap(lg, lg->regs->trapnum))
			continue;

		kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
			   lg->regs->trapnum, lg->regs->eip,
			   lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
	}
	return -ENOENT;
}

int find_free_guest(void)
{
	unsigned int i;
	for (i = 0; i < MAX_LGUEST_GUESTS; i++)
		if (!lguests[i].tsk)
			return i;
	return -1;
}

static void adjust_pge(void *on)
{
	if (on)
		write_cr4(read_cr4() | X86_CR4_PGE);
	else
		write_cr4(read_cr4() & ~X86_CR4_PGE);
}

static int __init init(void)
{
	int err;

	if (paravirt_enabled()) {
		printk("lguest is afraid of %s\n", paravirt_ops.name);
		return -EPERM;
	}

	err = map_switcher();
	if (err)
		return err;

	err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
	if (err) {
		unmap_switcher();
		return err;
	}
	lguest_io_init();

	err = lguest_device_init();
	if (err) {
		free_pagetables();
		unmap_switcher();
		return err;
	}
	lock_cpu_hotplug();
	if (cpu_has_pge) { /* We have a broader idea of "global". */
		cpu_had_pge = 1;
		on_each_cpu(adjust_pge, (void *)0, 0, 1);
		clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
	}
	unlock_cpu_hotplug();
	return 0;
}

static void __exit fini(void)
{
	lguest_device_remove();
	free_pagetables();
	unmap_switcher();
	lock_cpu_hotplug();
	if (cpu_had_pge) {
		set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
		on_each_cpu(adjust_pge, (void *)1, 0, 1);
	}
	unlock_cpu_hotplug();
}

module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");