src/background.c

   1 /* {{{ Copyright */
   2
   3 /* Background support.
   4
   5    Copyright (C) 1996-2014
   6    Free Software Foundation, Inc.
   7
   8    Written by:
   9    Miguel de Icaza, 1996
  10
  11    This file is part of the Midnight Commander.
  12
  13    The Midnight Commander is free software: you can redistribute it
  14    and/or modify it under the terms of the GNU General Public License as
  15    published by the Free Software Foundation, either version 3 of the License,
  16    or (at your option) any later version.
  17
  18    The Midnight Commander is distributed in the hope that it will be useful,
  19    but WITHOUT ANY WARRANTY; without even the implied warranty of
  20    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21    GNU General Public License for more details.
  22
  23    You should have received a copy of the GNU General Public License
  24    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  25  */
  26
  27 /* }}} */
  28
  29 /** \file background.c
  30  *  \brief Source: Background support
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdlib.h>
  36 #include <errno.h>
  37 #include <signal.h>
  38 #include <stdarg.h>
  39 #include <stdio.h>
  40 #include <string.h>
  41
  42 #include <sys/types.h>
  43 #include <sys/stat.h>
  44 #include <sys/wait.h>           /* waitpid() */
  45 #include <fcntl.h>
  46
  47 #include "lib/global.h"
  48
  49 #include "lib/unixcompat.h"
  50 #include "lib/tty/key.h"        /* add_select_channel(), delete_select_channel() */
  51 #include "lib/widget.h"         /* message() */
  52 #include "lib/event-types.h"
  53
  54 #include "filemanager/fileopctx.h"      /* file_op_context_t */
  55
  56 #include "background.h"
  57
  58 /*** global variables ****************************************************************************/
  59
  60 #define MAXCALLARGS 4           /* Number of arguments supported */
  61
  62 /*** file scope macro definitions ****************************************************************/
  63
  64 /*** file scope type declarations ****************************************************************/
  65
  66 enum ReturnType
  67 {
  68     Return_String,
  69     Return_Integer
  70 };
  71
  72 /*** file scope variables ************************************************************************/
  73
  74 /* File descriptor for talking to our parent */
  75 static int parent_fd;
  76
  77 /* File descriptor for messages from our parent */
  78 static int from_parent_fd;
  79
  80 struct TaskList *task_list = NULL;
  81
  82 static int background_attention (int fd, void *closure);
  83
  84 /*** file scope functions ************************************************************************/
  85 /* --------------------------------------------------------------------------------------------- */
  86
  87 static void
  88 register_task_running (file_op_context_t * ctx, pid_t pid, int fd, int to_child, char *info)
  89 {
  90     TaskList *new;
  91
  92     new = g_new (TaskList, 1);
  93     new->pid = pid;
  94     new->info = info;
  95     new->state = Task_Running;
  96     new->next = task_list;
  97     new->fd = fd;
  98     new->to_child_fd = to_child;
  99     task_list = new;
 100
 101     add_select_channel (fd, background_attention, ctx);
 102 }
 103
 104 /* --------------------------------------------------------------------------------------------- */
 105
 106 static int
 107 destroy_task_and_return_fd (pid_t pid)
 108 {
 109     TaskList *p = task_list;
 110     TaskList *prev = 0;
 111
 112     while (p)
 113     {
 114         if (p->pid == pid)
 115         {
 116             if (prev)
 117                 prev->next = p->next;
 118             else
 119                 task_list = p->next;
 120             g_free (p->info);
 121             g_free (p);
 122             return p->fd;
 123         }
 124         prev = p;
 125         p = p->next;
 126     }
 127
 128     /* pid not found */
 129     return -1;
 130 }
 131
 132 /* --------------------------------------------------------------------------------------------- */
 133 /* {{{ Parent handlers */
 134
 135 /* Parent/child protocol
 136  *
 137  * the child (the background) process send the following:
 138  * void *routine -- routine to be invoked in the parent
 139  * int  nargc    -- number of arguments
 140  * int  type     -- Return argument type.
