1//===-- MachException.cpp ---------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9//  Created by Greg Clayton on 6/18/07.
10//
11//===----------------------------------------------------------------------===//
12
13#include "MachException.h"
14#include "DNB.h"
15#include "DNBError.h"
16#include "DNBLog.h"
17#include "MachProcess.h"
18#include "PThreadMutex.h"
19#include "SysSignal.h"
20#include <cerrno>
21#include <sys/ptrace.h>
22#include <sys/types.h>
23
24// Routine mach_exception_raise
25extern "C" kern_return_t
26catch_mach_exception_raise(mach_port_t exception_port, mach_port_t thread,
27                           mach_port_t task, exception_type_t exception,
28                           mach_exception_data_t code,
29                           mach_msg_type_number_t codeCnt);
30
31extern "C" kern_return_t catch_mach_exception_raise_state(
32    mach_port_t exception_port, exception_type_t exception,
33    const mach_exception_data_t code, mach_msg_type_number_t codeCnt,
34    int *flavor, const thread_state_t old_state,
35    mach_msg_type_number_t old_stateCnt, thread_state_t new_state,
36    mach_msg_type_number_t *new_stateCnt);
37
38// Routine mach_exception_raise_state_identity
39extern "C" kern_return_t catch_mach_exception_raise_state_identity(
40    mach_port_t exception_port, mach_port_t thread, mach_port_t task,
41    exception_type_t exception, mach_exception_data_t code,
42    mach_msg_type_number_t codeCnt, int *flavor, thread_state_t old_state,
43    mach_msg_type_number_t old_stateCnt, thread_state_t new_state,
44    mach_msg_type_number_t *new_stateCnt);
45
46extern "C" boolean_t mach_exc_server(mach_msg_header_t *InHeadP,
47                                     mach_msg_header_t *OutHeadP);
48
49// Note: g_message points to the storage allocated to catch the data from
50// catching the current exception raise. It's populated when we catch a raised
51// exception which can't immediately be replied to.
52//
53// If it becomes possible to catch exceptions from multiple threads
54// simultaneously, accesses to g_message would need to be mutually exclusive.
55static MachException::Data *g_message = NULL;
56
57extern "C" kern_return_t catch_mach_exception_raise_state(
58    mach_port_t exc_port, exception_type_t exc_type,
59    const mach_exception_data_t exc_data, mach_msg_type_number_t exc_data_count,
60    int *flavor, const thread_state_t old_state,
61    mach_msg_type_number_t old_stateCnt, thread_state_t new_state,
62    mach_msg_type_number_t *new_stateCnt) {
63  if (DNBLogCheckLogBit(LOG_EXCEPTIONS)) {
64    DNBLogThreaded("::%s ( exc_port = 0x%4.4x, exc_type = %d ( %s ), exc_data "
65                   "= 0x%llx, exc_data_count = %d)",
66                   __FUNCTION__, exc_port, exc_type,
67                   MachException::Name(exc_type), (uint64_t)exc_data,
68                   exc_data_count);
69  }
70  return KERN_FAILURE;
71}
72
73extern "C" kern_return_t catch_mach_exception_raise_state_identity(
74    mach_port_t exc_port, mach_port_t thread_port, mach_port_t task_port,
75    exception_type_t exc_type, mach_exception_data_t exc_data,
76    mach_msg_type_number_t exc_data_count, int *flavor,
77    thread_state_t old_state, mach_msg_type_number_t old_stateCnt,
78    thread_state_t new_state, mach_msg_type_number_t *new_stateCnt) {
79  if (DNBLogCheckLogBit(LOG_EXCEPTIONS)) {
80    DNBLogThreaded("::%s ( exc_port = 0x%4.4x, thd_port = 0x%4.4x, tsk_port = "
81                   "0x%4.4x, exc_type = %d ( %s ), exc_data[%d] = { 0x%llx, "
