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/machine/thread_state.h>
  21 #include <mach/machine/thread_status.h>
  22 #include <sys/_types.h>
  23 #include <sys/ucontext.h>
  24 #include <pthread.h>
  25 #include <assert.h>
  26 #include <stdlib.h>
  27
  28 #ifdef LISP_FEATURE_SB_THREAD
  29
  30 pthread_mutex_t modify_ldt_lock = PTHREAD_MUTEX_INITIALIZER;
  31 pthread_mutex_t mach_exception_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, void *void_context);
 120 void sigtrap_handler(int signal, siginfo_t *siginfo, void *void_context);
 121 void memory_fault_handler(int signal, siginfo_t *siginfo, void *void_context);
 122
 123 /* exc_server handles mach exception messages from the kernel and
 124  * calls catch exception raise. We use the system-provided
 125  * mach_msg_server, which, I assume, calls exc_server in a loop.
 126  *
 127  */
 128 extern boolean_t exc_server();
 129
 130 /* This executes in the faulting thread as part of the signal
 131  * emulation.  It is passed a context with the uc_mcontext field
 132  * pointing to a valid block of memory. */
 133 void build_fake_signal_context(struct ucontext *context,
 134                                x86_thread_state32_t *thread_state,
 135                                x86_float_state32_t *float_state) {
 136     pthread_sigmask(0, NULL, &context->uc_sigmask);
 137     context->uc_mcontext->ss = *thread_state;
 138     context->uc_mcontext->fs = *float_state;
 139 }
 140
 141 /* This executes in the faulting thread as part of the signal
 142  * emulation.  It is effectively the inverse operation from above. */
 143 void update_thread_state_from_context(x86_thread_state32_t *thread_state,
 144                                       x86_float_state32_t *float_state,
 145                                       struct ucontext *context) {
 146     *thread_state = context->uc_mcontext->ss;
 147     *float_state = context->uc_mcontext->fs;
 148     pthread_sigmask(SIG_SETMASK, &context->uc_sigmask, NULL);
 149 }
 150
 151 /* Modify a context to push new data on its stack. */
 152 void push_context(u32 data, x86_thread_state32_t *context)
 153 {
 154     u32 *stack_pointer;
 155
 156     stack_pointer = (u32*) context->esp;
 157     *(--stack_pointer) = data;
 158     context->esp = (unsigned int) stack_pointer;
 159 }
 160
 161 void align_context_stack(x86_thread_state32_t *context)
 162 {
 163     /* 16byte align the stack (provided that the stack is, as it
 164      * should be, 4byte aligned. */
 165     while (context->esp & 15) push_context(0, context);
 166 }
 167
 168 /* Stack allocation starts with a context that has a mod-4 ESP value
 169  * and needs to leave a context with a mod-16 ESP that will restore
 170  * the old ESP value and other register state when activated.  The
 171  * first part of this is the recovery trampoline, which loads ESP from
 172  * EBP, pops EBP, and returns. */
 173 asm("_stack_allocation_recover: movl %ebp, %esp; popl %ebp; ret;");
 174
 175 void open_stack_allocation(x86_thread_state32_t *context)
 176 {
 177     void stack_allocation_recover(void);
 178
 179     push_context(context->eip, context);
 180     push_context(context->ebp, context);
 181     context->ebp = context->esp;
 182     context->eip = (unsigned int) stack_allocation_recover;
 183
 184     align_context_stack(context);
 185 }
 186
 187 /* Stack allocation of data starts with a context with a mod-16 ESP
 188  * value and reserves some space on it by manipulating the ESP
 189  * register. */
 190 void *stack_allocate(x86_thread_state32_t *context, size_t size)
 191 {
 192     /* round up size to 16byte multiple */
 193     size = (size + 15) & -16;
 194
 195     context->esp = ((u32)context->esp) - size;
 196
 197     return (void *)context->esp;
 198 }
 199
 200 /* Arranging to invoke a C function is tricky, as we have to assume
 201  * cdecl calling conventions (caller removes args) and x86/darwin
 202  * alignment requirements.  The simplest way to arrange this,
 203  * actually, is to open a new stack allocation.
