1 /*
2 * Copyright (C) 2017 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include <android/set_abort_message.h>
30
31 #include <pthread.h>
32 #include <stdint.h>
33 #include <stddef.h>
34 #include <string.h>
35 #include <sys/mman.h>
36 #include <sys/prctl.h>
37
38 #include "private/bionic_defs.h"
39 #include "private/bionic_globals.h"
40 #include "private/ScopedPthreadMutexLocker.h"
41
42 struct abort_msg_t {
43 size_t size;
44 char msg[0];
45 };
46 static_assert(
47 offsetof(abort_msg_t, msg) == sizeof(size_t),
48 "The in-memory layout of abort_msg_t is not consistent with what libdebuggerd expects.");
49
50 struct magic_abort_msg_t {
51 uint64_t magic1;
52 uint64_t magic2;
53 abort_msg_t msg;
54 };
55 static_assert(offsetof(magic_abort_msg_t, msg) == 2 * sizeof(uint64_t),
56 "The in-memory layout of magic_abort_msg_t is not consistent with what automated "
57 "tools expect.");
58
59 [[clang::optnone]]
fill_abort_message_magic(magic_abort_msg_t * new_magic_abort_message)60 static void fill_abort_message_magic(magic_abort_msg_t* new_magic_abort_message) {
61 // 128-bit magic for the abort message. Chosen by fair dice roll.
62 // This function is intentionally deoptimized to avoid the magic to be present
63 // in the final binary. This causes clang to only use instructions where parts
64 // of the magic are encoded into immediate arguments for the instructions in
65 // all supported architectures.
66 new_magic_abort_message->magic1 = 0xb18e40886ac388f0ULL;
67 new_magic_abort_message->magic2 = 0xc6dfba755a1de0b5ULL;
68 }
69
70 __BIONIC_WEAK_FOR_NATIVE_BRIDGE
android_set_abort_message(const char * msg)71 void android_set_abort_message(const char* msg) {
72 ScopedPthreadMutexLocker locker(&__libc_shared_globals()->abort_msg_lock);
73
74 if (__libc_shared_globals()->abort_msg != nullptr) {
75 // We already have an abort message.
76 // Assume that the first crash is the one most worth reporting.
77 return;
78 }
79
80 size_t size = sizeof(magic_abort_msg_t) + strlen(msg) + 1;
81 void* map = mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
82 if (map == MAP_FAILED) {
83 return;
84 }
85
86 // Name the abort message mapping to make it easier for tools to find the
87 // mapping.
88 prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map, size, "abort message");
89
90 magic_abort_msg_t* new_magic_abort_message = reinterpret_cast<magic_abort_msg_t*>(map);
91 fill_abort_message_magic(new_magic_abort_message);
92 new_magic_abort_message->msg.size = size;
93 strcpy(new_magic_abort_message->msg.msg, msg);
94 __libc_shared_globals()->abort_msg = &new_magic_abort_message->msg;
95 }
96