about summary refs log tree commit diff
path: root/hurd/hurdsig.c
blob: 6abad330214fa474c7c57006880383ca4714e0ba (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
/* Copyright (C) 1991, 92, 93, 94, 95, 96, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <stdlib.h>
#include <stdio.h>
#include <hurd.h>
#include <hurd/signal.h>
#include <cthreads.h>		/* For `struct mutex'.  */
#include <string.h>
#include "hurdfault.h"
#include "hurdmalloc.h"		/* XXX */

const char *_hurdsig_getenv (const char *);

struct mutex _hurd_siglock;
int _hurd_stopped;

/* Port that receives signals and other miscellaneous messages.  */
mach_port_t _hurd_msgport;

/* Thread listening on it.  */
thread_t _hurd_msgport_thread;

/* Thread which receives task-global signals.  */
thread_t _hurd_sigthread;

/* Linked-list of per-thread signal state.  */
struct hurd_sigstate *_hurd_sigstates;

/* Timeout for RPC's after interrupt_operation. */
mach_msg_timeout_t _hurd_interrupted_rpc_timeout = 3000;

static void
default_sigaction (struct sigaction actions[NSIG])
{
  int signo;

  __sigemptyset (&actions[0].sa_mask);
  actions[0].sa_flags = SA_RESTART;
  actions[0].sa_handler = SIG_DFL;

  for (signo = 1; signo < NSIG; ++signo)
    actions[signo] = actions[0];
}

struct hurd_sigstate *
_hurd_thread_sigstate (thread_t thread)
{
  struct hurd_sigstate *ss;
  __mutex_lock (&_hurd_siglock);
  for (ss = _hurd_sigstates; ss != NULL; ss = ss->next)
    if (ss->thread == thread)
       break;
  if (ss == NULL)
    {
      ss = malloc (sizeof (*ss));
      if (ss == NULL)
	__libc_fatal ("hurd: Can't allocate thread sigstate\n");
      ss->thread = thread;
      __spin_lock_init (&ss->lock);

      /* Initialize default state.  */
      __sigemptyset (&ss->blocked);
      __sigemptyset (&ss->pending);
      memset (&ss->sigaltstack, 0, sizeof (ss->sigaltstack));
      ss->preempters = NULL;
      ss->suspended = 0;
      ss->intr_port = MACH_PORT_NULL;
      ss->context = NULL;

      /* Initialize the sigaction vector from the default signal receiving
	 thread's state, and its from the system defaults.  */
      if (thread == _hurd_sigthread)
	default_sigaction (ss->actions);
      else
	{
	  struct hurd_sigstate *s;
	  for (s = _hurd_sigstates; s != NULL; s = s->next)
	    if (s->thread == _hurd_sigthread)
	      break;
	  if (s)
	    {
	      __spin_lock (&s->lock);
	      memcpy (ss->actions, s->actions, sizeof (s->actions));
	      __spin_unlock (&s->lock);
	    }
	  else
	    default_sigaction (ss->actions);
	}

      ss->next = _hurd_sigstates;
      _hurd_sigstates = ss;
    }
  __mutex_unlock (&_hurd_siglock);
  return ss;
}

/* Signal delivery itself is on this page.  */

#include <hurd/fd.h>
#include <hurd/crash.h>
#include <hurd/paths.h>
#include <setjmp.h>
#include <fcntl.h>
#include <sys/wait.h>
#include "thread_state.h"
#include <hurd/msg_server.h>
#include <hurd/msg_reply.h>	/* For __msg_sig_post_reply.  */
#include <hurd/interrupt.h>
#include <assert.h>
#include <unistd.h>

int _hurd_core_limit;	/* XXX */

/* Call the crash dump server to mummify us before we die.
   Returns nonzero if a core file was written.  */
static int
write_corefile (int signo, const struct hurd_signal_detail *detail)
{
  error_t err;
  mach_port_t coreserver;
  file_t file, coredir;
  const char *name;

  /* XXX RLIMIT_CORE:
     When we have a protocol to make the server return an error
     for RLIMIT_FSIZE, then tell the corefile fs server the RLIMIT_CORE
     value in place of the RLIMIT_FSIZE value.  */

  /* First get a port to the core dumping server.  */
  coreserver = MACH_PORT_NULL;
  name = _hurdsig_getenv ("CRASHSERVER");
  if (name != NULL)
    coreserver = __file_name_lookup (name, 0, 0);
  if (coreserver == MACH_PORT_NULL)
    coreserver = __file_name_lookup (_SERVERS_CRASH, 0, 0);
  if (coreserver == MACH_PORT_NULL)
    return 0;

  /* Get a port to the directory where the new core file will reside.  */
  name = _hurdsig_getenv ("COREFILE");
  if (name == NULL)
    name = "core";
  coredir = __file_name_split (name, (char **) &name);
  if (coredir == MACH_PORT_NULL)
    return 0;
  /* Create the new file, but don't link it into the directory yet.  */
  if (err = __dir_mkfile (coredir, O_WRONLY|O_CREAT,
			  0600 & ~_hurd_umask, /* XXX ? */
			  &file))
    return 0;

