/* Fault handler information. MacOSX version. Copyright (C) 1993-1999, 2002-2003 Bruno Haible Copyright (C) 2003 Paolo Bonzini Used under BSD license with permission from Paolo Bonzini and Bruno Haible, 2005-03-10: http://sourceforge.net/mailarchive/message.php?msg_name=200503102200.32002.bruno%40clisp.org Modified for Factor by Slava Pestov */ #include "master.h" /* The following sources were used as a *reference* for this exception handling code: 1. Apple's mach/xnu documentation 2. Timothy J. Wood's "Mach Exception Handlers 101" post to the omnigroup's macosx-dev list. http://www.wodeveloper.com/omniLists/macosx-dev/2000/June/msg00137.html */ /* Modify a suspended thread's thread_state so that when the thread resumes executing, the call frame of the current C primitive (if any) is rewound, and the appropriate Factor error is thrown from the top-most Factor frame. */ static void call_fault_handler(exception_type_t exception, MACH_EXC_STATE_TYPE *exc_state, MACH_THREAD_STATE_TYPE *thread_state) { /* There is a race condition here, but in practice an exception delivered during stack frame setup/teardown or while transitioning from Factor to C is a sign of things seriously gone wrong, not just a divide by zero or stack underflow in the listener */ /* Are we in compiled Factor code? Then use the current stack pointer */ if(in_code_heap_p(MACH_PROGRAM_COUNTER(thread_state))) signal_callstack_top = (void *)MACH_STACK_POINTER(thread_state); /* Are we in C? Then use the saved callstack top */ else signal_callstack_top = NULL; MACH_STACK_POINTER(thread_state) = fix_stack_pointer(MACH_STACK_POINTER(thread_state)); /* Now we point the program counter at the right handler function. */ if(exception == EXC_BAD_ACCESS) { signal_fault_addr = MACH_EXC_STATE_FAULT(exc_state); MACH_PROGRAM_COUNTER(thread_state) = (CELL)memory_signal_handler_impl; } else { if(exception == EXC_ARITHMETIC) signal_number = SIGFPE; else signal_number = SIGABRT; MACH_PROGRAM_COUNTER(thread_state) = (CELL)misc_signal_handler_impl; } } /* Handle an exception by invoking the user's fault handler and/or forwarding the duty to the previously installed handlers. */ kern_return_t catch_exception_raise (mach_port_t exception_port, mach_port_t thread, mach_port_t task, exception_type_t exception, exception_data_t code, mach_msg_type_number_t code_count) { MACH_EXC_STATE_TYPE exc_state; MACH_THREAD_STATE_TYPE thread_state; mach_msg_type_number_t state_count; /* Get fault information and the faulting thread's register contents.. See http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/thread_get_state.html. */ state_count = MACH_EXC_STATE_COUNT; if (thread_get_state (thread, MACH_EXC_STATE_FLAVOR, (void *) &exc_state, &state_count) != KERN_SUCCESS) { /* The thread is supposed to be suspended while the exception handler is called. This shouldn't fail. */ return KERN_FAILURE; } state_count = MACH_THREAD_STATE_COUNT; if (thread_get_state (thread, MACH_THREAD_STATE_FLAVOR, (void *) &thread_state, &state_count) != KERN_SUCCESS) { /* The thread is supposed to be suspended while the exception handler is called. This shouldn't fail. */ return KERN_FAILURE; } /* Modify registers so to have the thread resume executing the fault handler */ call_fault_handler(exception,&exc_state,&thread_state); /* Set the faulting thread's register contents.. See http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/thread_set_state.html. */ if (thread_set_state (thread, MACH_THREAD_STATE_FLAVOR, (void *) &thread_state, state_count) != KERN_SUCCESS) { return KERN_FAILURE; } return KERN_SUCCESS; } /* The main function of the thread listening for exceptions. */ static void * mach_exception_thread (void *arg) { for (;;) { /* These two structures contain some private kernel data. We don't need to access any of it so we don't bother defining a proper struct. The correct definitions are in the xnu source code. */ /* Buffer for a message to be received. */ struct { mach_msg_header_t head; mach_msg_body_t msgh_body; char data[1024]; } msg; /* Buffer for a reply message. */ struct { mach_msg_header_t head; char data[1024]; } reply; mach_msg_return_t retval; /* Wait for a message on the exception port. */ retval = mach_msg (&msg.head, MACH_RCV_MSG | MACH_RCV_LARGE, 0, sizeof (msg), our_exception_port, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL); if (retval != MACH_MSG_SUCCESS) { abort (); } /* Handle the message: Call exc_server, which will call catch_exception_raise and produce a reply message. */ exc_server (&msg.head, &reply.head); /* Send the reply. */ if (mach_msg (&reply.head, MACH_SEND_MSG, reply.head.msgh_size, 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL) != MACH_MSG_SUCCESS) { abort (); } } } /* Initialize the Mach exception handler thread. */ void mach_initialize (void) { mach_port_t self; exception_mask_t mask; pthread_attr_t attr; pthread_t thread; self = mach_task_self (); /* Allocate a port on which the thread shall listen for exceptions. */ if (mach_port_allocate (self, MACH_PORT_RIGHT_RECEIVE, &our_exception_port) != KERN_SUCCESS) fatal_error("mach_port_allocate() failed",0); /* See http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/mach_port_insert_right.html. */ if (mach_port_insert_right (self, our_exception_port, our_exception_port, MACH_MSG_TYPE_MAKE_SEND) != KERN_SUCCESS) fatal_error("mach_port_insert_right() failed",0); /* The exceptions we want to catch. */ mask = EXC_MASK_BAD_ACCESS | EXC_MASK_ARITHMETIC; /* Create the thread listening on the exception port. */ if (pthread_attr_init (&attr) != 0) fatal_error("pthread_attr_init() failed",0); if (pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED) != 0) fatal_error("pthread_attr_setdetachstate() failed",0); if (pthread_create (&thread, &attr, mach_exception_thread, NULL) != 0) fatal_error("pthread_create() failed",0); pthread_attr_destroy (&attr); /* Replace the exception port info for these exceptions with our own. Note that we replace the exception port for the entire task, not only for a particular thread. This has the effect that when our exception port gets the message, the thread specific exception port has already been asked, and we don't need to bother about it. See http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/task_set_exception_ports.html. */ if (task_set_exception_ports (self, mask, our_exception_port, EXCEPTION_DEFAULT, MACHINE_THREAD_STATE) != KERN_SUCCESS) fatal_error("task_set_exception_ports() failed",0); }