blob: a0788c12b392bbdfcca0bfea95cc088569db296f [file] [log] [blame]
Rusty Russellf938d2c2007-07-26 10:41:02 -07001/*P:400 This contains run_guest() which actually calls into the Host<->Guest
2 * Switcher and analyzes the return, such as determining if the Guest wants the
3 * Host to do something. This file also contains useful helper routines, and a
4 * couple of non-obvious setup and teardown pieces which were implemented after
5 * days of debugging pain. :*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -07006#include <linux/module.h>
7#include <linux/stringify.h>
8#include <linux/stddef.h>
9#include <linux/io.h>
10#include <linux/mm.h>
11#include <linux/vmalloc.h>
12#include <linux/cpu.h>
13#include <linux/freezer.h>
14#include <asm/paravirt.h>
15#include <asm/desc.h>
16#include <asm/pgtable.h>
17#include <asm/uaccess.h>
18#include <asm/poll.h>
19#include <asm/highmem.h>
20#include <asm/asm-offsets.h>
21#include <asm/i387.h>
22#include "lg.h"
23
24/* Found in switcher.S */
25extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
26extern unsigned long default_idt_entries[];
27
28/* Every guest maps the core switcher code. */
29#define SHARED_SWITCHER_PAGES \
30 DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE)
31/* Pages for switcher itself, then two pages per cpu */
32#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS)
33
34/* We map at -4M for ease of mapping into the guest (one PTE page). */
35#define SWITCHER_ADDR 0xFFC00000
36
37static struct vm_struct *switcher_vma;
38static struct page **switcher_page;
39
40static int cpu_had_pge;
41static struct {
42 unsigned long offset;
43 unsigned short segment;
44} lguest_entry;
45
46/* This One Big lock protects all inter-guest data structures. */
47DEFINE_MUTEX(lguest_lock);
48static DEFINE_PER_CPU(struct lguest *, last_guest);
49
50/* FIXME: Make dynamic. */
51#define MAX_LGUEST_GUESTS 16
52struct lguest lguests[MAX_LGUEST_GUESTS];
53
54/* Offset from where switcher.S was compiled to where we've copied it */
55static unsigned long switcher_offset(void)
56{
57 return SWITCHER_ADDR - (unsigned long)start_switcher_text;
58}
59
60/* This cpu's struct lguest_pages. */
61static struct lguest_pages *lguest_pages(unsigned int cpu)
62{
63 return &(((struct lguest_pages *)
64 (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
65}
66
Rusty Russellbff672e2007-07-26 10:41:04 -070067/*H:010 We need to set up the Switcher at a high virtual address. Remember the
68 * Switcher is a few hundred bytes of assembler code which actually changes the
69 * CPU to run the Guest, and then changes back to the Host when a trap or
70 * interrupt happens.
71 *
72 * The Switcher code must be at the same virtual address in the Guest as the
73 * Host since it will be running as the switchover occurs.
74 *
75 * Trying to map memory at a particular address is an unusual thing to do, so
76 * it's not a simple one-liner. We also set up the per-cpu parts of the
77 * Switcher here.
78 */
Rusty Russelld7e28ff2007-07-19 01:49:23 -070079static __init int map_switcher(void)
80{
81 int i, err;
82 struct page **pagep;
83
Rusty Russellbff672e2007-07-26 10:41:04 -070084 /*
85 * Map the Switcher in to high memory.
86 *
87 * It turns out that if we choose the address 0xFFC00000 (4MB under the
88 * top virtual address), it makes setting up the page tables really
89 * easy.
90 */
91
92 /* We allocate an array of "struct page"s. map_vm_area() wants the
93 * pages in this form, rather than just an array of pointers. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -070094 switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
95 GFP_KERNEL);
96 if (!switcher_page) {
97 err = -ENOMEM;
98 goto out;
99 }
100
Rusty Russellbff672e2007-07-26 10:41:04 -0700101 /* Now we actually allocate the pages. The Guest will see these pages,
102 * so we make sure they're zeroed. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700103 for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
104 unsigned long addr = get_zeroed_page(GFP_KERNEL);
105 if (!addr) {
106 err = -ENOMEM;
107 goto free_some_pages;
108 }
109 switcher_page[i] = virt_to_page(addr);
110 }
111
Rusty Russellbff672e2007-07-26 10:41:04 -0700112 /* Now we reserve the "virtual memory area" we want: 0xFFC00000
113 * (SWITCHER_ADDR). We might not get it in theory, but in practice
114 * it's worked so far. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700115 switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
116 VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
117 if (!switcher_vma) {
118 err = -ENOMEM;
119 printk("lguest: could not map switcher pages high\n");
120 goto free_pages;
121 }
122
Rusty Russellbff672e2007-07-26 10:41:04 -0700123 /* This code actually sets up the pages we've allocated to appear at
124 * SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the
125 * kind of pages we're mapping (kernel pages), and a pointer to our
126 * array of struct pages. It increments that pointer, but we don't
127 * care. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700128 pagep = switcher_page;
129 err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep);
130 if (err) {
131 printk("lguest: map_vm_area failed: %i\n", err);
132 goto free_vma;
133 }
Rusty Russellbff672e2007-07-26 10:41:04 -0700134
135 /* Now the switcher is mapped at the right address, we can't fail!