 204  * WARNING!!! THIS DOES NOT PRESERVE REGISTERS! */
 205 void call_c_function_in_context(x86_thread_state32_t *context,
 206                                 void *function,
 207                                 int nargs,
 208                                 ...)
 209 {
 210     va_list ap;
 211     int i;
 212     u32 *stack_pointer;
 213
 214     /* Set up to restore stack on exit. */
 215     open_stack_allocation(context);
 216
 217     /* Have to keep stack 16byte aligned on x86/darwin. */
 218     for (i = (3 & -nargs); i; i--) {
 219         push_context(0, context);
 220     }
 221
 222     context->esp = ((u32)context->esp) - nargs * 4;
 223     stack_pointer = (u32 *)context->esp;
 224
 225     va_start(ap, nargs);
 226     for (i = 0; i < nargs; i++) {
 227         //push_context(va_arg(ap, u32), context);
 228         stack_pointer[i] = va_arg(ap, u32);
 229     }
 230     va_end(ap);
 231
 232     push_context(context->eip, context);
 233     context->eip = (unsigned int) function;
 234 }
 235
 236 void signal_emulation_wrapper(x86_thread_state32_t *thread_state,
 237                               x86_float_state32_t *float_state,
 238                               int signal,
 239                               siginfo_t *siginfo,
 240                               void (*handler)(int, siginfo_t *, void *))
 241 {
 242
 243     /* CLH: FIXME **NOTE: HACK ALERT!** Ideally, we would allocate
 244      * context and regs on the stack as local variables, but this
 245      * causes problems for the lisp debugger. When it walks the stack
 246      * for a back trace, it sees the 1) address of the local variable
 247      * on the stack and thinks that is a frame pointer to a lisp
 248      * frame, and, 2) the address of the sap that we alloc'ed in
 249      * dynamic space and thinks that is a return address, so it,
 250      * heuristicly (and wrongly), chooses that this should be
 251      * interpreted as a lisp frame instead of as a C frame.
 252      * We can work around this in this case by os_validating the
 253      * context (and regs just for symmetry).
 254      */
 255
 256     struct ucontext *context;
 257     struct mcontext *regs;
 258
 259     context = (struct ucontext*) os_validate(0, sizeof(struct ucontext));
 260     regs = (struct mcontext*) os_validate(0, sizeof(struct mcontext));
 261     context->uc_mcontext = regs;
 262
 263     /* when BSD signals are fired, they mask they signals in sa_mask
 264        which always seem to be the blockable_sigset, for us, so we
 265        need to:
 266        1) save the current sigmask
 267        2) block blockable signals
 268        3) call the signal handler
 269        4) restore the sigmask */
 270
 271     build_fake_signal_context(context, thread_state, float_state);
 272
 273     block_blockable_signals();
 274
 275     handler(signal, siginfo, context);
 276
 277     update_thread_state_from_context(thread_state, float_state, context);
 278
 279     os_invalidate((os_vm_address_t)context, sizeof(struct ucontext));
 280     os_invalidate((os_vm_address_t)regs, sizeof(struct mcontext));
 281
 282     /* Trap to restore the signal context. */
 283     asm volatile ("movl %0, %%eax; movl %1, %%ebx; .long 0xffff0b0f"
 284                   : : "r" (thread_state), "r" (float_state));
 285 }
 286
 287 #if defined DUMP_CONTEXT
 288 void dump_context(x86_thread_state32_t *context)
 289 {
 290     int i;
 291     u32 *stack_pointer;
 292
 293     printf("eax: %08lx  ecx: %08lx  edx: %08lx  ebx: %08lx\n",
 294            context->eax, context->ecx, context->edx, context->ebx);
 295     printf("esp: %08lx  ebp: %08lx  esi: %08lx  edi: %08lx\n",
 296            context->esp, context->ebp, context->esi, context->edi);
 297     printf("eip: %08lx  eflags: %08lx\n",
 298            context->eip, context->eflags);
 299     printf("cs: %04hx  ds: %04hx  es: %04hx  "
 300            "ss: %04hx  fs: %04hx  gs: %04hx\n",
 301            context->cs, context->ds, context->es,
 302            context->ss, context->fs, context->gs);
 303
 304     stack_pointer = (u32 *)context->esp;
 305     for (i = 0; i < 48; i+=4) {
 306         printf("%08x:  %08x %08x %08x %08x\n",
 307                context->esp + (i * 4),
 308                stack_pointer[i],
 309                stack_pointer[i+1],
 310                stack_pointer[i+2],
