1 /*
2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3  * Licensed under the GPL
4  * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
5  *	Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
6  */
7 
8 #include "linux/cpumask.h"
9 #include "linux/hardirq.h"
10 #include "linux/interrupt.h"
11 #include "linux/kernel_stat.h"
12 #include "linux/module.h"
13 #include "linux/sched.h"
14 #include "linux/seq_file.h"
15 #include "linux/slab.h"
16 #include "as-layout.h"
17 #include "kern_util.h"
18 #include "os.h"
19 
20 /*
21  * This list is accessed under irq_lock, except in sigio_handler,
22  * where it is safe from being modified.  IRQ handlers won't change it -
23  * if an IRQ source has vanished, it will be freed by free_irqs just
24  * before returning from sigio_handler.  That will process a separate
25  * list of irqs to free, with its own locking, coming back here to
26  * remove list elements, taking the irq_lock to do so.
27  */
28 static struct irq_fd *active_fds = NULL;
29 static struct irq_fd **last_irq_ptr = &active_fds;
30 
31 extern void free_irqs(void);
32 
sigio_handler(int sig,struct uml_pt_regs * regs)33 void sigio_handler(int sig, struct uml_pt_regs *regs)
34 {
35 	struct irq_fd *irq_fd;
36 	int n;
37 
38 	if (smp_sigio_handler())
39 		return;
40 
41 	while (1) {
42 		n = os_waiting_for_events(active_fds);
43 		if (n <= 0) {
44 			if (n == -EINTR)
45 				continue;
46 			else break;
47 		}
48 
49 		for (irq_fd = active_fds; irq_fd != NULL;
50 		     irq_fd = irq_fd->next) {
51 			if (irq_fd->current_events != 0) {
52 				irq_fd->current_events = 0;
53 				do_IRQ(irq_fd->irq, regs);
54 			}
55 		}
56 	}
57 
58 	free_irqs();
59 }
60 
61 static DEFINE_SPINLOCK(irq_lock);
62 
activate_fd(int irq,int fd,int type,void * dev_id)63 static int activate_fd(int irq, int fd, int type, void *dev_id)
64 {
65 	struct pollfd *tmp_pfd;
66 	struct irq_fd *new_fd, *irq_fd;
67 	unsigned long flags;
68 	int events, err, n;
69 
70 	err = os_set_fd_async(fd);
71 	if (err < 0)
72 		goto out;
73 
74 	err = -ENOMEM;
75 	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
76 	if (new_fd == NULL)
77 		goto out;
78 
79 	if (type == IRQ_READ)
80 		events = UM_POLLIN | UM_POLLPRI;
81 	else events = UM_POLLOUT;
82 	*new_fd = ((struct irq_fd) { .next  		= NULL,
83 				     .id 		= dev_id,
84 				     .fd 		= fd,
85 				     .type 		= type,
86 				     .irq 		= irq,
87 				     .events 		= events,
88 				     .current_events 	= 0 } );
89 
90 	err = -EBUSY;
91 	spin_lock_irqsave(&irq_lock, flags);
92 	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
93 		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
94 			printk(KERN_ERR "Registering fd %d twice\n", fd);
95 			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
96 			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
97 			       dev_id);
98 			goto out_unlock;
99 		}
100 	}
101 
102 	if (type == IRQ_WRITE)
103 		fd = -1;
104 
105 	tmp_pfd = NULL;
106 	n = 0;
107 
108 	while (1) {
109 		n = os_create_pollfd(fd, events, tmp_pfd, n);
110 		if (n == 0)
111 			break;
112 
113 		/*
114 		 * n > 0
115 		 * It means we couldn't put new pollfd to current pollfds
116 		 * and tmp_fds is NULL or too small for new pollfds array.
117 		 * Needed size is equal to n as minimum.
118 		 *
119 		 * Here we have to drop the lock in order to call
120 		 * kmalloc, which might sleep.
121 		 * If something else came in and changed the pollfds array
122 		 * so we will not be able to put new pollfd struct to pollfds
123 		 * then we free the buffer tmp_fds and try again.
124 		 */
125 		spin_unlock_irqrestore(&irq_lock, flags);
126 		kfree(tmp_pfd);
127 
128 		tmp_pfd = kmalloc(n, GFP_KERNEL);
129 		if (tmp_pfd == NULL)
130 			goto out_kfree;
131 
132 		spin_lock_irqsave(&irq_lock, flags);
133 	}
134 
135 	*last_irq_ptr = new_fd;
136 	last_irq_ptr = &new_fd->next;
137 
138 	spin_unlock_irqrestore(&irq_lock, flags);
139 
140 	/*
141 	 * This calls activate_fd, so it has to be outside the critical
142 	 * section.
