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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
1d48922c DZ |
2 | /* |
3 | * Copyright (C) 1991, 1992 Linus Torvalds | |
4 | * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs | |
9c48f1c6 | 5 | * Copyright (C) 2011 Don Zickus Red Hat, Inc. |
1d48922c DZ |
6 | * |
7 | * Pentium III FXSR, SSE support | |
8 | * Gareth Hughes <gareth@valinux.com>, May 2000 | |
9 | */ | |
10 | ||
11 | /* | |
12 | * Handle hardware traps and faults. | |
13 | */ | |
14 | #include <linux/spinlock.h> | |
15 | #include <linux/kprobes.h> | |
16 | #include <linux/kdebug.h> | |
b17b0153 | 17 | #include <linux/sched/debug.h> |
1d48922c | 18 | #include <linux/nmi.h> |
2ab00456 | 19 | #include <linux/debugfs.h> |
c9126b2e DZ |
20 | #include <linux/delay.h> |
21 | #include <linux/hardirq.h> | |
c361db5c | 22 | #include <linux/ratelimit.h> |
c9126b2e | 23 | #include <linux/slab.h> |
69c60c88 | 24 | #include <linux/export.h> |
2a594d4c | 25 | #include <linux/atomic.h> |
e6017571 | 26 | #include <linux/sched/clock.h> |
1d48922c DZ |
27 | |
28 | #if defined(CONFIG_EDAC) | |
29 | #include <linux/edac.h> | |
30 | #endif | |
31 | ||
2a594d4c | 32 | #include <asm/cpu_entry_area.h> |
1d48922c DZ |
33 | #include <asm/traps.h> |
34 | #include <asm/mach_traps.h> | |
c9126b2e | 35 | #include <asm/nmi.h> |
6fd36ba0 | 36 | #include <asm/x86_init.h> |
b279d67d | 37 | #include <asm/reboot.h> |
8e2a7f5b | 38 | #include <asm/cache.h> |
04dcbdb8 | 39 | #include <asm/nospec-branch.h> |
c9126b2e | 40 | |
0c4df02d DH |
41 | #define CREATE_TRACE_POINTS |
42 | #include <trace/events/nmi.h> | |
43 | ||
c9126b2e | 44 | struct nmi_desc { |
c455fd92 | 45 | raw_spinlock_t lock; |
c9126b2e DZ |
46 | struct list_head head; |
47 | }; | |
48 | ||
49 | static struct nmi_desc nmi_desc[NMI_MAX] = | |
50 | { | |
51 | { | |
c455fd92 | 52 | .lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[0].lock), |
c9126b2e DZ |
53 | .head = LIST_HEAD_INIT(nmi_desc[0].head), |
54 | }, | |
55 | { | |
c455fd92 | 56 | .lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[1].lock), |
c9126b2e DZ |
57 | .head = LIST_HEAD_INIT(nmi_desc[1].head), |
58 | }, | |
553222f3 | 59 | { |
c455fd92 | 60 | .lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[2].lock), |
553222f3 DZ |
61 | .head = LIST_HEAD_INIT(nmi_desc[2].head), |
62 | }, | |
63 | { | |
c455fd92 | 64 | .lock = __RAW_SPIN_LOCK_UNLOCKED(&nmi_desc[3].lock), |
553222f3 DZ |
65 | .head = LIST_HEAD_INIT(nmi_desc[3].head), |
66 | }, | |
c9126b2e DZ |
67 | |
68 | }; | |
1d48922c | 69 | |
efc3aac5 DZ |
70 | struct nmi_stats { |
71 | unsigned int normal; | |
72 | unsigned int unknown; | |
73 | unsigned int external; | |
74 | unsigned int swallow; | |
75 | }; | |
76 | ||
77 | static DEFINE_PER_CPU(struct nmi_stats, nmi_stats); | |
78 | ||
8e2a7f5b | 79 | static int ignore_nmis __read_mostly; |
1d48922c DZ |
80 | |
81 | int unknown_nmi_panic; | |
82 | /* | |
83 | * Prevent NMI reason port (0x61) being accessed simultaneously, can | |
84 | * only be used in NMI handler. | |
85 | */ | |
86 | static DEFINE_RAW_SPINLOCK(nmi_reason_lock); | |
87 | ||
88 | static int __init setup_unknown_nmi_panic(char *str) | |
89 | { | |
90 | unknown_nmi_panic = 1; | |
91 | return 1; | |
92 | } | |
93 | __setup("unknown_nmi_panic", setup_unknown_nmi_panic); | |
94 | ||
c9126b2e DZ |