 311                stack_pointer[i+3]);
 312     }
 313 }
 314 #endif
 315
 316 void
 317 control_stack_exhausted_handler(int signal, siginfo_t *siginfo, void *void_context) {
 318     os_context_t *context = arch_os_get_context(&void_context);
 319
 320     arrange_return_to_lisp_function
 321         (context, SymbolFunction(CONTROL_STACK_EXHAUSTED_ERROR));
 322 }
 323
 324 void
 325 undefined_alien_handler(int signal, siginfo_t *siginfo, void *void_context) {
 326     os_context_t *context = arch_os_get_context(&void_context);
 327
 328     arrange_return_to_lisp_function
 329         (context, SymbolFunction(UNDEFINED_ALIEN_VARIABLE_ERROR));
 330 }
 331
 332 kern_return_t
 333 catch_exception_raise(mach_port_t exception_port,
 334                       mach_port_t thread,
 335                       mach_port_t task,
 336                       exception_type_t exception,
 337                       exception_data_t code_vector,
 338                       mach_msg_type_number_t code_count)
 339 {
 340     kern_return_t ret;
 341     int signal;
 342     siginfo_t* siginfo;
 343
 344     thread_mutex_lock(&mach_exception_lock);
 345
 346     x86_thread_state32_t thread_state;
 347     mach_msg_type_number_t thread_state_count = x86_THREAD_STATE32_COUNT;
 348
 349     x86_float_state32_t float_state;
 350     mach_msg_type_number_t float_state_count = x86_FLOAT_STATE32_COUNT;
 351
 352     x86_exception_state32_t exception_state;
 353     mach_msg_type_number_t exception_state_count = x86_EXCEPTION_STATE32_COUNT;
 354
 355     x86_thread_state32_t backup_thread_state;
 356     x86_thread_state32_t *target_thread_state;
 357     x86_float_state32_t *target_float_state;
 358
 359     os_vm_address_t addr;
 360
 361     struct thread *th = (struct thread*) exception_port;
 362
 363     FSHOW((stderr,"/entering catch_exception_raise with exception: %d\n", exception));
 364
 365     switch (exception) {
 366
 367     case EXC_BAD_ACCESS:
 368         signal = SIGBUS;
 369         ret = thread_get_state(thread,
 370                                x86_THREAD_STATE32,
 371                                (thread_state_t)&thread_state,
 372                                &thread_state_count);
 373         ret = thread_get_state(thread,
 374                                x86_FLOAT_STATE32,
 375                                (thread_state_t)&float_state,
 376                                &float_state_count);
 377         ret = thread_get_state(thread,
 378                                x86_EXCEPTION_STATE32,
 379                                (thread_state_t)&exception_state,
 380                                &exception_state_count);
 381         addr = (void*)exception_state.faultvaddr;
 382
 383
 384         /* note the os_context hackery here.  When the signal handler returns,
 385          * it won't go back to what it was doing ... */
 386         if(addr >= CONTROL_STACK_GUARD_PAGE(th) &&
 387            addr < CONTROL_STACK_GUARD_PAGE(th) + os_vm_page_size) {
 388             /* We hit the end of the control stack: disable guard page
 389              * protection so the error handler has some headroom, protect the
 390              * previous page so that we can catch returns from the guard page
 391              * and restore it. */
 392             protect_control_stack_guard_page_thread(0, th);
 393             protect_control_stack_return_guard_page_thread(1, th);
 394
 395             backup_thread_state = thread_state;
 396             open_stack_allocation(&thread_state);
 397
 398             /* Save thread state */
 399             target_thread_state =
 400                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 401             (*target_thread_state) = backup_thread_state;
 402
 403             /* Save float state */
 404             target_float_state =
 405                 stack_allocate(&thread_state, sizeof(*target_float_state));
 406             (*target_float_state) = float_state;
 407
 408             /* Set up siginfo */
 409             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 410             /* what do we need to put in our fake siginfo?  It looks like
 411              * the x86 code only uses si_signo and si_adrr. */
 412             siginfo->si_signo = signal;
 413             siginfo->si_addr = (void*)exception_state.faultvaddr;
 414
 415             call_c_function_in_context(&thread_state,
