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
  67         switch (exception) {
  68         case EXC_BAD_ACCESS:
  69                 if (code == KERN_INVALID_ADDRESS) {
  70                         return SIGSEGV;
  71                 } else {
  72                         return SIGBUS;
  73                 }
  74
  75         case EXC_BAD_INSTRUCTION:
  76                 return SIGILL;
  77
  78         case EXC_ARITHMETIC:
  79                 return SIGFPE;
  80
  81         case EXC_EMULATION:
  82                 return SIGEMT;
  83
  84         case EXC_SOFTWARE:
  85                 switch (code) {
  86                 case EXC_UNIX_BAD_SYSCALL:
  87                         return SIGSYS;
  88                 case EXC_UNIX_BAD_PIPE:
  89                         return SIGPIPE;
  90                 case EXC_UNIX_ABORT:
  91                         return SIGABRT;
  92                 case EXC_SOFT_SIGNAL:
  93                         return SIGKILL;
  94                 }
  95                 break;
  96
  97         case EXC_BREAKPOINT:
  98                 return SIGTRAP;
  99         }
 100
 101         return 0;
 102 }
 103
 104 /*
 105  * Sends the corresponding UNIX signal to a thread that has triggered a Mach exception.
 106  */
 107 kern_return_t
 108 handle_ux_exception(thread_t                    thread,
 109     int                         exception,
 110     mach_exception_code_t       code,
 111     mach_exception_subcode_t    subcode)
 112 {
 113         /* Returns +1 proc reference */
 114         proc_t p = proc_findthread(thread);
 115
 116         /* Can't deliver a signal without a bsd process reference */
 117         if (p == NULL) {
 118                 return KERN_FAILURE;
 119         }
 120
 121         /* Translate exception and code to signal type */
 122         int ux_signal = ux_exception(exception, code, subcode);
 123
 124         uthread_t ut = get_bsdthread_info(thread);
 125
 126         /*
 127          * Stack overflow should result in a SIGSEGV signal
 128          * on the alternate stack.
 129          * but we have one or more guard pages after the
 130          * stack top, so we would get a KERN_PROTECTION_FAILURE
 131          * exception instead of KERN_INVALID_ADDRESS, resulting in
 132          * a SIGBUS signal.
 133          * Detect that situation and select the correct signal.
 134          */
 135         if (code == KERN_PROTECTION_FAILURE &&
 136             ux_signal == SIGBUS) {
 137                 user_addr_t sp = subcode;
 138
 139                 user_addr_t stack_max = p->user_stack;
 140                 user_addr_t stack_min = p->user_stack - MAXSSIZ;
 141                 if (sp >= stack_min && sp < stack_max) {
 142                         /*
 143                          * This is indeed a stack overflow.  Deliver a
 144                          * SIGSEGV signal.
 145                          */
 146                         ux_signal = SIGSEGV;
 147
 148                         /*
 149                          * If the thread/process is not ready to handle
 150                          * SIGSEGV on an alternate stack, force-deliver
 151                          * SIGSEGV with a SIG_DFL handler.
 152                          */
 153                         int mask = sigmask(ux_signal);
 154                         struct sigacts *ps = p->p_sigacts;
 155                         if ((p->p_sigignore & mask) ||
 156                             (ut->uu_sigwait & mask) ||
 157                             (ut->uu_sigmask & mask) ||
 158                             (ps->ps_sigact[SIGSEGV] == SIG_IGN) ||
 159                             (!(ps->ps_sigonstack & mask))) {
 160                                 p->p_sigignore &= ~mask;
 161                                 p->p_sigcatch &= ~mask;
 162                                 ps->ps_sigact[SIGSEGV] = SIG_DFL;
 163                                 ut->uu_sigwait &= ~mask;
 164                                 ut->uu_sigmask &= ~mask;
 165                         }
 166                 }
 167         }
 168
 169         /* Send signal to thread */
 170         if (ux_signal != 0) {
 171                 ut->uu_exception = exception;
 172                 //ut->uu_code = code; // filled in by threadsignal
 173                 ut->uu_subcode = subcode;
 174                 threadsignal(thread, ux_signal, code, TRUE);
 175         }
 176
 177         proc_rele(p);
 178
 179         return KERN_SUCCESS;
 180 }