95 | #define nmi_to_desc(type) (&nmi_desc[type]) |
96 | ||
2ab00456 | 97 | static u64 nmi_longest_ns = 1 * NSEC_PER_MSEC; |
e90c7853 | 98 | |
2ab00456 DH |
99 | static int __init nmi_warning_debugfs(void) |
100 | { | |
101 | debugfs_create_u64("nmi_longest_ns", 0644, | |
102 | arch_debugfs_dir, &nmi_longest_ns); | |
103 | return 0; | |
104 | } | |
105 | fs_initcall(nmi_warning_debugfs); | |
106 | ||
248ed510 | 107 | static void nmi_check_duration(struct nmiaction *action, u64 duration) |
e90c7853 | 108 | { |
248ed510 | 109 | u64 whole_msecs = READ_ONCE(action->max_duration); |
e90c7853 | 110 | int remainder_ns, decimal_msecs; |
248ed510 CD |
111 | |
112 | if (duration < nmi_longest_ns || duration < action->max_duration) | |
113 | return; | |
114 | ||
115 | action->max_duration = duration; | |
e90c7853 PZ |
116 | |
117 | remainder_ns = do_div(whole_msecs, (1000 * 1000)); | |
118 | decimal_msecs = remainder_ns / 1000; | |
119 | ||
120 | printk_ratelimited(KERN_INFO | |
121 | "INFO: NMI handler (%ps) took too long to run: %lld.%03d msecs\n", | |
248ed510 | 122 | action->handler, whole_msecs, decimal_msecs); |
e90c7853 PZ |
123 | } |
124 | ||
bf9f2ee2 | 125 | static int nmi_handle(unsigned int type, struct pt_regs *regs) |
c9126b2e DZ |
126 | { |
127 | struct nmi_desc *desc = nmi_to_desc(type); | |
128 | struct nmiaction *a; | |
129 | int handled=0; | |
130 | ||
131 | rcu_read_lock(); | |
132 | ||
133 | /* | |
134 | * NMIs are edge-triggered, which means if you have enough | |
135 | * of them concurrently, you can lose some because only one | |
136 | * can be latched at any given time. Walk the whole list | |
137 | * to handle those situations. | |
138 | */ | |
2ab00456 | 139 | list_for_each_entry_rcu(a, &desc->head, list) { |
e90c7853 PZ |
140 | int thishandled; |
141 | u64 delta; | |
2ab00456 | 142 | |
e90c7853 | 143 | delta = sched_clock(); |
0c4df02d DH |
144 | thishandled = a->handler(type, regs); |
145 | handled += thishandled; | |
e90c7853 | 146 | delta = sched_clock() - delta; |
0c4df02d | 147 | trace_nmi_handler(a->handler, (int)delta, thishandled); |
2ab00456 | 148 | |
248ed510 | 149 | nmi_check_duration(a, delta); |
2ab00456 | 150 | } |
c9126b2e | 151 | |
c9126b2e DZ |
152 | rcu_read_unlock(); |
153 | ||
154 | /* return total number of NMI events handled */ | |
155 | return handled; | |
156 | } | |
9326638c | 157 | NOKPROBE_SYMBOL(nmi_handle); |
c9126b2e | 158 | |
72b3fb24 | 159 | int __register_nmi_handler(unsigned int type, struct nmiaction *action) |
c9126b2e DZ |
160 | { |
161 | struct nmi_desc *desc = nmi_to_desc(type); | |
162 | unsigned long flags; | |
163 | ||
72b3fb24 LZ |
164 | if (!action->handler) |
165 | return -EINVAL; | |
166 | ||
c455fd92 | 167 | raw_spin_lock_irqsave(&desc->lock, flags); |
c9126b2e | 168 | |
b227e233 | 169 | /* |
0d443b70 MT |
170 | * Indicate if there are multiple registrations on the |
171 | * internal NMI handler call chains (SERR and IO_CHECK). | |
b227e233 | 172 | */ |
553222f3 DZ |
173 | WARN_ON_ONCE(type == NMI_SERR && !list_empty(&desc->head)); |
174 | WARN_ON_ONCE(type == NMI_IO_CHECK && !list_empty(&desc->head)); | |
b227e233 | 175 | |
c9126b2e DZ |
176 | /* |
177 | * some handlers need to be executed first otherwise a fake | |
178 | * event confuses some handlers (kdump uses this flag) | |
179 | */ | |
180 | if (action->flags & NMI_FLAG_FIRST) | |
