src/runtime/x86-darwin-os.c

   1
   2
   3 #ifdef LISP_FEATURE_SB_THREAD
   4 #include <architecture/i386/table.h>
   5 #include <i386/user_ldt.h>
   6 #include <mach/mach_init.h>
   7 #endif
   8
   9 #include "thread.h"
  10 #include "validate.h"
  11 #include "runtime.h"
  12 #include "interrupt.h"
  13 #include "x86-darwin-os.h"
  14 #include "genesis/fdefn.h"
  15
  16 #include <mach/mach.h>
  17 #include <mach/mach_error.h>
  18 #include <mach/mach_types.h>
  19 #include <mach/sync_policy.h>
  20 #include <mach/vm_region.h>
  21 #include <mach/machine/thread_state.h>
  22 #include <mach/machine/thread_status.h>
  23 #include <sys/_types.h>
  24 #include <sys/ucontext.h>
  25 #include <pthread.h>
  26 #include <assert.h>
  27 #include <stdlib.h>
  28
  29 #ifdef LISP_FEATURE_SB_THREAD
  30
  31 pthread_mutex_t modify_ldt_lock = PTHREAD_MUTEX_INITIALIZER;
  32
  33 void set_data_desc_size(data_desc_t* desc, unsigned long size)
  34 {
  35     desc->limit00 = (size - 1) & 0xffff;
  36     desc->limit16 = ((size - 1) >> 16) &0xf;
  37 }
  38
  39 void set_data_desc_addr(data_desc_t* desc, void* addr)
  40 {
  41     desc->base00 = (unsigned int)addr & 0xffff;
  42     desc->base16 = ((unsigned int)addr & 0xff0000) >> 16;
  43     desc->base24 = ((unsigned int)addr & 0xff000000) >> 24;
  44 }
  45
  46 #endif
  47
  48 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
  49 kern_return_t mach_thread_init(mach_port_t thread_exception_port);
  50 #endif
  51
  52 int arch_os_thread_init(struct thread *thread) {
  53 #ifdef LISP_FEATURE_SB_THREAD
  54     int n;
  55     sel_t sel;
  56
  57     data_desc_t ldt_entry = { 0, 0, 0, DESC_DATA_WRITE,
  58                               3, 1, 0, DESC_DATA_32B, DESC_GRAN_BYTE, 0 };
  59
  60     set_data_desc_addr(&ldt_entry, thread);
  61     set_data_desc_size(&ldt_entry, dynamic_values_bytes);
  62
  63     thread_mutex_lock(&modify_ldt_lock);
  64     n = i386_set_ldt(LDT_AUTO_ALLOC, (union ldt_entry*) &ldt_entry, 1);
  65
  66     if (n < 0) {
  67         perror("i386_set_ldt");
  68         lose("unexpected i386_set_ldt(..) failure\n");
  69     }
  70     thread_mutex_unlock(&modify_ldt_lock);
  71
  72     FSHOW_SIGNAL((stderr, "/ TLS: Allocated LDT %x\n", n));
  73     sel.index = n;
  74     sel.rpl = USER_PRIV;
  75     sel.ti = SEL_LDT;
  76
  77     __asm__ __volatile__ ("mov %0, %%fs" : : "r"(sel));
  78
  79     thread->tls_cookie=n;
  80     pthread_setspecific(specials,thread);
  81 #endif
  82 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
  83     mach_thread_init(THREAD_STRUCT_TO_EXCEPTION_PORT(thread));
  84 #endif
  85
  86 #ifdef LISP_FEATURE_C_STACK_IS_CONTROL_STACK
  87     stack_t sigstack;
  88
  89     /* Signal handlers are run on the control stack, so if it is exhausted
  90      * we had better use an alternate stack for whatever signal tells us
  91      * we've exhausted it */
  92     sigstack.ss_sp=((void *) thread)+dynamic_values_bytes;
  93     sigstack.ss_flags=0;
  94     sigstack.ss_size = 32*SIGSTKSZ;
  95     sigaltstack(&sigstack,0);
  96 #endif
  97     return 1;                  /* success */
  98 }
  99
 100 int arch_os_thread_cleanup(struct thread *thread) {
 101 #if defined(LISP_FEATURE_SB_THREAD)
 102     int n = thread->tls_cookie;
 103
 104     /* Set the %%fs register back to 0 and free the ldt by setting it
 105      * to NULL.