143 	 */
144 	maybe_sigio_broken(fd, (type == IRQ_READ));
145 
146 	return 0;
147 
148  out_unlock:
149 	spin_unlock_irqrestore(&irq_lock, flags);
150  out_kfree:
151 	kfree(new_fd);
152  out:
153 	return err;
154 }
155 
free_irq_by_cb(int (* test)(struct irq_fd *,void *),void * arg)156 static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
157 {
158 	unsigned long flags;
159 
160 	spin_lock_irqsave(&irq_lock, flags);
161 	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
162 	spin_unlock_irqrestore(&irq_lock, flags);
163 }
164 
165 struct irq_and_dev {
166 	int irq;
167 	void *dev;
168 };
169 
same_irq_and_dev(struct irq_fd * irq,void * d)170 static int same_irq_and_dev(struct irq_fd *irq, void *d)
171 {
172 	struct irq_and_dev *data = d;
173 
174 	return ((irq->irq == data->irq) && (irq->id == data->dev));
175 }
176 
free_irq_by_irq_and_dev(unsigned int irq,void * dev)177 static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
178 {
179 	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
180 							  .dev  = dev });
181 
182 	free_irq_by_cb(same_irq_and_dev, &data);
183 }
184 
same_fd(struct irq_fd * irq,void * fd)185 static int same_fd(struct irq_fd *irq, void *fd)
186 {
187 	return (irq->fd == *((int *)fd));
188 }
189 
free_irq_by_fd(int fd)190 void free_irq_by_fd(int fd)
191 {
192 	free_irq_by_cb(same_fd, &fd);
193 }
194 
195 /* Must be called with irq_lock held */
find_irq_by_fd(int fd,int irqnum,int * index_out)196 static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
197 {
198 	struct irq_fd *irq;
199 	int i = 0;
200 	int fdi;
201 
202 	for (irq = active_fds; irq != NULL; irq = irq->next) {
203 		if ((irq->fd == fd) && (irq->irq == irqnum))
204 			break;
205 		i++;
206 	}
207 	if (irq == NULL) {
208 		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
209 		       fd);
210 		goto out;
211 	}
212 	fdi = os_get_pollfd(i);
213 	if ((fdi != -1) && (fdi != fd)) {
214 		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
215 		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
216 		       fdi, fd);
217 		irq = NULL;
218 		goto out;
219 	}
220 	*index_out = i;
221  out:
222 	return irq;
223 }
224 
reactivate_fd(int fd,int irqnum)225 void reactivate_fd(int fd, int irqnum)
226 {
227 	struct irq_fd *irq;
228 	unsigned long flags;
229 	int i;
230 
231 	spin_lock_irqsave(&irq_lock, flags);
232 	irq = find_irq_by_fd(fd, irqnum, &i);
233 	if (irq == NULL) {
234 		spin_unlock_irqrestore(&irq_lock, flags);
235 		return;
236 	}
237 	os_set_pollfd(i, irq->fd);
238 	spin_unlock_irqrestore(&irq_lock, flags);
239 
240 	add_sigio_fd(fd);
241 }
242 
deactivate_fd(int fd,int irqnum)243 void deactivate_fd(int fd, int irqnum)
244 {
245 	struct irq_fd *irq;
246 	unsigned long flags;
247 	int i;
248 
249 	spin_lock_irqsave(&irq_lock, flags);
250 	irq = find_irq_by_fd(fd, irqnum, &i);
251 	if (irq == NULL) {
252 		spin_unlock_irqrestore(&irq_lock, flags);
253 		return;
254 	}
255 
256 	os_set_pollfd(i, -1);
257 	spin_unlock_irqrestore(&irq_lock, flags);
258 
259 	ignore_sigio_fd(fd);
260 }
261 EXPORT_SYMBOL(deactivate_fd);
262 
263 /*
264  * Called just before shutdown in order to provide a clean exec
265  * environment in case the system is rebooting.  No locking because
266  * that would cause a pointless shutdown hang if something hadn't
267  * released the lock.
268  */
deactivate_all_fds(void)269 int deactivate_all_fds(void)
270 {
271 	struct irq_fd *irq;
272 	int err;
273 
274 	for (irq = active_fds; irq != NULL; irq = irq->next) {
275 		err = os_clear_fd_async(irq->fd);
276 		if (err)
277 			return err;
278 	}
279 	/* If there is a signal already queued, after unblocking ignore it */
280 	os_set_ioignore();
281 
282 	return 0;
283 }
284 
285 /*
286  * do_IRQ handles all normal device IRQs (the special
287  * SMP cross-CPU interrupts have their own specific
288  * handlers).
289  */
do_IRQ(int irq,struct uml_pt_regs * regs)290 unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
291 {
292 	struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
293 	irq_enter();
294 	generic_handle_irq(irq);
295 	irq_exit();
296 	set_irq_regs(old_regs);
297 	return 1;
298 }
299 
um_request_irq(unsigned int irq,int fd,int type,irq_handler_t handler,unsigned long irqflags,const char * devname,void * dev_id)300 int um_request_irq(unsigned int irq, int fd, int type,
301 		   irq_handler_t handler,
302 		   unsigned long irqflags, const char * devname,
303 		   void *dev_id)
304 {
305 	int err;
306 
307 	if (fd != -1) {
308 		err = activate_fd(irq, fd, type, dev_id);
309 		if (err)
310 			return err;
311 	}
312 
313 	return request_irq(irq, handler, irqflags, devname, dev_id);
314 }
315 
316 EXPORT_SYMBOL(um_request_irq);
317 EXPORT_SYMBOL(reactivate_fd);
318 
319 /*
320  * irq_chip must define at least enable/disable and ack when
321  * the edge handler is used.
