1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2017 - Cambridge Greys Ltd
4 * Copyright (C) 2011 - 2014 Cisco Systems Inc
5 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
6 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
7 * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
8 */
9
10 #include <linux/cpumask.h>
11 #include <linux/hardirq.h>
12 #include <linux/interrupt.h>
13 #include <linux/kernel_stat.h>
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/seq_file.h>
17 #include <linux/slab.h>
18 #include <as-layout.h>
19 #include <kern_util.h>
20 #include <os.h>
21 #include <irq_user.h>
22
23
24 extern void free_irqs(void);
25
26 /* When epoll triggers we do not know why it did so
27 * we can also have different IRQs for read and write.
28 * This is why we keep a small irq_fd array for each fd -
29 * one entry per IRQ type
30 */
31
32 struct irq_entry {
33 struct irq_entry *next;
34 int fd;
35 struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
36 };
37
38 static struct irq_entry *active_fds;
39
40 static DEFINE_SPINLOCK(irq_lock);
41
42 static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
43 {
44 /*
45 * irq->active guards against reentry
46 * irq->pending accumulates pending requests
47 * if pending is raised the irq_handler is re-run
48 * until pending is cleared
49 */
50 if (irq->active) {
51 irq->active = false;
52 do {
53 irq->pending = false;
54 do_IRQ(irq->irq, regs);
55 } while (irq->pending && (!irq->purge));
56 if (!irq->purge)
57 irq->active = true;
58 } else {
59 irq->pending = true;
60 }
61 }
62
63 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
64 {
65 struct irq_entry *irq_entry;
66 struct irq_fd *irq;
67
68 int n, i, j;
69
70 while (1) {
71 /* This is now lockless - epoll keeps back-referencesto the irqs
72 * which have trigger it so there is no need to walk the irq
73 * list and lock it every time. We avoid locking by turning off
74 * IO for a specific fd by executing os_del_epoll_fd(fd) before
75 * we do any changes to the actual data structures
76 */
77 n = os_waiting_for_events_epoll();
78
79 if (n <= 0) {
80 if (n == -EINTR)
81 continue;
82 else
83 break;
84 }
85
86 for (i = 0; i < n ; i++) {
87 /* Epoll back reference is the entry with 3 irq_fd
88 * leaves - one for each irq type.
89 */
90 irq_entry = (struct irq_entry *)
91 os_epoll_get_data_pointer(i);
92 for (j = 0; j < MAX_IRQ_TYPE ; j++) {
93 irq = irq_entry->irq_array[j];
94 if (irq == NULL)
95 continue;
96 if (os_epoll_triggered(i, irq->events) > 0)
97 irq_io_loop(irq, regs);
98 if (irq->purge) {
99 irq_entry->irq_array[j] = NULL;
100 kfree(irq);
101 }
102 }
103 }
104 }
105
106 free_irqs();
107 }
108
109 static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
110 {
111 int i;
112 int events = 0;
113 struct irq_fd *irq;
114
115 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
116 irq = irq_entry->irq_array[i];
117 if (irq != NULL)
118 events = irq->events | events;
119 }
120 if (events > 0) {
121 /* os_add_epoll will call os_mod_epoll if this already exists */
122 return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
123 }
124 /* No events - delete */
125 return os_del_epoll_fd(irq_entry->fd);
126 }
127
128
129
130 static int activate_fd(int irq, int fd, int type, void *dev_id)
131 {
132 struct irq_fd *new_fd;
133 struct irq_entry *irq_entry;
134 int i, err, events;
135 unsigned long flags;
136
137 err = os_set_fd_async(fd);
138 if (err < 0)
139 goto out;
140
141 spin_lock_irqsave(&irq_lock, flags);
142
143 /* Check if we have an entry for this fd */
144
145 err = -EBUSY;
146 for (irq_entry = active_fds;
147 irq_entry != NULL; irq_entry = irq_entry->next) {
148 if (irq_entry->fd == fd)
149 break;
150 }
151
152 if (irq_entry == NULL) {
153 /* This needs to be atomic as it may be called from an
154 * IRQ context.
