gdb/ser-base.c

   1 /* Generic serial interface functions.
   2
   3    Copyright (C) 1992-2015 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "serial.h"
  22 #include "ser-base.h"
  23 #include "event-loop.h"
  24
  25 #include "gdb_select.h"
  26 #include <sys/time.h>
  27 #ifdef USE_WIN32API
  28 #include <winsock2.h>
  29 #endif
  30
  31
  32 static timer_handler_func push_event;
  33 static handler_func fd_event;
  34
  35 /* Event handling for ASYNC serial code.
  36
  37    At any time the SERIAL device either: has an empty FIFO and is
  38    waiting on a FD event; or has a non-empty FIFO/error condition and
  39    is constantly scheduling timer events.
  40
  41    ASYNC only stops pestering its client when it is de-async'ed or it
  42    is told to go away.  */
  43
  44 /* Value of scb->async_state: */
  45 enum {
  46   /* >= 0 (TIMER_SCHEDULED) */
  47   /* The ID of the currently scheduled timer event.  This state is
  48      rarely encountered.  Timer events are one-off so as soon as the
  49      event is delivered the state is shanged to NOTHING_SCHEDULED.  */
  50   FD_SCHEDULED = -1,
  51   /* The fd_event() handler is scheduled.  It is called when ever the
  52      file descriptor becomes ready.  */
  53   NOTHING_SCHEDULED = -2
  54   /* Either no task is scheduled (just going into ASYNC mode) or a
  55      timer event has just gone off and the current state has been
  56      forced into nothing scheduled.  */
  57 };
  58
  59 /* Identify and schedule the next ASYNC task based on scb->async_state
  60    and scb->buf* (the input FIFO).  A state machine is used to avoid
  61    the need to make redundant calls into the event-loop - the next
  62    scheduled task is only changed when needed.  */
  63
  64 static void
  65 reschedule (struct serial *scb)
  66 {
  67   if (serial_is_async_p (scb))
  68     {
  69       int next_state;
  70
  71       switch (scb->async_state)
  72         {
  73         case FD_SCHEDULED:
  74           if (scb->bufcnt == 0)
  75             next_state = FD_SCHEDULED;
  76           else
  77             {
  78               delete_file_handler (scb->fd);
  79               next_state = create_timer (0, push_event, scb);
  80             }
  81           break;
  82         case NOTHING_SCHEDULED:
  83           if (scb->bufcnt == 0)
  84             {
  85               add_file_handler (scb->fd, fd_event, scb);
  86               next_state = FD_SCHEDULED;
  87             }
  88           else
  89             {
  90               next_state = create_timer (0, push_event, scb);
  91             }
  92           break;
  93         default: /* TIMER SCHEDULED */
  94           if (scb->bufcnt == 0)
  95             {
  96               delete_timer (scb->async_state);
  97               add_file_handler (scb->fd, fd_event, scb);
  98               next_state = FD_SCHEDULED;
  99             }
 100           else
 101             next_state = scb->async_state;
 102           break;
 103         }
 104       if (serial_debug_p (scb))
 105         {
 106           switch (next_state)
 107             {
 108             case FD_SCHEDULED:
 109               if (scb->async_state != FD_SCHEDULED)
 110                 fprintf_unfiltered (gdb_stdlog, "[fd%d->fd-scheduled]\n",
 111                                     scb->fd);
 112               break;
 113             default: /* TIMER SCHEDULED */
 114               if (scb->async_state == FD_SCHEDULED)
 115                 fprintf_unfiltered (gdb_stdlog, "[fd%d->timer-scheduled]\n",
 116                                     scb->fd);
 117               break;
 118             }
 119         }
 120       scb->async_state = next_state;
 121     }
 122 }
 123
 124 /* Run the SCB's async handle, and reschedule, if the handler doesn't
 125    close SCB.  */
 126
 127 static void
 128 run_async_handler_and_reschedule (struct serial *scb)
 129 {
 130   int is_open;
 131
 132   /* Take a reference, so a serial_close call within the handler
 133      doesn't make SCB a dangling pointer.  */
 134   serial_ref (scb);
 135
 136   /* Run the handler.  */
 137   scb->async_handler (scb, scb->async_context);
 138
 139   is_open = serial_is_open (scb);
 140   serial_unref (scb);
 141
 142   /* Get ready for more, if not already closed.  */