82                   "0x%llx })",
83                   __FUNCTION__, exc_port, thread_port, task_port, exc_type,
84                   MachException::Name(exc_type), exc_data_count,
85                   (uint64_t)(exc_data_count > 0 ? exc_data[0] : 0xBADDBADD),
86                   (uint64_t)(exc_data_count > 1 ? exc_data[1] : 0xBADDBADD));
87  }
88
89  return KERN_FAILURE;
90}
91
92extern "C" kern_return_t
93catch_mach_exception_raise(mach_port_t exc_port, mach_port_t thread_port,
94                           mach_port_t task_port, exception_type_t exc_type,
95                           mach_exception_data_t exc_data,
96                           mach_msg_type_number_t exc_data_count) {
97  if (DNBLogCheckLogBit(LOG_EXCEPTIONS)) {
98    DNBLogThreaded("::%s ( exc_port = 0x%4.4x, thd_port = 0x%4.4x, tsk_port = "
99                   "0x%4.4x, exc_type = %d ( %s ), exc_data[%d] = { 0x%llx, "
100                   "0x%llx })",
101                   __FUNCTION__, exc_port, thread_port, task_port, exc_type,
102                   MachException::Name(exc_type), exc_data_count,
103                   (uint64_t)(exc_data_count > 0 ? exc_data[0] : 0xBADDBADD),
104                   (uint64_t)(exc_data_count > 1 ? exc_data[1] : 0xBADDBADD));
105  }
106  g_message->exc_type = 0;
107  g_message->exc_data.clear();
108
109  if (task_port == g_message->task_port) {
110    g_message->task_port = task_port;
111    g_message->thread_port = thread_port;
112    g_message->exc_type = exc_type;
113    g_message->AppendExceptionData(exc_data, exc_data_count);
114    return KERN_SUCCESS;
115  } else if (!MachTask::IsValid(g_message->task_port)) {
116    // Our original exception port isn't valid anymore check for a SIGTRAP
117    if (exc_type == EXC_SOFTWARE && exc_data_count == 2 &&
118        exc_data[0] == EXC_SOFT_SIGNAL && exc_data[1] == SIGTRAP) {
119      // We got a SIGTRAP which indicates we might have exec'ed and possibly
120      // lost our old task port during the exec, so we just need to switch over
121      // to using this new task port
122      g_message->task_port = task_port;
123      g_message->thread_port = thread_port;
124      g_message->exc_type = exc_type;
125      g_message->AppendExceptionData(exc_data, exc_data_count);
126      return KERN_SUCCESS;
127    }
128  }
129  return KERN_FAILURE;
130}
131
132void MachException::Message::Dump() const {
133  DNBLogThreadedIf(LOG_EXCEPTIONS, "  exc_msg { bits = 0x%8.8x size = 0x%8.8x "
134                                   "remote-port = 0x%8.8x local-port = 0x%8.8x "
135                                   "reserved = 0x%8.8x id = 0x%8.8x } ",
136                   exc_msg.hdr.msgh_bits, exc_msg.hdr.msgh_size,
137                   exc_msg.hdr.msgh_remote_port, exc_msg.hdr.msgh_local_port,
138                   exc_msg.hdr.msgh_reserved, exc_msg.hdr.msgh_id);
139
140  DNBLogThreadedIf(LOG_EXCEPTIONS, "reply_msg { bits = 0x%8.8x size = 0x%8.8x "
141                                   "remote-port = 0x%8.8x local-port = 0x%8.8x "
142                                   "reserved = 0x%8.8x id = 0x%8.8x }",
143                   reply_msg.hdr.msgh_bits, reply_msg.hdr.msgh_size,
144                   reply_msg.hdr.msgh_remote_port,
145                   reply_msg.hdr.msgh_local_port, reply_msg.hdr.msgh_reserved,
146                   reply_msg.hdr.msgh_id);
147
148  state.Dump();
149}
150
151bool MachException::Data::GetStopInfo(
152    struct DNBThreadStopInfo *stop_info) const {
153  // Zero out the structure.