136 * Copy in the compiled-in Switcher code (from switcher.S). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700137 memcpy(switcher_vma->addr, start_switcher_text,
138 end_switcher_text - start_switcher_text);
139
Rusty Russellbff672e2007-07-26 10:41:04 -0700140 /* Most of the switcher.S doesn't care that it's been moved; on Intel,
141 * jumps are relative, and it doesn't access any references to external
142 * code or data.
143 *
144 * The only exception is the interrupt handlers in switcher.S: their
145 * addresses are placed in a table (default_idt_entries), so we need to
146 * update the table with the new addresses. switcher_offset() is a
147 * convenience function which returns the distance between the builtin
148 * switcher code and the high-mapped copy we just made. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700149 for (i = 0; i < IDT_ENTRIES; i++)
150 default_idt_entries[i] += switcher_offset();
151
Rusty Russellbff672e2007-07-26 10:41:04 -0700152 /*
153 * Set up the Switcher's per-cpu areas.
154 *
155 * Each CPU gets two pages of its own within the high-mapped region
156 * (aka. "struct lguest_pages"). Much of this can be initialized now,
157 * but some depends on what Guest we are running (which is set up in
158 * copy_in_guest_info()).
159 */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700160 for_each_possible_cpu(i) {
Rusty Russellbff672e2007-07-26 10:41:04 -0700161 /* lguest_pages() returns this CPU's two pages. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700162 struct lguest_pages *pages = lguest_pages(i);
Rusty Russellbff672e2007-07-26 10:41:04 -0700163 /* This is a convenience pointer to make the code fit one
164 * statement to a line. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700165 struct lguest_ro_state *state = &pages->state;
166
Rusty Russellbff672e2007-07-26 10:41:04 -0700167 /* The Global Descriptor Table: the Host has a different one
168 * for each CPU. We keep a descriptor for the GDT which says
169 * where it is and how big it is (the size is actually the last
170 * byte, not the size, hence the "-1"). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700171 state->host_gdt_desc.size = GDT_SIZE-1;
172 state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
Rusty Russellbff672e2007-07-26 10:41:04 -0700173
174 /* All CPUs on the Host use the same Interrupt Descriptor
175 * Table, so we just use store_idt(), which gets this CPU's IDT
176 * descriptor. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700177 store_idt(&state->host_idt_desc);
Rusty Russellbff672e2007-07-26 10:41:04 -0700178
179 /* The descriptors for the Guest's GDT and IDT can be filled
180 * out now, too. We copy the GDT & IDT into ->guest_gdt and
181 * ->guest_idt before actually running the Guest. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700182 state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
183 state->guest_idt_desc.address = (long)&state->guest_idt;
184 state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
185 state->guest_gdt_desc.address = (long)&state->guest_gdt;
Rusty Russellbff672e2007-07-26 10:41:04 -0700186
187 /* We know where we want the stack to be when the Guest enters
188 * the switcher: in pages->regs. The stack grows upwards, so
189 * we start it at the end of that structure. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700190 state->guest_tss.esp0 = (long)(&pages->regs + 1);
Rusty Russellbff672e2007-07-26 10:41:04 -0700191 /* And this is the GDT entry to use for the stack: we keep a
192 * couple of special LGUEST entries. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700193 state->guest_tss.ss0 = LGUEST_DS;
Rusty Russellbff672e2007-07-26 10:41:04 -0700194
195 /* x86 can have a finegrained bitmap which indicates what I/O
196 * ports the process can use. We set it to the end of our
197 * structure, meaning "none". */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700198 state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
Rusty Russellbff672e2007-07-26 10:41:04 -0700199
200 /* Some GDT entries are the same across all Guests, so we can
201 * set them up now. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700202 setup_default_gdt_entries(state);
Rusty Russellbff672e2007-07-26 10:41:04 -0700203 /* Most IDT entries are the same for all Guests, too.*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700204 setup_default_idt_entries(state, default_idt_entries);
205
Rusty Russellbff672e2007-07-26 10:41:04 -0700206 /* The Host needs to be able to use the LGUEST segments on this
