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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 siginfo * unused_si,struct uml_pt_regs * regs)33 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
34 {
35 	struct irq_fd *irq_fd;
36 	int n;
37 
38 	while (1) {
39 		n = os_waiting_for_events(active_fds);
40 		if (n <= 0) {
41 			if (n == -EINTR)
42 				continue;
43 			else break;
44 		}
45 
46 		for (irq_fd = active_fds; irq_fd != NULL;
47 		     irq_fd = irq_fd->next) {
48 			if (irq_fd->current_events != 0) {
49 				irq_fd->current_events = 0;
50 				do_IRQ(irq_fd->irq, regs);
51 			}
52 		}
53 	}
54 
55 	free_irqs();
56 }
57 
58 static DEFINE_SPINLOCK(irq_lock);
59 
activate_fd(int irq,int fd,int type,void * dev_id)60 static int activate_fd(int irq, int fd, int type, void *dev_id)
61 {
62 	struct pollfd *tmp_pfd;
63 	struct irq_fd *new_fd, *irq_fd;
64 	unsigned long flags;
65 	int events, err, n;
66 
67 	err = os_set_fd_async(fd);
68 	if (err < 0)
69 		goto out;
70 
71 	err = -ENOMEM;
72 	new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
73 	if (new_fd == NULL)
74 		goto out;
75 
76 	if (type == IRQ_READ)
77 		events = UM_POLLIN | UM_POLLPRI;
78 	else events = UM_POLLOUT;
79 	*new_fd = ((struct irq_fd) { .next  		= NULL,
80 				     .id 		= dev_id,
81 				     .fd 		= fd,
82 				     .type 		= type,
83 				     .irq 		= irq,
84 				     .events 		= events,
85 				     .current_events 	= 0 } );
86 
87 	err = -EBUSY;
88 	spin_lock_irqsave(&irq_lock, flags);
89 	for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
90 		if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
91 			printk(KERN_ERR "Registering fd %d twice\n", fd);
92 			printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
93 			printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
94 			       dev_id);
95 			goto out_unlock;
96 		}
97 	}
98 
99 	if (type == IRQ_WRITE)
100 		fd = -1;
101 
102 	tmp_pfd = NULL;
103 	n = 0;
104 
105 	while (1) {
106 		n = os_create_pollfd(fd, events, tmp_pfd, n);
107 		if (n == 0)
108 			break;
109 
110 		/*
111 		 * n > 0
112 		 * It means we couldn't put new pollfd to current pollfds
113 		 * and tmp_fds is NULL or too small for new pollfds array.
114 		 * Needed size is equal to n as minimum.
115 		 *
116 		 * Here we have to drop the lock in order to call
117 		 * kmalloc, which might sleep.
118 		 * If something else came in and changed the pollfds array
119 		 * so we will not be able to put new pollfd struct to pollfds
120 		 * then we free the buffer tmp_fds and try again.
121 		 */
122 		spin_unlock_irqrestore(&irq_lock, flags);
123 		kfree(tmp_pfd);
124 
125 		tmp_pfd = kmalloc(n, GFP_KERNEL);
126 		if (tmp_pfd == NULL)
127 			goto out_kfree;
128 
129 		spin_lock_irqsave(&irq_lock, flags);
130 	}
131 
132 	*last_irq_ptr = new_fd;
133 	last_irq_ptr = &new_fd->next;
134 
135 	spin_unlock_irqrestore(&irq_lock, flags);
136 
137 	/*
138 	 * This calls activate_fd, so it has to be outside the critical
139 	 * section.
