hurd/hurdfault.c

   1 /* Handle faults in the signal thread.
   2 Copyright (C) 1994, 1995, 1996 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <hurd.h>
  21 #include <hurd/signal.h>
  22 #include "hurdfault.h"
  23 #include <errno.h>
  24 #include <string.h>
  25 #include <setjmp.h>
  26 #include <stdio.h>
  27 #include "thread_state.h"
  28 #include "faultexc.h"           /* mig-generated header for our exc server.  */
  29 #include <assert.h>
  30
  31 jmp_buf _hurdsig_fault_env;
  32 struct hurd_signal_preempter _hurdsig_fault_preempter;
  33
  34 static mach_port_t forward_sigexc;
  35
  36 kern_return_t
  37 _hurdsig_fault_catch_exception_raise (mach_port_t port,
  38                                       thread_t thread,
  39                                       task_t task,
  40                                       int exception,
  41                                       int code,
  42                                       int subcode)
  43 {
  44   int signo;
  45   long int sigcode;
  46   int sigerror;
  47
  48   if (port != forward_sigexc ||
  49       thread != _hurd_msgport_thread || task != __mach_task_self ())
  50     return EPERM;               /* Strange bogosity.  */
  51
  52   /* Call the machine-dependent function to translate the Mach exception
  53      codes into a signal number and subcode.  */
  54   _hurd_exception2signal (exception, code, subcode,
  55                           &signo, &sigcode, &sigerror);
  56
  57   return HURD_PREEMPT_SIGNAL_P (&_hurdsig_fault_preempter, signo, sigcode)
  58     ? 0 : EGREGIOUS;
  59 }
  60
  61 static void
  62 faulted (void)
  63 {
  64   struct
  65     {
  66       mach_msg_header_t head;
  67       char buf[64];
  68     } request;
  69   struct
  70     {
  71       mach_msg_header_t head;
  72       mach_msg_type_t type;
  73       int result;
  74     } reply;
  75   extern int _hurdsig_fault_exc_server (mach_msg_header_t *,
  76                                         mach_msg_header_t *);
  77
  78  /* Wait for the exception_raise message forwarded by the proc server.  */
  79
  80  if (__mach_msg (&request.head, MACH_RCV_MSG, 0,
  81                   sizeof request, forward_sigexc,
  82                   MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL)
  83       != MACH_MSG_SUCCESS)
  84     __libc_fatal ("msg receive failed on signal thread exc\n");
  85
  86   /* Run the exc demuxer which should call the server function above.
  87      That function returns 0 if the exception was expected.  */
  88   _hurdsig_fault_exc_server (&request.head, &reply.head);
  89   if (reply.head.msgh_remote_port != MACH_PORT_NULL)
  90     __mach_msg (&reply.head, MACH_SEND_MSG, reply.head.msgh_size,
  91                 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
  92   if (reply.result == MIG_BAD_ID)
  93     __mach_msg_destroy (&request.head);
  94
  95   if (reply.result)
  96     __libc_fatal ("BUG: unexpected fault in signal thread\n");
  97
  98   _hurdsig_fault_preempter.signals = 0;
  99   longjmp (_hurdsig_fault_env, 1);
 100 }
 101
 102 static char faultstack[1024];
 103
 104 /* Send exceptions for the signal thread to the proc server.
 105    It will forward the message on to our message port,
 106    and then restore the thread's state to code which
 107    does `longjmp (_hurd_sigthread_fault_env, 1)'.  */
 108
 109 void
 110 _hurdsig_fault_init (void)
 111 {
 112   error_t err;
 113   struct machine_thread_state state;
 114   mach_port_t sigexc;
 115
 116   /* Allocate a port to receive signal thread exceptions.
 117      We will move this receive right to the proc server.  */
 118   err = __mach_port_allocate (__mach_task_self (),
 119                               MACH_PORT_RIGHT_RECEIVE, &sigexc);
 120   assert_perror (err);
 121   err = __mach_port_allocate (__mach_task_self (),
 122                               MACH_PORT_RIGHT_RECEIVE, &forward_sigexc);
 123   assert_perror (err);
 124
 125   /* Allocate a port to receive the exception msgs forwarded
 126      from the proc server.  */
 127   err = __mach_port_insert_right (__mach_task_self (), sigexc,
 128                                   sigexc, MACH_MSG_TYPE_MAKE_SEND);
 129   assert_perror (err);
 130
 131   /* Set the queue limit for this port to just one.  The proc server will
 132      notice if we ever get a second exception while one remains queued and
 133      unreceived, and decide we are hopelessly buggy.  */
 134   err = __mach_port_set_qlimit (__mach_task_self (), forward_sigexc, 1);
 135   assert_perror (err);
 136
 137   /* This state will be restored when we fault.
 138      It runs the function above.  */
 139   memset (&state, 0, sizeof state);
 140   MACHINE_THREAD_STATE_SET_PC (&state, faulted);
 141   MACHINE_THREAD_STATE_SET_SP (&state, faultstack, sizeof faultstack);
 142
 143   err = __USEPORT
 144     (PROC,
 145      __proc_handle_exceptions (port,
 146                                sigexc,
 147                                forward_sigexc, MACH_MSG_TYPE_MAKE_SEND,
 148                                MACHINE_THREAD_STATE_FLAVOR,
 149                                (natural_t *) &state,
 150                                MACHINE_THREAD_STATE_COUNT));
 151   assert_perror (err);
 152
 153   /* Direct signal thread exceptions to the proc server.  */
 154   err = __thread_set_special_port (_hurd_msgport_thread,
 155                                    THREAD_EXCEPTION_PORT, sigexc);
 156   __mach_port_deallocate (__mach_task_self (), sigexc);
 157   assert_perror (err);
 158 }
 159