155 */
156 irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
157 if (irq_entry == NULL) {
158 printk(KERN_ERR
159 "Failed to allocate new IRQ entry\n");
160 goto out_unlock;
161 }
162 irq_entry->fd = fd;
163 for (i = 0; i < MAX_IRQ_TYPE; i++)
164 irq_entry->irq_array[i] = NULL;
165 irq_entry->next = active_fds;
166 active_fds = irq_entry;
167 }
168
169 /* Check if we are trying to re-register an interrupt for a
170 * particular fd
171 */
172
173 if (irq_entry->irq_array[type] != NULL) {
174 printk(KERN_ERR
175 "Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
176 irq, fd, type, dev_id
177 );
178 goto out_unlock;
179 } else {
180 /* New entry for this fd */
181
182 err = -ENOMEM;
183 new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
184 if (new_fd == NULL)
185 goto out_unlock;
186
187 events = os_event_mask(type);
188
189 *new_fd = ((struct irq_fd) {
190 .id = dev_id,
191 .irq = irq,
192 .type = type,
193 .events = events,
194 .active = true,
195 .pending = false,
196 .purge = false
197 });
198 /* Turn off any IO on this fd - allows us to
199 * avoid locking the IRQ loop
200 */
201 os_del_epoll_fd(irq_entry->fd);
202 irq_entry->irq_array[type] = new_fd;
203 }
204
205 /* Turn back IO on with the correct (new) IO event mask */
206 assign_epoll_events_to_irq(irq_entry);
207 spin_unlock_irqrestore(&irq_lock, flags);
208 maybe_sigio_broken(fd, (type != IRQ_NONE));
209
210 return 0;
211 out_unlock:
212 spin_unlock_irqrestore(&irq_lock, flags);
213 out:
214 return err;
215 }
216
217 /*
218 * Walk the IRQ list and dispose of any unused entries.
219 * Should be done under irq_lock.
220 */
221
222 static void garbage_collect_irq_entries(void)
223 {
224 int i;
225 bool reap;
226 struct irq_entry *walk;
227 struct irq_entry *previous = NULL;
228 struct irq_entry *to_free;
229
230 if (active_fds == NULL)
231 return;
232 walk = active_fds;
233 while (walk != NULL) {
234 reap = true;
235 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
236 if (walk->irq_array[i] != NULL) {
237 reap = false;
238 break;
239 }
240 }
241 if (reap) {
242 if (previous == NULL)
243 active_fds = walk->next;
244 else
245 previous->next = walk->next;
246 to_free = walk;
247 } else {
248 to_free = NULL;
249 }
250 walk = walk->next;
251 kfree(to_free);
252 }
253 }
254
255 /*
256 * Walk the IRQ list and get the descriptor for our FD
257 */
258
259 static struct irq_entry *get_irq_entry_by_fd(int fd)
260 {
261 struct irq_entry *walk = active_fds;
262
263 while (walk != NULL) {
264 if (walk->fd == fd)
265 return walk;
266 walk = walk->next;
267 }
268 return NULL;
269 }
270
271
272 /*
273 * Walk the IRQ list and dispose of an entry for a specific
274 * device, fd and number. Note - if sharing an IRQ for read
275 * and writefor the same FD it will be disposed in either case.
276 * If this behaviour is undesirable use different IRQ ids.