181 | list_add_rcu(&action->list, &desc->head); | |
182 | else | |
183 | list_add_tail_rcu(&action->list, &desc->head); | |
184 | ||
c455fd92 | 185 | raw_spin_unlock_irqrestore(&desc->lock, flags); |
c9126b2e DZ |
186 | return 0; |
187 | } | |
72b3fb24 | 188 | EXPORT_SYMBOL(__register_nmi_handler); |
c9126b2e | 189 | |
72b3fb24 | 190 | void unregister_nmi_handler(unsigned int type, const char *name) |
c9126b2e DZ |
191 | { |
192 | struct nmi_desc *desc = nmi_to_desc(type); | |
193 | struct nmiaction *n; | |
194 | unsigned long flags; | |
195 | ||
c455fd92 | 196 | raw_spin_lock_irqsave(&desc->lock, flags); |
c9126b2e DZ |
197 | |
198 | list_for_each_entry_rcu(n, &desc->head, list) { | |
199 | /* | |
200 | * the name passed in to describe the nmi handler | |
201 | * is used as the lookup key | |
202 | */ | |
203 | if (!strcmp(n->name, name)) { | |
204 | WARN(in_nmi(), | |
205 | "Trying to free NMI (%s) from NMI context!\n", n->name); | |
206 | list_del_rcu(&n->list); | |
207 | break; | |
208 | } | |
209 | } | |
210 | ||
c455fd92 | 211 | raw_spin_unlock_irqrestore(&desc->lock, flags); |
c9126b2e | 212 | synchronize_rcu(); |
c9126b2e | 213 | } |
c9126b2e DZ |
214 | EXPORT_SYMBOL_GPL(unregister_nmi_handler); |
215 | ||
9326638c | 216 | static void |
1d48922c DZ |
217 | pci_serr_error(unsigned char reason, struct pt_regs *regs) |
218 | { | |
553222f3 | 219 | /* check to see if anyone registered against these types of errors */ |
bf9f2ee2 | 220 | if (nmi_handle(NMI_SERR, regs)) |
553222f3 DZ |
221 | return; |
222 | ||
1d48922c DZ |
223 | pr_emerg("NMI: PCI system error (SERR) for reason %02x on CPU %d.\n", |
224 | reason, smp_processor_id()); | |
225 | ||
1d48922c | 226 | if (panic_on_unrecovered_nmi) |
58c5661f | 227 | nmi_panic(regs, "NMI: Not continuing"); |
1d48922c DZ |
228 | |
229 | pr_emerg("Dazed and confused, but trying to continue\n"); | |
230 | ||
231 | /* Clear and disable the PCI SERR error line. */ | |
232 | reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_SERR; | |
233 | outb(reason, NMI_REASON_PORT); | |
234 | } | |
9326638c | 235 | NOKPROBE_SYMBOL(pci_serr_error); |
1d48922c | 236 | |
9326638c | 237 | static void |
1d48922c DZ |
238 | io_check_error(unsigned char reason, struct pt_regs *regs) |
239 | { | |
240 | unsigned long i; | |
241 | ||
553222f3 | 242 | /* check to see if anyone registered against these types of errors */ |
bf9f2ee2 | 243 | if (nmi_handle(NMI_IO_CHECK, regs)) |
553222f3 DZ |
244 | return; |
245 | ||
1d48922c DZ |
246 | pr_emerg( |
247 | "NMI: IOCK error (debug interrupt?) for reason %02x on CPU %d.\n", | |
248 | reason, smp_processor_id()); | |
57da8b96 | 249 | show_regs(regs); |
1d48922c | 250 | |
1717f209 | 251 | if (panic_on_io_nmi) { |
58c5661f | 252 | nmi_panic(regs, "NMI IOCK error: Not continuing"); |
1717f209 HK |
253 | |
254 | /* | |
255 | * If we end up here, it means we have received an NMI while | |
256 | * processing panic(). Simply return without delaying and | |
257 | * re-enabling NMIs. | |
258 | */ | |
259 | return; | |
260 | } | |
1d48922c DZ |
261 | |
262 | /* Re-enable the IOCK line, wait for a few seconds */ | |
263 | reason = (reason & NMI_REASON_CLEAR_MASK) | NMI_REASON_CLEAR_IOCHK; | |
264 | outb(reason, NMI_REASON_PORT); | |
265 | ||
266 | i = 20000; | |
267 | while (--i) { | |
268 | touch_nmi_watchdog(); | |
