src/runtime/x86-64-darwin-os.c

   1
   2 #ifdef LISP_FEATURE_SB_THREAD
   3 #include <architecture/i386/table.h>
   4 #include <i386/user_ldt.h>
   5 #include <mach/mach_init.h>
   6 #endif
   7
   8 #include "thread.h"
   9 #include "validate.h"
  10 #include "runtime.h"
  11 #include "interrupt.h"
  12 #include "x86-64-darwin-os.h"
  13 #include "genesis/fdefn.h"
  14
  15 #include <mach/mach.h>
  16 #include <mach/mach_error.h>
  17 #include <mach/mach_types.h>
  18 #include <mach/sync_policy.h>
  19 #include <mach/machine/thread_state.h>
  20 #include <mach/machine/thread_status.h>
  21 #include <sys/_types.h>
  22 #include <sys/ucontext.h>
  23 #include <pthread.h>
  24 #include <assert.h>
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27
  28 #if __DARWIN_UNIX03
  29 #include <sys/_structs.h>
  30 #endif
  31
  32 #if __DARWIN_UNIX03
  33
  34 typedef struct __darwin_ucontext darwin_ucontext;
  35 typedef struct __darwin_mcontext64 darwin_mcontext;
  36
  37 #define rip __rip
  38 #define rsp __rsp
  39 #define rbp __rbp
  40 #define rax __rax
  41 #define rbx __rbx
  42 #define rcx __rcx
  43 #define rdx __rdx
  44 #define rsi __rsi
  45 #define rdi __rdi
  46 #define r8 __r8
  47 #define r9 __r9
  48 #define faultvaddr __faultvaddr
  49 #define ss __ss
  50 #define es __es
  51 #define fs __fs
  52
  53 #else
  54
  55 typedef struct ucontext darwin_ucontext;
  56 typedef struct mcontext darwin_mcontext;
  57
  58 #endif
  59
  60 #ifdef LISP_FEATURE_SB_THREAD
  61 pthread_mutex_t mach_exception_lock = PTHREAD_MUTEX_INITIALIZER;
  62 #endif
  63
  64 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
  65
  66 kern_return_t mach_thread_init(mach_port_t thread_exception_port);
  67
  68 void sigill_handler(int signal, siginfo_t *siginfo, void *void_context);
  69 void sigtrap_handler(int signal, siginfo_t *siginfo, void *void_context);
  70 void memory_fault_handler(int signal, siginfo_t *siginfo, void *void_context);
  71
  72 /* exc_server handles mach exception messages from the kernel and
  73  * calls catch exception raise. We use the system-provided
  74  * mach_msg_server, which, I assume, calls exc_server in a loop.
  75  *
  76  */
  77 extern boolean_t exc_server();
  78
  79 /* This executes in the faulting thread as part of the signal
  80  * emulation.  It is passed a context with the uc_mcontext field
  81  * pointing to a valid block of memory. */
  82 void build_fake_signal_context(darwin_ucontext *context,
  83                                x86_thread_state64_t *thread_state,
  84                                x86_float_state64_t *float_state) {
  85     pthread_sigmask(0, NULL, &context->uc_sigmask);
  86     context->uc_mcontext->ss = *thread_state;
  87     context->uc_mcontext->fs = *float_state;
  88 }
  89
  90 /* This executes in the faulting thread as part of the signal
  91  * emulation.  It is effectively the inverse operation from above. */
  92 void update_thread_state_from_context(x86_thread_state64_t *thread_state,
  93                                       x86_float_state64_t *float_state,
  94                                       darwin_ucontext  *context) {
  95     *thread_state = context->uc_mcontext->ss;
  96     *float_state = context->uc_mcontext->fs;
  97     pthread_sigmask(SIG_SETMASK, &context->uc_sigmask, NULL);
  98 }
  99
 100 /* Modify a context to push new data on its stack. */
 101 void push_context(u64 data, x86_thread_state64_t *context)
 102 {
 103     u64 *stack_pointer;
 104
 105     stack_pointer = (u64*) context->rsp;
 106     *(--stack_pointer) = data;
 107     context->rsp = (u64) stack_pointer;
 108 }
 109
 110 void align_context_stack(x86_thread_state64_t *context)
 111 {
 112     /* 16byte align the stack (provided that the stack is, as it
 113      * should be, 8byte aligned. */
 114     while (context->rsp & 15) push_context(0, context);
 115 }
 116
 117 /* Stack allocation starts with a context that has a mod-4 ESP value
 118  * and needs to leave a context with a mod-16 ESP that will restore