 106      */
 107     FSHOW_SIGNAL((stderr, "/ TLS: Freeing LDT %x\n", n));
 108
 109     __asm__ __volatile__ ("mov %0, %%fs" : : "r"(0));
 110     thread_mutex_lock(&modify_ldt_lock);
 111     i386_set_ldt(n, NULL, 1);
 112     thread_mutex_unlock(&modify_ldt_lock);
 113 #endif
 114     return 1;                  /* success */
 115 }
 116
 117 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 118
 119 void sigill_handler(int signal, siginfo_t *siginfo, os_context_t *context);
 120 void sigtrap_handler(int signal, siginfo_t *siginfo, os_context_t *context);
 121 void memory_fault_handler(int signal, siginfo_t *siginfo,
 122                           os_context_t *context);
 123
 124 /* exc_server handles mach exception messages from the kernel and
 125  * calls catch exception raise. We use the system-provided
 126  * mach_msg_server, which, I assume, calls exc_server in a loop.
 127  *
 128  */
 129 extern boolean_t exc_server();
 130
 131 /* This executes in the faulting thread as part of the signal
 132  * emulation.  It is passed a context with the uc_mcontext field
 133  * pointing to a valid block of memory. */
 134 void build_fake_signal_context(os_context_t *context,
 135                                x86_thread_state32_t *thread_state,
 136                                x86_float_state32_t *float_state) {
 137     pthread_sigmask(0, NULL, &context->uc_sigmask);
 138     context->uc_mcontext->SS = *thread_state;
 139     context->uc_mcontext->FS = *float_state;
 140 }
 141
 142 /* This executes in the faulting thread as part of the signal
 143  * emulation.  It is effectively the inverse operation from above. */
 144 void update_thread_state_from_context(x86_thread_state32_t *thread_state,
 145                                       x86_float_state32_t *float_state,
 146                                       os_context_t *context) {
 147     *thread_state = context->uc_mcontext->SS;
 148     *float_state = context->uc_mcontext->FS;
 149     pthread_sigmask(SIG_SETMASK, &context->uc_sigmask, NULL);
 150 }
 151
 152 /* Modify a context to push new data on its stack. */
 153 void push_context(u32 data, x86_thread_state32_t *thread_state)
 154 {
 155     u32 *stack_pointer;
 156
 157     stack_pointer = (u32*) thread_state->ESP;
 158     *(--stack_pointer) = data;
 159     thread_state->ESP = (unsigned int) stack_pointer;
 160 }
 161
 162 void align_context_stack(x86_thread_state32_t *thread_state)
 163 {
 164     /* 16byte align the stack (provided that the stack is, as it
 165      * should be, 4byte aligned. */
 166     while (thread_state->ESP & 15) push_context(0, thread_state);
 167 }
 168
 169 /* Stack allocation starts with a context that has a mod-4 ESP value
 170  * and needs to leave a context with a mod-16 ESP that will restore
 171  * the old ESP value and other register state when activated.  The
 172  * first part of this is the recovery trampoline, which loads ESP from
 173  * EBP, pops EBP, and returns. */
 174 asm("_stack_allocation_recover: movl %ebp, %esp; popl %ebp; ret;");
 175
 176 void open_stack_allocation(x86_thread_state32_t *thread_state)
 177 {
 178     void stack_allocation_recover(void);
 179
 180     push_context(thread_state->EIP, thread_state);
 181     push_context(thread_state->EBP, thread_state);
 182     thread_state->EBP = thread_state->ESP;
 183     thread_state->EIP = (unsigned int) stack_allocation_recover;
 184
 185     align_context_stack(thread_state);
 186 }
 187
 188 /* Stack allocation of data starts with a context with a mod-16 ESP
 189  * value and reserves some space on it by manipulating the ESP
 190  * register. */
 191 void *stack_allocate(x86_thread_state32_t *thread_state, size_t size)
 192 {
 193     /* round up size to 16byte multiple */
 194     size = (size + 15) & -16;
 195
 196     thread_state->ESP = ((u32)thread_state->ESP) - size;
 197
 198     return (void *)thread_state->ESP;
 199 }
 200
 201 /* Arranging to invoke a C function is tricky, as we have to assume
 202  * cdecl calling conventions (caller removes args) and x86/darwin
 203  * alignment requirements.  The simplest way to arrange this,
 204  * actually, is to open a new stack allocation.