277 */
278
279 #define IGNORE_IRQ 1
280 #define IGNORE_DEV (1<<1)
281
282 static void do_free_by_irq_and_dev(
283 struct irq_entry *irq_entry,
284 unsigned int irq,
285 void *dev,
286 int flags
287 )
288 {
289 int i;
290 struct irq_fd *to_free;
291
292 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
293 if (irq_entry->irq_array[i] != NULL) {
294 if (
295 ((flags & IGNORE_IRQ) ||
296 (irq_entry->irq_array[i]->irq == irq)) &&
297 ((flags & IGNORE_DEV) ||
298 (irq_entry->irq_array[i]->id == dev))
299 ) {
300 /* Turn off any IO on this fd - allows us to
301 * avoid locking the IRQ loop
302 */
303 os_del_epoll_fd(irq_entry->fd);
304 to_free = irq_entry->irq_array[i];
305 irq_entry->irq_array[i] = NULL;
306 assign_epoll_events_to_irq(irq_entry);
307 if (to_free->active)
308 to_free->purge = true;
309 else
310 kfree(to_free);
311 }
312 }
313 }
314 }
315
316 void free_irq_by_fd(int fd)
317 {
318 struct irq_entry *to_free;
319 unsigned long flags;
320
321 spin_lock_irqsave(&irq_lock, flags);
322 to_free = get_irq_entry_by_fd(fd);
323 if (to_free != NULL) {
324 do_free_by_irq_and_dev(
325 to_free,
326 -1,
327 NULL,
328 IGNORE_IRQ | IGNORE_DEV
329 );
330 }
331 garbage_collect_irq_entries();
332 spin_unlock_irqrestore(&irq_lock, flags);
333 }
334 EXPORT_SYMBOL(free_irq_by_fd);
335
336 static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
337 {
338 struct irq_entry *to_free;
339 unsigned long flags;
340
341 spin_lock_irqsave(&irq_lock, flags);
342 to_free = active_fds;
343 while (to_free != NULL) {
344 do_free_by_irq_and_dev(
345 to_free,
346 irq,
347 dev,
348 0
349 );
350 to_free = to_free->next;
351 }
352 garbage_collect_irq_entries();
353 spin_unlock_irqrestore(&irq_lock, flags);
354 }
355
356
357 void deactivate_fd(int fd, int irqnum)
358 {
359 struct irq_entry *to_free;
360 unsigned long flags;
361
362 os_del_epoll_fd(fd);
363 spin_lock_irqsave(&irq_lock, flags);
364 to_free = get_irq_entry_by_fd(fd);
365 if (to_free != NULL) {
366 do_free_by_irq_and_dev(
367 to_free,
368 irqnum,
369 NULL,
370 IGNORE_DEV
371 );
372 }
373 garbage_collect_irq_entries();
374 spin_unlock_irqrestore(&irq_lock, flags);
375 ignore_sigio_fd(fd);
376 }
377 EXPORT_SYMBOL(deactivate_fd);
378
379 /*
380 * Called just before shutdown in order to provide a clean exec
381 * environment in case the system is rebooting. No locking because
382 * that would cause a pointless shutdown hang if something hadn't
383 * released the lock.
384 */
385 int deactivate_all_fds(void)
386 {
387 struct irq_entry *to_free;
388
389 /* Stop IO. The IRQ loop has no lock so this is our
390 * only way of making sure we are safe to dispose
391 * of all IRQ handlers
392 */
393 os_set_ioignore();
394 to_free = active_fds;
395 while (to_free != NULL) {
396 do_free_by_irq_and_dev(
397 to_free,
398 -1,
399 NULL,
400 IGNORE_IRQ | IGNORE_DEV
401 );
402 to_free = to_free->next;
403 }
404 /* don't garbage collect - we can no longer call kfree() here */
405 os_close_epoll_fd();
406 return 0;
407 }
408
409 /*
410 * do_IRQ handles all normal device IRQs (the special
411 * SMP cross-CPU interrupts have their own specific
412 * handlers).
413 */
414 unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
415 {
416 struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
417 irq_enter();
418 generic_handle_irq(irq);
419 irq_exit();
420 set_irq_regs(old_regs);
421 return 1;
422 }
423
424 void um_free_irq(unsigned int irq, void *dev)
425 {
426 free_irq_by_irq_and_dev(irq, dev);
427 free_irq(irq, dev);
428 }
429 EXPORT_SYMBOL(um_free_irq);
430
431 int um_request_irq(unsigned int irq, int fd, int type,
432 irq_handler_t handler,
433 unsigned long irqflags, const char * devname,
434 void *dev_id)
435 {
436 int err;
437
438 if (fd != -1) {
439 err = activate_fd(irq, fd, type, dev_id);
440 if (err)
441 return err;
442 }
443
444 return request_irq(irq, handler, irqflags, devname, dev_id);
445 }
446
447 EXPORT_SYMBOL(um_request_irq);
448
449 /*
450 * irq_chip must define at least enable/disable and ack when
451 * the edge handler is used.