 119  * the old ESP value and other register state when activated.  The
 120  * first part of this is the recovery trampoline, which loads ESP from
 121  * EBP, pops EBP, and returns. */
 122 asm(".globl _stack_allocation_recover; .align 4; _stack_allocation_recover: mov %rbp, %rsp; pop %rsi; pop %rdi; pop \
 123 %rdx; pop %rcx; pop %r8; pop %r9; pop %rbp; ret;");
 124
 125 void open_stack_allocation(x86_thread_state64_t *context)
 126 {
 127     void stack_allocation_recover(void);
 128
 129     push_context(context->rip, context);
 130     push_context(context->rbp, context);
 131
 132     push_context(context->r9, context);
 133     push_context(context->r8, context);
 134     push_context(context->rcx, context);
 135     push_context(context->rdx, context);
 136     push_context(context->rsi, context);
 137     push_context(context->rdi, context);
 138
 139     context->rbp = context->rsp;
 140     context->rip = (u64) stack_allocation_recover;
 141
 142     align_context_stack(context);
 143 }
 144
 145 /* Stack allocation of data starts with a context with a mod-16 ESP
 146  * value and reserves some space on it by manipulating the ESP
 147  * register. */
 148 void *stack_allocate(x86_thread_state64_t *context, size_t size)
 149 {
 150     /* round up size to 16byte multiple */
 151     size = (size + 15) & -16;
 152
 153     context->rsp = ((u64)context->rsp) - size;
 154
 155     return (void *)context->rsp;
 156 }
 157
 158 /* Arranging to invoke a C function is tricky, as we have to assume
 159  * cdecl calling conventions (caller removes args) and x86/darwin
 160  * alignment requirements.  The simplest way to arrange this,
 161  * actually, is to open a new stack allocation.
 162  * WARNING!!! THIS DOES NOT PRESERVE REGISTERS! */
 163 void call_c_function_in_context(x86_thread_state64_t *context,
 164                                 void *function,
 165                                 int nargs,
 166                                 ...)
 167 {
 168     va_list ap;
 169     int i;
 170     u64 *stack_pointer;
 171
 172     /* Set up to restore stack on exit. */
 173     open_stack_allocation(context);
 174
 175     /* Have to keep stack 16byte aligned on x86/darwin. */
 176     for (i = (1 & -nargs); i; i--) {
 177         push_context(0, context);
 178     }
 179
 180     context->rsp = ((u64)context->rsp) - nargs * 8;
 181     stack_pointer = (u64 *)context->rsp;
 182
 183     va_start(ap, nargs);
 184     if (nargs > 0) context->rdi = va_arg(ap, u64);
 185     if (nargs > 1) context->rsi = va_arg(ap, u64);
 186     if (nargs > 2) context->rdx = va_arg(ap, u64);
 187     if (nargs > 3) context->rcx = va_arg(ap, u64);
 188     if (nargs > 4) context->r8 = va_arg(ap, u64);
 189     if (nargs > 5) context->r9 = va_arg(ap, u64);
 190     for (i = 6; i < nargs; i++) {
 191         stack_pointer[i] = va_arg(ap, u64);
 192     }
 193     va_end(ap);
 194
 195     push_context(context->rip, context);
 196     context->rip = (u64) function;
 197 }
 198
 199 void signal_emulation_wrapper(x86_thread_state64_t *thread_state,
 200                               x86_float_state64_t *float_state,
 201                               int signal,
 202                               siginfo_t *siginfo,
 203                               void (*handler)(int, siginfo_t *, void *))
 204 {
 205
 206     /* CLH: FIXME **NOTE: HACK ALERT!** Ideally, we would allocate
 207      * context and regs on the stack as local variables, but this
 208      * causes problems for the lisp debugger. When it walks the stack
 209      * for a back trace, it sees the 1) address of the local variable
 210      * on the stack and thinks that is a frame pointer to a lisp
 211      * frame, and, 2) the address of the sap that we alloc'ed in
 212      * dynamic space and thinks that is a return address, so it,
 213      * heuristicly (and wrongly), chooses that this should be
 214      * interpreted as a lisp frame instead of as a C frame.
 215      * We can work around this in this case by os_validating the
 216      * context (and regs just for symmetry).