 205  * WARNING!!! THIS DOES NOT PRESERVE REGISTERS! */
 206 void call_c_function_in_context(x86_thread_state32_t *thread_state,
 207                                 void *function,
 208                                 int nargs,
 209                                 ...)
 210 {
 211     va_list ap;
 212     int i;
 213     u32 *stack_pointer;
 214
 215     /* Set up to restore stack on exit. */
 216     open_stack_allocation(thread_state);
 217
 218     /* Have to keep stack 16byte aligned on x86/darwin. */
 219     for (i = (3 & -nargs); i; i--) {
 220         push_context(0, thread_state);
 221     }
 222
 223     thread_state->ESP = ((u32)thread_state->ESP) - nargs * 4;
 224     stack_pointer = (u32 *)thread_state->ESP;
 225
 226     va_start(ap, nargs);
 227     for (i = 0; i < nargs; i++) {
 228         //push_context(va_arg(ap, u32), thread_state);
 229         stack_pointer[i] = va_arg(ap, u32);
 230     }
 231     va_end(ap);
 232
 233     push_context(thread_state->EIP, thread_state);
 234     thread_state->EIP = (unsigned int) function;
 235 }
 236
 237 void signal_emulation_wrapper(x86_thread_state32_t *thread_state,
 238                               x86_float_state32_t *float_state,
 239                               int signal,
 240                               siginfo_t *siginfo,
 241                               void (*handler)(int, siginfo_t *, void *))
 242 {
 243
 244     /* CLH: FIXME **NOTE: HACK ALERT!** Ideally, we would allocate
 245      * context and regs on the stack as local variables, but this
 246      * causes problems for the lisp debugger. When it walks the stack
 247      * for a back trace, it sees the 1) address of the local variable
 248      * on the stack and thinks that is a frame pointer to a lisp
 249      * frame, and, 2) the address of the sap that we alloc'ed in
 250      * dynamic space and thinks that is a return address, so it,
 251      * heuristicly (and wrongly), chooses that this should be
 252      * interpreted as a lisp frame instead of as a C frame.
 253      * We can work around this in this case by os_validating the
 254      * context (and regs just for symmetry).
 255      */
 256
 257     os_context_t *context;
 258     mcontext_t *regs;
 259
 260     context = (os_context_t*) os_validate(0, sizeof(os_context_t));
 261     regs = (mcontext_t*) os_validate(0, sizeof(mcontext_t));
 262     context->uc_mcontext = regs;
 263
 264     /* when BSD signals are fired, they mask they signals in sa_mask
 265        which always seem to be the blockable_sigset, for us, so we
 266        need to:
 267        1) save the current sigmask
 268        2) block blockable signals
 269        3) call the signal handler
 270        4) restore the sigmask */
 271
 272     build_fake_signal_context(context, thread_state, float_state);
 273
 274     block_blockable_signals();
 275
 276     handler(signal, siginfo, context);
 277
 278     update_thread_state_from_context(thread_state, float_state, context);
 279
 280     os_invalidate((os_vm_address_t)context, sizeof(os_context_t));
 281     os_invalidate((os_vm_address_t)regs, sizeof(mcontext_t));
 282
 283     /* Trap to restore the signal context. */
 284     asm volatile ("movl %0, %%eax; movl %1, %%ebx; .long 0xffff0b0f"
 285                   : : "r" (thread_state), "r" (float_state));
 286 }
 287
 288 /* Convenience wrapper for the above */
 289 void call_handler_on_thread(mach_port_t thread,
 290                             x86_thread_state32_t *thread_state,
 291                             int signal,
 292                             siginfo_t *siginfo,
 293                             void (*handler)(int, siginfo_t *, void *))
 294 {
 295     x86_thread_state32_t new_state;
 296     x86_thread_state32_t *save_thread_state;
 297     x86_float_state32_t *save_float_state;
 298     mach_msg_type_number_t state_count;
 299     siginfo_t *save_siginfo;
 300     kern_return_t ret;
 301     /* Initialize the new state */
 302     new_state = *thread_state;
 303     open_stack_allocation(&new_state);
 304     stack_allocate(&new_state, 256);
 305     /* Save old state */
 306     save_thread_state = (x86_thread_state32_t *)stack_allocate(&new_state, sizeof(*save_thread_state));
 307     *save_thread_state = *thread_state;
