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1d48922c DZ |
1 | /* |
2 | * Copyright (C) 1991, 1992 Linus Torvalds | |
3 | * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs | |
9c48f1c6 | 4 | * Copyright (C) 2011 Don Zickus Red Hat, Inc. |
1d48922c DZ |
5 | * |
6 | * Pentium III FXSR, SSE support | |
7 | * Gareth Hughes <gareth@valinux.com>, May 2000 | |
8 | */ | |
9 | ||
10 | /* | |
11 | * Handle hardware traps and faults. | |
12 | */ | |
13 | #include <linux/spinlock.h> | |
14 | #include <linux/kprobes.h> | |
15 | #include <linux/kdebug.h> | |
16 | #include <linux/nmi.h> | |
c9126b2e DZ |
17 | #include <linux/delay.h> |
18 | #include <linux/hardirq.h> | |
19 | #include <linux/slab.h> | |
69c60c88 | 20 | #include <linux/export.h> |
1d48922c | 21 | |
d48b0e17 IM |
22 | #include <linux/mca.h> |
23 | ||
1d48922c DZ |
24 | #if defined(CONFIG_EDAC) |
25 | #include <linux/edac.h> | |
26 | #endif | |
27 | ||
28 | #include <linux/atomic.h> | |
29 | #include <asm/traps.h> | |
30 | #include <asm/mach_traps.h> | |
c9126b2e | 31 | #include <asm/nmi.h> |
6fd36ba0 | 32 | #include <asm/x86_init.h> |
c9126b2e DZ |
33 | |
34 | #define NMI_MAX_NAMELEN 16 | |
35 | struct nmiaction { | |
36 | struct list_head list; | |
37 | nmi_handler_t handler; | |
38 | unsigned int flags; | |
39 | char *name; | |
40 | }; | |
41 | ||
42 | struct nmi_desc { | |
43 | spinlock_t lock; | |
44 | struct list_head head; | |
45 | }; | |
46 | ||
47 | static struct nmi_desc nmi_desc[NMI_MAX] = | |
48 | { | |
49 | { | |
50 | .lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[0].lock), | |
51 | .head = LIST_HEAD_INIT(nmi_desc[0].head), | |
52 | }, | |
53 | { | |
54 | .lock = __SPIN_LOCK_UNLOCKED(&nmi_desc[1].lock), | |
55 | .head = LIST_HEAD_INIT(nmi_desc[1].head), | |
56 | }, | |
57 | ||
58 | }; | |
1d48922c | 59 | |
efc3aac5 DZ |
60 | struct nmi_stats { |
61 | unsigned int normal; | |
62 | unsigned int unknown; | |
63 | unsigned int external; | |
64 | unsigned int swallow; | |
65 | }; | |
66 | ||
67 | static DEFINE_PER_CPU(struct nmi_stats, nmi_stats); | |
68 | ||
1d48922c DZ |
69 | static int ignore_nmis; |
70 | ||
71 | int unknown_nmi_panic; | |
72 | /* | |
73 | * Prevent NMI reason port (0x61) being accessed simultaneously, can | |
74 | * only be used in NMI handler. | |
75 | */ | |
76 | static DEFINE_RAW_SPINLOCK(nmi_reason_lock); | |
77 | ||
78 | static int __init setup_unknown_nmi_panic(char *str) | |
79 | { | |
80 | unknown_nmi_panic = 1; | |
81 | return 1; | |
82 | } | |
83 | __setup("unknown_nmi_panic", setup_unknown_nmi_panic); | |
84 | ||
c9126b2e DZ |
85 | #define nmi_to_desc(type) (&nmi_desc[type]) |
86 | ||
b227e233 | 87 | static int notrace __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2b) |
c9126b2e DZ |
88 | { |
89 | struct nmi_desc *desc = nmi_to_desc(type); | |
90 | struct nmiaction *a; | |
91 | int handled=0; | |
92 | ||
93 | rcu_read_lock(); | |
94 | ||
95 | /* | |
96 | * NMIs are edge-triggered, which means if you have enough | |
97 | * of them concurrently, you can lose some because only one | |
98 | * can be latched at any given time. Walk the whole list | |
99 | * to handle those situations. | |
100 | */ | |
b227e233 | 101 | list_for_each_entry_rcu(a, &desc->head, list) |
