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]] 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 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
