hurd/hurdfault.c

   1 /* Handle faults in the signal thread.
   2    Copyright (C) 1994-2023 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <hurd.h>
  20 #include <hurd/signal.h>
  21 #include "hurdfault.h"
  22 #include <errno.h>
  23 #include <string.h>
  24 #include <setjmp.h>
  25 #include <stdio.h>
  26 #include <thread_state.h>
  27 #include "faultexc_server.h"    /* mig-generated header for our exc server.  */
  28 #include <assert.h>
  29
  30 jmp_buf _hurdsig_fault_env;
  31 struct hurd_signal_preemptor _hurdsig_fault_preemptor = {0};
  32
  33 /* XXX temporary to deal with spelling fix */
  34 weak_alias (_hurdsig_fault_preemptor, _hurdsig_fault_preempter)
  35
  36 static mach_port_t forward_sigexc;
  37
  38 kern_return_t
  39 _hurdsig_fault_catch_exception_raise (mach_port_t port,
  40                                       thread_t thread,
  41                                       task_t task,
  42 #ifdef EXC_MASK_ALL             /* New interface flavor.  */
  43                                       exception_type_t exception,
  44                                       exception_data_t code,
  45                                       mach_msg_type_number_t codeCnt
  46 #else                           /* Vanilla Mach 3.0 interface.  */
  47                                       integer_t exception,
  48                                       integer_t code, long_integer_t subcode
  49 #endif
  50                                       )
  51 {
  52   int signo;
  53   struct hurd_signal_detail d;
  54
  55   if (port != forward_sigexc
  56       || thread != _hurd_msgport_thread || task != __mach_task_self ())
  57     return EPERM;               /* Strange bogosity.  */
  58
  59   d.exc = exception;
  60 #ifdef EXC_MASK_ALL
  61   assert (codeCnt >= 2);
  62   d.exc_code = code[0];
  63   d.exc_subcode = code[1];
  64 #else
  65   d.exc_code = code;
  66   d.exc_subcode = subcode;
  67 #endif
  68
  69   /* Call the machine-dependent function to translate the Mach exception
  70      codes into a signal number and subcode.  */
  71   _hurd_exception2signal (&d, &signo);
  72
  73   return HURD_PREEMPT_SIGNAL_P (&_hurdsig_fault_preemptor, signo, d.exc_subcode)
  74     ? 0 : EGREGIOUS;
  75 }
  76
  77 #ifdef EXC_MASK_ALL
  78 /* XXX New interface flavor has additional RPCs that we could be using
  79    instead.  These RPCs roll a thread_get_state/thread_set_state into
  80    the message, so the signal thread ought to use these to save some calls.
  81  */
  82 kern_return_t
  83 _hurdsig_fault_catch_exception_raise_state
  84 (mach_port_t port,
  85  exception_type_t exception,
  86  exception_data_t code,
  87  mach_msg_type_number_t codeCnt,
  88  int *flavor,
  89  thread_state_t old_state,
  90  mach_msg_type_number_t old_stateCnt,
  91  thread_state_t new_state,
  92  mach_msg_type_number_t *new_stateCnt)
  93 {
  94   abort ();
  95   return KERN_FAILURE;
  96 }
  97
  98 kern_return_t
  99 _hurdsig_fault_catch_exception_raise_state_identity
 100 (mach_port_t exception_port,
 101  thread_t thread,
 102  task_t task,
 103  exception_type_t exception,
 104  exception_data_t code,
 105  mach_msg_type_number_t codeCnt,
 106  int *flavor,
 107  thread_state_t old_state,
 108  mach_msg_type_number_t old_stateCnt,
 109  thread_state_t new_state,
 110  mach_msg_type_number_t *new_stateCnt)
 111 {
 112   abort ();
 113   return KERN_FAILURE;
 114 }
 115 #endif
 116
 117
 118 static void
 119 faulted (void)
 120 {
 121   struct
 122     {
 123       mach_msg_header_t head;
 124       char buf[64];
 125     } request;
 126   mig_reply_header_t reply;
 127   extern int _hurdsig_fault_exc_server (mach_msg_header_t *,
 128                                         mach_msg_header_t *);
 129
 130  /* Wait for the exception_raise message forwarded by the proc server.  */
 131
 132  if (__mach_msg (&request.head, MACH_RCV_MSG, 0,
 133                   sizeof request, forward_sigexc,
 134                   MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL)
 135       != MACH_MSG_SUCCESS)
 136     __libc_fatal ("msg receive failed on signal thread exc\n");
 137
 138   /* Run the exc demuxer which should call the server function above.