  /* Call the core dumping server to write the core file.  */
  err = __crash_dump_task (coreserver,
			   __mach_task_self (),
			   file,
			   signo, detail->code, detail->error,
			   detail->exc, detail->exc_code, detail->exc_subcode,
			   _hurd_ports[INIT_PORT_CTTYID].port,
			   MACH_MSG_TYPE_COPY_SEND);
  __mach_port_deallocate (__mach_task_self (), coreserver);
  if (! err)
    /* The core dump into FILE succeeded, so now link it into the
       directory.  */
    err = __dir_link (file, coredir, name, 1);
  __mach_port_deallocate (__mach_task_self (), file);
  __mach_port_deallocate (__mach_task_self (), coredir);
  return !err;
}


/* The lowest-numbered thread state flavor value is 1,
   so we use bit 0 in machine_thread_all_state.set to
   record whether we have done thread_abort.  */
#define THREAD_ABORTED 1

/* SS->thread is suspended.  Abort the thread and get its basic state.  */
static void
abort_thread (struct hurd_sigstate *ss, struct machine_thread_all_state *state,
	      void (*reply) (void))
{
  if (!(state->set & THREAD_ABORTED))
    {
      error_t err = __thread_abort (ss->thread);
      assert_perror (err);
      /* Clear all thread state flavor set bits, because thread_abort may
	 have changed the state.  */
      state->set = THREAD_ABORTED;
    }

  if (reply)
    (*reply) ();

  machine_get_basic_state (ss->thread, state);
}

/* Find the location of the MiG reply port cell in use by the thread whose
   state is described by THREAD_STATE.  If SIGTHREAD is nonzero, make sure
   that this location can be set without faulting, or else return NULL.  */

static mach_port_t *
interrupted_reply_port_location (struct machine_thread_all_state *thread_state,
				 int sigthread)
{
  mach_port_t *portloc = (mach_port_t *) __hurd_threadvar_location_from_sp
    (_HURD_THREADVAR_MIG_REPLY, (void *) thread_state->basic.SP);

  if (sigthread && _hurdsig_catch_memory_fault (portloc))
    /* Faulted trying to read the stack.  */
    return NULL;

  /* Fault now if this pointer is bogus.  */
  *(volatile mach_port_t *) portloc = *portloc;

  if (sigthread)
    _hurdsig_end_catch_fault ();

  return portloc;
}

#include <hurd/sigpreempt.h>
#include "intr-msg.h"

/* Timeout on interrupt_operation calls.  */
mach_msg_timeout_t _hurdsig_interrupt_timeout = 1000;

/* SS->thread is suspended.

   Abort any interruptible RPC operation the thread is doing.

   This uses only the constant member SS->thread and the unlocked, atomically
   set member SS->intr_port, so no locking is needed.

   If successfully sent an interrupt_operation and therefore the thread should
   wait for its pending RPC to return (possibly EINTR) before taking the
   incoming signal, returns the reply port to be received on.  Otherwise
   returns MACH_PORT_NULL.

   SIGNO is used to find the applicable SA_RESTART bit.  If SIGNO is zero,
   the RPC fails with EINTR instead of restarting (thread_cancel).

   *STATE_CHANGE is set nonzero if STATE->basic was modified and should
   be applied back to the thread if it might ever run again, else zero.  */

mach_port_t
_hurdsig_abort_rpcs (struct hurd_sigstate *ss, int signo, int sigthread,
		     struct machine_thread_all_state *state, int *state_change,
		     void (*reply) (void))
{
  extern const void _hurd_intr_rpc_msg_in_trap;
  mach_port_t rcv_port = MACH_PORT_NULL;
  mach_port_t intr_port;

  *state_change = 0;

  intr_port = ss->intr_port;
  if (intr_port == MACH_PORT_NULL)
    /* No interruption needs done.  */
    return MACH_PORT_NULL;

  /* Abort the thread's kernel context, so any pending message send or
     receive completes immediately or aborts.  */
  abort_thread (ss, state, reply);

  if (state->basic.PC < (natural_t) &_hurd_intr_rpc_msg_in_trap)
    {
      /* The thread is about to do the RPC, but hasn't yet entered
	 mach_msg.  Mutate the thread's state so it knows not to try
	 the RPC.  */
      INTR_MSG_BACK_OUT (&state->basic);
      MACHINE_THREAD_STATE_SET_PC (&state->basic,
				   &_hurd_intr_rpc_msg_in_trap);
      state->basic.SYSRETURN = MACH_SEND_INTERRUPTED;
      *state_change = 1;
    }
  else if (state->basic.PC == (natural_t) &_hurd_intr_rpc_msg_in_trap &&
	   /* The thread was blocked in the system call.  After thread_abort,
	      the return value register indicates what state the RPC was in
	      when interrupted.  */
	   state->basic.SYSRETURN == MACH_RCV_INTERRUPTED)
      {
	/* The RPC request message was sent and the thread was waiting for
	   the reply message; now the message receive has been aborted, so
	   the mach_msg call will return MACH_RCV_INTERRUPTED.  We must tell
	   the server to interrupt the pending operation.  The thread must
	   wait for the reply message before running the signal handler (to
	   guarantee that the operation has finished being interrupted), so
	   our nonzero return tells the trampoline code to finish the message
	   receive operation before running the handler.  */

	mach_port_t *reply = interrupted_reply_port_location (state,
							      sigthread);
	error_t err = __interrupt_operation (intr_port, _hurdsig_interrupt_timeout);

	if (err)
	  {
	    if (reply)
	      {
		/* The interrupt didn't work.
		   Destroy the receive right the thread is blocked on.  */
		__mach_port_destroy (__mach_task_self (), *reply);
		*reply = MACH_PORT_NULL;
	      }