207 * CPU, too, so put them in the Host GDT. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700208 get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
209 get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
210 }
211
Rusty Russellbff672e2007-07-26 10:41:04 -0700212 /* In the Switcher, we want the %cs segment register to use the
213 * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
214 * it will be undisturbed when we switch. To change %cs and jump we
215 * need this structure to feed to Intel's "lcall" instruction. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700216 lguest_entry.offset = (long)switch_to_guest + switcher_offset();
217 lguest_entry.segment = LGUEST_CS;
218
219 printk(KERN_INFO "lguest: mapped switcher at %p\n",
220 switcher_vma->addr);
Rusty Russellbff672e2007-07-26 10:41:04 -0700221 /* And we succeeded... */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700222 return 0;
223
224free_vma:
225 vunmap(switcher_vma->addr);
226free_pages:
227 i = TOTAL_SWITCHER_PAGES;
228free_some_pages:
229 for (--i; i >= 0; i--)
230 __free_pages(switcher_page[i], 0);
231 kfree(switcher_page);
232out:
233 return err;
234}
Rusty Russellbff672e2007-07-26 10:41:04 -0700235/*:*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700236
Rusty Russellbff672e2007-07-26 10:41:04 -0700237/* Cleaning up the mapping when the module is unloaded is almost...
238 * too easy. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700239static void unmap_switcher(void)
240{
241 unsigned int i;
242
Rusty Russellbff672e2007-07-26 10:41:04 -0700243 /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700244 vunmap(switcher_vma->addr);
Rusty Russellbff672e2007-07-26 10:41:04 -0700245 /* Now we just need to free the pages we copied the switcher into */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700246 for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)
247 __free_pages(switcher_page[i], 0);
248}
249
Rusty Russellbff672e2007-07-26 10:41:04 -0700250/*H:130 Our Guest is usually so well behaved; it never tries to do things it
Jeremy Fitzhardinge93b1eab2007-10-16 11:51:29 -0700251 * isn't allowed to. Unfortunately, Linux's paravirtual infrastructure isn't
252 * quite complete, because it doesn't contain replacements for the Intel I/O
Rusty Russellbff672e2007-07-26 10:41:04 -0700253 * instructions. As a result, the Guest sometimes fumbles across one during
254 * the boot process as it probes for various things which are usually attached
255 * to a PC.
256 *
257 * When the Guest uses one of these instructions, we get trap #13 (General
258 * Protection Fault) and come here. We see if it's one of those troublesome
259 * instructions and skip over it. We return true if we did. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700260static int emulate_insn(struct lguest *lg)
261{
262 u8 insn;
263 unsigned int insnlen = 0, in = 0, shift = 0;
Rusty Russellbff672e2007-07-26 10:41:04 -0700264 /* The eip contains the *virtual* address of the Guest's instruction:
265 * guest_pa just subtracts the Guest's page_offset. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700266 unsigned long physaddr = guest_pa(lg, lg->regs->eip);
267
Rusty Russellbff672e2007-07-26 10:41:04 -0700268 /* The guest_pa() function only works for Guest kernel addresses, but
269 * that's all we're trying to do anyway. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700270 if (lg->regs->eip < lg->page_offset)
271 return 0;
Rusty Russellbff672e2007-07-26 10:41:04 -0700272
273 /* Decoding x86 instructions is icky. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700274 lgread(lg, &insn, physaddr, 1);
275
Rusty Russellbff672e2007-07-26 10:41:04 -0700276 /* 0x66 is an "operand prefix". It means it's using the upper 16 bits
277 of the eax register. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700278 if (insn == 0x66) {
279 shift = 16;
Rusty Russellbff672e2007-07-26 10:41:04 -0700280 /* The instruction is 1 byte so far, read the next byte. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700281 insnlen = 1;
282 lgread(lg, &insn, physaddr + insnlen, 1);
283 }
284
Rusty Russellbff672e2007-07-26 10:41:04 -0700285 /* We can ignore the lower bit for the moment and decode the 4 opcodes
286 * we need to emulate. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700287 switch (insn & 0xFE) {
288 case 0xE4: /* in <next byte>,%al */
289 insnlen += 2;
290 in = 1;
291 break;
292 case 0xEC: /* in (%dx),%al */
293 insnlen += 1;
294 in = 1;
295 break;
296 case 0xE6: /* out %al,<next byte> */
297 insnlen += 2;
298 break;
299 case 0xEE: /* out %al,(%dx) */