c9126b2e DZ |
102 | handled += a->handler(type, regs); |
103 | ||
c9126b2e DZ |
104 | rcu_read_unlock(); |
105 | ||
106 | /* return total number of NMI events handled */ | |
107 | return handled; | |
108 | } | |
109 | ||
110 | static int __setup_nmi(unsigned int type, struct nmiaction *action) | |
111 | { | |
112 | struct nmi_desc *desc = nmi_to_desc(type); | |
113 | unsigned long flags; | |
114 | ||
115 | spin_lock_irqsave(&desc->lock, flags); | |
116 | ||
b227e233 DZ |
117 | /* |
118 | * most handlers of type NMI_UNKNOWN never return because | |
119 | * they just assume the NMI is theirs. Just a sanity check | |
120 | * to manage expectations | |
121 | */ | |
122 | WARN_ON_ONCE(type == NMI_UNKNOWN && !list_empty(&desc->head)); | |
123 | ||
c9126b2e DZ |
124 | /* |
125 | * some handlers need to be executed first otherwise a fake | |
126 | * event confuses some handlers (kdump uses this flag) | |
127 | */ | |
128 | if (action->flags & NMI_FLAG_FIRST) | |
129 | list_add_rcu(&action->list, &desc->head); | |
130 | else | |
131 | list_add_tail_rcu(&action->list, &desc->head); | |
132 | ||
133 | spin_unlock_irqrestore(&desc->lock, flags); | |
134 | return 0; | |
135 | } | |
136 | ||
137 | static struct nmiaction *__free_nmi(unsigned int type, const char *name) | |
138 | { | |
139 | struct nmi_desc *desc = nmi_to_desc(type); | |
140 | struct nmiaction *n; | |
141 | unsigned long flags; | |
142 | ||
143 | spin_lock_irqsave(&desc->lock, flags); | |
144 | ||
145 | list_for_each_entry_rcu(n, &desc->head, list) { | |
146 | /* | |
147 | * the name passed in to describe the nmi handler | |
148 | * is used as the lookup key | |
149 | */ | |
150 | if (!strcmp(n->name, name)) { | |
151 | WARN(in_nmi(), | |
152 | "Trying to free NMI (%s) from NMI context!\n", n->name); | |
153 | list_del_rcu(&n->list); | |
154 | break; | |
155 | } | |
156 | } | |
157 | ||
158 | spin_unlock_irqrestore(&desc->lock, flags); | |
159 | synchronize_rcu(); | |
160 | return (n); | |
161 | } | |
162 | ||
163 | int register_nmi_handler(unsigned int type, nmi_handler_t handler, | |
164 | unsigned long nmiflags, const char *devname) | |
165 | { | |
166 | struct nmiaction *action; | |
167 | int retval = -ENOMEM; | |
168 | ||
169 | if (!handler) | |
170 | return -EINVAL; | |
171 | ||
172 | action = kzalloc(sizeof(struct nmiaction), GFP_KERNEL); | |
173 | if (!action) | |
174 | goto fail_action; | |
175 | ||
176 | action->handler = handler; | |
177 | action->flags = nmiflags; | |
178 | action->name = kstrndup(devname, NMI_MAX_NAMELEN, GFP_KERNEL); | |
179 | if (!action->name) | |
180 | goto fail_action_name; | |
181 | ||
182 | retval = __setup_nmi(type, action); | |
183 | ||
184 | if (retval) | |
185 | goto fail_setup_nmi; | |
186 | ||
187 | return retval; | |
188 | ||
189 | fail_setup_nmi: | |
190 | kfree(action->name); | |
191 | fail_action_name: | |
192 | kfree(action); | |
193 | fail_action: | |
194 | ||
195 | return retval; | |
196 | } | |
197 | EXPORT_SYMBOL_GPL(register_nmi_handler); | |
198 | ||
199 | void unregister_nmi_handler(unsigned int type, const char *name) | |
200 | { | |
201 | struct nmiaction *a; | |
202 | ||
203 | a = __free_nmi(type, name); | |
204 | if (a) { | |
205 | kfree(a->name); | |
206 | kfree(a); | |
207 | } | |