154  memset(stop_info, 0, sizeof(struct DNBThreadStopInfo));
155
156  if (exc_type == 0) {
157    stop_info->reason = eStopTypeInvalid;
158    return true;
159  }
160
161  // We always stop with a mach exceptions
162  stop_info->reason = eStopTypeException;
163  // Save the EXC_XXXX exception type
164  stop_info->details.exception.type = exc_type;
165
166  // Fill in a text description
167  const char *exc_name = MachException::Name(exc_type);
168  char *desc = stop_info->description;
169  const char *end_desc = desc + DNB_THREAD_STOP_INFO_MAX_DESC_LENGTH;
170  if (exc_name)
171    desc +=
172        snprintf(desc, DNB_THREAD_STOP_INFO_MAX_DESC_LENGTH, "%s", exc_name);
173  else
174    desc +=
175        snprintf(desc, DNB_THREAD_STOP_INFO_MAX_DESC_LENGTH, "%i", exc_type);
176
177  stop_info->details.exception.data_count = exc_data.size();
178
179  int soft_signal = SoftSignal();
180  if (soft_signal) {
181    if (desc < end_desc) {
182      const char *sig_str = SysSignal::Name(soft_signal);
183      snprintf(desc, end_desc - desc, " EXC_SOFT_SIGNAL( %i ( %s ))",
184               soft_signal, sig_str ? sig_str : "unknown signal");
185    }
186  } else {
187    // No special disassembly for exception data, just
188    size_t idx;
189    if (desc < end_desc) {
190      desc += snprintf(desc, end_desc - desc, " data[%llu] = {",
191                       (uint64_t)stop_info->details.exception.data_count);
192
193      for (idx = 0;
194           desc < end_desc && idx < stop_info->details.exception.data_count;
195           ++idx)
196        desc += snprintf(
197            desc, end_desc - desc, "0x%llx%c", (uint64_t)exc_data[idx],
198            ((idx + 1 == stop_info->details.exception.data_count) ? '}' : ','));
199    }
200  }
201
202  // Copy the exception data
203  size_t i;
204  for (i = 0; i < stop_info->details.exception.data_count; i++)
205    stop_info->details.exception.data[i] = exc_data[i];
206
207  return true;
208}
209
210void MachException::Data::DumpStopReason() const {
211  int soft_signal = SoftSignal();
212  if (soft_signal) {
213    const char *signal_str = SysSignal::Name(soft_signal);
214    if (signal_str)
215      DNBLog("signal(%s)", signal_str);
216    else
217      DNBLog("signal(%i)", soft_signal);
218    return;
219  }
220  DNBLog("%s", Name(exc_type));
221}
222
223kern_return_t MachException::Message::Receive(mach_port_t port,
224                                              mach_msg_option_t options,
225                                              mach_msg_timeout_t timeout,
226                                              mach_port_t notify_port) {
227  DNBError err;
228  const bool log_exceptions = DNBLogCheckLogBit(LOG_EXCEPTIONS);
229  mach_msg_timeout_t mach_msg_timeout =
230      options & MACH_RCV_TIMEOUT ? timeout : 0;
231  if (log_exceptions && ((options & MACH_RCV_TIMEOUT) == 0)) {
232    // Dump this log message if we have no timeout in case it never returns
233    DNBLogThreaded("::mach_msg ( msg->{bits = %#x, size = %u remote_port = "
234                   "%#x, local_port = %#x, reserved = 0x%x, id = 0x%x}, option "
235                   "= %#x, send_size = 0, rcv_size = %llu, rcv_name = %#x, "
236                   "timeout = %u, notify = %#x)",
237                   exc_msg.hdr.msgh_bits, exc_msg.hdr.msgh_size,
238                   exc_msg.hdr.msgh_remote_port, exc_msg.hdr.msgh_local_port,
239                   exc_msg.hdr.msgh_reserved, exc_msg.hdr.msgh_id, options,
240                   (uint64_t)sizeof(exc_msg.data), port, mach_msg_timeout,
241                   notify_port);
242  }
243
244  err = ::mach_msg(&exc_msg.hdr,
245                   options,              // options
246                   0,                    // Send size
247                   sizeof(exc_msg.data), // Receive size
248                   port,             // exception port to watch for exception on
249                   mach_msg_timeout, // timeout in msec (obeyed only if
250                                     // MACH_RCV_TIMEOUT is ORed into the
251                                     // options parameter)
252                   notify_port);
253
254  // Dump any errors we get
255  if (log_exceptions) {
256    err.LogThreaded("::mach_msg ( msg->{bits = %#x, size = %u remote_port = "
257                    "%#x, local_port = %#x, reserved = 0x%x, id = 0x%x}, "
258                    "option = %#x, send_size = %u, rcv_size = %u, rcv_name = "
259                    "%#x, timeout = %u, notify = %#x)",
260                    exc_msg.hdr.msgh_bits, exc_msg.hdr.msgh_size,
261                    exc_msg.hdr.msgh_remote_port, exc_msg.hdr.msgh_local_port,
262                    exc_msg.hdr.msgh_reserved, exc_msg.hdr.msgh_id, options, 0,
263                    sizeof(exc_msg.data), port, mach_msg_timeout, notify_port);
264  }
265  return err.Status();
266}
267
268bool MachException::Message::CatchExceptionRaise(task_t task) {
269  bool success = false;
270  state.task_port = task;
271  g_message = &state;
272  // The exc_server function is the MIG generated server handling function
273  // to handle messages from the kernel relating to the occurrence of an
274  // exception in a thread. Such messages are delivered to the exception port
275  // set via thread_set_exception_ports or task_set_exception_ports. When an
276  // exception occurs in a thread, the thread sends an exception message to
277  // its exception port, blocking in the kernel waiting for the receipt of a
278  // reply. The exc_server function performs all necessary argument handling
279  // for this kernel message and calls catch_exception_raise,
280  // catch_exception_raise_state or catch_exception_raise_state_identity,
281  // which should handle the exception. If the called routine returns
282  // KERN_SUCCESS, a reply message will be sent, allowing the thread to
283  // continue from the point of the exception; otherwise, no reply message
284  // is sent and the called routine must have dealt with the exception
285  // thread directly.