269 | udelay(100); | |
270 | } | |
271 | ||
272 | reason &= ~NMI_REASON_CLEAR_IOCHK; | |
273 | outb(reason, NMI_REASON_PORT); | |
274 | } | |
9326638c | 275 | NOKPROBE_SYMBOL(io_check_error); |
1d48922c | 276 | |
9326638c | 277 | static void |
1d48922c DZ |
278 | unknown_nmi_error(unsigned char reason, struct pt_regs *regs) |
279 | { | |
9c48f1c6 DZ |
280 | int handled; |
281 | ||
b227e233 DZ |
282 | /* |
283 | * Use 'false' as back-to-back NMIs are dealt with one level up. | |
284 | * Of course this makes having multiple 'unknown' handlers useless | |
285 | * as only the first one is ever run (unless it can actually determine | |
286 | * if it caused the NMI) | |
287 | */ | |
bf9f2ee2 | 288 | handled = nmi_handle(NMI_UNKNOWN, regs); |
efc3aac5 DZ |
289 | if (handled) { |
290 | __this_cpu_add(nmi_stats.unknown, handled); | |
1d48922c | 291 | return; |
efc3aac5 DZ |
292 | } |
293 | ||
294 | __this_cpu_add(nmi_stats.unknown, 1); | |
295 | ||
1d48922c DZ |
296 | pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n", |
297 | reason, smp_processor_id()); | |
298 | ||
299 | pr_emerg("Do you have a strange power saving mode enabled?\n"); | |
300 | if (unknown_nmi_panic || panic_on_unrecovered_nmi) | |
58c5661f | 301 | nmi_panic(regs, "NMI: Not continuing"); |
1d48922c DZ |
302 | |
303 | pr_emerg("Dazed and confused, but trying to continue\n"); | |
304 | } | |
9326638c | 305 | NOKPROBE_SYMBOL(unknown_nmi_error); |
1d48922c | 306 | |
b227e233 DZ |
307 | static DEFINE_PER_CPU(bool, swallow_nmi); |
308 | static DEFINE_PER_CPU(unsigned long, last_nmi_rip); | |
309 | ||
9326638c | 310 | static void default_do_nmi(struct pt_regs *regs) |
1d48922c DZ |
311 | { |
312 | unsigned char reason = 0; | |
9c48f1c6 | 313 | int handled; |
b227e233 | 314 | bool b2b = false; |
1d48922c DZ |
315 | |
316 | /* | |
317 | * CPU-specific NMI must be processed before non-CPU-specific | |
318 | * NMI, otherwise we may lose it, because the CPU-specific | |
319 | * NMI can not be detected/processed on other CPUs. | |
320 | */ | |
b227e233 DZ |
321 | |
322 | /* | |
323 | * Back-to-back NMIs are interesting because they can either | |
324 | * be two NMI or more than two NMIs (any thing over two is dropped | |
325 | * due to NMI being edge-triggered). If this is the second half | |
326 | * of the back-to-back NMI, assume we dropped things and process | |
327 | * more handlers. Otherwise reset the 'swallow' NMI behaviour | |
328 | */ | |
329 | if (regs->ip == __this_cpu_read(last_nmi_rip)) | |
330 | b2b = true; | |
331 | else | |
332 | __this_cpu_write(swallow_nmi, false); | |
333 | ||
334 | __this_cpu_write(last_nmi_rip, regs->ip); | |
335 | ||
bf9f2ee2 | 336 | handled = nmi_handle(NMI_LOCAL, regs); |
efc3aac5 | 337 | __this_cpu_add(nmi_stats.normal, handled); |
b227e233 DZ |
338 | if (handled) { |
339 | /* | |
340 | * There are cases when a NMI handler handles multiple | |
341 | * events in the current NMI. One of these events may | |
342 | * be queued for in the next NMI. Because the event is | |
343 | * already handled, the next NMI will result in an unknown | |
344 | * NMI. Instead lets flag this for a potential NMI to | |
345 | * swallow. | |
346 | */ | |
347 | if (handled > 1) | |
348 | __this_cpu_write(swallow_nmi, true); | |
1d48922c | 349 | return; |
b227e233 | 350 | } |
1d48922c | 351 | |
b279d67d HK |