208 | } | |
209 | ||
210 | EXPORT_SYMBOL_GPL(unregister_nmi_handler); | |
211 | ||
1d48922c DZ |
212 | static notrace __kprobes void |
213 | pci_serr_error(unsigned char reason, struct pt_regs *regs) | |
214 | { | |
215 | pr_emerg("NMI: PCI system error (SERR) for reason %02x on CPU %d.\n", | |
216 | reason, smp_processor_id()); | |
217 | ||
218 | /* | |
219 | * On some machines, PCI SERR line is used to report memory | |
220 | * errors. EDAC makes use of it. | |
221 | */ | |
222 | #if defined(CONFIG_EDAC) | |
223 | if (edac_handler_set()) { | |
224 | edac_atomic_assert_error(); | |
225 | return; | |
226 | } | |
227 | #endif | |
228 | ||
229 | if (panic_on_unrecovered_nmi) | |
230 | panic("NMI: Not continuing"); | |
231 | ||
232 | pr_emerg("Dazed and confused, but trying to continue\n"); | |
233 | ||
234 | /* Clear and disable the PCI SERR error line. */ | |
235 | reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_SERR; | |
236 | outb(reason, NMI_REASON_PORT); | |
237 | } | |
238 | ||
239 | static notrace __kprobes void | |
240 | io_check_error(unsigned char reason, struct pt_regs *regs) | |
241 | { | |
242 | unsigned long i; | |
243 | ||
244 | pr_emerg( | |
245 | "NMI: IOCK error (debug interrupt?) for reason %02x on CPU %d.\n", | |
246 | reason, smp_processor_id()); | |
247 | show_registers(regs); | |
248 | ||
249 | if (panic_on_io_nmi) | |
250 | panic("NMI IOCK error: Not continuing"); | |
251 | ||
252 | /* Re-enable the IOCK line, wait for a few seconds */ | |
253 | reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_IOCHK; | |
254 | outb(reason, NMI_REASON_PORT); | |
255 | ||
256 | i = 20000; | |
257 | while (--i) { | |
258 | touch_nmi_watchdog(); | |
259 | udelay(100); | |
260 | } | |
261 | ||
262 | reason &= ~NMI_REASON_CLEAR_IOCHK; | |
263 | outb(reason, NMI_REASON_PORT); | |
264 | } | |
265 | ||
266 | static notrace __kprobes void | |
267 | unknown_nmi_error(unsigned char reason, struct pt_regs *regs) | |
268 | { | |
9c48f1c6 DZ |
269 | int handled; |
270 | ||
b227e233 DZ |
271 | /* |
272 | * Use 'false' as back-to-back NMIs are dealt with one level up. | |
273 | * Of course this makes having multiple 'unknown' handlers useless | |
274 | * as only the first one is ever run (unless it can actually determine | |
275 | * if it caused the NMI) | |
276 | */ | |
277 | handled = nmi_handle(NMI_UNKNOWN, regs, false); | |
efc3aac5 DZ |
278 | if (handled) { |
279 | __this_cpu_add(nmi_stats.unknown, handled); | |
1d48922c | 280 | return; |
efc3aac5 DZ |
281 | } |
282 | ||
283 | __this_cpu_add(nmi_stats.unknown, 1); | |
284 | ||
1d48922c DZ |
285 | #ifdef CONFIG_MCA |
286 | /* | |
287 | * Might actually be able to figure out what the guilty party | |
288 | * is: | |
289 | */ | |
290 | if (MCA_bus) { | |
291 | mca_handle_nmi(); | |
292 | return; | |
293 | } | |
294 | #endif | |
295 | pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n", | |
296 | reason, smp_processor_id()); | |
297 | ||
298 | pr_emerg("Do you have a strange power saving mode enabled?\n"); | |
299 | if (unknown_nmi_panic || panic_on_unrecovered_nmi) | |
300 | panic("NMI: Not continuing"); | |
301 | ||
302 | pr_emerg("Dazed and confused, but trying to continue\n"); | |
303 | } | |
304 | ||
b227e233 DZ |