 139      That function returns 0 if the exception was expected.  */
 140   _hurdsig_fault_exc_server (&request.head, &reply.Head);
 141   if (reply.Head.msgh_remote_port != MACH_PORT_NULL)
 142     __mach_msg (&reply.Head, MACH_SEND_MSG, reply.Head.msgh_size,
 143                 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
 144   if (reply.RetCode == MIG_BAD_ID)
 145     __mach_msg_destroy (&request.head);
 146
 147   if (reply.RetCode)
 148     __libc_fatal ("BUG: unexpected fault in signal thread\n");
 149
 150   _hurdsig_fault_preemptor.signals = 0;
 151   longjmp (_hurdsig_fault_env, 1);
 152 }
 153
 154 static char faultstack[1024];
 155
 156 /* Send exceptions for the signal thread to the proc server.
 157    It will forward the message on to our message port,
 158    and then restore the thread's state to code which
 159    does `longjmp (_hurd_sigthread_fault_env, 1)'.  */
 160
 161 void
 162 _hurdsig_fault_init (void)
 163 {
 164   error_t err;
 165   struct machine_thread_state state;
 166   mach_port_t sigexc;
 167
 168   /* Allocate a port to receive signal thread exceptions.
 169      We will move this receive right to the proc server.  */
 170   err = __mach_port_allocate (__mach_task_self (),
 171                               MACH_PORT_RIGHT_RECEIVE, &sigexc);
 172   assert_perror (err);
 173   err = __mach_port_insert_right (__mach_task_self (), sigexc,
 174                                   sigexc, MACH_MSG_TYPE_MAKE_SEND);
 175   assert_perror (err);
 176
 177   /* Allocate a port to receive the exception msgs forwarded
 178      from the proc server.  */
 179   err = __mach_port_allocate (__mach_task_self (),
 180                               MACH_PORT_RIGHT_RECEIVE, &forward_sigexc);
 181   assert_perror (err);
 182
 183   /* Set the queue limit for this port to just one.  The proc server will
 184      notice if we ever get a second exception while one remains queued and
 185      unreceived, and decide we are hopelessly buggy.  */
 186 #ifdef MACH_PORT_RECEIVE_STATUS_COUNT
 187   {
 188     const mach_port_limits_t lim = { mpl_qlimit: 1 };
 189     assert (MACH_PORT_RECEIVE_STATUS_COUNT == sizeof lim / sizeof (natural_t));
 190     err = __mach_port_set_attributes (__mach_task_self (), forward_sigexc,
 191                                       MACH_PORT_RECEIVE_STATUS,
 192                                       (mach_port_info_t) &lim,
 193                                       MACH_PORT_RECEIVE_STATUS_COUNT);
 194   }
 195 #else
 196   err = __mach_port_set_qlimit (__mach_task_self (), forward_sigexc, 1);
 197 #endif
 198   assert_perror (err);
 199
 200   /* This state will be restored when we fault.
 201      It runs the function above.  */
 202   memset (&state, 0, sizeof state);
 203   MACHINE_THREAD_STATE_FIX_NEW (&state);
 204   MACHINE_THREAD_STATE_SETUP_CALL (&state, faultstack,
 205                                    sizeof faultstack, faulted);
 206
 207   err = __USEPORT
 208     (PROC,
 209      __proc_handle_exceptions (port,
 210                                sigexc,
 211                                forward_sigexc, MACH_MSG_TYPE_MAKE_SEND,
 212                                MACHINE_THREAD_STATE_FLAVOR,
 213                                (natural_t *) &state,
 214                                MACHINE_THREAD_STATE_COUNT));
 215   assert_perror (err);
 216
 217   /* Direct signal thread exceptions to the proc server.  */
 218 #ifdef THREAD_EXCEPTION_PORT
 219   err = __thread_set_special_port (_hurd_msgport_thread,
 220                                    THREAD_EXCEPTION_PORT, sigexc);
 221 #elif defined (EXC_MASK_ALL)
 222   __thread_set_exception_ports (_hurd_msgport_thread,
 223                                 EXC_MASK_ALL & ~(EXC_MASK_SYSCALL
 224                                                  | EXC_MASK_MACH_SYSCALL
 225                                                  | EXC_MASK_RPC_ALERT),
 226                                 sigexc,
 227                                 EXCEPTION_STATE_IDENTITY,
 228                                 MACHINE_THREAD_STATE);
 229 #else
 230 # error thread_set_exception_ports?
 231 #endif
 232   __mach_port_deallocate (__mach_task_self (), sigexc);
 233   assert_perror (err);
 234 }