352 | /* |
353 | * Non-CPU-specific NMI: NMI sources can be processed on any CPU. | |
354 | * | |
355 | * Another CPU may be processing panic routines while holding | |
356 | * nmi_reason_lock. Check if the CPU issued the IPI for crash dumping, | |
357 | * and if so, call its callback directly. If there is no CPU preparing | |
358 | * crash dump, we simply loop here. | |
359 | */ | |
360 | while (!raw_spin_trylock(&nmi_reason_lock)) { | |
361 | run_crash_ipi_callback(regs); | |
362 | cpu_relax(); | |
363 | } | |
364 | ||
064a59b6 | 365 | reason = x86_platform.get_nmi_reason(); |
1d48922c DZ |
366 | |
367 | if (reason & NMI_REASON_MASK) { | |
368 | if (reason & NMI_REASON_SERR) | |
369 | pci_serr_error(reason, regs); | |
370 | else if (reason & NMI_REASON_IOCHK) | |
371 | io_check_error(reason, regs); | |
372 | #ifdef CONFIG_X86_32 | |
373 | /* | |
374 | * Reassert NMI in case it became active | |
375 | * meanwhile as it's edge-triggered: | |
376 | */ | |
377 | reassert_nmi(); | |
378 | #endif | |
efc3aac5 | 379 | __this_cpu_add(nmi_stats.external, 1); |
1d48922c DZ |
380 | raw_spin_unlock(&nmi_reason_lock); |
381 | return; | |
382 | } | |
383 | raw_spin_unlock(&nmi_reason_lock); | |
384 | ||
b227e233 DZ |
385 | /* |
386 | * Only one NMI can be latched at a time. To handle | |
387 | * this we may process multiple nmi handlers at once to | |
388 | * cover the case where an NMI is dropped. The downside | |
389 | * to this approach is we may process an NMI prematurely, | |
390 | * while its real NMI is sitting latched. This will cause | |
391 | * an unknown NMI on the next run of the NMI processing. | |
392 | * | |
393 | * We tried to flag that condition above, by setting the | |
394 | * swallow_nmi flag when we process more than one event. | |
395 | * This condition is also only present on the second half | |
396 | * of a back-to-back NMI, so we flag that condition too. | |
397 | * | |
398 | * If both are true, we assume we already processed this | |
399 | * NMI previously and we swallow it. Otherwise we reset | |
400 | * the logic. | |
401 | * | |
402 | * There are scenarios where we may accidentally swallow | |
403 | * a 'real' unknown NMI. For example, while processing | |
404 | * a perf NMI another perf NMI comes in along with a | |
405 | * 'real' unknown NMI. These two NMIs get combined into | |
406 | * one (as descibed above). When the next NMI gets | |
407 | * processed, it will be flagged by perf as handled, but | |
408 | * noone will know that there was a 'real' unknown NMI sent | |
409 | * also. As a result it gets swallowed. Or if the first | |
410 | * perf NMI returns two events handled then the second | |
411 | * NMI will get eaten by the logic below, again losing a | |
412 | * 'real' unknown NMI. But this is the best we can do | |
413 | * for now. | |
414 | */ | |
415 | if (b2b && __this_cpu_read(swallow_nmi)) | |
efc3aac5 | 416 | __this_cpu_add(nmi_stats.swallow, 1); |
b227e233 DZ |
417 | else |
418 | unknown_nmi_error(reason, regs); | |
1d48922c | 419 | } |
9326638c | 420 | NOKPROBE_SYMBOL(default_do_nmi); |
1d48922c | 421 | |
ccd49c23 | 422 | /* |
0b22930e AL |
423 | * NMIs can page fault or hit breakpoints which will cause it to lose |
424 | * its NMI context with the CPU when the breakpoint or page fault does an IRET. | |
9d050416 AL |
425 | * |