	    /* The system call return value register now contains
	       MACH_RCV_INTERRUPTED; when mach_msg resumes, it will retry the
	       call.  Since we have just destroyed the receive right, the
	       retry will fail with MACH_RCV_INVALID_NAME.  Instead, just
	       change the return value here to EINTR so mach_msg will not
	       retry and the EINTR error code will propagate up.  */
	    state->basic.SYSRETURN = EINTR;
	    *state_change = 1;
	  }
	else if (reply)
	  rcv_port = *reply;

	/* All threads whose RPCs were interrupted by the interrupt_operation
	   call above will retry their RPCs unless we clear SS->intr_port.
	   So we clear it for the thread taking a signal when SA_RESTART is
	   clear, so that its call returns EINTR.  */
	if (! signo || !(ss->actions[signo].sa_flags & SA_RESTART))
	  ss->intr_port = MACH_PORT_NULL;
      }

  return rcv_port;
}


/* Abort the RPCs being run by all threads but this one;
   all other threads should be suspended.  If LIVE is nonzero, those
   threads may run again, so they should be adjusted as necessary to be
   happy when resumed.  STATE is clobbered as a scratch area; its initial
   contents are ignored, and its contents on return are not useful.  */

static void
abort_all_rpcs (int signo, struct machine_thread_all_state *state, int live)
{
  /* We can just loop over the sigstates.  Any thread doing something
     interruptible must have one.  We needn't bother locking because all
     other threads are stopped.  */

  struct hurd_sigstate *ss;
  size_t nthreads;
  mach_port_t *reply_ports;

  /* First loop over the sigstates to count them.
     We need to know how big a vector we will need for REPLY_PORTS.  */
  nthreads = 0;
  for (ss = _hurd_sigstates; ss != NULL; ss = ss->next)
    ++nthreads;

  reply_ports = alloca (nthreads * sizeof *reply_ports);

  nthreads = 0;
  for (ss = _hurd_sigstates; ss != NULL; ss = ss->next, ++nthreads)
    if (ss->thread == _hurd_msgport_thread)
      reply_ports[nthreads] = MACH_PORT_NULL;
    else
      {
	int state_changed;
	state->set = 0;		/* Reset scratch area.  */

	/* Abort any operation in progress with interrupt_operation.
	   Record the reply port the thread is waiting on.
	   We will wait for all the replies below.  */
	reply_ports[nthreads] = _hurdsig_abort_rpcs (ss, signo, 1,
						     state, &state_changed,
						     NULL);
	if (live)
	  {
	    if (reply_ports[nthreads] != MACH_PORT_NULL)
	      {
		/* We will wait for the reply to this RPC below, so the
		   thread must issue a new RPC rather than waiting for the
		   reply to the one it sent.  */
		state->basic.SYSRETURN = EINTR;
		state_changed = 1;
	      }
	    if (state_changed)
	      /* Aborting the RPC needed to change this thread's state,
		 and it might ever run again.  So write back its state.  */
	      __thread_set_state (ss->thread, MACHINE_THREAD_STATE_FLAVOR,
				  (natural_t *) &state->basic,
				  MACHINE_THREAD_STATE_COUNT);
	  }
      }

  /* Wait for replies from all the successfully interrupted RPCs.  */
  while (nthreads-- > 0)
    if (reply_ports[nthreads] != MACH_PORT_NULL)
      {
	error_t err;
	mach_msg_header_t head;
	err = __mach_msg (&head, MACH_RCV_MSG|MACH_RCV_TIMEOUT, 0, sizeof head,
			  reply_ports[nthreads],
			  _hurd_interrupted_rpc_timeout, MACH_PORT_NULL);
	switch (err)
	  {
	  case MACH_RCV_TIMED_OUT:
	  case MACH_RCV_TOO_LARGE:
	    break;

	  default:
	    assert_perror (err);
	  }
      }
}

struct hurd_signal_preempter *_hurdsig_preempters;
sigset_t _hurdsig_preempted_set;

/* Mask of stop signals.  */
#define STOPSIGS (sigmask (SIGTTIN) | sigmask (SIGTTOU) | \
		  sigmask (SIGSTOP) | sigmask (SIGTSTP))

/* Deliver a signal.  SS is not locked.  */
void
_hurd_internal_post_signal (struct hurd_sigstate *ss,
			    int signo, struct hurd_signal_detail *detail,
			    mach_port_t reply_port,
			    mach_msg_type_name_t reply_port_type,
			    int untraced)
{
  error_t err;
  struct machine_thread_all_state thread_state;
  enum { stop, ignore, core, term, handle } act;
  struct hurd_signal_preempter *pe;
  sighandler_t handler;
  sigset_t pending;
  int ss_suspended;