 217      */
 218
 219     darwin_ucontext  *context;
 220     darwin_mcontext *regs;
 221
 222     context = (darwin_ucontext *) os_validate(0, sizeof(darwin_ucontext));
 223     regs = (darwin_mcontext*) os_validate(0, sizeof(darwin_mcontext));
 224     context->uc_mcontext = regs;
 225
 226     /* when BSD signals are fired, they mask they signals in sa_mask
 227        which always seem to be the blockable_sigset, for us, so we
 228        need to:
 229        1) save the current sigmask
 230        2) block blockable signals
 231        3) call the signal handler
 232        4) restore the sigmask */
 233
 234     build_fake_signal_context(context, thread_state, float_state);
 235
 236     block_blockable_signals();
 237
 238     handler(signal, siginfo, context);
 239
 240     update_thread_state_from_context(thread_state, float_state, context);
 241
 242     os_invalidate((os_vm_address_t)context, sizeof(darwin_ucontext));
 243     os_invalidate((os_vm_address_t)regs, sizeof(darwin_mcontext));
 244
 245     /* Trap to restore the signal context. */
 246     asm volatile ("mov %0, %%rax; mov %1, %%rbx; .quad 0xffffffffffff0b0f"
 247                   : : "r" (thread_state), "r" (float_state));
 248 }
 249
 250 #if defined DUMP_CONTEXT
 251 void dump_context(x86_thread_state64_t *context)
 252 {
 253     int i;
 254     u64 *stack_pointer;
 255
 256     printf("rax: %08lx  rcx: %08lx  rdx: %08lx  rbx: %08lx\n",
 257            context->rax, context->rcx, context->rdx, context->rbx);
 258     printf("rsp: %08lx  rbp: %08lx  rsi: %08lx  rdi: %08lx\n",
 259            context->rsp, context->rbp, context->rsi, context->rdi);
 260     printf("rip: %08lx  eflags: %08lx\n",
 261            context->rip, context->rflags);
 262     printf("cs: %04hx  ds: %04hx  es: %04hx  "
 263            "ss: %04hx  fs: %04hx  gs: %04hx\n",
 264            context->cs, context->ds, context->rs,
 265            context->ss, context->fs, context->gs);
 266
 267     stack_pointer = (u64 *)context->rsp;
 268     for (i = 0; i < 48; i+=4) {
 269         printf("%08x:  %08x %08x %08x %08x\n",
 270                context->rsp + (i * 4),
 271                stack_pointer[i],
 272                stack_pointer[i+1],
 273                stack_pointer[i+2],
 274                stack_pointer[i+3]);
 275     }
 276 }
 277 #endif
 278
 279 void
 280 control_stack_exhausted_handler(int signal, siginfo_t *siginfo, void *void_context) {
 281     os_context_t *context = arch_os_get_context(&void_context);
 282
 283     arrange_return_to_lisp_function
 284         (context, SymbolFunction(CONTROL_STACK_EXHAUSTED_ERROR));
 285 }
 286
 287 void
 288 undefined_alien_handler(int signal, siginfo_t *siginfo, void *void_context) {
 289     os_context_t *context = arch_os_get_context(&void_context);
 290
 291     arrange_return_to_lisp_function
 292         (context, SymbolFunction(UNDEFINED_ALIEN_VARIABLE_ERROR));
 293 }
 294
 295 kern_return_t
 296 catch_exception_raise(mach_port_t exception_port,
 297                       mach_port_t thread,
 298                       mach_port_t task,
 299                       exception_type_t exception,
 300                       exception_data_t code_vector,
 301                       mach_msg_type_number_t code_count)
 302 {
 303     kern_return_t ret;
 304     int signal;
 305     siginfo_t* siginfo;
 306
 307 #ifdef LISP_FEATURE_SB_THREAD
 308     thread_mutex_lock(&mach_exception_lock);
 309 #endif
 310
 311     x86_thread_state64_t thread_state;
 312     mach_msg_type_number_t thread_state_count = x86_THREAD_STATE64_COUNT;
 313
 314     x86_float_state64_t float_state;
 315     mach_msg_type_number_t float_state_count = x86_FLOAT_STATE64_COUNT;
 316
 317     x86_exception_state64_t exception_state;
 318     mach_msg_type_number_t exception_state_count = x86_EXCEPTION_STATE64_COUNT;
 319
 320     x86_thread_state64_t backup_thread_state;
 321     x86_thread_state64_t *target_thread_state;
 322     x86_float_state64_t *target_float_state;
 323
 324     os_vm_address_t addr;
 325
 326     struct thread *th = (struct thread*) exception_port;
 327
 328     FSHOW((stderr,"/entering catch_exception_raise with exception: %d\n", exception));
 329
 330     switch (exception) {
 331
 332     case EXC_BAD_ACCESS:
 333         signal = SIGBUS;
 334         ret = thread_get_state(thread,
 335                                x86_THREAD_STATE64,
 336                                (thread_state_t)&thread_state,
 337                                &thread_state_count);
 338         ret = thread_get_state(thread,
 339                                x86_FLOAT_STATE64,
 340                                (thread_state_t)&float_state,
 341                                &float_state_count);
 342         ret = thread_get_state(thread,
 343                                x86_EXCEPTION_STATE64,
 344                                (thread_state_t)&exception_state,
 345                                &exception_state_count);