 141  *
 142  * If the routine is zero, then it is a way to tell the parent
 143  * that the process is dying.
 144  *
 145  * nargc arguments in the following format:
 146  * int size of the coming block
 147  * size bytes with the block
 148  *
 149  * Now, the parent loads all those and then invokes
 150  * the routine with pointers to the information passed
 151  * (we just support pointers).
 152  *
 153  * If the return type is integer:
 154  *
 155  *     the parent then writes an int to the child with
 156  *     the return value from the routine and the values
 157  *     of any global variable that is modified in the parent
 158  *     currently: do_append and recursive_result.
 159  *
 160  * If the return type is a string:
 161  *
 162  *     the parent writes the resulting string length
 163  *     if the result string was NULL or the empty string,
 164  *     then the length is zero.
 165  *     The parent then writes the string length and frees
 166  *     the result string.
 167  */
 168 /*
 169  * Receive requests from background process and invoke the
 170  * specified routine
 171  */
 172
 173 static int
 174 background_attention (int fd, void *closure)
 175 {
 176     file_op_context_t *ctx;
 177     int have_ctx;
 178     union
 179     {
 180         int (*have_ctx0) (int);
 181         int (*have_ctx1) (int, char *);
 182         int (*have_ctx2) (int, char *, char *);
 183         int (*have_ctx3) (int, char *, char *, char *);
 184         int (*have_ctx4) (int, char *, char *, char *, char *);
 185
 186         int (*non_have_ctx0) (file_op_context_t *, int);
 187         int (*non_have_ctx1) (file_op_context_t *, int, char *);
 188         int (*non_have_ctx2) (file_op_context_t *, int, char *, char *);
 189         int (*non_have_ctx3) (file_op_context_t *, int, char *, char *, char *);
 190         int (*non_have_ctx4) (file_op_context_t *, int, char *, char *, char *, char *);
 191
 192         char *(*ret_str0) ();
 193         char *(*ret_str1) (char *);
 194         char *(*ret_str2) (char *, char *);
 195         char *(*ret_str3) (char *, char *, char *);
 196         char *(*ret_str4) (char *, char *, char *, char *);
 197
 198         void *pointer;
 199     } routine;
 200     /*    void *routine; */
 201     int argc, i, status;
 202     char *data[MAXCALLARGS];
 203     ssize_t bytes, ret;
 204     struct TaskList *p;
 205     int to_child_fd = -1;
 206     enum ReturnType type;
 207
 208     ctx = closure;
 209
 210     bytes = read (fd, &routine.pointer, sizeof (routine));
 211     if (bytes == -1 || (size_t) bytes < (sizeof (routine)))
 212     {
 213         const char *background_process_error = _("Background process error");
 214
 215         unregister_task_running (ctx->pid, fd);
 216         if (!waitpid (ctx->pid, &status, WNOHANG))
 217         {
 218             /* the process is still running, but it misbehaves - kill it */
 219             kill (ctx->pid, SIGTERM);
 220             message (D_ERROR, background_process_error, _("Unknown error in child"));
 221             return 0;
 222         }
 223
 224         /* 0 means happy end */
 225         if (WIFEXITED (status) && (WEXITSTATUS (status) == 0))
 226             return 0;
 227
 228         message (D_ERROR, background_process_error, _("Child died unexpectedly"));
 229
 230         return 0;
 231     }
 232
 233     if ((read (fd, &argc, sizeof (argc)) != sizeof (argc)) ||
 234         (read (fd, &type, sizeof (type)) != sizeof (type)) ||
 235         (read (fd, &have_ctx, sizeof (have_ctx)) != sizeof (have_ctx)))
 236     {
 237         message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 238         return 0;
 239     }
 240
 241     if (argc > MAXCALLARGS)
 242     {
 243         message (D_ERROR, _("Background protocol error"),
 244                  _("Background process sent us a request for more arguments\n"
 245                    "than we can handle."));
 246     }
 247
 248     if (have_ctx)
 249     {
 250         if (read (fd, ctx, sizeof (file_op_context_t)) != sizeof (file_op_context_t))
 251         {
 252             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 253             return 0;
 254         }
 255     }
 256
 257     for (i = 0; i < argc; i++)
 258     {
 259         int size;
 260
 261         if (read (fd, &size, sizeof (size)) != sizeof (size))
 262         {
 263             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 264             return 0;
 265         }
 266         data[i] = g_malloc (size + 1);
 267         if (read (fd, data[i], size) != size)