426 | * As a result, NMIs can nest if NMIs get unmasked due an IRET during | |
427 | * NMI processing. On x86_64, the asm glue protects us from nested NMIs | |
428 | * if the outer NMI came from kernel mode, but we can still nest if the | |
429 | * outer NMI came from user mode. | |
430 | * | |
431 | * To handle these nested NMIs, we have three states: | |
ccd49c23 SR |
432 | * |
433 | * 1) not running | |
434 | * 2) executing | |
435 | * 3) latched | |
436 | * | |
437 | * When no NMI is in progress, it is in the "not running" state. | |
438 | * When an NMI comes in, it goes into the "executing" state. | |
439 | * Normally, if another NMI is triggered, it does not interrupt | |
440 | * the running NMI and the HW will simply latch it so that when | |
441 | * the first NMI finishes, it will restart the second NMI. | |
442 | * (Note, the latch is binary, thus multiple NMIs triggering, | |
443 | * when one is running, are ignored. Only one NMI is restarted.) | |
444 | * | |
9d050416 AL |
445 | * If an NMI executes an iret, another NMI can preempt it. We do not |
446 | * want to allow this new NMI to run, but we want to execute it when the | |
447 | * first one finishes. We set the state to "latched", and the exit of | |
448 | * the first NMI will perform a dec_return, if the result is zero | |
449 | * (NOT_RUNNING), then it will simply exit the NMI handler. If not, the | |
450 | * dec_return would have set the state to NMI_EXECUTING (what we want it | |
451 | * to be when we are running). In this case, we simply jump back to | |
452 | * rerun the NMI handler again, and restart the 'latched' NMI. | |
c7d65a78 SR |
453 | * |
454 | * No trap (breakpoint or page fault) should be hit before nmi_restart, | |
455 | * thus there is no race between the first check of state for NOT_RUNNING | |
456 | * and setting it to NMI_EXECUTING. The HW will prevent nested NMIs | |
457 | * at this point. | |
70fb74a5 SR |
458 | * |
459 | * In case the NMI takes a page fault, we need to save off the CR2 | |
460 | * because the NMI could have preempted another page fault and corrupt | |
461 | * the CR2 that is about to be read. As nested NMIs must be restarted | |
462 | * and they can not take breakpoints or page faults, the update of the | |
463 | * CR2 must be done before converting the nmi state back to NOT_RUNNING. | |
464 | * Otherwise, there would be a race of another nested NMI coming in | |
465 | * after setting state to NOT_RUNNING but before updating the nmi_cr2. | |
ccd49c23 SR |
466 | */ |
467 | enum nmi_states { | |
c7d65a78 | 468 | NMI_NOT_RUNNING = 0, |
ccd49c23 SR |
469 | NMI_EXECUTING, |
470 | NMI_LATCHED, | |
471 | }; | |
472 | static DEFINE_PER_CPU(enum nmi_states, nmi_state); | |
70fb74a5 | 473 | static DEFINE_PER_CPU(unsigned long, nmi_cr2); |
ccd49c23 | 474 | |
9d050416 | 475 | #ifdef CONFIG_X86_64 |
ccd49c23 | 476 | /* |
9d050416 AL |
477 | * In x86_64, we need to handle breakpoint -> NMI -> breakpoint. Without |
478 | * some care, the inner breakpoint will clobber the outer breakpoint's | |
479 | * stack. | |
ccd49c23 | 480 | * |
9d050416 AL |
481 | * If a breakpoint is being processed, and the debug stack is being |
482 | * used, if an NMI comes in and also hits a breakpoint, the stack | |
483 | * pointer will be set to the same fixed address as the breakpoint that | |