 416                                        signal_emulation_wrapper,
 417                                        5,
 418                                        target_thread_state,
 419                                        target_float_state,
 420                                        signal,
 421                                        siginfo,
 422                                        control_stack_exhausted_handler);
 423         }
 424         else if(addr >= CONTROL_STACK_RETURN_GUARD_PAGE(th) &&
 425                 addr < CONTROL_STACK_RETURN_GUARD_PAGE(th) + os_vm_page_size) {
 426             /* We're returning from the guard page: reprotect it, and
 427              * unprotect this one. This works even if we somehow missed
 428              * the return-guard-page, and hit it on our way to new
 429              * exhaustion instead. */
 430             protect_control_stack_guard_page_thread(1, th);
 431             protect_control_stack_return_guard_page_thread(0, th);
 432         }
 433         else if (addr >= undefined_alien_address &&
 434                  addr < undefined_alien_address + os_vm_page_size) {
 435             backup_thread_state = thread_state;
 436             open_stack_allocation(&thread_state);
 437
 438             /* Save thread state */
 439             target_thread_state =
 440                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 441             (*target_thread_state) = backup_thread_state;
 442
 443             target_float_state =
 444                 stack_allocate(&thread_state, sizeof(*target_float_state));
 445             (*target_float_state) = float_state;
 446
 447             /* Set up siginfo */
 448             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 449             /* what do we need to put in our fake siginfo?  It looks like
 450              * the x86 code only uses si_signo and si_adrr. */
 451             siginfo->si_signo = signal;
 452             siginfo->si_addr = (void*)exception_state.faultvaddr;
 453
 454             call_c_function_in_context(&thread_state,
 455                                        signal_emulation_wrapper,
 456                                        5,
 457                                        target_thread_state,
 458                                        target_float_state,
 459                                        signal,
 460                                        siginfo,
 461                                        undefined_alien_handler);
 462         } else {
 463
 464             backup_thread_state = thread_state;
 465             open_stack_allocation(&thread_state);
 466
 467             /* Save thread state */
 468             target_thread_state =
 469                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 470             (*target_thread_state) = backup_thread_state;
 471
 472             target_float_state =
 473                 stack_allocate(&thread_state, sizeof(*target_float_state));
 474             (*target_float_state) = float_state;
 475
 476             /* Set up siginfo */
 477             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 478             /* what do we need to put in our fake siginfo?  It looks like
 479              * the x86 code only uses si_signo and si_adrr. */
 480             siginfo->si_signo = signal;
 481             siginfo->si_addr = (void*)exception_state.faultvaddr;
 482
 483             call_c_function_in_context(&thread_state,
 484                                        signal_emulation_wrapper,
 485                                        5,
 486                                        target_thread_state,
 487                                        target_float_state,
 488                                        signal,
 489                                        siginfo,
 490                                        memory_fault_handler);
 491         }
 492         ret = thread_set_state(thread,
 493                                x86_THREAD_STATE32,
 494                                (thread_state_t)&thread_state,
 495                                thread_state_count);
 496
 497         ret = thread_set_state(thread,
 498                                x86_FLOAT_STATE32,
 499                                (thread_state_t)&float_state,
 500                                float_state_count);