 268         {
 269             message (D_ERROR, _("Background protocol error"), _("Reading failed"));
 270             return 0;
 271         }
 272         data[i][size] = 0;      /* NULL terminate the blocks (they could be strings) */
 273     }
 274
 275     /* Find child task info by descriptor */
 276     /* Find before call, because process can destroy self after */
 277     for (p = task_list; p; p = p->next)
 278     {
 279         if (p->fd == fd)
 280             break;
 281     }
 282
 283     if (p)
 284         to_child_fd = p->to_child_fd;
 285
 286     if (to_child_fd == -1)
 287         message (D_ERROR, _("Background process error"), _("Unknown error in child"));
 288
 289     /* Handle the call */
 290     if (type == Return_Integer)
 291     {
 292         int result = 0;
 293
 294         if (!have_ctx)
 295             switch (argc)
 296             {
 297             case 0:
 298                 result = routine.have_ctx0 (Background);
 299                 break;
 300             case 1:
 301                 result = routine.have_ctx1 (Background, data[0]);
 302                 break;
 303             case 2:
 304                 result = routine.have_ctx2 (Background, data[0], data[1]);
 305                 break;
 306             case 3:
 307                 result = routine.have_ctx3 (Background, data[0], data[1], data[2]);
 308                 break;
 309             case 4:
 310                 result = routine.have_ctx4 (Background, data[0], data[1], data[2], data[3]);
 311                 break;
 312             }
 313         else
 314             switch (argc)
 315             {
 316             case 0:
 317                 result = routine.non_have_ctx0 (ctx, Background);
 318                 break;
 319             case 1:
 320                 result = routine.non_have_ctx1 (ctx, Background, data[0]);
 321                 break;
 322             case 2:
 323                 result = routine.non_have_ctx2 (ctx, Background, data[0], data[1]);
 324                 break;
 325             case 3:
 326                 result = routine.non_have_ctx3 (ctx, Background, data[0], data[1], data[2]);
 327                 break;
 328             case 4:
 329                 result =
 330                     routine.non_have_ctx4 (ctx, Background, data[0], data[1], data[2], data[3]);
 331                 break;
 332             }
 333
 334         /* Send the result code and the value for shared variables */
 335         ret = write (to_child_fd, &result, sizeof (int));
 336         if (have_ctx && to_child_fd != -1)
 337             ret = write (to_child_fd, ctx, sizeof (file_op_context_t));
 338     }
 339     else if (type == Return_String)
 340     {
 341         int len;
 342         char *resstr = NULL;
 343
 344         /* FIXME: string routines should also use the Foreground/Background
 345          * parameter.  Currently, this is not used here
 346          */
 347         switch (argc)
 348         {
 349         case 0:
 350             resstr = routine.ret_str0 ();
 351             break;
 352         case 1:
 353             resstr = routine.ret_str1 (data[0]);
 354             break;
 355         case 2:
 356             resstr = routine.ret_str2 (data[0], data[1]);
 357             break;
 358         case 3:
 359             resstr = routine.ret_str3 (data[0], data[1], data[2]);
 360             break;
 361         case 4:
 362             resstr = routine.ret_str4 (data[0], data[1], data[2], data[3]);
 363             break;
 364         default:
 365             g_assert_not_reached ();
 366         }
 367         if (resstr)
 368         {
 369             len = strlen (resstr);
 370             ret = write (to_child_fd, &len, sizeof (len));
 371             if (len != 0)
 372                 ret = write (to_child_fd, resstr, len);
 373             g_free (resstr);
 374         }
 375         else
 376         {
 377             len = 0;
 378             ret = write (to_child_fd, &len, sizeof (len));
 379         }
 380     }
 381     for (i = 0; i < argc; i++)
 382         g_free (data[i]);
 383
 384     repaint_screen ();
 385     (void) ret;
 386     return 0;
 387 }
 388
 389
 390 /* --------------------------------------------------------------------------------------------- */
 391 /* }}} */
 392
 393 /* {{{ client RPC routines */
 394
 395 /* Sends the header for a call to a routine in the parent process.  If the file
 396  * operation context is not NULL, then it requests that the first parameter of
 397  * the call be a file operation context.