 346         addr = (void*)exception_state.faultvaddr;
 347
 348
 349         /* note the os_context hackery here.  When the signal handler returns,
 350          * it won't go back to what it was doing ... */
 351         if(addr >= CONTROL_STACK_GUARD_PAGE(th) &&
 352            addr < CONTROL_STACK_GUARD_PAGE(th) + os_vm_page_size) {
 353             /* We hit the end of the control stack: disable guard page
 354              * protection so the error handler has some headroom, protect the
 355              * previous page so that we can catch returns from the guard page
 356              * and restore it. */
 357             protect_control_stack_guard_page_thread(0, th);
 358             protect_control_stack_return_guard_page_thread(1, th);
 359
 360             backup_thread_state = thread_state;
 361             open_stack_allocation(&thread_state);
 362
 363             /* Save thread state */
 364             target_thread_state =
 365                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 366             (*target_thread_state) = backup_thread_state;
 367
 368             /* Save float state */
 369             target_float_state =
 370                 stack_allocate(&thread_state, sizeof(*target_float_state));
 371             (*target_float_state) = float_state;
 372
 373             /* Set up siginfo */
 374             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 375             /* what do we need to put in our fake siginfo?  It looks like
 376              * the x86 code only uses si_signo and si_adrr. */
 377             siginfo->si_signo = signal;
 378             siginfo->si_addr = (void*)exception_state.faultvaddr;
 379
 380             call_c_function_in_context(&thread_state,
 381                                        signal_emulation_wrapper,
 382                                        5,
 383                                        target_thread_state,
 384                                        target_float_state,
 385                                        signal,
 386                                        siginfo,
 387                                        control_stack_exhausted_handler);
 388         }
 389         else if(addr >= CONTROL_STACK_RETURN_GUARD_PAGE(th) &&
 390                 addr < CONTROL_STACK_RETURN_GUARD_PAGE(th) + os_vm_page_size) {
 391             /* We're returning from the guard page: reprotect it, and
 392              * unprotect this one. This works even if we somehow missed
 393              * the return-guard-page, and hit it on our way to new
 394              * exhaustion instead. */
 395             protect_control_stack_guard_page_thread(1, th);
 396             protect_control_stack_return_guard_page_thread(0, th);
 397         }
 398         else if (addr >= undefined_alien_address &&
 399                  addr < undefined_alien_address + os_vm_page_size) {
 400             backup_thread_state = thread_state;
 401             open_stack_allocation(&thread_state);
 402
 403             /* Save thread state */
 404             target_thread_state =
 405                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 406             (*target_thread_state) = backup_thread_state;
 407
 408             target_float_state =
 409                 stack_allocate(&thread_state, sizeof(*target_float_state));
 410             (*target_float_state) = float_state;
 411
 412             /* Set up siginfo */
 413             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 414             /* what do we need to put in our fake siginfo?  It looks like
 415              * the x86 code only uses si_signo and si_adrr. */
 416             siginfo->si_signo = signal;
 417             siginfo->si_addr = (void*)exception_state.faultvaddr;
 418
 419             call_c_function_in_context(&thread_state,
 420                                        signal_emulation_wrapper,
 421                                        5,
 422                                        target_thread_state,
 423                                        target_float_state,
 424                                        signal,
 425                                        siginfo,
 426                                        undefined_alien_handler);
 427         } else {
 428
 429             backup_thread_state = thread_state;
 430             open_stack_allocation(&thread_state);
 431
 432             /* Save thread state */
 433             target_thread_state =
 434                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 435             (*target_thread_state) = backup_thread_state;
 436
 437             target_float_state =
 438                 stack_allocate(&thread_state, sizeof(*target_float_state));
 439             (*target_float_state) = float_state;
 440
 441             /* Set up siginfo */
 442             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 443             /* what do we need to put in our fake siginfo?  It looks like