286  if (mach_exc_server(&exc_msg.hdr, &reply_msg.hdr)) {
287    success = true;
288  } else if (DNBLogCheckLogBit(LOG_EXCEPTIONS)) {
289    DNBLogThreaded("mach_exc_server returned zero...");
290  }
291  g_message = NULL;
292  return success;
293}
294
295kern_return_t MachException::Message::Reply(MachProcess *process, int signal) {
296  // Reply to the exception...
297  DNBError err;
298
299  // If we had a soft signal, we need to update the thread first so it can
300  // continue without signaling
301  int soft_signal = state.SoftSignal();
302  if (soft_signal) {
303    int state_pid = -1;
304    if (process->Task().TaskPort() == state.task_port) {
305      // This is our task, so we can update the signal to send to it
306      state_pid = process->ProcessID();
307      soft_signal = signal;
308    } else {
309      err = ::pid_for_task(state.task_port, &state_pid);
310    }
311
312    assert(state_pid != -1);
313    if (state_pid != -1) {
314      errno = 0;
315      if (::ptrace(PT_THUPDATE, state_pid,
316                   (caddr_t)((uintptr_t)state.thread_port), soft_signal) != 0)
317        err.SetError(errno, DNBError::POSIX);
318      else
319        err.Clear();
320
321      if (DNBLogCheckLogBit(LOG_EXCEPTIONS) || err.Fail())
322        err.LogThreaded("::ptrace (request = PT_THUPDATE, pid = 0x%4.4x, tid = "
323                        "0x%4.4x, signal = %i)",
324                        state_pid, state.thread_port, soft_signal);
325    }
326  }
327
328  DNBLogThreadedIf(
329      LOG_EXCEPTIONS, "::mach_msg ( msg->{bits = %#x, size = %u, remote_port = "
330                      "%#x, local_port = %#x, reserved = 0x%x, id = 0x%x}, "
331                      "option = %#x, send_size = %u, rcv_size = %u, rcv_name = "
332                      "%#x, timeout = %u, notify = %#x)",
333      reply_msg.hdr.msgh_bits, reply_msg.hdr.msgh_size,
334      reply_msg.hdr.msgh_remote_port, reply_msg.hdr.msgh_local_port,
335      reply_msg.hdr.msgh_reserved, reply_msg.hdr.msgh_id,
336      MACH_SEND_MSG | MACH_SEND_INTERRUPT, reply_msg.hdr.msgh_size, 0,
337      MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
338
339  err = ::mach_msg(&reply_msg.hdr, MACH_SEND_MSG | MACH_SEND_INTERRUPT,
340                   reply_msg.hdr.msgh_size, 0, MACH_PORT_NULL,
341                   MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
342
343  if (err.Fail()) {
344    if (err.Status() == MACH_SEND_INTERRUPTED) {
345      if (DNBLogCheckLogBit(LOG_EXCEPTIONS))
346        err.LogThreaded("::mach_msg() - send interrupted");
347      // TODO: keep retrying to reply???