140 	 */
141 	maybe_sigio_broken(fd, (type == IRQ_READ));
142 
143 	return 0;
144 
145  out_unlock:
146 	spin_unlock_irqrestore(&irq_lock, flags);
147  out_kfree:
148 	kfree(new_fd);
149  out:
150 	return err;
151 }
152 
free_irq_by_cb(int (* test)(struct irq_fd *,void *),void * arg)153 static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
154 {
155 	unsigned long flags;
156 
157 	spin_lock_irqsave(&irq_lock, flags);
158 	os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
159 	spin_unlock_irqrestore(&irq_lock, flags);
160 }
161 
162 struct irq_and_dev {
163 	int irq;
164 	void *dev;
165 };
166 
same_irq_and_dev(struct irq_fd * irq,void * d)167 static int same_irq_and_dev(struct irq_fd *irq, void *d)
168 {
169 	struct irq_and_dev *data = d;
170 
171 	return ((irq->irq == data->irq) && (irq->id == data->dev));
172 }
173 
free_irq_by_irq_and_dev(unsigned int irq,void * dev)174 static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
175 {
176 	struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
177 							  .dev  = dev });
178 
179 	free_irq_by_cb(same_irq_and_dev, &data);
180 }
181 
same_fd(struct irq_fd * irq,void * fd)182 static int same_fd(struct irq_fd *irq, void *fd)
183 {
184 	return (irq->fd == *((int *)fd));
185 }
186 
free_irq_by_fd(int fd)187 void free_irq_by_fd(int fd)
188 {
189 	free_irq_by_cb(same_fd, &fd);
190 }
191 
192 /* Must be called with irq_lock held */
find_irq_by_fd(int fd,int irqnum,int * index_out)193 static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
194 {
195 	struct irq_fd *irq;
196 	int i = 0;
197 	int fdi;
198 
199 	for (irq = active_fds; irq != NULL; irq = irq->next) {
200 		if ((irq->fd == fd) && (irq->irq == irqnum))
201 			break;
202 		i++;
203 	}
204 	if (irq == NULL) {
205 		printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
206 		       fd);
207 		goto out;
208 	}
209 	fdi = os_get_pollfd(i);
210 	if ((fdi != -1) && (fdi != fd)) {
211 		printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
212 		       "and pollfds, fd %d vs %d, need %d\n", irq->fd,
213 		       fdi, fd);
214 		irq = NULL;
215 		goto out;
216 	}
217 	*index_out = i;
218  out:
219 	return irq;
220 }
221 
reactivate_fd(int fd,int irqnum)222 void reactivate_fd(int fd, int irqnum)
223 {
224 	struct irq_fd *irq;
225 	unsigned long flags;
226 	int i;
227 
228 	spin_lock_irqsave(&irq_lock, flags);
229 	irq = find_irq_by_fd(fd, irqnum, &i);
230 	if (irq == NULL) {
231 		spin_unlock_irqrestore(&irq_lock, flags);
232 		return;
233 	}
234 	os_set_pollfd(i, irq->fd);
235 	spin_unlock_irqrestore(&irq_lock, flags);
236 
237 	add_sigio_fd(fd);
238 }
239 
deactivate_fd(int fd,int irqnum)240 void deactivate_fd(int fd, int irqnum)
241 {
242 	struct irq_fd *irq;
243 	unsigned long flags;
244 	int i;
245 
246 	spin_lock_irqsave(&irq_lock, flags);
247 	irq = find_irq_by_fd(fd, irqnum, &i);
248 	if (irq == NULL) {
249 		spin_unlock_irqrestore(&irq_lock, flags);
250 		return;
251 	}
252 
253 	os_set_pollfd(i, -1);
254 	spin_unlock_irqrestore(&irq_lock, flags);
255 
256 	ignore_sigio_fd(fd);
257 }
258 EXPORT_SYMBOL(deactivate_fd);
259 
260 /*
261  * Called just before shutdown in order to provide a clean exec
262  * environment in case the system is rebooting.  No locking because
263  * that would cause a pointless shutdown hang if something hadn't
264  * released the lock.
265  */
deactivate_all_fds(void)266 int deactivate_all_fds(void)
267 {
268 	struct irq_fd *irq;
269 	int err;
270 
271 	for (irq = active_fds; irq != NULL; irq = irq->next) {
272 		err = os_clear_fd_async(irq->fd);
273 		if (err)
274 			return err;
275 	}
276 	/* If there is a signal already queued, after unblocking ignore it */
277 	os_set_ioignore();
278 
279 	return 0;
280 }
281 
282 /*
283  * do_IRQ handles all normal device IRQs (the special
284  * SMP cross-CPU interrupts have their own specific
285  * handlers).
286  */
do_IRQ(int irq,struct uml_pt_regs * regs)287 unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
288 {
289 	struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
290 	irq_enter();
291 	generic_handle_irq(irq);
292 	irq_exit();
293 	set_irq_regs(old_regs);
294 	return 1;
295 }
296 
um_free_irq(unsigned int irq,void * dev)297 void um_free_irq(unsigned int irq, void *dev)
298 {
299 	free_irq_by_irq_and_dev(irq, dev);
300 	free_irq(irq, dev);
301 }
302 EXPORT_SYMBOL(um_free_irq);
303 
um_request_irq(unsigned int irq,int fd,int type,irq_handler_t handler,unsigned long irqflags,const char * devname,void * dev_id)304 int um_request_irq(unsigned int irq, int fd, int type,
305 		   irq_handler_t handler,
306 		   unsigned long irqflags, const char * devname,
307 		   void *dev_id)
308 {
309 	int err;
310 
311 	if (fd != -1) {
312 		err = activate_fd(irq, fd, type, dev_id);
313 		if (err)
314 			return err;
315 	}
316 
317 	return request_irq(irq, handler, irqflags, devname, dev_id);
318 }
319 
320 EXPORT_SYMBOL(um_request_irq);
321 EXPORT_SYMBOL(reactivate_fd);
322 
323 /*
324  * irq_chip must define at least enable/disable and ack when
325  * the edge handler is used.