300 insnlen += 1;
301 break;
302 default:
Rusty Russellbff672e2007-07-26 10:41:04 -0700303 /* OK, we don't know what this is, can't emulate. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700304 return 0;
305 }
306
Rusty Russellbff672e2007-07-26 10:41:04 -0700307 /* If it was an "IN" instruction, they expect the result to be read
308 * into %eax, so we change %eax. We always return all-ones, which
309 * traditionally means "there's nothing there". */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700310 if (in) {
311 /* Lower bit tells is whether it's a 16 or 32 bit access */
312 if (insn & 0x1)
313 lg->regs->eax = 0xFFFFFFFF;
314 else
315 lg->regs->eax |= (0xFFFF << shift);
316 }
Rusty Russellbff672e2007-07-26 10:41:04 -0700317 /* Finally, we've "done" the instruction, so move past it. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700318 lg->regs->eip += insnlen;
Rusty Russellbff672e2007-07-26 10:41:04 -0700319 /* Success! */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700320 return 1;
321}
Rusty Russellbff672e2007-07-26 10:41:04 -0700322/*:*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700323
Rusty Russelldde79782007-07-26 10:41:03 -0700324/*L:305
325 * Dealing With Guest Memory.
326 *
327 * When the Guest gives us (what it thinks is) a physical address, we can use
328 * the normal copy_from_user() & copy_to_user() on that address: remember,
329 * Guest physical == Launcher virtual.
330 *
331 * But we can't trust the Guest: it might be trying to access the Launcher
332 * code. We have to check that the range is below the pfn_limit the Launcher
333 * gave us. We have to make sure that addr + len doesn't give us a false
334 * positive by overflowing, too. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700335int lguest_address_ok(const struct lguest *lg,
336 unsigned long addr, unsigned long len)
337{
338 return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
339}
340
Rusty Russelldde79782007-07-26 10:41:03 -0700341/* This is a convenient routine to get a 32-bit value from the Guest (a very
342 * common operation). Here we can see how useful the kill_lguest() routine we
343 * met in the Launcher can be: we return a random value (0) instead of needing
344 * to return an error. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700345u32 lgread_u32(struct lguest *lg, unsigned long addr)
346{
347 u32 val = 0;
348
Rusty Russelldde79782007-07-26 10:41:03 -0700349 /* Don't let them access lguest binary. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700350 if (!lguest_address_ok(lg, addr, sizeof(val))
351 || get_user(val, (u32 __user *)addr) != 0)
352 kill_guest(lg, "bad read address %#lx", addr);
353 return val;
354}
355
Rusty Russelldde79782007-07-26 10:41:03 -0700356/* Same thing for writing a value. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700357void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val)
358{
359 if (!lguest_address_ok(lg, addr, sizeof(val))
360 || put_user(val, (u32 __user *)addr) != 0)
361 kill_guest(lg, "bad write address %#lx", addr);
362}
363
Rusty Russelldde79782007-07-26 10:41:03 -0700364/* This routine is more generic, and copies a range of Guest bytes into a
365 * buffer. If the copy_from_user() fails, we fill the buffer with zeroes, so
366 * the caller doesn't end up using uninitialized kernel memory. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700367void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes)
368{
369 if (!lguest_address_ok(lg, addr, bytes)
370 || copy_from_user(b, (void __user *)addr, bytes) != 0) {
371 /* copy_from_user should do this, but as we rely on it... */
372 memset(b, 0, bytes);
373 kill_guest(lg, "bad read address %#lx len %u", addr, bytes);
374 }
375}
376
Rusty Russelldde79782007-07-26 10:41:03 -0700377/* Similarly, our generic routine to copy into a range of Guest bytes. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700378void lgwrite(struct lguest *lg, unsigned long addr, const void *b,
379 unsigned bytes)
380{
381 if (!lguest_address_ok(lg, addr, bytes)
382 || copy_to_user((void __user *)addr, b, bytes) != 0)
383 kill_guest(lg, "bad write address %#lx len %u", addr, bytes);
384}
Rusty Russelldde79782007-07-26 10:41:03 -0700385/* (end of memory access helper routines) :*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700386
387static void set_ts(void)
388{
389 u32 cr0;
390
391 cr0 = read_cr0();
392 if (!(cr0 & 8))
393 write_cr0(cr0|8);
394}
395
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700396/*S:010
397 * We are getting close to the Switcher.