348    } else {
349      if (state.task_port == process->Task().TaskPort()) {
350        DNBLogThreaded("error: mach_msg() returned an error when replying to a "
351                       "mach exception: error = %u",
352                       err.Status());
353      } else {
354        if (DNBLogCheckLogBit(LOG_EXCEPTIONS))
355          err.LogThreaded("::mach_msg() - failed (child of task)");
356      }
357    }
358  }
359
360  return err.Status();
361}
362
363void MachException::Data::Dump() const {
364  const char *exc_type_name = MachException::Name(exc_type);
365  DNBLogThreadedIf(
366      LOG_EXCEPTIONS, "    state { task_port = 0x%4.4x, thread_port =  "
367                      "0x%4.4x, exc_type = %i (%s) ...",
368      task_port, thread_port, exc_type, exc_type_name ? exc_type_name : "???");
369
370  const size_t exc_data_count = exc_data.size();
371  // Dump any special exception data contents
372  int soft_signal = SoftSignal();
373  if (soft_signal != 0) {
374    const char *sig_str = SysSignal::Name(soft_signal);
375    DNBLogThreadedIf(LOG_EXCEPTIONS,
376                     "            exc_data: EXC_SOFT_SIGNAL (%i (%s))",
377                     soft_signal, sig_str ? sig_str : "unknown signal");
378  } else {
379    // No special disassembly for this data, just dump the data
380    size_t idx;
381    for (idx = 0; idx < exc_data_count; ++idx) {
382      DNBLogThreadedIf(LOG_EXCEPTIONS, "            exc_data[%llu]: 0x%llx",
383                       (uint64_t)idx, (uint64_t)exc_data[idx]);
384    }
385  }
386}
387
388// The EXC_MASK_ALL value hard-coded here so that lldb can be built
389// on a new OS with an older deployment target .  The new OS may have
390// an addition to its EXC_MASK_ALL that the old OS will not recognize -
391// <mach/exception_types.h> doesn't vary the value based on the deployment
392// target.  So we need a known set of masks that can be assumed to be
393// valid when running on an older OS.  We'll fall back to trying
394// PREV_EXC_MASK_ALL if the EXC_MASK_ALL value lldb was compiled with is
395// not recognized.
396
397#define PREV_EXC_MASK_ALL (EXC_MASK_BAD_ACCESS |                \
398                         EXC_MASK_BAD_INSTRUCTION |             \
399                         EXC_MASK_ARITHMETIC |                  \
400                         EXC_MASK_EMULATION |                   \
401                         EXC_MASK_SOFTWARE |                    \
402                         EXC_MASK_BREAKPOINT |                  \
403                         EXC_MASK_SYSCALL |                     \
404                         EXC_MASK_MACH_SYSCALL |                \
405                         EXC_MASK_RPC_ALERT |                   \
406                         EXC_MASK_RESOURCE |                    \
407                         EXC_MASK_GUARD |                       \
408                         EXC_MASK_MACHINE)
409
410#define LLDB_EXC_MASK EXC_MASK_ALL
411
412kern_return_t MachException::PortInfo::Save(task_t task) {
413  DNBLogThreadedIf(LOG_EXCEPTIONS | LOG_VERBOSE,
414                   "MachException::PortInfo::Save ( task = 0x%4.4x )", task);
415  // Be careful to be able to have debugserver built on a newer OS than what
416  // it is currently running on by being able to start with all exceptions
417  // and back off to just what is supported on the current system
418  DNBError err;
419
420  mask = LLDB_EXC_MASK;
421
422  count = (sizeof(ports) / sizeof(ports[0]));
423  err = ::task_get_exception_ports(task, mask, masks, &count, ports, behaviors,
424                                   flavors);
425  if (DNBLogCheckLogBit(LOG_EXCEPTIONS) || err.Fail())
426    err.LogThreaded("::task_get_exception_ports ( task = 0x%4.4x, mask = 0x%x, "
427                    "maskCnt => %u, ports, behaviors, flavors )",
428                    task, mask, count);
429
430  if (err.Status() == KERN_INVALID_ARGUMENT && mask != PREV_EXC_MASK_ALL) {
431    mask = PREV_EXC_MASK_ALL;
432    count = (sizeof(ports) / sizeof(ports[0]));