326  */
dummy(struct irq_data * d)327 static void dummy(struct irq_data *d)
328 {
329 }
330 
331 /* This is used for everything else than the timer. */
332 static struct irq_chip normal_irq_type = {
333 	.name = "SIGIO",
334 	.irq_disable = dummy,
335 	.irq_enable = dummy,
336 	.irq_ack = dummy,
337 	.irq_mask = dummy,
338 	.irq_unmask = dummy,
339 };
340 
341 static struct irq_chip SIGVTALRM_irq_type = {
342 	.name = "SIGVTALRM",
343 	.irq_disable = dummy,
344 	.irq_enable = dummy,
345 	.irq_ack = dummy,
346 	.irq_mask = dummy,
347 	.irq_unmask = dummy,
348 };
349 
init_IRQ(void)350 void __init init_IRQ(void)
351 {
352 	int i;
353 
354 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
355 
356 	for (i = 1; i < NR_IRQS; i++)
357 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
358 }
359 
360 /*
361  * IRQ stack entry and exit:
362  *
363  * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
364  * and switch over to the IRQ stack after some preparation.  We use
365  * sigaltstack to receive signals on a separate stack from the start.
366  * These two functions make sure the rest of the kernel won't be too
367  * upset by being on a different stack.  The IRQ stack has a
368  * thread_info structure at the bottom so that current et al continue
369  * to work.
370  *
371  * to_irq_stack copies the current task's thread_info to the IRQ stack
372  * thread_info and sets the tasks's stack to point to the IRQ stack.
373  *
374  * from_irq_stack copies the thread_info struct back (flags may have
375  * been modified) and resets the task's stack pointer.
376  *
377  * Tricky bits -
378  *
379  * What happens when two signals race each other?  UML doesn't block
380  * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
381  * could arrive while a previous one is still setting up the
382  * thread_info.
383  *
384  * There are three cases -
385  *     The first interrupt on the stack - sets up the thread_info and
386  * handles the interrupt
387  *     A nested interrupt interrupting the copying of the thread_info -
388  * can't handle the interrupt, as the stack is in an unknown state
389  *     A nested interrupt not interrupting the copying of the
390  * thread_info - doesn't do any setup, just handles the interrupt
391  *
392  * The first job is to figure out whether we interrupted stack setup.
393  * This is done by xchging the signal mask with thread_info->pending.
394  * If the value that comes back is zero, then there is no setup in
395  * progress, and the interrupt can be handled.  If the value is
396  * non-zero, then there is stack setup in progress.  In order to have
397  * the interrupt handled, we leave our signal in the mask, and it will
398  * be handled by the upper handler after it has set up the stack.
399  *
400  * Next is to figure out whether we are the outer handler or a nested
401  * one.  As part of setting up the stack, thread_info->real_thread is
402  * set to non-NULL (and is reset to NULL on exit).  This is the
403  * nesting indicator.  If it is non-NULL, then the stack is already
404  * set up and the handler can run.
405  */
406 
407 static unsigned long pending_mask;
408 
to_irq_stack(unsigned long * mask_out)409 unsigned long to_irq_stack(unsigned long *mask_out)
410 {
411 	struct thread_info *ti;
412 	unsigned long mask, old;
413 	int nested;
414 
415 	mask = xchg(&pending_mask, *mask_out);
416 	if (mask != 0) {
417 		/*
418 		 * If any interrupts come in at this point, we want to
419 		 * make sure that their bits aren't lost by our
420 		 * putting our bit in.  So, this loop accumulates bits
421 		 * until xchg returns the same value that we put in.
422 		 * When that happens, there were no new interrupts,
423 		 * and pending_mask contains a bit for each interrupt
424 		 * that came in.
425 		 */
426 		old = *mask_out;
427 		do {
428 			old |= mask;
429 			mask = xchg(&pending_mask, old);
430 		} while (mask != old);
431 		return 1;
432 	}
433 
434 	ti = current_thread_info();
435 	nested = (ti->real_thread != NULL);
436 	if (!nested) {
437 		struct task_struct *task;
438 		struct thread_info *tti;
439 
440 		task = cpu_tasks[ti->cpu].task;
441 		tti = task_thread_info(task);
442 
443 		*ti = *tti;
444 		ti->real_thread = tti;
445 		task->stack = ti;
446 	}
447 
448 	mask = xchg(&pending_mask, 0);
449 	*mask_out |= mask | nested;
450 	return 0;
451 }
452 
from_irq_stack(int nested)453 unsigned long from_irq_stack(int nested)
454 {
455 	struct thread_info *ti, *to;
456 	unsigned long mask;
457 
458 	ti = current_thread_info();
459 
460 	pending_mask = 1;
461 
462 	to = ti->real_thread;
463 	current->stack = to;
464 	ti->real_thread = NULL;
465 	*to = *ti;
466 
467 	mask = xchg(&pending_mask, 0);
468 	return mask & ~1;
469 }
470 
471