bsd/uxkern/ux_exception.c

   1 /*
   2  * Copyright (c) 2000-2017 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29  * Mach Operating System
  30  * Copyright (c) 1987 Carnegie-Mellon University
  31  * All rights reserved.  The CMU software License Agreement specifies
  32  * the terms and conditions for use and redistribution.
  33  */
  34
  35 #include <sys/param.h>
  36
  37 #include <mach/boolean.h>
  38 #include <mach/exception.h>
  39 #include <mach/kern_return.h>
  40
  41 #include <sys/proc.h>
  42 #include <sys/user.h>
  43 #include <sys/systm.h>
  44 #include <sys/vmparam.h>        /* MAXSSIZ */
  45
  46 #include <sys/ux_exception.h>
  47
  48 /*
  49  * Translate Mach exceptions to UNIX signals.
  50  *
  51  * ux_exception translates a mach exception, code and subcode to
  52  * a signal.  Calls machine_exception (machine dependent)
  53  * to attempt translation first.
  54  */
  55 static int
  56 ux_exception(int                        exception,
  57              mach_exception_code_t      code,
  58              mach_exception_subcode_t   subcode)
  59 {
  60         int machine_signal = 0;
  61
  62         /* Try machine-dependent translation first. */
  63         if ((machine_signal = machine_exception(exception, code, subcode)) != 0)
  64                 return machine_signal;
  65
  66         switch(exception) {
  67                 case EXC_BAD_ACCESS:
  68                         if (code == KERN_INVALID_ADDRESS)
  69                                 return SIGSEGV;
  70                         else
  71                                 return SIGBUS;
  72
  73                 case EXC_BAD_INSTRUCTION:
  74                         return SIGILL;
  75
  76                 case EXC_ARITHMETIC:
  77                         return SIGFPE;
  78
  79                 case EXC_EMULATION:
  80                         return SIGEMT;
  81
  82                 case EXC_SOFTWARE:
  83                         switch (code) {
  84                                 case EXC_UNIX_BAD_SYSCALL:
  85                                         return SIGSYS;
  86                                 case EXC_UNIX_BAD_PIPE:
  87                                         return SIGPIPE;
  88                                 case EXC_UNIX_ABORT:
  89                                         return SIGABRT;
  90                                 case EXC_SOFT_SIGNAL:
  91                                         return SIGKILL;
  92                         }
  93                         break;
  94
  95                 case EXC_BREAKPOINT:
  96                         return SIGTRAP;
  97         }
  98
  99         return 0;
 100 }
 101
 102 /*
 103  * Sends the corresponding UNIX signal to a thread that has triggered a Mach exception.
 104  */
 105 kern_return_t
 106 handle_ux_exception(thread_t                    thread,
 107                     int                         exception,
 108                     mach_exception_code_t       code,
 109                     mach_exception_subcode_t    subcode)
 110 {
 111         /* Returns +1 proc reference */
 112         proc_t p = proc_findthread(thread);
 113
 114         /* Can't deliver a signal without a bsd process reference */
 115         if (p == NULL)
 116                 return KERN_FAILURE;
 117
 118         /* Translate exception and code to signal type */
 119         int ux_signal = ux_exception(exception, code, subcode);
 120
 121         uthread_t ut = get_bsdthread_info(thread);
 122
 123         /*
 124          * Stack overflow should result in a SIGSEGV signal
 125          * on the alternate stack.
 126          * but we have one or more guard pages after the
 127          * stack top, so we would get a KERN_PROTECTION_FAILURE
 128          * exception instead of KERN_INVALID_ADDRESS, resulting in
 129          * a SIGBUS signal.
 130          * Detect that situation and select the correct signal.
 131          */
 132         if (code == KERN_PROTECTION_FAILURE &&
 133             ux_signal == SIGBUS) {
 134                 user_addr_t sp = subcode;
 135
 136                 user_addr_t stack_max = p->user_stack;
 137                 user_addr_t stack_min = p->user_stack - MAXSSIZ;
 138                 if (sp >= stack_min && sp < stack_max) {
 139                         /*
 140                          * This is indeed a stack overflow.  Deliver a
 141                          * SIGSEGV signal.
 142                          */
 143                         ux_signal = SIGSEGV;
 144
 145                         /*
 146                          * If the thread/process is not ready to handle
 147                          * SIGSEGV on an alternate stack, force-deliver
 148                          * SIGSEGV with a SIG_DFL handler.
 149                          */
 150                         int mask = sigmask(ux_signal);
 151                         struct sigacts *ps = p->p_sigacts;
 152                         if ((p->p_sigignore & mask) ||
 153                             (ut->uu_sigwait & mask) ||
 154                             (ut->uu_sigmask & mask) ||
 155                             (ps->ps_sigact[SIGSEGV] == SIG_IGN) ||
 156                             (! (ps->ps_sigonstack & mask))) {
 157                                 p->p_sigignore &= ~mask;
 158                                 p->p_sigcatch &= ~mask;
 159                                 ps->ps_sigact[SIGSEGV] = SIG_DFL;
 160                                 ut->uu_sigwait &= ~mask;
 161                                 ut->uu_sigmask &= ~mask;
 162                         }
 163                 }
 164         }
 165
 166         /* Send signal to thread */
 167         if (ux_signal != 0) {
 168                 ut->uu_exception = exception;
 169                 //ut->uu_code = code; // filled in by threadsignal
 170                 ut->uu_subcode = subcode;
 171                 threadsignal(thread, ux_signal, code, TRUE);
 172         }
 173
 174         proc_rele(p);
 175
 176         return KERN_SUCCESS;
 177 }
 178