 143   if (is_open)
 144     reschedule (scb);
 145 }
 146
 147 /* FD_EVENT: This is scheduled when the input FIFO is empty (and there
 148    is no pending error).  As soon as data arrives, it is read into the
 149    input FIFO and the client notified.  The client should then drain
 150    the FIFO using readchar().  If the FIFO isn't immediatly emptied,
 151    push_event() is used to nag the client until it is.  */
 152
 153 static void
 154 fd_event (int error, void *context)
 155 {
 156   struct serial *scb = context;
 157   if (error != 0)
 158     {
 159       scb->bufcnt = SERIAL_ERROR;
 160     }
 161   else if (scb->bufcnt == 0)
 162     {
 163       /* Prime the input FIFO.  The readchar() function is used to
 164          pull characters out of the buffer.  See also
 165          generic_readchar().  */
 166       int nr;
 167       nr = scb->ops->read_prim (scb, BUFSIZ);
 168       if (nr == 0)
 169         {
 170           scb->bufcnt = SERIAL_EOF;
 171         }
 172       else if (nr > 0)
 173         {
 174           scb->bufcnt = nr;
 175           scb->bufp = scb->buf;
 176         }
 177       else
 178         {
 179           scb->bufcnt = SERIAL_ERROR;
 180         }
 181     }
 182   run_async_handler_and_reschedule (scb);
 183 }
 184
 185 /* PUSH_EVENT: The input FIFO is non-empty (or there is a pending
 186    error).  Nag the client until all the data has been read.  In the
 187    case of errors, the client will need to close or de-async the
 188    device before naging stops.  */
 189
 190 static void
 191 push_event (void *context)
 192 {
 193   struct serial *scb = context;
 194
 195   scb->async_state = NOTHING_SCHEDULED; /* Timers are one-off */
 196   run_async_handler_and_reschedule (scb);
 197 }
 198
 199 /* Wait for input on scb, with timeout seconds.  Returns 0 on success,
 200    otherwise SERIAL_TIMEOUT or SERIAL_ERROR.  */
 201
 202 static int
 203 ser_base_wait_for (struct serial *scb, int timeout)
 204 {
 205   while (1)
 206     {
 207       int numfds;
 208       struct timeval tv;
 209       fd_set readfds, exceptfds;
 210
 211       /* NOTE: Some OS's can scramble the READFDS when the select()
 212          call fails (ex the kernel with Red Hat 5.2).  Initialize all
 213          arguments before each call.  */
 214
 215       tv.tv_sec = timeout;
 216       tv.tv_usec = 0;
 217
 218       FD_ZERO (&readfds);
 219       FD_ZERO (&exceptfds);
 220       FD_SET (scb->fd, &readfds);
 221       FD_SET (scb->fd, &exceptfds);
 222
 223       if (timeout >= 0)
 224         numfds = gdb_select (scb->fd + 1, &readfds, 0, &exceptfds, &tv);
 225       else
 226         numfds = gdb_select (scb->fd + 1, &readfds, 0, &exceptfds, 0);
 227
 228       if (numfds <= 0)
 229         {
 230           if (numfds == 0)
 231             return SERIAL_TIMEOUT;
 232           else if (errno == EINTR)
 233             continue;
 234           else
 235             return SERIAL_ERROR;        /* Got an error from select or
 236                                            poll.  */
 237         }
 238
 239       return 0;
 240     }
 241 }
 242
 243 /* Read any error output we might have.  */
 244
 245 static void
 246 ser_base_read_error_fd (struct serial *scb, int close_fd)
 247 {
 248   if (scb->error_fd != -1)
 249     {
 250       ssize_t s;
 251       char buf[GDB_MI_MSG_WIDTH + 1];
 252
 253       for (;;)
 254         {
 255           char *current;
 256           char *newline;
 257           int to_read = GDB_MI_MSG_WIDTH;
 258           int num_bytes = -1;
 259
 260           if (scb->ops->avail)
 261             num_bytes = (scb->ops->avail)(scb, scb->error_fd);
 262
 263           if (num_bytes != -1)
 264             to_read = (num_bytes < to_read) ? num_bytes : to_read;
 265
 266           if (to_read == 0)
 267             break;
 268
 269           s = read (scb->error_fd, &buf, to_read);
 270           if ((s == -1) || (s == 0 && !close_fd))
 271             break;
 272
 273           if (s == 0 && close_fd)
 274             {
 275               /* End of file.  */
 276               close (scb->error_fd);
 277               scb->error_fd = -1;
 278               break;
 279             }
 280
 281           /* In theory, embedded newlines are not a problem.