 308     /* Save float state */
 309     save_float_state = (x86_float_state32_t *)stack_allocate(&new_state, sizeof(*save_float_state));
 310     state_count = x86_FLOAT_STATE32_COUNT;
 311     if ((ret = thread_get_state(thread,
 312                                 x86_FLOAT_STATE32,
 313                                 (thread_state_t)save_float_state,
 314                                 &state_count)) != KERN_SUCCESS)
 315         lose("thread_get_state (x86_THREAD_STATE32) failed %d\n", ret);
 316     /* Set up siginfo */
 317     save_siginfo = stack_allocate(&new_state, sizeof(*siginfo));
 318     if (siginfo == NULL)
 319         save_siginfo = siginfo;
 320     else
 321         *save_siginfo = *siginfo;
 322     /* Prepare to call */
 323     call_c_function_in_context(&new_state,
 324                                signal_emulation_wrapper,
 325                                5,
 326                                save_thread_state,
 327                                save_float_state,
 328                                signal,
 329                                save_siginfo,
 330                                handler);
 331     /* Update the thread state */
 332     state_count = x86_THREAD_STATE32_COUNT;
 333     if ((ret = thread_set_state(thread,
 334                                 x86_THREAD_STATE32,
 335                                 (thread_state_t)&new_state,
 336                                 state_count)) != KERN_SUCCESS)
 337         lose("thread_set_state (x86_FLOAT_STATE32) failed %d\n", ret);
 338
 339 }
 340
 341 #if defined DUMP_CONTEXT
 342 void dump_context(x86_thread_state32_t *thread_state)
 343 {
 344     int i;
 345     u32 *stack_pointer;
 346
 347     printf("eax: %08lx  ecx: %08lx  edx: %08lx  ebx: %08lx\n",
 348            thread_state->EAX, thread_state->ECX, thread_state->EDX, thread_state->EAX);
 349     printf("esp: %08lx  ebp: %08lx  esi: %08lx  edi: %08lx\n",
 350            thread_state->ESP, thread_state->EBP, thread_state->ESI, thread_state->EDI);
 351     printf("eip: %08lx  eflags: %08lx\n",
 352            thread_state->EIP, thread_state->EFLAGS);
 353     printf("cs: %04hx  ds: %04hx  es: %04hx  "
 354            "ss: %04hx  fs: %04hx  gs: %04hx\n",
 355            thread_state->CS,
 356            thread_state->DS,
 357            thread_state->ES,
 358            thread_state->SS,
 359            thread_state->FS,
 360            thread_state->GS);
 361
 362     stack_pointer = (u32 *)thread_state->ESP;
 363     for (i = 0; i < 48; i+=4) {
 364         printf("%08x:  %08x %08x %08x %08x\n",
 365                thread_state->ESP + (i * 4),
 366                stack_pointer[i],
 367                stack_pointer[i+1],
 368                stack_pointer[i+2],
 369                stack_pointer[i+3]);
 370     }
 371 }
 372 #endif
 373
 374 void
 375 control_stack_exhausted_handler(int signal, siginfo_t *siginfo,
 376                                 os_context_t *context) {
 377
 378     unblock_signals_in_context_and_maybe_warn(context);
 379     arrange_return_to_lisp_function
 380         (context, StaticSymbolFunction(CONTROL_STACK_EXHAUSTED_ERROR));
 381 }
 382
 383 void
 384 undefined_alien_handler(int signal, siginfo_t *siginfo, os_context_t *context) {
 385     arrange_return_to_lisp_function
 386         (context, StaticSymbolFunction(UNDEFINED_ALIEN_VARIABLE_ERROR));
 387 }
 388
 389 kern_return_t
 390 catch_exception_raise(mach_port_t exception_port,
 391                       mach_port_t thread,
 392                       mach_port_t task,
 393                       exception_type_t exception,
 394                       exception_data_t code_vector,
 395                       mach_msg_type_number_t code_count)
 396 {
 397     struct thread *th = (struct thread*) exception_port;
 398     x86_thread_state32_t thread_state;
 399     mach_msg_type_number_t state_count;
 400     vm_address_t region_addr;
 401     vm_size_t region_size;
 402     vm_region_basic_info_data_t region_info;
 403     mach_msg_type_number_t info_count;
 404     mach_port_t region_name;
 405     void *addr = NULL;
 406     int signal = 0;
 407     void (*handler)(int, siginfo_t *, void *) = NULL;
 408     siginfo_t siginfo;
 409     kern_return_t ret;
 410