  /* Reply to this sig_post message.  */
  __typeof (__msg_sig_post_reply) *reply_rpc
    = (untraced ? __msg_sig_post_untraced_reply : __msg_sig_post_reply);
  void reply (void)
    {
      error_t err;
      if (reply_port == MACH_PORT_NULL)
	return;
      err = (*reply_rpc) (reply_port, reply_port_type, 0);
      reply_port = MACH_PORT_NULL;
      if (err != MACH_SEND_INVALID_DEST) /* Ignore dead reply port.  */
	assert_perror (err);
    }

  /* Mark the signal as pending.  */
  void mark_pending (void)
    {
      __sigaddset (&ss->pending, signo);
      /* Save the details to be given to the handler when SIGNO is
	 unblocked.  */
      ss->pending_data[signo] = *detail;
    }

  /* Suspend the process with SIGNO.  */
  void suspend (void)
    {
      /* Stop all other threads and mark ourselves stopped.  */
      __USEPORT (PROC,
		 ({
		   /* Hold the siglock while stopping other threads to be
		      sure it is not held by another thread afterwards.  */
		   __mutex_lock (&_hurd_siglock);
		   __proc_dostop (port, _hurd_msgport_thread);
		   __mutex_unlock (&_hurd_siglock);
		   abort_all_rpcs (signo, &thread_state, 1);
		   reply ();
		   __proc_mark_stop (port, signo, detail->code);
		 }));
      _hurd_stopped = 1;
    }
  /* Resume the process after a suspension.  */
  void resume (void)
    {
      /* Resume the process from being stopped.  */
      thread_t *threads;
      mach_msg_type_number_t nthreads, i;
      error_t err;

      if (! _hurd_stopped)
	return;

      /* Tell the proc server we are continuing.  */
      __USEPORT (PROC, __proc_mark_cont (port));
      /* Fetch ports to all our threads and resume them.  */
      err = __task_threads (__mach_task_self (), &threads, &nthreads);
      assert_perror (err);
      for (i = 0; i < nthreads; ++i)
	{
	  if (threads[i] != _hurd_msgport_thread &&
	      (act != handle || threads[i] != ss->thread))
	    {
	      err = __thread_resume (threads[i]);
	      assert_perror (err);
	    }
	  err = __mach_port_deallocate (__mach_task_self (),
					threads[i]);
	  assert_perror (err);
	}
      __vm_deallocate (__mach_task_self (),
		       (vm_address_t) threads,
		       nthreads * sizeof *threads);
      _hurd_stopped = 0;
      /* The thread that will run the handler is already suspended.  */
      ss_suspended = 1;
    }

  if (signo == 0)
    {
      if (untraced)
	/* This is PTRACE_CONTINUE.  */
	resume ();

      /* This call is just to check for pending signals.  */
      __spin_lock (&ss->lock);
      goto check_pending_signals;
    }

 post_signal:

  thread_state.set = 0;		/* We know nothing.  */

  __spin_lock (&ss->lock);

  /* Check for a preempted signal.  Preempted signals can arrive during
     critical sections.  */

  handler = SIG_ERR;
  for (pe = ss->preempters; pe && handler == SIG_ERR; pe = pe->next)
    if (HURD_PREEMPT_SIGNAL_P (pe, signo, detail->code))
      handler = (*pe->preempter) (pe, ss, &signo, detail);

  if (handler == SIG_ERR && (__sigmask (signo) & _hurdsig_preempted_set))
    {
      __mutex_lock (&_hurd_siglock);
      for (pe = _hurdsig_preempters; pe && handler == SIG_ERR; pe = pe->next)
	if (HURD_PREEMPT_SIGNAL_P (pe, signo, detail->code))
	  handler = (*pe->preempter) (pe, ss, &signo, detail);
      __mutex_unlock (&_hurd_siglock);
    }

  ss_suspended = 0;

  if (handler == SIG_IGN)
    /* Ignore the signal altogether.  */
    act = ignore;
  if (handler != SIG_ERR)
    /* Run the preemption-provided handler.  */
    act = handle;
  else
    {
      /* No preemption.  Do normal handling.  */

      if (!untraced && __sigismember (&_hurdsig_traced, signo))
	{
	  /* We are being traced.  Stop to tell the debugger of the signal.  */
	  if (_hurd_stopped)
	    /* Already stopped.  Mark the signal as pending;
	       when resumed, we will notice it and stop again.  */
	    mark_pending ();
	  else
	    suspend ();
	  __spin_unlock (&ss->lock);
	  reply ();
	  return;
	}

      handler = ss->actions[signo].sa_handler;

      if (handler == SIG_DFL)
	/* Figure out the default action for this signal.  */
	switch (signo)
	  {
	  case 0:
	    /* A sig_post msg with SIGNO==0 is sent to
	       tell us to check for pending signals.  */
	    act = ignore;
	    break;

	  case SIGTTIN:
	  case SIGTTOU:
	  case SIGSTOP:
	  case SIGTSTP:
	    act = stop;
	    break;

	  case SIGCONT:
	  case SIGIO:
	  case SIGURG:
	  case SIGCHLD:
	  case SIGWINCH:
	    act = ignore;
	    break;