305 | static DEFINE_PER_CPU(bool, swallow_nmi); |
306 | static DEFINE_PER_CPU(unsigned long, last_nmi_rip); | |
307 | ||
1d48922c DZ |
308 | static notrace __kprobes void default_do_nmi(struct pt_regs *regs) |
309 | { | |
310 | unsigned char reason = 0; | |
9c48f1c6 | 311 | int handled; |
b227e233 | 312 | bool b2b = false; |
1d48922c DZ |
313 | |
314 | /* | |
315 | * CPU-specific NMI must be processed before non-CPU-specific | |
316 | * NMI, otherwise we may lose it, because the CPU-specific | |
317 | * NMI can not be detected/processed on other CPUs. | |
318 | */ | |
b227e233 DZ |
319 | |
320 | /* | |
321 | * Back-to-back NMIs are interesting because they can either | |
322 | * be two NMI or more than two NMIs (any thing over two is dropped | |
323 | * due to NMI being edge-triggered). If this is the second half | |
324 | * of the back-to-back NMI, assume we dropped things and process | |
325 | * more handlers. Otherwise reset the 'swallow' NMI behaviour | |
326 | */ | |
327 | if (regs->ip == __this_cpu_read(last_nmi_rip)) | |
328 | b2b = true; | |
329 | else | |
330 | __this_cpu_write(swallow_nmi, false); | |
331 | ||
332 | __this_cpu_write(last_nmi_rip, regs->ip); | |
333 | ||
334 | handled = nmi_handle(NMI_LOCAL, regs, b2b); | |
efc3aac5 | 335 | __this_cpu_add(nmi_stats.normal, handled); |
b227e233 DZ |
336 | if (handled) { |
337 | /* | |
338 | * There are cases when a NMI handler handles multiple | |
339 | * events in the current NMI. One of these events may | |
340 | * be queued for in the next NMI. Because the event is | |
341 | * already handled, the next NMI will result in an unknown | |
342 | * NMI. Instead lets flag this for a potential NMI to | |
343 | * swallow. | |
344 | */ | |
345 | if (handled > 1) | |
346 | __this_cpu_write(swallow_nmi, true); | |
1d48922c | 347 | return; |
b227e233 | 348 | } |
1d48922c DZ |
349 | |
350 | /* Non-CPU-specific NMI: NMI sources can be processed on any CPU */ | |
351 | raw_spin_lock(&nmi_reason_lock); | |
064a59b6 | 352 | reason = x86_platform.get_nmi_reason(); |
1d48922c DZ |
353 | |
354 | if (reason & NMI_REASON_MASK) { | |
355 | if (reason & NMI_REASON_SERR) | |
356 | pci_serr_error(reason, regs); | |
357 | else if (reason & NMI_REASON_IOCHK) | |
358 | io_check_error(reason, regs); | |
359 | #ifdef CONFIG_X86_32 | |
360 | /* | |
361 | * Reassert NMI in case it became active | |
362 | * meanwhile as it's edge-triggered: | |
363 | */ | |
364 | reassert_nmi(); | |
365 | #endif | |
efc3aac5 | 366 | __this_cpu_add(nmi_stats.external, 1); |
1d48922c DZ |
367 | raw_spin_unlock(&nmi_reason_lock); |
368 | return; | |
369 | } | |
370 | raw_spin_unlock(&nmi_reason_lock); | |
371 | ||
b227e233 DZ |
372 | /* |
373 | * Only one NMI can be latched at a time. To handle | |
374 | * this we may process multiple nmi handlers at once to | |
375 | * cover the case where an NMI is dropped. The downside | |
376 | * to this approach is we may process an NMI prematurely, | |
377 | * while its real NMI is sitting latched. This will cause | |
378 | * an unknown NMI on the next run of the NMI processing. | |
379 | * | |
380 | * We tried to flag that condition above, by setting the | |
381 | * swallow_nmi flag when we process more than one event. | |