 444              * the x86 code only uses si_signo and si_adrr. */
 445             siginfo->si_signo = signal;
 446             siginfo->si_addr = (void*)exception_state.faultvaddr;
 447
 448             call_c_function_in_context(&thread_state,
 449                                        signal_emulation_wrapper,
 450                                        5,
 451                                        target_thread_state,
 452                                        target_float_state,
 453                                        signal,
 454                                        siginfo,
 455                                        memory_fault_handler);
 456         }
 457         ret = thread_set_state(thread,
 458                                x86_THREAD_STATE64,
 459                                (thread_state_t)&thread_state,
 460                                thread_state_count);
 461
 462         ret = thread_set_state(thread,
 463                                x86_FLOAT_STATE64,
 464                                (thread_state_t)&float_state,
 465                                float_state_count);
 466 #ifdef LISP_FEATURE_SB_THREAD
 467         thread_mutex_unlock(&mach_exception_lock);
 468 #endif
 469         return KERN_SUCCESS;
 470
 471     case EXC_BAD_INSTRUCTION:
 472
 473         ret = thread_get_state(thread,
 474                                x86_THREAD_STATE64,
 475                                (thread_state_t)&thread_state,
 476                                &thread_state_count);
 477         ret = thread_get_state(thread,
 478                                x86_FLOAT_STATE64,
 479                                (thread_state_t)&float_state,
 480                                &float_state_count);
 481         ret = thread_get_state(thread,
 482                                x86_EXCEPTION_STATE64,
 483                                (thread_state_t)&exception_state,
 484                                &exception_state_count);
 485         if (0xffffffffffff0b0f == *((u64 *)thread_state.rip)) {
 486             /* fake sigreturn. */
 487
 488             /* When we get here, thread_state.rax is a pointer to a
 489              * thread_state to restore. */
 490             /* thread_state = *((thread_state_t *)thread_state.rax); */
 491
 492             ret = thread_set_state(thread,
 493                                    x86_THREAD_STATE64,
 494                                    (thread_state_t) thread_state.rax,
 495                                    /* &thread_state, */
 496                                    thread_state_count);
 497
 498             ret = thread_set_state(thread,
 499                                    x86_FLOAT_STATE64,
 500                                    (thread_state_t) thread_state.rbx,
 501                                    /* &thread_state, */
 502                                    float_state_count);
 503         } else {
 504
 505             backup_thread_state = thread_state;
 506             open_stack_allocation(&thread_state);
 507
 508             /* Save thread state */
 509             target_thread_state =
 510                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 511             (*target_thread_state) = backup_thread_state;
 512
 513             target_float_state =
 514                 stack_allocate(&thread_state, sizeof(*target_float_state));
 515             (*target_float_state) = float_state;
 516
 517             /* Set up siginfo */
 518             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 519             /* what do we need to put in our fake siginfo?  It looks like
 520              * the x86 code only uses si_signo and si_adrr. */
 521             if (*((unsigned short *)target_thread_state->rip) == 0x0b0f) {
 522                 signal = SIGTRAP;
 523                 siginfo->si_signo = signal;
 524                 siginfo->si_addr = (void*)exception_state.faultvaddr;
 525                 target_thread_state->rip += 2;
 526                 call_c_function_in_context(&thread_state,
 527                                            signal_emulation_wrapper,
 528                                            5,
 529                                            target_thread_state,
 530                                            target_float_state,
 531                                            signal,
 532                                            siginfo,
 533                                            sigtrap_handler);
 534             } else {
 535                 signal = SIGILL;
 536                 siginfo->si_signo = signal;
 537                 siginfo->si_addr = (void*)exception_state.faultvaddr;
 538
 539                 call_c_function_in_context(&thread_state,
 540                                            signal_emulation_wrapper,
 541                                            5,
 542                                            target_thread_state,