 501         thread_mutex_unlock(&mach_exception_lock);
 502         return KERN_SUCCESS;
 503
 504     case EXC_BAD_INSTRUCTION:
 505
 506         ret = thread_get_state(thread,
 507                                x86_THREAD_STATE32,
 508                                (thread_state_t)&thread_state,
 509                                &thread_state_count);
 510         ret = thread_get_state(thread,
 511                                x86_FLOAT_STATE32,
 512                                (thread_state_t)&float_state,
 513                                &float_state_count);
 514         ret = thread_get_state(thread,
 515                                x86_EXCEPTION_STATE32,
 516                                (thread_state_t)&exception_state,
 517                                &exception_state_count);
 518         if (0xffff0b0f == *((u32 *)thread_state.eip)) {
 519             /* fake sigreturn. */
 520
 521             /* When we get here, thread_state.eax is a pointer to a
 522              * thread_state to restore. */
 523             /* thread_state = *((thread_state_t *)thread_state.eax); */
 524
 525             ret = thread_set_state(thread,
 526                                    x86_THREAD_STATE32,
 527                                    (thread_state_t) thread_state.eax,
 528                                    /* &thread_state, */
 529                                    thread_state_count);
 530
 531             ret = thread_set_state(thread,
 532                                    x86_FLOAT_STATE32,
 533                                    (thread_state_t) thread_state.ebx,
 534                                    /* &thread_state, */
 535                                    float_state_count);
 536         } else {
 537
 538             backup_thread_state = thread_state;
 539             open_stack_allocation(&thread_state);
 540
 541             /* Save thread state */
 542             target_thread_state =
 543                 stack_allocate(&thread_state, sizeof(*target_thread_state));
 544             (*target_thread_state) = backup_thread_state;
 545
 546             target_float_state =
 547                 stack_allocate(&thread_state, sizeof(*target_float_state));
 548             (*target_float_state) = float_state;
 549
 550             /* Set up siginfo */
 551             siginfo = stack_allocate(&thread_state, sizeof(*siginfo));
 552             /* what do we need to put in our fake siginfo?  It looks like
 553              * the x86 code only uses si_signo and si_adrr. */
 554             if (*((unsigned short *)target_thread_state->eip) == 0x0b0f) {
 555                 signal = SIGTRAP;
 556                 siginfo->si_signo = signal;
 557                 siginfo->si_addr = (void*)exception_state.faultvaddr;
 558                 target_thread_state->eip += 2;
 559                 call_c_function_in_context(&thread_state,
 560                                            signal_emulation_wrapper,
 561                                            5,
 562                                            target_thread_state,
 563                                            target_float_state,
 564                                            signal,
 565                                            siginfo,
 566                                            sigtrap_handler);
 567             } else {
 568                 signal = SIGILL;
 569                 siginfo->si_signo = signal;
 570                 siginfo->si_addr = (void*)exception_state.faultvaddr;
 571
 572                 call_c_function_in_context(&thread_state,
 573                                            signal_emulation_wrapper,
 574                                            5,
 575                                            target_thread_state,
 576                                            target_float_state,
 577                                            signal,
 578                                            siginfo,
 579                                            sigill_handler);
 580             }
 581             ret = thread_set_state(thread,
 582                                    x86_THREAD_STATE32,
 583                                    (thread_state_t)&thread_state,
 584                                    thread_state_count);
 585             ret = thread_set_state(thread,
 586                                    x86_FLOAT_STATE32,