	  case SIGQUIT:
	  case SIGILL:
	  case SIGTRAP:
	  case SIGIOT:
	  case SIGEMT:
	  case SIGFPE:
	  case SIGBUS:
	  case SIGSEGV:
	  case SIGSYS:
	    act = core;
	    break;

	  case SIGINFO:
	    if (_hurd_pgrp == _hurd_pid)
	      {
		/* We are the process group leader.  Since there is no
		   user-specified handler for SIGINFO, we use a default one
		   which prints something interesting.  We use the normal
		   handler mechanism instead of just doing it here to avoid
		   the signal thread faulting or blocking in this
		   potentially hairy operation.  */
		act = handle;
		handler = _hurd_siginfo_handler;
	      }
	    else
	      act = ignore;
	    break;

	  default:
	    act = term;
	    break;
	  }
      else if (handler == SIG_IGN)
	act = ignore;
      else
	act = handle;

      if (__sigmask (signo) & STOPSIGS)
	/* Stop signals clear a pending SIGCONT even if they
	   are handled or ignored (but not if preempted).  */
	ss->pending &= ~sigmask (SIGCONT);
      else
	{
	  if (signo == SIGCONT)
	    /* Even if handled or ignored (but not preempted), SIGCONT clears
	       stop signals and resumes the process.  */
	    ss->pending &= ~STOPSIGS;

	  if (_hurd_stopped && act != stop && (untraced || signo == SIGCONT))
	    resume ();
	}
    }

  if (_hurd_orphaned && act == stop &&
      (__sigmask (signo) & (__sigmask (SIGTTIN) | __sigmask (SIGTTOU) |
			    __sigmask (SIGTSTP))))
    {
      /* If we would ordinarily stop for a job control signal, but we are
	 orphaned so noone would ever notice and continue us again, we just
	 quietly die, alone and in the dark.  */
      detail->code = signo;
      signo = SIGKILL;
      act = term;
    }

  /* Handle receipt of a blocked signal, or any signal while stopped.  */
  if (__sigismember (&ss->blocked, signo) ||
      (signo != SIGKILL && _hurd_stopped))
    {
      mark_pending ();
      /* If there was a call to resume above in SIGCONT processing
	 and we've left a thread suspended, now's the time to
	 set it going. */
      if (ss_suspended)
	{
	  err = __thread_resume (ss->thread);
	  assert_perror (err);
	  ss_suspended = 0;
	}
      act = ignore;
    }

  /* Perform the chosen action for the signal.  */
  switch (act)
    {
    case stop:
      if (_hurd_stopped)
	{
	  /* We are already stopped, but receiving an untraced stop
	     signal.  Instead of resuming and suspending again, just
	     notify the proc server of the new stop signal.  */
	  error_t err = __USEPORT (PROC, __proc_mark_stop
				   (port, signo, detail->code));
	  assert_perror (err);
	}
      else
	/* Suspend the process.  */
	suspend ();
      break;

    case ignore:
      /* Nobody cares about this signal.  */
      break;

    sigbomb:
      /* We got a fault setting up the stack frame for the handler.
	 Nothing to do but die; BSD gets SIGILL in this case.  */
      detail->code = signo;	/* XXX ? */
      signo = SIGILL;
      act = core;
      /* FALLTHROUGH */

    case term:			/* Time to die.  */
    case core:			/* And leave a rotting corpse.  */
      /* Have the proc server stop all other threads in our task.  */
      err = __USEPORT (PROC, __proc_dostop (port, _hurd_msgport_thread));
      assert_perror (err);
      /* No more user instructions will be executed.
	 The signal can now be considered delivered.  */
      reply ();
      /* Abort all server operations now in progress.  */
      abort_all_rpcs (signo, &thread_state, 0);

      {
	int status = W_EXITCODE (0, signo);
	/* Do a core dump if desired.  Only set the wait status bit saying we
	   in fact dumped core if the operation was actually successful.  */
	if (act == core && write_corefile (signo, detail))
	  status |= WCOREFLAG;
	/* Tell proc how we died and then stick the saber in the gut.  */
	_hurd_exit (status);
	/* NOTREACHED */
      }

    case handle:
      /* Call a handler for this signal.  */
      {
	struct sigcontext *scp, ocontext;
	int wait_for_reply, state_changed;

	/* Stop the thread and abort its pending RPC operations.  */
	if (! ss_suspended)
	  {
	    err = __thread_suspend (ss->thread);
	    assert_perror (err);
	  }

	/* Abort the thread's kernel context, so any pending message send
	   or receive completes immediately or aborts.  If an interruptible
	   RPC is in progress, abort_rpcs will do this.  But we must always
	   do it before fetching the thread's state, because
	   thread_get_state is never kosher before thread_abort.  */
	abort_thread (ss, &thread_state, NULL);

	if (ss->context)
	  {
	    /* We have a previous sigcontext that sigreturn was about
	       to restore when another signal arrived.  */

	    mach_port_t *loc;

	    if (_hurdsig_catch_memory_fault (ss->context))
	      {
		/* We faulted reading the thread's stack.  Forget that
		   context and pretend it wasn't there.  It almost
		   certainly crash if this handler returns, but that's it's
		   problem.  */
		ss->context = NULL;
	      }
	    else
	      {
		/* Copy the context from the thread's stack before
		   we start diddling the stack to set up the handler.  */
		ocontext = *ss->context;
		ss->context = &ocontext;
	      }
	    _hurdsig_end_catch_fault ();

	    if (! machine_get_basic_state (ss->thread, &thread_state))
	      goto sigbomb;
	    loc = interrupted_reply_port_location (&thread_state, 1);
	    if (loc && *loc != MACH_PORT_NULL)
	      /* This is the reply port for the context which called
		 sigreturn.  Since we are abandoning that context entirely
		 and restoring SS->context instead, destroy this port.  */
	      __mach_port_destroy (__mach_task_self (), *loc);