382 | * This condition is also only present on the second half | |
383 | * of a back-to-back NMI, so we flag that condition too. | |
384 | * | |
385 | * If both are true, we assume we already processed this | |
386 | * NMI previously and we swallow it. Otherwise we reset | |
387 | * the logic. | |
388 | * | |
389 | * There are scenarios where we may accidentally swallow | |
390 | * a 'real' unknown NMI. For example, while processing | |
391 | * a perf NMI another perf NMI comes in along with a | |
392 | * 'real' unknown NMI. These two NMIs get combined into | |
393 | * one (as descibed above). When the next NMI gets | |
394 | * processed, it will be flagged by perf as handled, but | |
395 | * noone will know that there was a 'real' unknown NMI sent | |
396 | * also. As a result it gets swallowed. Or if the first | |
397 | * perf NMI returns two events handled then the second | |
398 | * NMI will get eaten by the logic below, again losing a | |
399 | * 'real' unknown NMI. But this is the best we can do | |
400 | * for now. | |
401 | */ | |
402 | if (b2b && __this_cpu_read(swallow_nmi)) | |
efc3aac5 | 403 | __this_cpu_add(nmi_stats.swallow, 1); |
b227e233 DZ |
404 | else |
405 | unknown_nmi_error(reason, regs); | |
1d48922c DZ |
406 | } |
407 | ||
ccd49c23 SR |
408 | /* |
409 | * NMIs can hit breakpoints which will cause it to lose its | |
410 | * NMI context with the CPU when the breakpoint does an iret. | |
411 | */ | |
412 | #ifdef CONFIG_X86_32 | |
413 | /* | |
414 | * For i386, NMIs use the same stack as the kernel, and we can | |
415 | * add a workaround to the iret problem in C. Simply have 3 states | |
416 | * the NMI can be in. | |
417 | * | |
418 | * 1) not running | |
419 | * 2) executing | |
420 | * 3) latched | |
421 | * | |
422 | * When no NMI is in progress, it is in the "not running" state. | |
423 | * When an NMI comes in, it goes into the "executing" state. | |
424 | * Normally, if another NMI is triggered, it does not interrupt | |
425 | * the running NMI and the HW will simply latch it so that when | |
426 | * the first NMI finishes, it will restart the second NMI. | |
427 | * (Note, the latch is binary, thus multiple NMIs triggering, | |
428 | * when one is running, are ignored. Only one NMI is restarted.) | |
429 | * | |
430 | * If an NMI hits a breakpoint that executes an iret, another | |
431 | * NMI can preempt it. We do not want to allow this new NMI | |
432 | * to run, but we want to execute it when the first one finishes. | |
433 | * We set the state to "latched", and the first NMI will perform | |
434 | * an cmpxchg on the state, and if it doesn't successfully | |
435 | * reset the state to "not running" it will restart the next | |
436 | * NMI. | |
437 | */ | |
438 | enum nmi_states { | |
439 | NMI_NOT_RUNNING, | |
440 | NMI_EXECUTING, | |
441 | NMI_LATCHED, | |
442 | }; | |
443 | static DEFINE_PER_CPU(enum nmi_states, nmi_state); | |
444 | ||
445 | #define nmi_nesting_preprocess(regs) \ | |
446 | do { \ | |
447 | if (__get_cpu_var(nmi_state) != NMI_NOT_RUNNING) { \ | |
448 | __get_cpu_var(nmi_state) = NMI_LATCHED; \ | |
449 | return; \ | |
450 | } \ | |
451 | nmi_restart: \ | |
452 | __get_cpu_var(nmi_state) = NMI_EXECUTING; \ | |
453 | } while (0) | |
454 | ||