 282              But for MI, we want each output line to have just
 283              one newline for legibility.  So output things
 284              in newline chunks.  */
 285           gdb_assert (s > 0 && s <= GDB_MI_MSG_WIDTH);
 286           buf[s] = '\0';
 287           current = buf;
 288           while ((newline = strstr (current, "\n")) != NULL)
 289             {
 290               *newline = '\0';
 291               fputs_unfiltered (current, gdb_stderr);
 292               fputs_unfiltered ("\n", gdb_stderr);
 293               current = newline + 1;
 294             }
 295
 296           fputs_unfiltered (current, gdb_stderr);
 297        }
 298     }
 299 }
 300
 301 /* Read a character with user-specified timeout.  TIMEOUT is number of seconds
 302    to wait, or -1 to wait forever.  Use timeout of 0 to effect a poll.  Returns
 303    char if successful.  Returns -2 if timeout expired, EOF if line dropped
 304    dead, or -3 for any other error (see errno in that case).  */
 305
 306 static int
 307 do_ser_base_readchar (struct serial *scb, int timeout)
 308 {
 309   int status;
 310   int delta;
 311
 312   /* We have to be able to keep the GUI alive here, so we break the
 313      original timeout into steps of 1 second, running the "keep the
 314      GUI alive" hook each time through the loop.
 315
 316      Also, timeout = 0 means to poll, so we just set the delta to 0,
 317      so we will only go through the loop once.  */
 318
 319   delta = (timeout == 0 ? 0 : 1);
 320   while (1)
 321     {
 322       /* N.B. The UI may destroy our world (for instance by calling
 323          remote_stop,) in which case we want to get out of here as
 324          quickly as possible.  It is not safe to touch scb, since
 325          someone else might have freed it.  The
 326          deprecated_ui_loop_hook signals that we should exit by
 327          returning 1.  */
 328
 329       if (deprecated_ui_loop_hook)
 330         {
 331           if (deprecated_ui_loop_hook (0))
 332             return SERIAL_TIMEOUT;
 333         }
 334
 335       status = ser_base_wait_for (scb, delta);
 336       if (timeout > 0)
 337         timeout -= delta;
 338
 339       /* If we got a character or an error back from wait_for, then we can
 340          break from the loop before the timeout is completed.  */
 341       if (status != SERIAL_TIMEOUT)
 342         break;
 343
 344       /* If we have exhausted the original timeout, then generate
 345          a SERIAL_TIMEOUT, and pass it out of the loop.  */
 346       else if (timeout == 0)
 347         {
 348           status = SERIAL_TIMEOUT;
 349           break;
 350         }
 351
 352       /* We also need to check and consume the stderr because it could
 353          come before the stdout for some stubs.  If we just sit and wait
 354          for stdout, we would hit a deadlock for that case.  */
 355       ser_base_read_error_fd (scb, 0);
 356     }
 357
 358   if (status < 0)
 359     return status;
 360
 361   status = scb->ops->read_prim (scb, BUFSIZ);
 362
 363   if (status <= 0)
 364     {
 365       if (status == 0)
 366         return SERIAL_EOF;
 367       else
 368         /* Got an error from read.  */
 369         return SERIAL_ERROR;
 370     }
 371
 372   scb->bufcnt = status;
 373   scb->bufcnt--;
 374   scb->bufp = scb->buf;
 375   return *scb->bufp++;
 376 }
 377
 378 /* Perform operations common to both old and new readchar.  */
 379
 380 /* Return the next character from the input FIFO.  If the FIFO is
 381    empty, call the SERIAL specific routine to try and read in more
 382    characters.