	    /* The thread was in sigreturn, not in any interruptible RPC.  */
	    wait_for_reply = 0;

	    assert (! __spin_lock_locked (&ss->critical_section_lock));
	  }
	else
	  {
	    wait_for_reply
	      = (_hurdsig_abort_rpcs (ss, signo, 1,
				      &thread_state, &state_changed,
				      &reply)
		 != MACH_PORT_NULL);

	    if (__spin_lock_locked (&ss->critical_section_lock))
	      {
		/* The thread is in a critical section.  Mark the signal as
		   pending.  When it finishes the critical section, it will
		   check for pending signals.  */
		mark_pending ();
		assert (! state_changed);
		__thread_resume (ss->thread);
		break;
	      }
	  }

	/* Call the machine-dependent function to set the thread up
	   to run the signal handler, and preserve its old context.  */
	scp = _hurd_setup_sighandler (ss, handler, signo, detail,
				      wait_for_reply, &thread_state);
	if (scp == NULL)
	  goto sigbomb;

	/* Set the machine-independent parts of the signal context.  */

	{
	  /* Fetch the thread variable for the MiG reply port,
	     and set it to MACH_PORT_NULL.  */
	  mach_port_t *loc = interrupted_reply_port_location (&thread_state,
							      1);
	  if (loc)
	    {
	      scp->sc_reply_port = *loc;
	      *loc = MACH_PORT_NULL;
	    }
	  else
	    scp->sc_reply_port = MACH_PORT_NULL;

	  /* Save the intr_port in use by the interrupted code,
	     and clear the cell before running the trampoline.  */
	  scp->sc_intr_port = ss->intr_port;
	  ss->intr_port = MACH_PORT_NULL;

	  if (ss->context)
	    {
	      /* After the handler runs we will restore to the state in
		 SS->context, not the state of the thread now.  So restore
		 that context's reply port and intr port.  */

	      scp->sc_reply_port = ss->context->sc_reply_port;
	      scp->sc_intr_port = ss->context->sc_intr_port;

	      ss->context = NULL;
	    }
	}

	/* Backdoor extra argument to signal handler.  */
	scp->sc_error = detail->error;

	/* Block SIGNO and requested signals while running the handler.  */
	scp->sc_mask = ss->blocked;
	ss->blocked |= __sigmask (signo) | ss->actions[signo].sa_mask;

	/* Start the thread running the handler (or possibly waiting for an
	   RPC reply before running the handler).  */
	err = __thread_set_state (ss->thread, MACHINE_THREAD_STATE_FLAVOR,
				  (natural_t *) &thread_state.basic,
				  MACHINE_THREAD_STATE_COUNT);
	assert_perror (err);
	err = __thread_resume (ss->thread);
	assert_perror (err);
	thread_state.set = 0;	/* Everything we know is now wrong.  */
	break;
      }
    }

  /* The signal has either been ignored or is now being handled.  We can
     consider it delivered and reply to the killer.  */
  reply ();

  /* We get here unless the signal was fatal.  We still hold SS->lock.
     Check for pending signals, and loop to post them.  */
  {
    /* Return nonzero if SS has any signals pending we should worry about.
       We don't worry about any pending signals if we are stopped, nor if
       SS is in a critical section.  We are guaranteed to get a sig_post
       message before any of them become deliverable: either the SIGCONT
       signal, or a sig_post with SIGNO==0 as an explicit poll when the
       thread finishes its critical section.  */
    inline int signals_pending (void)
      {
	if (_hurd_stopped || __spin_lock_locked (&ss->critical_section_lock))
	  return 0;
	return pending = ss->pending & ~ss->blocked;
      }

  check_pending_signals:
    untraced = 0;

    if (signals_pending ())
      {
      pending:
	for (signo = 1; signo < NSIG; ++signo)
	  if (__sigismember (&pending, signo))
	    {
	      __sigdelset (&ss->pending, signo);
	      *detail = ss->pending_data[signo];
	      __spin_unlock (&ss->lock);
	      goto post_signal;
	    }
      }