484 | * was interrupted, causing that stack to be corrupted. To handle this | |
485 | * case, check if the stack that was interrupted is the debug stack, and | |
486 | * if so, change the IDT so that new breakpoints will use the current | |
487 | * stack and not switch to the fixed address. On return of the NMI, | |
488 | * switch back to the original IDT. | |
ccd49c23 SR |
489 | */ |
490 | static DEFINE_PER_CPU(int, update_debug_stack); | |
2a594d4c TG |
491 | |
492 | static bool notrace is_debug_stack(unsigned long addr) | |
493 | { | |
494 | struct cea_exception_stacks *cs = __this_cpu_read(cea_exception_stacks); | |
495 | unsigned long top = CEA_ESTACK_TOP(cs, DB); | |
496 | unsigned long bot = CEA_ESTACK_BOT(cs, DB1); | |
497 | ||
498 | if (__this_cpu_read(debug_stack_usage)) | |
499 | return true; | |
500 | /* | |
501 | * Note, this covers the guard page between DB and DB1 as well to | |
502 | * avoid two checks. But by all means @addr can never point into | |
503 | * the guard page. | |
504 | */ | |
505 | return addr >= bot && addr < top; | |
506 | } | |
507 | NOKPROBE_SYMBOL(is_debug_stack); | |
9d050416 | 508 | #endif |
228bdaa9 | 509 | |
9d050416 AL |
510 | dotraplinkage notrace void |
511 | do_nmi(struct pt_regs *regs, long error_code) | |
ccd49c23 | 512 | { |
60dcaad5 TG |
513 | if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id())) |
514 | return; | |
515 | ||
9d050416 AL |
516 | if (this_cpu_read(nmi_state) != NMI_NOT_RUNNING) { |
517 | this_cpu_write(nmi_state, NMI_LATCHED); | |
518 | return; | |
519 | } | |
520 | this_cpu_write(nmi_state, NMI_EXECUTING); | |
521 | this_cpu_write(nmi_cr2, read_cr2()); | |
522 | nmi_restart: | |
523 | ||
524 | #ifdef CONFIG_X86_64 | |
228bdaa9 SR |
525 | /* |
526 | * If we interrupted a breakpoint, it is possible that | |
527 | * the nmi handler will have breakpoints too. We need to | |
528 | * change the IDT such that breakpoints that happen here | |
529 | * continue to use the NMI stack. | |
530 | */ | |
531 | if (unlikely(is_debug_stack(regs->sp))) { | |
532 | debug_stack_set_zero(); | |
c0525a69 | 533 | this_cpu_write(update_debug_stack, 1); |
228bdaa9 | 534 | } |
ccd49c23 SR |
535 | #endif |
536 | ||
1d48922c DZ |
537 | nmi_enter(); |
538 | ||
539 | inc_irq_stat(__nmi_count); | |
540 | ||
541 | if (!ignore_nmis) | |
542 | default_do_nmi(regs); | |
543 | ||
544 | nmi_exit(); | |
228bdaa9 | 545 | |
9d050416 AL |
546 | #ifdef CONFIG_X86_64 |
547 | if (unlikely(this_cpu_read(update_debug_stack))) { | |
548 | debug_stack_reset(); | |
549 | this_cpu_write(update_debug_stack, 0); | |
550 | } | |
551 | #endif | |
552 | ||
553 | if (unlikely(this_cpu_read(nmi_cr2) != read_cr2())) | |
554 | write_cr2(this_cpu_read(nmi_cr2)); | |
555 | if (this_cpu_dec_return(nmi_state)) | |
556 | goto nmi_restart; | |
04dcbdb8 TG |
557 | |
558 | if (user_mode(regs)) | |
559 | mds_user_clear_cpu_buffers(); | |
1d48922c | 560 | } |
9326638c | 561 | NOKPROBE_SYMBOL(do_nmi); |
1d48922c DZ |
562 | |
563 | void stop_nmi(void) | |
564 | { | |
565 | ignore_nmis++; | |
566 | } | |
567 | ||
568 | void restart_nmi(void) | |
569 | { | |
570 | ignore_nmis--; | |
571 | } | |
b227e233 DZ |
572 | |
573 | /* reset the back-to-back NMI logic */ | |
574 | void local_touch_nmi(void) | |
575 | { | |
576 | __this_cpu_write(last_nmi_rip, 0); | |
577 | } | |
29c6fb7b | 578 | EXPORT_SYMBOL_GPL(local_touch_nmi); |