398 *
399 * Remember that each CPU has two pages which are visible to the Guest when it
400 * runs on that CPU. This has to contain the state for that Guest: we copy the
401 * state in just before we run the Guest.
402 *
403 * Each Guest has "changed" flags which indicate what has changed in the Guest
404 * since it last ran. We saw this set in interrupts_and_traps.c and
405 * segments.c.
406 */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700407static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)
408{
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700409 /* Copying all this data can be quite expensive. We usually run the
410 * same Guest we ran last time (and that Guest hasn't run anywhere else
411 * meanwhile). If that's not the case, we pretend everything in the
412 * Guest has changed. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700413 if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) {
414 __get_cpu_var(last_guest) = lg;
415 lg->last_pages = pages;
416 lg->changed = CHANGED_ALL;
417 }
418
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700419 /* These copies are pretty cheap, so we do them unconditionally: */
420 /* Save the current Host top-level page directory. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700421 pages->state.host_cr3 = __pa(current->mm->pgd);
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700422 /* Set up the Guest's page tables to see this CPU's pages (and no
423 * other CPU's pages). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700424 map_switcher_in_guest(lg, pages);
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700425 /* Set up the two "TSS" members which tell the CPU what stack to use
426 * for traps which do directly into the Guest (ie. traps at privilege
427 * level 1). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700428 pages->state.guest_tss.esp1 = lg->esp1;
429 pages->state.guest_tss.ss1 = lg->ss1;
430
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700431 /* Copy direct-to-Guest trap entries. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700432 if (lg->changed & CHANGED_IDT)
433 copy_traps(lg, pages->state.guest_idt, default_idt_entries);
434
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700435 /* Copy all GDT entries which the Guest can change. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700436 if (lg->changed & CHANGED_GDT)
437 copy_gdt(lg, pages->state.guest_gdt);
438 /* If only the TLS entries have changed, copy them. */
439 else if (lg->changed & CHANGED_GDT_TLS)
440 copy_gdt_tls(lg, pages->state.guest_gdt);
441
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700442 /* Mark the Guest as unchanged for next time. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700443 lg->changed = 0;
444}
445
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700446/* Finally: the code to actually call into the Switcher to run the Guest. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700447static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)
448{
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700449 /* This is a dummy value we need for GCC's sake. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700450 unsigned int clobber;
451
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700452 /* Copy the guest-specific information into this CPU's "struct
453 * lguest_pages". */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700454 copy_in_guest_info(lg, pages);
455
Rusty Russell0d027c02007-08-09 20:57:13 +1000456 /* Set the trap number to 256 (impossible value). If we fault while
457 * switching to the Guest (bad segment registers or bug), this will
458 * cause us to abort the Guest. */
459 lg->regs->trapnum = 256;
460
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700461 /* Now: we push the "eflags" register on the stack, then do an "lcall".
462 * This is how we change from using the kernel code segment to using
463 * the dedicated lguest code segment, as well as jumping into the
464 * Switcher.
465 *
466 * The lcall also pushes the old code segment (KERNEL_CS) onto the
467 * stack, then the address of this call. This stack layout happens to
468 * exactly match the stack of an interrupt... */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700469 asm volatile("pushf; lcall *lguest_entry"
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700470 /* This is how we tell GCC that %eax ("a") and %ebx ("b")
471 * are changed by this routine. The "=" means output. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700472 : "=a"(clobber), "=b"(clobber)
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700473 /* %eax contains the pages pointer. ("0" refers to the
474 * 0-th argument above, ie "a"). %ebx contains the
475 * physical address of the Guest's top-level page
476 * directory. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700477 : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700478 /* We tell gcc that all these registers could change,
479 * which means we don't have to save and restore them in
480 * the Switcher. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700481 : "memory", "%edx", "%ecx", "%edi", "%esi");
482}
Rusty Russellf8f0fdc2007-07-26 10:41:04 -0700483/*:*/
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700484
Rusty Russellbff672e2007-07-26 10:41:04 -0700485/*H:030 Let's jump straight to the the main loop which runs the Guest.