 543                                            target_float_state,
 544                                            signal,
 545                                            siginfo,
 546                                            sigill_handler);
 547             }
 548             ret = thread_set_state(thread,
 549                                    x86_THREAD_STATE64,
 550                                    (thread_state_t)&thread_state,
 551                                    thread_state_count);
 552             ret = thread_set_state(thread,
 553                                    x86_FLOAT_STATE64,
 554                                    (thread_state_t)&float_state,
 555                                    float_state_count);
 556         }
 557 #ifdef LISP_FEATURE_SB_THREAD
 558         thread_mutex_unlock(&mach_exception_lock);
 559 #endif
 560         return KERN_SUCCESS;
 561
 562     default:
 563 #ifdef LISP_FEATURE_SB_THREAD
 564         thread_mutex_unlock(&mach_exception_lock);
 565 #endif
 566         return KERN_INVALID_RIGHT;
 567     }
 568 }
 569
 570 void *
 571 mach_exception_handler(void *port)
 572 {
 573   mach_msg_server(exc_server, 2048, (mach_port_t) port, 0);
 574   /* mach_msg_server should never return, but it should dispatch mach
 575    * exceptions to our catch_exception_raise function
 576    */
 577   abort();
 578 }
 579
 580 /* Sets up the thread that will listen for mach exceptions. note that
 581    the exception handlers will be run on this thread. This is
 582    different from the BSD-style signal handling situation in which the
 583    signal handlers run in the relevant thread directly. */
 584
 585 mach_port_t mach_exception_handler_port_set = MACH_PORT_NULL;
 586
 587 pthread_t
 588 setup_mach_exception_handling_thread()
 589 {
 590     kern_return_t ret;
 591     pthread_t mach_exception_handling_thread = NULL;
 592     pthread_attr_t attr;
 593
 594     /* allocate a mach_port for this process */
 595     ret = mach_port_allocate(mach_task_self(),
 596                              MACH_PORT_RIGHT_PORT_SET,
 597                              &mach_exception_handler_port_set);
 598
 599     /* create the thread that will receive the mach exceptions */
 600
 601     FSHOW((stderr, "Creating mach_exception_handler thread!\n"));
 602
 603     pthread_attr_init(&attr);
 604     pthread_create(&mach_exception_handling_thread,
 605                    &attr,
 606                    mach_exception_handler,
 607                    (void*) mach_exception_handler_port_set);
 608     pthread_attr_destroy(&attr);
 609
 610     return mach_exception_handling_thread;
 611 }
 612
 613 /* tell the kernel that we want EXC_BAD_ACCESS exceptions sent to the
 614    exception port (which is being listened to do by the mach
 615    exception handling thread). */
 616 kern_return_t
 617 mach_thread_init(mach_port_t thread_exception_port)
 618 {
 619     kern_return_t ret;
 620     /* allocate a named port for the thread */
 621
 622     FSHOW((stderr, "Allocating mach port %x\n", thread_exception_port));
 623
 624     ret = mach_port_allocate_name(mach_task_self(),
 625                                   MACH_PORT_RIGHT_RECEIVE,
 626                                   thread_exception_port);
 627     if (ret) {
 628         lose("mach_port_allocate_name failed with return_code %d\n", ret);
 629     }
 630
 631     /* establish the right for the thread_exception_port to send messages */
 632     ret = mach_port_insert_right(mach_task_self(),
 633                                  thread_exception_port,
 634                                  thread_exception_port,
 635                                  MACH_MSG_TYPE_MAKE_SEND);
 636     if (ret) {
 637         lose("mach_port_insert_right failed with return_code %d\n", ret);
 638     }
 639
 640     ret = thread_set_exception_ports(mach_thread_self(),
 641                                      EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION,
 642                                      thread_exception_port,
 643                                      EXCEPTION_DEFAULT,
 644                                      THREAD_STATE_NONE);
 645     if (ret) {
 646         lose("thread_set_exception_port failed with return_code %d\n", ret);
 647     }
 648
 649     ret = mach_port_move_member(mach_task_self(),
 650                                 thread_exception_port,
 651                                 mach_exception_handler_port_set);
 652     if (ret) {
 653         lose("mach_port_ failed with return_code %d\n", ret);
 654     }
 655
 656     return ret;
 657 }
 658
 659 void
 660 setup_mach_exceptions() {
 661     setup_mach_exception_handling_thread();
 662     mach_thread_init(THREAD_STRUCT_TO_EXCEPTION_PORT(all_threads));
 663 }
 664
 665 pid_t
 666 mach_fork() {
 667     pid_t pid = fork();
 668     if (pid == 0) {
 669         setup_mach_exceptions();
 670         return pid;
 671     } else {
 672         return pid;
 673     }
 674 }
 675
 676 #endif