 587                                    (thread_state_t)&float_state,
 588                                    float_state_count);
 589         }
 590         thread_mutex_unlock(&mach_exception_lock);
 591         return KERN_SUCCESS;
 592
 593     default:
 594         thread_mutex_unlock(&mach_exception_lock);
 595         return KERN_INVALID_RIGHT;
 596     }
 597 }
 598
 599 void *
 600 mach_exception_handler(void *port)
 601 {
 602   mach_msg_server(exc_server, 2048, (mach_port_t) port, 0);
 603   /* mach_msg_server should never return, but it should dispatch mach
 604    * exceptions to our catch_exception_raise function
 605    */
 606   abort();
 607 }
 608
 609 #endif
 610
 611 #ifdef LISP_FEATURE_MACH_EXCEPTION_HANDLER
 612
 613 /* Sets up the thread that will listen for mach exceptions. note that
 614    the exception handlers will be run on this thread. This is
 615    different from the BSD-style signal handling situation in which the
 616    signal handlers run in the relevant thread directly. */
 617
 618 mach_port_t mach_exception_handler_port_set = MACH_PORT_NULL;
 619
 620 pthread_t
 621 setup_mach_exception_handling_thread()
 622 {
 623     kern_return_t ret;
 624     pthread_t mach_exception_handling_thread = NULL;
 625     pthread_attr_t attr;
 626
 627     /* allocate a mach_port for this process */
 628     ret = mach_port_allocate(mach_task_self(),
 629                              MACH_PORT_RIGHT_PORT_SET,
 630                              &mach_exception_handler_port_set);
 631
 632     /* create the thread that will receive the mach exceptions */
 633
 634     FSHOW((stderr, "Creating mach_exception_handler thread!\n"));
 635
 636     pthread_attr_init(&attr);
 637     pthread_create(&mach_exception_handling_thread,
 638                    &attr,
 639                    mach_exception_handler,
 640                    (void*) mach_exception_handler_port_set);
 641     pthread_attr_destroy(&attr);
 642
 643     return mach_exception_handling_thread;
 644 }
 645
 646 /* tell the kernel that we want EXC_BAD_ACCESS exceptions sent to the
 647    exception port (which is being listened to do by the mach
 648    exception handling thread). */
 649 kern_return_t
 650 mach_thread_init(mach_port_t thread_exception_port)
 651 {
 652     kern_return_t ret;
 653     /* allocate a named port for the thread */
 654
 655     FSHOW((stderr, "Allocating mach port %x\n", thread_exception_port));
 656
 657     ret = mach_port_allocate_name(mach_task_self(),
 658                                   MACH_PORT_RIGHT_RECEIVE,
 659                                   thread_exception_port);
 660     if (ret) {
 661         lose("mach_port_allocate_name failed with return_code %d\n", ret);
 662     }
 663
 664     /* establish the right for the thread_exception_port to send messages */
 665     ret = mach_port_insert_right(mach_task_self(),
 666                                  thread_exception_port,
 667                                  thread_exception_port,
 668                                  MACH_MSG_TYPE_MAKE_SEND);
 669     if (ret) {
 670         lose("mach_port_insert_right failed with return_code %d\n", ret);
 671     }
 672
 673     ret = thread_set_exception_ports(mach_thread_self(),
 674                                      EXC_MASK_BAD_ACCESS | EXC_MASK_BAD_INSTRUCTION,
 675                                      thread_exception_port,
 676                                      EXCEPTION_DEFAULT,
 677                                      THREAD_STATE_NONE);
 678     if (ret) {
 679         lose("thread_set_exception_port failed with return_code %d\n", ret);
 680     }
 681
 682     ret = mach_port_move_member(mach_task_self(),
 683                                 thread_exception_port,
 684                                 mach_exception_handler_port_set);
 685     if (ret) {
 686         lose("mach_port_ failed with return_code %d\n", ret);
 687     }
 688
 689     return ret;
 690 }
 691
 692 void
 693 setup_mach_exceptions() {
 694     setup_mach_exception_handling_thread();
 695     mach_thread_init(THREAD_STRUCT_TO_EXCEPTION_PORT(all_threads));
 696 }
 697
 698 pid_t
 699 mach_fork() {
 700     pid_t pid = fork();
 701     if (pid == 0) {
 702         setup_mach_exceptions();
 703         return pid;
 704     } else {
 705         return pid;
 706     }
 707 }
 708
 709 #endif