486 * Remember, this is called by the Launcher reading /dev/lguest, and we keep
487 * going around and around until something interesting happens. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700488int run_guest(struct lguest *lg, unsigned long __user *user)
489{
Rusty Russellbff672e2007-07-26 10:41:04 -0700490 /* We stop running once the Guest is dead. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700491 while (!lg->dead) {
Rusty Russellbff672e2007-07-26 10:41:04 -0700492 /* We need to initialize this, otherwise gcc complains. It's
493 * not (yet) clever enough to see that it's initialized when we
494 * need it. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700495 unsigned int cr2 = 0; /* Damn gcc */
496
Rusty Russellbff672e2007-07-26 10:41:04 -0700497 /* First we run any hypercalls the Guest wants done: either in
498 * the hypercall ring in "struct lguest_data", or directly by
499 * using int 31 (LGUEST_TRAP_ENTRY). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700500 do_hypercalls(lg);
Rusty Russellbff672e2007-07-26 10:41:04 -0700501 /* It's possible the Guest did a SEND_DMA hypercall to the
502 * Launcher, in which case we return from the read() now. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700503 if (lg->dma_is_pending) {
504 if (put_user(lg->pending_dma, user) ||
505 put_user(lg->pending_key, user+1))
506 return -EFAULT;
507 return sizeof(unsigned long)*2;
508 }
509
Rusty Russellbff672e2007-07-26 10:41:04 -0700510 /* Check for signals */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700511 if (signal_pending(current))
512 return -ERESTARTSYS;
513
514 /* If Waker set break_out, return to Launcher. */
515 if (lg->break_out)
516 return -EAGAIN;
517
Rusty Russellbff672e2007-07-26 10:41:04 -0700518 /* Check if there are any interrupts which can be delivered
519 * now: if so, this sets up the hander to be executed when we
520 * next run the Guest. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700521 maybe_do_interrupt(lg);
522
Rusty Russellbff672e2007-07-26 10:41:04 -0700523 /* All long-lived kernel loops need to check with this horrible
524 * thing called the freezer. If the Host is trying to suspend,
525 * it stops us. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700526 try_to_freeze();
527
Rusty Russellbff672e2007-07-26 10:41:04 -0700528 /* Just make absolutely sure the Guest is still alive. One of
529 * those hypercalls could have been fatal, for example. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700530 if (lg->dead)
531 break;
532
Rusty Russellbff672e2007-07-26 10:41:04 -0700533 /* If the Guest asked to be stopped, we sleep. The Guest's
534 * clock timer or LHCALL_BREAK from the Waker will wake us. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700535 if (lg->halted) {
536 set_current_state(TASK_INTERRUPTIBLE);
537 schedule();
538 continue;
539 }
540
Rusty Russellbff672e2007-07-26 10:41:04 -0700541 /* OK, now we're ready to jump into the Guest. First we put up
542 * the "Do Not Disturb" sign: */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700543 local_irq_disable();
544
Rusty Russellbff672e2007-07-26 10:41:04 -0700545 /* Remember the awfully-named TS bit? If the Guest has asked
546 * to set it we set it now, so we can trap and pass that trap
547 * to the Guest if it uses the FPU. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700548 if (lg->ts)
549 set_ts();
550
Rusty Russellbff672e2007-07-26 10:41:04 -0700551 /* SYSENTER is an optimized way of doing system calls. We
552 * can't allow it because it always jumps to privilege level 0.
