arch/um/kernel/irq.c

   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
  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
  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
 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
 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
 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
 182 static int same_fd(struct irq_fd *irq, void *fd)
 183 {
 184         return (irq->fd == *((int *)fd));
 185 }
 186
 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 */
 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
 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
 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  */
 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  */
 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
 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
 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  */
 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
 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
 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
 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