452 */
453 static void dummy(struct irq_data *d)
454 {
455 }
456
457 /* This is used for everything else than the timer. */
458 static struct irq_chip normal_irq_type = {
459 .name = "SIGIO",
460 .irq_disable = dummy,
461 .irq_enable = dummy,
462 .irq_ack = dummy,
463 .irq_mask = dummy,
464 .irq_unmask = dummy,
465 };
466
467 static struct irq_chip SIGVTALRM_irq_type = {
468 .name = "SIGVTALRM",
469 .irq_disable = dummy,
470 .irq_enable = dummy,
471 .irq_ack = dummy,
472 .irq_mask = dummy,
473 .irq_unmask = dummy,
474 };
475
476 void __init init_IRQ(void)
477 {
478 int i;
479
480 irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
481
482
483 for (i = 1; i <= LAST_IRQ; i++)
484 irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
485 /* Initialize EPOLL Loop */
486 os_setup_epoll();
487 }
488
489 /*
490 * IRQ stack entry and exit:
491 *
492 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
493 * and switch over to the IRQ stack after some preparation. We use
494 * sigaltstack to receive signals on a separate stack from the start.
495 * These two functions make sure the rest of the kernel won't be too
496 * upset by being on a different stack. The IRQ stack has a
497 * thread_info structure at the bottom so that current et al continue
498 * to work.
499 *
500 * to_irq_stack copies the current task's thread_info to the IRQ stack
501 * thread_info and sets the tasks's stack to point to the IRQ stack.
502 *
503 * from_irq_stack copies the thread_info struct back (flags may have
504 * been modified) and resets the task's stack pointer.
505 *
506 * Tricky bits -
507 *
508 * What happens when two signals race each other? UML doesn't block
509 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
510 * could arrive while a previous one is still setting up the
511 * thread_info.
512 *
513 * There are three cases -
514 * The first interrupt on the stack - sets up the thread_info and
515 * handles the interrupt
516 * A nested interrupt interrupting the copying of the thread_info -
517 * can't handle the interrupt, as the stack is in an unknown state
518 * A nested interrupt not interrupting the copying of the
519 * thread_info - doesn't do any setup, just handles the interrupt
520 *
521 * The first job is to figure out whether we interrupted stack setup.
522 * This is done by xchging the signal mask with thread_info->pending.
523 * If the value that comes back is zero, then there is no setup in
524 * progress, and the interrupt can be handled. If the value is
525 * non-zero, then there is stack setup in progress. In order to have
526 * the interrupt handled, we leave our signal in the mask, and it will
527 * be handled by the upper handler after it has set up the stack.
528 *
529 * Next is to figure out whether we are the outer handler or a nested
530 * one. As part of setting up the stack, thread_info->real_thread is
531 * set to non-NULL (and is reset to NULL on exit). This is the
532 * nesting indicator. If it is non-NULL, then the stack is already
533 * set up and the handler can run.
534 */
535
536 static unsigned long pending_mask;
537
538 unsigned long to_irq_stack(unsigned long *mask_out)
539 {
540 struct thread_info *ti;
541 unsigned long mask, old;
542 int nested;
543
544 mask = xchg(&pending_mask, *mask_out);
545 if (mask != 0) {
546 /*
547 * If any interrupts come in at this point, we want to
548 * make sure that their bits aren't lost by our
549 * putting our bit in. So, this loop accumulates bits
550 * until xchg returns the same value that we put in.
551 * When that happens, there were no new interrupts,
552 * and pending_mask contains a bit for each interrupt
553 * that came in.
554 */
555 old = *mask_out;
556 do {
557 old |= mask;
558 mask = xchg(&pending_mask, old);
559 } while (mask != old);
560 return 1;
561 }
562
563 ti = current_thread_info();
564 nested = (ti->real_thread != NULL);
565 if (!nested) {
566 struct task_struct *task;
567 struct thread_info *tti;
568
569 task = cpu_tasks[ti->cpu].task;
570 tti = task_thread_info(task);
571
572 *ti = *tti;
573 ti->real_thread = tti;
574 task->stack = ti;
575 }
576
577 mask = xchg(&pending_mask, 0);
578 *mask_out |= mask | nested;
579 return 0;
580 }
581
582 unsigned long from_irq_stack(int nested)
583 {
584 struct thread_info *ti, *to;
585 unsigned long mask;
586
587 ti = current_thread_info();
588
589 pending_mask = 1;
590
591 to = ti->real_thread;
592 current->stack = to;
593 ti->real_thread = NULL;
594 *to = *ti;
595
596 mask = xchg(&pending_mask, 0);
597 return mask & ~1;
598 }
599