553 * A normal Guest won't try it because we don't advertise it in
554 * CPUID, but a malicious Guest (or malicious Guest userspace
555 * program) could, so we tell the CPU to disable it before
556 * running the Guest. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700557 if (boot_cpu_has(X86_FEATURE_SEP))
558 wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
559
Rusty Russellbff672e2007-07-26 10:41:04 -0700560 /* Now we actually run the Guest. It will pop back out when
561 * something interesting happens, and we can examine its
562 * registers to see what it was doing. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700563 run_guest_once(lg, lguest_pages(raw_smp_processor_id()));
564
Rusty Russellbff672e2007-07-26 10:41:04 -0700565 /* The "regs" pointer contains two extra entries which are not
566 * really registers: a trap number which says what interrupt or
567 * trap made the switcher code come back, and an error code
568 * which some traps set. */
569
570 /* If the Guest page faulted, then the cr2 register will tell
571 * us the bad virtual address. We have to grab this now,
572 * because once we re-enable interrupts an interrupt could
573 * fault and thus overwrite cr2, or we could even move off to a
574 * different CPU. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700575 if (lg->regs->trapnum == 14)
576 cr2 = read_cr2();
Rusty Russellbff672e2007-07-26 10:41:04 -0700577 /* Similarly, if we took a trap because the Guest used the FPU,
578 * we have to restore the FPU it expects to see. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700579 else if (lg->regs->trapnum == 7)
580 math_state_restore();
581
Rusty Russellbff672e2007-07-26 10:41:04 -0700582 /* Restore SYSENTER if it's supposed to be on. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700583 if (boot_cpu_has(X86_FEATURE_SEP))
584 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
Rusty Russellbff672e2007-07-26 10:41:04 -0700585
586 /* Now we're ready to be interrupted or moved to other CPUs */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700587 local_irq_enable();
588
Rusty Russellbff672e2007-07-26 10:41:04 -0700589 /* OK, so what happened? */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700590 switch (lg->regs->trapnum) {
591 case 13: /* We've intercepted a GPF. */
Rusty Russellbff672e2007-07-26 10:41:04 -0700592 /* Check if this was one of those annoying IN or OUT
593 * instructions which we need to emulate. If so, we
594 * just go back into the Guest after we've done it. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700595 if (lg->regs->errcode == 0) {
596 if (emulate_insn(lg))
597 continue;
598 }
599 break;
600 case 14: /* We've intercepted a page fault. */
Rusty Russellbff672e2007-07-26 10:41:04 -0700601 /* The Guest accessed a virtual address that wasn't
602 * mapped. This happens a lot: we don't actually set
603 * up most of the page tables for the Guest at all when
604 * we start: as it runs it asks for more and more, and
605 * we set them up as required. In this case, we don't
606 * even tell the Guest that the fault happened.
607 *
608 * The errcode tells whether this was a read or a
609 * write, and whether kernel or userspace code. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700610 if (demand_page(lg, cr2, lg->regs->errcode))
611 continue;
612
Rusty Russellbff672e2007-07-26 10:41:04 -0700613 /* OK, it's really not there (or not OK): the Guest
614 * needs to know. We write out the cr2 value so it
615 * knows where the fault occurred.
616 *
617 * Note that if the Guest were really messed up, this
618 * could happen before it's done the INITIALIZE
619 * hypercall, so lg->lguest_data will be NULL, so
620 * &lg->lguest_data->cr2 will be address 8. Writing
621 * into that address won't hurt the Host at all,
622 * though. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700623 if (put_user(cr2, &lg->lguest_data->cr2))
624 kill_guest(lg, "Writing cr2");
625 break;
626 case 7: /* We've intercepted a Device Not Available fault. */
Rusty Russellbff672e2007-07-26 10:41:04 -0700627 /* If the Guest doesn't want to know, we already
628 * restored the Floating Point Unit, so we just
629 * continue without telling it. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700630 if (!lg->ts)
631 continue;
632 break;
Rusty Russellbff672e2007-07-26 10:41:04 -0700633 case 32 ... 255:
634 /* These values mean a real interrupt occurred, in
635 * which case the Host handler has already been run.
636 * We just do a friendly check if another process
637 * should now be run, then fall through to loop
638 * around: */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700639 cond_resched();
640 case LGUEST_TRAP_ENTRY: /* Handled at top of loop */
641 continue;
642 }
643
Rusty Russellbff672e2007-07-26 10:41:04 -0700644 /* If we get here, it's a trap the Guest wants to know
645 * about. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700646 if (deliver_trap(lg, lg->regs->trapnum))
647 continue;
648
Rusty Russellbff672e2007-07-26 10:41:04 -0700649 /* If the Guest doesn't have a handler (either it hasn't
650 * registered any yet, or it's one of the faults we don't let
651 * it handle), it dies with a cryptic error message. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700652 kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",
653 lg->regs->trapnum, lg->regs->eip,
654 lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);
655 }
Rusty Russellbff672e2007-07-26 10:41:04 -0700656 /* The Guest is dead => "No such file or directory" */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700657 return -ENOENT;
658}
659
Rusty Russellbff672e2007-07-26 10:41:04 -0700660/* Now we can look at each of the routines this calls, in increasing order of
661 * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
662 * deliver_trap() and demand_page(). After all those, we'll be ready to
663 * examine the Switcher, and our philosophical understanding of the Host/Guest
664 * duality will be complete. :*/
665
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700666int find_free_guest(void)
667{
668 unsigned int i;
669 for (i = 0; i < MAX_LGUEST_GUESTS; i++)
670 if (!lguests[i].tsk)
671 return i;
672 return -1;
673}
674
675static void adjust_pge(void *on)
676{
677 if (on)
678 write_cr4(read_cr4() | X86_CR4_PGE);
679 else
680 write_cr4(read_cr4() & ~X86_CR4_PGE);
681}
682
Rusty Russellbff672e2007-07-26 10:41:04 -0700683/*H:000
684 * Welcome to the Host!