    /* No pending signals left undelivered for this thread.
       If we were sent signal 0, we need to check for pending
       signals for all threads.  */
    if (signo == 0)
      {
	__spin_unlock (&ss->lock);
	__mutex_lock (&_hurd_siglock);
	for (ss = _hurd_sigstates; ss != NULL; ss = ss->next)
	  {
	    __spin_lock (&ss->lock);
	    if (signals_pending ())
	      goto pending;
	    __spin_unlock (&ss->lock);
	  }
	__mutex_unlock (&_hurd_siglock);
      }
    else
      {
	/* No more signals pending; SS->lock is still locked.
	   Wake up any sigsuspend call that is blocking SS->thread.  */
	if (ss->suspended != MACH_PORT_NULL)
	  {
	    /* There is a sigsuspend waiting.  Tell it to wake up.  */
	    error_t err;
	    mach_msg_header_t msg;
	    err = __mach_port_insert_right (__mach_task_self (),
					    ss->suspended, ss->suspended,
					    MACH_MSG_TYPE_MAKE_SEND);
	    assert_perror (err);
	    msg.msgh_bits = MACH_MSGH_BITS (MACH_MSG_TYPE_MOVE_SEND, 0);
	    msg.msgh_remote_port = ss->suspended;
	    msg.msgh_local_port = MACH_PORT_NULL;
	    /* These values do not matter.  */
	    msg.msgh_id = 8675309; /* Jenny, Jenny.  */
	    msg.msgh_seqno = 17; /* Random.  */
	    ss->suspended = MACH_PORT_NULL;
	    err = __mach_msg (&msg, MACH_SEND_MSG, sizeof msg, 0,
			      MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE,
			      MACH_PORT_NULL);
	    assert_perror (err);
	  }
	__spin_unlock (&ss->lock);
      }
  }

  /* All pending signals delivered to all threads.
     Now we can send the reply message even for signal 0.  */
  reply ();
}

/* Decide whether REFPORT enables the sender to send us a SIGNO signal.
   Returns zero if so, otherwise the error code to return to the sender.  */

static error_t
signal_allowed (int signo, mach_port_t refport)
{
  if (signo < 0 || signo >= NSIG)
    return EINVAL;

  if (refport == __mach_task_self ())
    /* Can send any signal.  */
    goto win;

  /* Avoid needing to check for this below.  */
  if (refport == MACH_PORT_NULL)
    return EPERM;

  switch (signo)
    {
    case SIGINT:
    case SIGQUIT:
    case SIGTSTP:
    case SIGHUP:
    case SIGINFO:
    case SIGTTIN:
    case SIGTTOU:
      /* Job control signals can be sent by the controlling terminal.  */
      if (__USEPORT (CTTYID, port == refport))
	goto win;
      break;

    case SIGCONT:
      {
	/* A continue signal can be sent by anyone in the session.  */
	mach_port_t sessport;
	if (! __USEPORT (PROC, __proc_getsidport (port, &sessport)))
	  {
	    __mach_port_deallocate (__mach_task_self (), sessport);
	    if (refport == sessport)
	      goto win;
	  }
      }
      break;

    case SIGIO:
    case SIGURG:
      {
	/* Any io object a file descriptor refers to might send us
	   one of these signals using its async ID port for REFPORT.

	   This is pretty wide open; it is not unlikely that some random
	   process can at least open for reading something we have open,
	   get its async ID port, and send us a spurious SIGIO or SIGURG
	   signal.  But BSD is actually wider open than that!--you can set
	   the owner of an io object to any process or process group
	   whatsoever and send them gratuitous signals.

	   Someday we could implement some reasonable scheme for
	   authorizing SIGIO and SIGURG signals properly.  */

	int d;
	int lucky = 0;		/* True if we find a match for REFPORT.  */
	__mutex_lock (&_hurd_dtable_lock);
	for (d = 0; !lucky && (unsigned) d < (unsigned) _hurd_dtablesize; ++d)
	  {
	    struct hurd_userlink ulink;
	    io_t port;
	    mach_port_t asyncid;
	    if (_hurd_dtable[d] == NULL)
	      continue;
	    port = _hurd_port_get (&_hurd_dtable[d]->port, &ulink);
	    if (! __io_get_icky_async_id (port, &asyncid))
	      {
		if (refport == asyncid)
		  /* Break out of the loop on the next iteration.  */
		  lucky = 1;
		__mach_port_deallocate (__mach_task_self (), asyncid);
	      }
	    _hurd_port_free (&_hurd_dtable[d]->port, &ulink, port);
	  }
	/* If we found a lucky winner, we've set D to -1 in the loop.  */
	if (lucky)
	  goto win;
      }
    }

  /* If this signal is legit, we have done `goto win' by now.
     When we return the error, mig deallocates REFPORT.  */
  return EPERM;

 win:
  /* Deallocate the REFPORT send right; we are done with it.  */
  __mach_port_deallocate (__mach_task_self (), refport);

  return 0;
}

/* Implement the sig_post RPC from <hurd/msg.defs>;
   sent when someone wants us to get a signal.  */
kern_return_t
_S_msg_sig_post (mach_port_t me,
		 mach_port_t reply_port, mach_msg_type_name_t reply_port_type,
		 int signo, natural_t sigcode,
		 mach_port_t refport)
{
  error_t err;
  struct hurd_signal_detail d;

  if (err = signal_allowed (signo, refport))
    return err;

  d.code = sigcode;
  d.exc = 0;