433    err = ::task_get_exception_ports(task, mask, masks, &count, ports,
434                                     behaviors, flavors);
435    if (DNBLogCheckLogBit(LOG_EXCEPTIONS) || err.Fail())
436      err.LogThreaded("::task_get_exception_ports ( task = 0x%4.4x, mask = "
437                      "0x%x, maskCnt => %u, ports, behaviors, flavors )",
438                      task, mask, count);
439  }
440  if (err.Fail()) {
441    mask = 0;
442    count = 0;
443  }
444  return err.Status();
445}
446
447kern_return_t MachException::PortInfo::Restore(task_t task) {
448  DNBLogThreadedIf(LOG_EXCEPTIONS | LOG_VERBOSE,
449                   "MachException::PortInfo::Restore( task = 0x%4.4x )", task);
450  uint32_t i = 0;
451  DNBError err;
452  if (count > 0) {
453    for (i = 0; i < count; i++) {
454      err = ::task_set_exception_ports(task, masks[i], ports[i], behaviors[i],
455                                       flavors[i]);
456      if (DNBLogCheckLogBit(LOG_EXCEPTIONS) || err.Fail()) {
457        err.LogThreaded("::task_set_exception_ports ( task = 0x%4.4x, "
458                        "exception_mask = 0x%8.8x, new_port = 0x%4.4x, "
459                        "behavior = 0x%8.8x, new_flavor = 0x%8.8x )",
460                        task, masks[i], ports[i], behaviors[i], flavors[i]);
461        // Bail if we encounter any errors
462      }
463
464      if (err.Fail())
465        break;
466    }
467  }
468  count = 0;
469  return err.Status();
470}
471
472const char *MachException::Name(exception_type_t exc_type) {
473  switch (exc_type) {
474  case EXC_BAD_ACCESS:
475    return "EXC_BAD_ACCESS";
476  case EXC_BAD_INSTRUCTION:
477    return "EXC_BAD_INSTRUCTION";
478  case EXC_ARITHMETIC:
479    return "EXC_ARITHMETIC";
480  case EXC_EMULATION:
481    return "EXC_EMULATION";
482  case EXC_SOFTWARE:
483    return "EXC_SOFTWARE";
484  case EXC_BREAKPOINT:
485    return "EXC_BREAKPOINT";
486  case EXC_SYSCALL:
487    return "EXC_SYSCALL";
488  case EXC_MACH_SYSCALL:
489    return "EXC_MACH_SYSCALL";
490  case EXC_RPC_ALERT:
491    return "EXC_RPC_ALERT";
492#ifdef EXC_CRASH
493  case EXC_CRASH:
494    return "EXC_CRASH";
495#endif
496  case EXC_RESOURCE:
497    return "EXC_RESOURCE";
498#ifdef EXC_GUARD
499  case EXC_GUARD:
500    return "EXC_GUARD";
501#endif
502#ifdef EXC_CORPSE_NOTIFY
503  case EXC_CORPSE_NOTIFY:
504    return "EXC_CORPSE_NOTIFY";
505#endif
506#ifdef EXC_CORPSE_VARIANT_BIT
507  case EXC_CORPSE_VARIANT_BIT:
508    return "EXC_CORPSE_VARIANT_BIT";
509#endif
510  default:
511    break;
512  }
513  return NULL;
514}
515
516// Returns the exception mask for a given exception name.
517// 0 is not a legit mask, so we return that in the case of an error.
518exception_mask_t MachException::ExceptionMask(const char *name) {
519  static const char *exception_prefix = "EXC_";
520  static const int prefix_len = strlen(exception_prefix);
521
522  // All mach exceptions start with this prefix:
523  if (strstr(name, exception_prefix) != name)
524    return 0;
525
526  name += prefix_len;
527  std::string name_str = name;
528  if (name_str == "BAD_ACCESS")
529    return EXC_MASK_BAD_ACCESS;
530  if (name_str == "BAD_INSTRUCTION")
531    return EXC_MASK_BAD_INSTRUCTION;
532  if (name_str == "ARITHMETIC")
533    return EXC_MASK_ARITHMETIC;
534  if (name_str == "EMULATION")
535    return EXC_MASK_EMULATION;
536  if (name_str == "SOFTWARE")
537    return EXC_MASK_SOFTWARE;
538  if (name_str == "BREAKPOINT")
539    return EXC_MASK_BREAKPOINT;
540  if (name_str == "SYSCALL")
541    return EXC_MASK_SYSCALL;
542  if (name_str == "MACH_SYSCALL")
543    return EXC_MASK_MACH_SYSCALL;
544  if (name_str == "RPC_ALERT")
545    return EXC_MASK_RPC_ALERT;
546#ifdef EXC_CRASH
547  if (name_str == "CRASH")
548    return EXC_MASK_CRASH;
549#endif
550  if (name_str == "RESOURCE")
551    return EXC_MASK_RESOURCE;
552#ifdef EXC_GUARD
553  if (name_str == "GUARD")
554    return EXC_MASK_GUARD;
555#endif
556#ifdef EXC_CORPSE_NOTIFY
557  if (name_str == "CORPSE_NOTIFY")
558    return EXC_MASK_CORPSE_NOTIFY;
559#endif
560  return 0;
561}
562