685 *
686 * By this point your brain has been tickled by the Guest code and numbed by
687 * the Launcher code; prepare for it to be stretched by the Host code. This is
688 * the heart. Let's begin at the initialization routine for the Host's lg
689 * module.
690 */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700691static int __init init(void)
692{
693 int err;
694
Rusty Russellbff672e2007-07-26 10:41:04 -0700695 /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700696 if (paravirt_enabled()) {
Jeremy Fitzhardinge93b1eab2007-10-16 11:51:29 -0700697 printk("lguest is afraid of %s\n", pv_info.name);
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700698 return -EPERM;
699 }
700
Rusty Russellbff672e2007-07-26 10:41:04 -0700701 /* First we put the Switcher up in very high virtual memory. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700702 err = map_switcher();
703 if (err)
704 return err;
705
Rusty Russellbff672e2007-07-26 10:41:04 -0700706 /* Now we set up the pagetable implementation for the Guests. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700707 err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);
708 if (err) {
709 unmap_switcher();
710 return err;
711 }
Rusty Russellbff672e2007-07-26 10:41:04 -0700712
713 /* The I/O subsystem needs some things initialized. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700714 lguest_io_init();
715
Rusty Russellbff672e2007-07-26 10:41:04 -0700716 /* /dev/lguest needs to be registered. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700717 err = lguest_device_init();
718 if (err) {
719 free_pagetables();
720 unmap_switcher();
721 return err;
722 }
Rusty Russellbff672e2007-07-26 10:41:04 -0700723
724 /* Finally, we need to turn off "Page Global Enable". PGE is an
725 * optimization where page table entries are specially marked to show
726 * they never change. The Host kernel marks all the kernel pages this
727 * way because it's always present, even when userspace is running.
728 *
729 * Lguest breaks this: unbeknownst to the rest of the Host kernel, we
730 * switch to the Guest kernel. If you don't disable this on all CPUs,
731 * you'll get really weird bugs that you'll chase for two days.
732 *
733 * I used to turn PGE off every time we switched to the Guest and back
734 * on when we return, but that slowed the Switcher down noticibly. */
735
736 /* We don't need the complexity of CPUs coming and going while we're
737 * doing this. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700738 lock_cpu_hotplug();
739 if (cpu_has_pge) { /* We have a broader idea of "global". */
Rusty Russellbff672e2007-07-26 10:41:04 -0700740 /* Remember that this was originally set (for cleanup). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700741 cpu_had_pge = 1;
Rusty Russellbff672e2007-07-26 10:41:04 -0700742 /* adjust_pge is a helper function which sets or unsets the PGE
743 * bit on its CPU, depending on the argument (0 == unset). */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700744 on_each_cpu(adjust_pge, (void *)0, 0, 1);
Rusty Russellbff672e2007-07-26 10:41:04 -0700745 /* Turn off the feature in the global feature set. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700746 clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
747 }
748 unlock_cpu_hotplug();
Rusty Russellbff672e2007-07-26 10:41:04 -0700749
750 /* All good! */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700751 return 0;
752}
753
Rusty Russellbff672e2007-07-26 10:41:04 -0700754/* Cleaning up is just the same code, backwards. With a little French. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700755static void __exit fini(void)
756{
757 lguest_device_remove();
758 free_pagetables();
759 unmap_switcher();
Rusty Russellbff672e2007-07-26 10:41:04 -0700760
761 /* If we had PGE before we started, turn it back on now. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700762 lock_cpu_hotplug();
763 if (cpu_had_pge) {
764 set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);
Rusty Russellbff672e2007-07-26 10:41:04 -0700765 /* adjust_pge's argument "1" means set PGE. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700766 on_each_cpu(adjust_pge, (void *)1, 0, 1);
767 }
768 unlock_cpu_hotplug();
769}
770
Rusty Russellbff672e2007-07-26 10:41:04 -0700771/* The Host side of lguest can be a module. This is a nice way for people to
772 * play with it. */
Rusty Russelld7e28ff2007-07-19 01:49:23 -0700773module_init(init);
774module_exit(fini);
775MODULE_LICENSE("GPL");
776MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");