 383
 384    Initially data from the input FIFO is returned (fd_event()
 385    pre-reads the input into that FIFO.  Once that has been emptied,
 386    further data is obtained by polling the input FD using the device
 387    specific readchar() function.  Note: reschedule() is called after
 388    every read.  This is because there is no guarentee that the lower
 389    level fd_event() poll_event() code (which also calls reschedule())
 390    will be called.  */
 391
 392 int
 393 generic_readchar (struct serial *scb, int timeout,
 394                   int (do_readchar) (struct serial *scb, int timeout))
 395 {
 396   int ch;
 397   if (scb->bufcnt > 0)
 398     {
 399       ch = *scb->bufp;
 400       scb->bufcnt--;
 401       scb->bufp++;
 402     }
 403   else if (scb->bufcnt < 0)
 404     {
 405       /* Some errors/eof are are sticky.  */
 406       ch = scb->bufcnt;
 407     }
 408   else
 409     {
 410       ch = do_readchar (scb, timeout);
 411       if (ch < 0)
 412         {
 413           switch ((enum serial_rc) ch)
 414             {
 415             case SERIAL_EOF:
 416             case SERIAL_ERROR:
 417               /* Make the error/eof stick.  */
 418               scb->bufcnt = ch;
 419               break;
 420             case SERIAL_TIMEOUT:
 421               scb->bufcnt = 0;
 422               break;
 423             }
 424         }
 425     }
 426
 427   /* Read any error output we might have.  */
 428   ser_base_read_error_fd (scb, 1);
 429
 430   reschedule (scb);
 431   return ch;
 432 }
 433
 434 int
 435 ser_base_readchar (struct serial *scb, int timeout)
 436 {
 437   return generic_readchar (scb, timeout, do_ser_base_readchar);
 438 }
 439
 440 int
 441 ser_base_write (struct serial *scb, const void *buf, size_t count)
 442 {
 443   const char *str = buf;
 444   int cc;
 445
 446   while (count > 0)
 447     {
 448       cc = scb->ops->write_prim (scb, str, count);
 449
 450       if (cc < 0)
 451         return 1;
 452       count -= cc;
 453       str += cc;
 454     }
 455   return 0;
 456 }
 457
 458 int
 459 ser_base_flush_output (struct serial *scb)
 460 {
 461   return 0;
 462 }
 463
 464 int
 465 ser_base_flush_input (struct serial *scb)
 466 {
 467   if (scb->bufcnt >= 0)
 468     {
 469       scb->bufcnt = 0;
 470       scb->bufp = scb->buf;
 471       return 0;
 472     }
 473   else
 474     return SERIAL_ERROR;
 475 }
 476
 477 int
 478 ser_base_send_break (struct serial *scb)
 479 {
 480   return 0;
 481 }
 482
 483 int
 484 ser_base_drain_output (struct serial *scb)
 485 {
 486   return 0;
 487 }
 488
 489 void
 490 ser_base_raw (struct serial *scb)
 491 {
 492   return;                       /* Always in raw mode.  */
 493 }
 494
 495 serial_ttystate
 496 ser_base_get_tty_state (struct serial *scb)
 497 {
 498   /* Allocate a dummy.  */
 499   return (serial_ttystate) XNEW (int);
 500 }
 501
 502 serial_ttystate
 503 ser_base_copy_tty_state (struct serial *scb, serial_ttystate ttystate)
 504 {
 505   /* Allocate another dummy.  */
 506   return (serial_ttystate) XNEW (int);
 507 }
 508
 509 int
 510 ser_base_set_tty_state (struct serial *scb, serial_ttystate ttystate)
 511 {
 512   return 0;
 513 }
 514
 515 int
 516 ser_base_noflush_set_tty_state (struct serial *scb,
 517                                 serial_ttystate new_ttystate,
 518                                 serial_ttystate old_ttystate)
 519 {
 520   return 0;
 521 }
 522
 523 void
 524 ser_base_print_tty_state (struct serial *scb,
 525                           serial_ttystate ttystate,
 526                           struct ui_file *stream)
 527 {
 528   /* Nothing to print.  */
 529   return;
 530 }
 531
 532 int
 533 ser_base_setbaudrate (struct serial *scb, int rate)
 534 {
 535   return 0;                     /* Never fails!  */
 536 }
 537
 538 int
 539 ser_base_setstopbits (struct serial *scb, int num)
 540 {
 541   return 0;                     /* Never fails!  */
 542 }
 543
 544 /* Implement the "setparity" serial_ops callback.  */
 545
 546 int
 547 ser_base_setparity (struct serial *scb, int parity)
 548 {
 549   return 0;                     /* Never fails!  */
 550 }
 551
 552 /* Put the SERIAL device into/out-of ASYNC mode.  */
 553
 554 void
 555 ser_base_async (struct serial *scb,
 556                 int async_p)
 557 {
 558   if (async_p)
 559     {
 560       /* Force a re-schedule.  */
 561       scb->async_state = NOTHING_SCHEDULED;
 562       if (serial_debug_p (scb))
 563         fprintf_unfiltered (gdb_stdlog, "[fd%d->asynchronous]\n",
 564                             scb->fd);
 565       reschedule (scb);
 566     }
 567   else
 568     {
 569       if (serial_debug_p (scb))
 570         fprintf_unfiltered (gdb_stdlog, "[fd%d->synchronous]\n",
 571                             scb->fd);
 572       /* De-schedule whatever tasks are currently scheduled.  */
 573       switch (scb->async_state)
 574         {
 575         case FD_SCHEDULED:
 576           delete_file_handler (scb->fd);
 577           break;
 578         case NOTHING_SCHEDULED:
 579           break;
 580         default: /* TIMER SCHEDULED */
 581           delete_timer (scb->async_state);
 582           break;
 583         }
 584     }
 585 }