 411     /* Get state and info */
 412     state_count = x86_THREAD_STATE32_COUNT;
 413     if ((ret = thread_get_state(thread,
 414                                 x86_THREAD_STATE32,
 415                                 (thread_state_t)&thread_state,
 416                                 &state_count)) != KERN_SUCCESS)
 417         lose("thread_get_state (x86_THREAD_STATE32) failed %d\n", ret);
 418     switch (exception) {
 419     case EXC_BAD_ACCESS:
 420         signal = SIGBUS;
 421         /* Check if write protection fault */
 422         if ((code_vector[0] & OS_VM_PROT_ALL) == 0) {
 423             ret = KERN_INVALID_RIGHT;
 424             break;
 425         }
 426         addr = (void*)code_vector[1];
 427         /* Undefined alien */
 428         if (os_trunc_to_page(addr) == undefined_alien_address) {
 429             handler = undefined_alien_handler;
 430             break;
 431         }
 432         /* At stack guard */
 433         if (os_trunc_to_page(addr) == CONTROL_STACK_GUARD_PAGE(th)) {
 434             protect_control_stack_guard_page(0, th);
 435             protect_control_stack_return_guard_page(1, th);
 436             handler = control_stack_exhausted_handler;
 437             break;
 438         }
 439         /* Return from stack guard */
 440         if (os_trunc_to_page(addr) == CONTROL_STACK_RETURN_GUARD_PAGE(th)) {
 441             protect_control_stack_guard_page(1, th);
 442             protect_control_stack_return_guard_page(0, th);
 443             break;
 444         }
 445         /* Regular memory fault */
 446         handler = memory_fault_handler;
 447         break;
 448     case EXC_BAD_INSTRUCTION:
 449         signal = SIGTRAP;
 450         /* Check if illegal instruction trap */
 451         if (code_vector[0] != EXC_I386_INVOP) {
 452             ret = KERN_INVALID_RIGHT;
 453             break;
 454         }
 455         /* Check if UD2 instruction */
 456         if (*(unsigned short *)thread_state.EIP != 0x0b0f) {
 457             /* KLUDGE: There are two ways we could get here:
 458              * 1) We're executing data and we've hit some truly
 459              *    illegal opcode, of which there are a few, see
 460              *    Intel 64 and IA-32 Architectures
 461              *    Sofware Developer's Manual
 462              *    Volume 3A page 5-34)
 463              * 2) The kernel started an unrelated signal handler
 464              *    before we got a chance to run. The context that
 465              *    caused the exception is saved in a stack frame
 466              *    somewhere down below.
 467              * In either case we rely on the exception to retrigger,
 468              * eventually bailing out if we're spinning on case 2).
 469              */
 470             static mach_port_t last_thread;
 471             static unsigned int last_eip;
 472             if (last_thread == thread && last_eip == thread_state.EIP)
 473                 ret = KERN_INVALID_RIGHT;
 474             else
 475                 ret = KERN_SUCCESS;
 476             last_thread = thread;
 477             last_eip = thread_state.EIP;
 478             break;
 479         }
 480         /* Skip the trap code */
 481         thread_state.EIP += 2;
 482         /* Return from handler? */
 483         if (*(unsigned short *)thread_state.EIP == 0xffff) {
 484             if ((ret = thread_set_state(thread,
 485                                         x86_THREAD_STATE32,
 486                                         (thread_state_t)thread_state.EAX,
 487                                         x86_THREAD_STATE32_COUNT)) != KERN_SUCCESS)
 488                 lose("thread_set_state (x86_THREAD_STATE32) failed %d\n", ret);
 489             if ((ret = thread_set_state(thread,
 490                                         x86_FLOAT_STATE32,
 491                                         (thread_state_t)thread_state.EBX,
 492                                         x86_FLOAT_STATE32_COUNT)) != KERN_SUCCESS)
 493                 lose("thread_set_state (x86_FLOAT_STATE32) failed %d\n", ret);
 494             break;
 495         }
 496         /* Trap call */
 497         handler = sigtrap_handler;
 498         break;
 499     default:
 500         ret = KERN_INVALID_RIGHT;