 398  */
 399
 400 static void
 401 parent_call_header (void *routine, int argc, enum ReturnType type, file_op_context_t * ctx)
 402 {
 403     int have_ctx;
 404     ssize_t ret;
 405
 406     have_ctx = (ctx != NULL);
 407
 408     ret = write (parent_fd, &routine, sizeof (routine));
 409     ret = write (parent_fd, &argc, sizeof (int));
 410     ret = write (parent_fd, &type, sizeof (type));
 411     ret = write (parent_fd, &have_ctx, sizeof (have_ctx));
 412
 413     if (have_ctx)
 414         ret = write (parent_fd, ctx, sizeof (file_op_context_t));
 415     (void) ret;
 416 }
 417
 418 /* --------------------------------------------------------------------------------------------- */
 419
 420 static int
 421 parent_va_call (void *routine, gpointer data, int argc, va_list ap)
 422 {
 423     int i;
 424     ssize_t ret;
 425     file_op_context_t *ctx = (file_op_context_t *) data;
 426
 427     parent_call_header (routine, argc, Return_Integer, ctx);
 428     for (i = 0; i < argc; i++)
 429     {
 430         int len;
 431         void *value;
 432
 433         len = va_arg (ap, int);
 434         value = va_arg (ap, void *);
 435         ret = write (parent_fd, &len, sizeof (int));
 436         ret = write (parent_fd, value, len);
 437     }
 438
 439     ret = read (from_parent_fd, &i, sizeof (int));
 440     if (ctx)
 441         ret = read (from_parent_fd, ctx, sizeof (file_op_context_t));
 442
 443     (void) ret;
 444     return i;
 445 }
 446
 447 /* --------------------------------------------------------------------------------------------- */
 448
 449 static char *
 450 parent_va_call_string (void *routine, int argc, va_list ap)
 451 {
 452     char *str;
 453     int i;
 454
 455     parent_call_header (routine, argc, Return_String, NULL);
 456     for (i = 0; i < argc; i++)
 457     {
 458         int len;
 459         void *value;
 460
 461         len = va_arg (ap, int);
 462         value = va_arg (ap, void *);
 463         if ((write (parent_fd, &len, sizeof (int)) != sizeof (int)) ||
 464             (write (parent_fd, value, len) != len))
 465         {
 466             return NULL;
 467         }
 468     }
 469
 470     if (read (from_parent_fd, &i, sizeof (int)) != sizeof (int))
 471         return NULL;
 472     if (!i)
 473         return NULL;
 474     str = g_malloc (i + 1);
 475     if (read (from_parent_fd, str, i) != i)
 476     {
 477         g_free (str);
 478         return NULL;
 479     }
 480     str[i] = 0;
 481     return str;
 482 }
 483
 484 /* --------------------------------------------------------------------------------------------- */
 485 /*** public functions ****************************************************************************/
 486 /* --------------------------------------------------------------------------------------------- */
 487
 488 void
 489 unregister_task_running (pid_t pid, int fd)
 490 {
 491     destroy_task_and_return_fd (pid);
 492     delete_select_channel (fd);
 493 }
 494
 495 /* --------------------------------------------------------------------------------------------- */
 496
 497 void
 498 unregister_task_with_pid (pid_t pid)
 499 {
 500     int fd = destroy_task_and_return_fd (pid);
 501     if (fd != -1)
 502         delete_select_channel (fd);
 503 }
 504
 505
 506 /* --------------------------------------------------------------------------------------------- */
 507 /**
 508  * Try to make the Midnight Commander a background job
 509  *
 510  * Returns:
 511  *  1 for parent
 512  *  0 for child
 513  * -1 on failure
 514  */
 515 int
 516 do_background (file_op_context_t * ctx, char *info)
 517 {
 518     int comm[2];                /* control connection stream */
 519     int back_comm[2];           /* back connection */