322  */
dummy(struct irq_data * d)323 static void dummy(struct irq_data *d)
324 {
325 }
326 
327 /* This is used for everything else than the timer. */
328 static struct irq_chip normal_irq_type = {
329 	.name = "SIGIO",
330 	.release = free_irq_by_irq_and_dev,
331 	.irq_disable = dummy,
332 	.irq_enable = dummy,
333 	.irq_ack = dummy,
334 };
335 
336 static struct irq_chip SIGVTALRM_irq_type = {
337 	.name = "SIGVTALRM",
338 	.release = free_irq_by_irq_and_dev,
339 	.irq_disable = dummy,
340 	.irq_enable = dummy,
341 	.irq_ack = dummy,
342 };
343 
init_IRQ(void)344 void __init init_IRQ(void)
345 {
346 	int i;
347 
348 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
349 
350 	for (i = 1; i < NR_IRQS; i++)
351 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
352 }
353 
354 /*
355  * IRQ stack entry and exit:
356  *
357  * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
358  * and switch over to the IRQ stack after some preparation.  We use
359  * sigaltstack to receive signals on a separate stack from the start.
360  * These two functions make sure the rest of the kernel won't be too
361  * upset by being on a different stack.  The IRQ stack has a
362  * thread_info structure at the bottom so that current et al continue
363  * to work.
364  *
365  * to_irq_stack copies the current task's thread_info to the IRQ stack
366  * thread_info and sets the tasks's stack to point to the IRQ stack.
367  *
368  * from_irq_stack copies the thread_info struct back (flags may have
369  * been modified) and resets the task's stack pointer.
370  *
371  * Tricky bits -
372  *
373  * What happens when two signals race each other?  UML doesn't block
374  * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
375  * could arrive while a previous one is still setting up the
376  * thread_info.
377  *
378  * There are three cases -
379  *     The first interrupt on the stack - sets up the thread_info and
380  * handles the interrupt
381  *     A nested interrupt interrupting the copying of the thread_info -
382  * can't handle the interrupt, as the stack is in an unknown state
383  *     A nested interrupt not interrupting the copying of the
384  * thread_info - doesn't do any setup, just handles the interrupt
385  *
386  * The first job is to figure out whether we interrupted stack setup.
387  * This is done by xchging the signal mask with thread_info->pending.
388  * If the value that comes back is zero, then there is no setup in
389  * progress, and the interrupt can be handled.  If the value is
390  * non-zero, then there is stack setup in progress.  In order to have
391  * the interrupt handled, we leave our signal in the mask, and it will
392  * be handled by the upper handler after it has set up the stack.
393  *
394  * Next is to figure out whether we are the outer handler or a nested
395  * one.  As part of setting up the stack, thread_info->real_thread is
396  * set to non-NULL (and is reset to NULL on exit).  This is the
397  * nesting indicator.  If it is non-NULL, then the stack is already
398  * set up and the handler can run.
399  */
400 
401 static unsigned long pending_mask;
402 
to_irq_stack(unsigned long * mask_out)403 unsigned long to_irq_stack(unsigned long *mask_out)
404 {
405 	struct thread_info *ti;
406 	unsigned long mask, old;
407 	int nested;
408 
409 	mask = xchg(&pending_mask, *mask_out);
410 	if (mask != 0) {
411 		/*
412 		 * If any interrupts come in at this point, we want to
413 		 * make sure that their bits aren't lost by our
414 		 * putting our bit in.  So, this loop accumulates bits
415 		 * until xchg returns the same value that we put in.
416 		 * When that happens, there were no new interrupts,
417 		 * and pending_mask contains a bit for each interrupt
418 		 * that came in.
419 		 */
420 		old = *mask_out;
421 		do {
422 			old |= mask;
423 			mask = xchg(&pending_mask, old);
424 		} while (mask != old);
425 		return 1;
426 	}
427 
428 	ti = current_thread_info();
429 	nested = (ti->real_thread != NULL);
430 	if (!nested) {
431 		struct task_struct *task;
432 		struct thread_info *tti;
433 
434 		task = cpu_tasks[ti->cpu].task;
435 		tti = task_thread_info(task);
436 
437 		*ti = *tti;
438 		ti->real_thread = tti;
439 		task->stack = ti;
440 	}
441 
442 	mask = xchg(&pending_mask, 0);
443 	*mask_out |= mask | nested;
444 	return 0;
445 }
446 
from_irq_stack(int nested)447 unsigned long from_irq_stack(int nested)
448 {
449 	struct thread_info *ti, *to;
450 	unsigned long mask;
451 
452 	ti = current_thread_info();
453 
454 	pending_mask = 1;
455 
456 	to = ti->real_thread;
457 	current->stack = to;
458 	ti->real_thread = NULL;
459 	*to = *ti;
460 
461 	mask = xchg(&pending_mask, 0);
462 	return mask & ~1;
463 }
464 
465