 501     }
 502     /* Call handler */
 503     if (handler != 0) {
 504       siginfo.si_signo = signal;
 505       siginfo.si_addr = addr;
 506       call_handler_on_thread(thread, &thread_state, signal, &siginfo, handler);
 507     }
 508     return ret;
 509 }
 510
 511 void *
 512 mach_exception_handler(void *port)
 513 {
 514   mach_msg_server(exc_server, 2048, (mach_port_t) port, 0);
 515   /* mach_msg_server should never return, but it should dispatch mach
 516    * exceptions to our catch_exception_raise function
 517    */
 518   abort();
 519 }
 520
 521 #endif
 522
 523 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 524
 525 /* Sets up the thread that will listen for mach exceptions. note that
 526    the exception handlers will be run on this thread. This is
 527    different from the BSD-style signal handling situation in which the
 528    signal handlers run in the relevant thread directly. */
 529
 530 mach_port_t mach_exception_handler_port_set = MACH_PORT_NULL;
 531
 532 pthread_t
 533 setup_mach_exception_handling_thread()
 534 {
 535     kern_return_t ret;
 536     pthread_t mach_exception_handling_thread = NULL;
 537     pthread_attr_t attr;
 538
 539     /* allocate a mach_port for this process */
 540     ret = mach_port_allocate(mach_task_self(),
 541                              MACH_PORT_RIGHT_PORT_SET,
 542                              &mach_exception_handler_port_set);
 543
 544     /* create the thread that will receive the mach exceptions */
 545
 546     FSHOW((stderr, "Creating mach_exception_handler thread!\n"));
 547
 548     pthread_attr_init(&attr);
 549     pthread_create(&mach_exception_handling_thread,
 550                    &attr,
 551                    mach_exception_handler,
 552                    (void*) mach_exception_handler_port_set);
 553     pthread_attr_destroy(&attr);
 554
 555     return mach_exception_handling_thread;
 556 }
 557
 558 /* tell the kernel that we want EXC_BAD_ACCESS exceptions sent to the
 559    exception port (which is being listened to do by the mach
 560    exception handling thread). */
 561 kern_return_t
 562 mach_thread_init(mach_port_t thread_exception_port)
 563 {
 564     kern_return_t ret;
 565     /* allocate a named port for the thread */
 566
 567     FSHOW((stderr, "Allocating mach port %x\n", thread_exception_port));
 568
 569     ret = mach_port_allocate_name(mach_task_self(),
 570                                   MACH_PORT_RIGHT_RECEIVE,
 571                                   thread_exception_port);
 572     if (ret) {
 573         lose("mach_port_allocate_name failed with return_code %d\n", ret);
 574     }
 575
 576     /* establish the right for the thread_exception_port to send messages */
 577     ret = mach_port_insert_right(mach_task_self(),
 578                                  thread_exception_port,
 579                                  thread_exception_port,
 580                                  MACH_MSG_TYPE_MAKE_SEND);
 581     if (ret) {
 582         lose("mach_port_insert_right failed with return_code %d\n", ret);
 583     }
 584
 585     ret = thread_set_exception_ports(mach_thread_self(),
 586                                      EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION,
 587                                      thread_exception_port,
 588                                      EXCEPTION_DEFAULT,
 589                                      THREAD_STATE_NONE);
 590     if (ret) {
 591         lose("thread_set_exception_port failed with return_code %d\n", ret);
 592     }
 593
 594     ret = mach_port_move_member(mach_task_self(),
 595                                 thread_exception_port,
 596                                 mach_exception_handler_port_set);
 597     if (ret) {
 598         lose("mach_port_ failed with return_code %d\n", ret);
 599     }
 600
 601     return ret;
 602 }
 603
 604 void
 605 setup_mach_exceptions() {
 606     setup_mach_exception_handling_thread();
 607     mach_thread_init(THREAD_STRUCT_TO_EXCEPTION_PORT(all_threads));
 608 }
 609
 610 pid_t
 611 mach_fork() {
 612     pid_t pid = fork();
 613     if (pid == 0) {
 614         setup_mach_exceptions();
 615         return pid;
 616     } else {
 617         return pid;
 618     }
 619 }
 620
 621 #endif