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
ux_exception(int exception,mach_exception_code_t code,mach_exception_subcode_t subcode)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_SYSCALL:
76 if (send_sigsys) {
77 return SIGSYS;
78 }
79 break;
80
81 case EXC_BAD_INSTRUCTION:
82 return SIGILL;
83
84 case EXC_ARITHMETIC:
85 return SIGFPE;
86
87 case EXC_EMULATION:
88 return SIGEMT;
89
90 case EXC_SOFTWARE:
91 switch (code) {
92 case EXC_UNIX_BAD_SYSCALL:
93 return SIGSYS;
94 case EXC_UNIX_BAD_PIPE:
95 return SIGPIPE;
96 case EXC_UNIX_ABORT:
97 return SIGABRT;
98 case EXC_SOFT_SIGNAL:
99 return SIGKILL;
100 }
101 break;
102
103 case EXC_BREAKPOINT:
104 return SIGTRAP;
105 }
106
107 return 0;
108 }
109
110 /*
111 * Sends the corresponding UNIX signal to a thread that has triggered a Mach exception.
112 */
113 kern_return_t
handle_ux_exception(thread_t thread,int exception,mach_exception_code_t code,mach_exception_subcode_t subcode)114 handle_ux_exception(thread_t thread,
115 int exception,
116 mach_exception_code_t code,
117 mach_exception_subcode_t subcode)
118 {
119 /* Returns +1 proc reference */
120 proc_t p = proc_findthread(thread);
121
122 /* Can't deliver a signal without a bsd process reference */
123 if (p == NULL) {
124 return KERN_FAILURE;
125 }
126
127 /* Translate exception and code to signal type */
128 int ux_signal = ux_exception(exception, code, subcode);
129
130 uthread_t ut = get_bsdthread_info(thread);
131
132 /*
133 * Stack overflow should result in a SIGSEGV signal
134 * on the alternate stack.
135 * but we have one or more guard pages after the
136 * stack top, so we would get a KERN_PROTECTION_FAILURE
137 * exception instead of KERN_INVALID_ADDRESS, resulting in
138 * a SIGBUS signal.
139 * Detect that situation and select the correct signal.
140 */
141 if (code == KERN_PROTECTION_FAILURE &&
142 ux_signal == SIGBUS) {
143 user_addr_t sp = subcode;
144
145 user_addr_t stack_max = p->user_stack;
146 user_addr_t stack_min = p->user_stack - MAXSSIZ;
147 if (sp >= stack_min && sp < stack_max) {
148 /*
149 * This is indeed a stack overflow. Deliver a
150 * SIGSEGV signal.
151 */
152 ux_signal = SIGSEGV;
153
154 /*
155 * If the thread/process is not ready to handle
156 * SIGSEGV on an alternate stack, force-deliver
157 * SIGSEGV with a SIG_DFL handler.
158 */
159 int mask = sigmask(ux_signal);
160 struct sigacts *ps = &p->p_sigacts;
161 if ((p->p_sigignore & mask) ||
162 (ut->uu_sigwait & mask) ||
163 (ut->uu_sigmask & mask) ||
164 (SIGACTION(p, SIGSEGV) == SIG_IGN) ||
165 (!(ps->ps_sigonstack & mask))) {
166 p->p_sigignore &= ~mask;
167 p->p_sigcatch &= ~mask;
168 proc_set_sigact(p, SIGSEGV, SIG_DFL);
169 ut->uu_sigwait &= ~mask;
170 ut->uu_sigmask &= ~mask;
171 }
172 }
173 }
174
175 /* Send signal to thread */
176 if (ux_signal != 0) {
177 ut->uu_exception = exception;
178 //ut->uu_code = code; // filled in by threadsignal
179 ut->uu_subcode = subcode;
180 threadsignal(thread, ux_signal, code, TRUE);
181 }
182
183 proc_rele(p);
184
185 return KERN_SUCCESS;
186 }
187