 520     pid_t pid;
 521
 522     if (pipe (comm) == -1)
 523         return -1;
 524
 525     if (pipe (back_comm) == -1)
 526         return -1;
 527
 528     pid = fork ();
 529     if (pid == -1)
 530     {
 531         int saved_errno = errno;
 532
 533         (void) close (comm[0]);
 534         (void) close (comm[1]);
 535         (void) close (back_comm[0]);
 536         (void) close (back_comm[1]);
 537         errno = saved_errno;
 538         return -1;
 539     }
 540
 541     if (pid == 0)
 542     {
 543         int nullfd;
 544
 545         parent_fd = comm[1];
 546         from_parent_fd = back_comm[0];
 547
 548         mc_global.we_are_background = TRUE;
 549         top_dlg = NULL;
 550
 551         /* Make stdin/stdout/stderr point somewhere */
 552         close (STDIN_FILENO);
 553         close (STDOUT_FILENO);
 554         close (STDERR_FILENO);
 555
 556         nullfd = open ("/dev/null", O_RDWR);
 557         if (nullfd != -1)
 558         {
 559             while (dup2 (nullfd, STDIN_FILENO) == -1 && errno == EINTR)
 560                 ;
 561             while (dup2 (nullfd, STDOUT_FILENO) == -1 && errno == EINTR)
 562                 ;
 563             while (dup2 (nullfd, STDERR_FILENO) == -1 && errno == EINTR)
 564                 ;
 565         }
 566
 567         return 0;
 568     }
 569     else
 570     {
 571         ctx->pid = pid;
 572         register_task_running (ctx, pid, comm[0], back_comm[1], info);
 573         return 1;
 574     }
 575 }
 576
 577 /* --------------------------------------------------------------------------------------------- */
 578
 579 int
 580 parent_call (void *routine, file_op_context_t * ctx, int argc, ...)
 581 {
 582     int ret;
 583     va_list ap;
 584
 585     va_start (ap, argc);
 586     ret = parent_va_call (routine, (gpointer) ctx, argc, ap);
 587     va_end (ap);
 588
 589     return ret;
 590 }
 591
 592 /* --------------------------------------------------------------------------------------------- */
 593
 594 char *
 595 parent_call_string (void *routine, int argc, ...)
 596 {
 597     va_list ap;
 598     char *str;
 599
 600     va_start (ap, argc);
 601     str = parent_va_call_string (routine, argc, ap);
 602     va_end (ap);
 603
 604     return str;
 605 }
 606
 607 /* --------------------------------------------------------------------------------------------- */
 608
 609 /* event callback */
 610 gboolean
 611 background_parent_call (const gchar * event_group_name, const gchar * event_name,
 612                         gpointer init_data, gpointer data)
 613 {
 614     ev_background_parent_call_t *event_data = (ev_background_parent_call_t *) data;
 615
 616     (void) event_group_name;
 617     (void) event_name;
 618     (void) init_data;
 619
 620     event_data->ret.i =
 621         parent_va_call (event_data->routine, event_data->ctx, event_data->argc, event_data->ap);
 622
 623     return TRUE;
 624 }
 625
 626 /* --------------------------------------------------------------------------------------------- */
 627
 628 /* event callback */
 629 gboolean
 630 background_parent_call_string (const gchar * event_group_name, const gchar * event_name,
 631                                gpointer init_data, gpointer data)
 632 {
 633     ev_background_parent_call_t *event_data = (ev_background_parent_call_t *) data;
 634
 635     (void) event_group_name;
 636     (void) event_name;
 637     (void) init_data;
 638
 639     event_data->ret.s =
 640         parent_va_call_string (event_data->routine, event_data->argc, event_data->ap);
 641
 642     return TRUE;
 643 }
 644
 645 /* --------------------------------------------------------------------------------------------- */