  /* Post the signal to the designated signal-receiving thread.  This will
     reply when the signal can be considered delivered.  */
  _hurd_internal_post_signal (_hurd_thread_sigstate (_hurd_sigthread),
			      signo, &d, reply_port, reply_port_type,
			      0); /* Stop if traced.  */

  return MIG_NO_REPLY;		/* Already replied.  */
}

/* Implement the sig_post_untraced RPC from <hurd/msg.defs>;
   sent when the debugger wants us to really get a signal
   even if we are traced.  */
kern_return_t
_S_msg_sig_post_untraced (mach_port_t me,
			  mach_port_t reply_port,
			  mach_msg_type_name_t reply_port_type,
			  int signo, natural_t sigcode,
			  mach_port_t refport)
{
  error_t err;
  struct hurd_signal_detail d;

  if (err = signal_allowed (signo, refport))
    return err;

  d.code = sigcode;
  d.exc = 0;

  /* Post the signal to the designated signal-receiving thread.  This will
     reply when the signal can be considered delivered.  */
  _hurd_internal_post_signal (_hurd_thread_sigstate (_hurd_sigthread),
			      signo, &d, reply_port, reply_port_type,
			      1); /* Untraced flag. */

  return MIG_NO_REPLY;		/* Already replied.  */
}

extern void __mig_init (void *);

#include <mach/task_special_ports.h>

/* Initialize the message port and _hurd_sigthread and start the signal
   thread.  */

void
_hurdsig_init (void)
{
  error_t err;
  vm_size_t stacksize;

  __mutex_init (&_hurd_siglock);

  err = __mach_port_allocate (__mach_task_self (),
			      MACH_PORT_RIGHT_RECEIVE,
			      &_hurd_msgport);
  assert_perror (err);

  /* Make a send right to the signal port.  */
  err = __mach_port_insert_right (__mach_task_self (),
				  _hurd_msgport,
				  _hurd_msgport,
				  MACH_MSG_TYPE_MAKE_SEND);
  assert_perror (err);

  /* Set the default thread to receive task-global signals
     to this one, the main (first) user thread.  */
  _hurd_sigthread = __mach_thread_self ();

  /* Start the signal thread listening on the message port.  */

  err = __thread_create (__mach_task_self (), &_hurd_msgport_thread);
  assert_perror (err);

  stacksize = __vm_page_size * 4; /* Small stack for signal thread.  */
  err = __mach_setup_thread (__mach_task_self (), _hurd_msgport_thread,
			     _hurd_msgport_receive,
			     (vm_address_t *) &__hurd_sigthread_stack_base,
			     &stacksize);
  assert_perror (err);

  __hurd_sigthread_stack_end = __hurd_sigthread_stack_base + stacksize;
  __hurd_sigthread_variables =
    malloc (__hurd_threadvar_max * sizeof (unsigned long int));
  if (__hurd_sigthread_variables == NULL)
    __libc_fatal ("hurd: Can't allocate thread variables for signal thread\n");

  /* Reinitialize the MiG support routines so they will use a per-thread
     variable for the cached reply port.  */
  __mig_init ((void *) __hurd_sigthread_stack_base);

  err = __thread_resume (_hurd_msgport_thread);
  assert_perror (err);

  /* Receive exceptions on the signal port.  */
  __task_set_special_port (__mach_task_self (),
			   TASK_EXCEPTION_PORT, _hurd_msgport);
}
				/* XXXX */
/* Reauthenticate with the proc server.  */

static void
reauth_proc (mach_port_t new)
{
  mach_port_t ref, ignore;

  ref = __mach_reply_port ();
  if (! HURD_PORT_USE (&_hurd_ports[INIT_PORT_PROC],
		       __proc_reauthenticate (port, ref,
					      MACH_MSG_TYPE_MAKE_SEND) ||
		       __auth_user_authenticate (new, ref,
						 MACH_MSG_TYPE_MAKE_SEND,
						 &ignore))
      && ignore != MACH_PORT_NULL)
    __mach_port_deallocate (__mach_task_self (), ignore);
  __mach_port_destroy (__mach_task_self (), ref);

  (void) &reauth_proc;		/* Silence compiler warning.  */
}
text_set_element (_hurd_reauth_hook, reauth_proc);

/* Like `getenv', but safe for the signal thread to run.
   If the environment is trashed, this will just return NULL.  */

const char *
_hurdsig_getenv (const char *variable)
{
  if (_hurdsig_catch_memory_fault (__environ))
    /* We bombed in getenv.  */
    return NULL;
  else
    {
      const size_t len = strlen (variable);
      char *value = NULL;
      char *volatile *ep = __environ;
      while (*ep)
	{
	  const char *p = *ep;
	  _hurdsig_fault_preempter.first = (long int) p;
	  _hurdsig_fault_preempter.last = VM_MAX_ADDRESS;
	  if (! strncmp (p, variable, len) && p[len] == '=')
	    {
	      char *value;
	      size_t valuelen;
	      p += len + 1;
	      valuelen = strlen (p);
	      _hurdsig_fault_preempter.last = (long int) (p + valuelen);
	      value = malloc (++valuelen);
	      if (value)
		memcpy (value, p, valuelen);
	      break;
	    }
	  _hurdsig_fault_preempter.first = (long int) ++ep;
	  _hurdsig_fault_preempter.last = (long int) (ep + 1);
	}
      _hurdsig_end_catch_fault ();
      return value;
    }
}