455 | #define nmi_nesting_postprocess() \ | |
456 | do { \ | |
457 | if (cmpxchg(&__get_cpu_var(nmi_state), \ | |
458 | NMI_EXECUTING, NMI_NOT_RUNNING) != NMI_EXECUTING) \ | |
459 | goto nmi_restart; \ | |
460 | } while (0) | |
461 | #else /* x86_64 */ | |
462 | /* | |
463 | * In x86_64 things are a bit more difficult. This has the same problem | |
464 | * where an NMI hitting a breakpoint that calls iret will remove the | |
465 | * NMI context, allowing a nested NMI to enter. What makes this more | |
466 | * difficult is that both NMIs and breakpoints have their own stack. | |
467 | * When a new NMI or breakpoint is executed, the stack is set to a fixed | |
468 | * point. If an NMI is nested, it will have its stack set at that same | |
469 | * fixed address that the first NMI had, and will start corrupting the | |
470 | * stack. This is handled in entry_64.S, but the same problem exists with | |
471 | * the breakpoint stack. | |
472 | * | |
473 | * If a breakpoint is being processed, and the debug stack is being used, | |
474 | * if an NMI comes in and also hits a breakpoint, the stack pointer | |
475 | * will be set to the same fixed address as the breakpoint that was | |
476 | * interrupted, causing that stack to be corrupted. To handle this case, | |
477 | * check if the stack that was interrupted is the debug stack, and if | |
478 | * so, change the IDT so that new breakpoints will use the current stack | |
479 | * and not switch to the fixed address. On return of the NMI, switch back | |
480 | * to the original IDT. | |
481 | */ | |
482 | static DEFINE_PER_CPU(int, update_debug_stack); | |
228bdaa9 | 483 | |
ccd49c23 SR |
484 | static inline void nmi_nesting_preprocess(struct pt_regs *regs) |
485 | { | |
228bdaa9 SR |
486 | /* |
487 | * If we interrupted a breakpoint, it is possible that | |
488 | * the nmi handler will have breakpoints too. We need to | |
489 | * change the IDT such that breakpoints that happen here | |
490 | * continue to use the NMI stack. | |
491 | */ | |
492 | if (unlikely(is_debug_stack(regs->sp))) { | |
493 | debug_stack_set_zero(); | |
ccd49c23 | 494 | __get_cpu_var(update_debug_stack) = 1; |
228bdaa9 | 495 | } |
ccd49c23 SR |
496 | } |
497 | ||
498 | static inline void nmi_nesting_postprocess(void) | |
499 | { | |
500 | if (unlikely(__get_cpu_var(update_debug_stack))) | |
501 | debug_stack_reset(); | |
502 | } | |
503 | #endif | |
504 | ||
505 | dotraplinkage notrace __kprobes void | |
506 | do_nmi(struct pt_regs *regs, long error_code) | |
507 | { | |
508 | nmi_nesting_preprocess(regs); | |
509 | ||
1d48922c DZ |
510 | nmi_enter(); |
511 | ||
512 | inc_irq_stat(__nmi_count); | |
513 | ||
514 | if (!ignore_nmis) | |
515 | default_do_nmi(regs); | |
516 | ||
517 | nmi_exit(); | |
228bdaa9 | 518 | |
ccd49c23 SR |
519 | /* On i386, may loop back to preprocess */ |
520 | nmi_nesting_postprocess(); | |
1d48922c DZ |
521 | } |
522 | ||
523 | void stop_nmi(void) | |
524 | { | |
525 | ignore_nmis++; | |
526 | } | |
527 | ||
528 | void restart_nmi(void) | |
529 | { | |
530 | ignore_nmis--; | |
531 | } | |
b227e233 DZ |
532 | |
533 | /* reset the back-to-back NMI logic */ | |
534 | void local_touch_nmi(void) | |
535 | { | |
536 | __this_cpu_write(last_nmi_rip, 0); | |
537 | } |