1 /* 2 * Copyright (C) 2008 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 "libc_init_common.h" 30 31 #include "private/KernelArgumentBlock.h" 32 #include "private/bionic_arc4random.h" 33 #include "private/bionic_auxv.h" 34 #include "private/bionic_defs.h" 35 #include "private/bionic_globals.h" 36 #include "private/bionic_ssp.h" 37 #include "pthread_internal.h" 38 39 extern "C" int __set_tls(void* ptr); 40 extern "C" int __set_tid_address(int* tid_address); 41 42 // Declared in "private/bionic_ssp.h". 43 uintptr_t __stack_chk_guard = 0; 44 45 void __libc_init_global_stack_chk_guard(KernelArgumentBlock& args) { 46 __libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard), args); 47 } 48 49 // Setup for the main thread. For dynamic executables, this is called by the 50 // linker _before_ libc is mapped in memory. This means that all writes to 51 // globals from this function will apply to linker-private copies and will not 52 // be visible from libc later on. 53 // 54 // Note: this function creates a pthread_internal_t for the initial thread and 55 // stores the pointer in TLS, but does not add it to pthread's thread list. This 56 // has to be done later from libc itself (see __libc_init_common). 57 // 58 // This is in a file by itself because it needs to be built with 59 // -fno-stack-protector because it's responsible for setting up the main 60 // thread's TLS (which stack protector relies on). 61 62 __BIONIC_WEAK_FOR_NATIVE_BRIDGE 63 void __libc_init_main_thread(KernelArgumentBlock& args) { 64 __libc_auxv = args.auxv; 65 #if defined(__i386__) 66 __libc_init_sysinfo(args); 67 #endif 68 69 static pthread_internal_t main_thread; 70 71 // The -fstack-protector implementation uses TLS, so make sure that's 72 // set up before we call any function that might get a stack check inserted. 73 // TLS also needs to be set up before errno (and therefore syscalls) can be used. 74 __set_tls(main_thread.tls); 75 if (!__init_tls(&main_thread)) async_safe_fatal("failed to initialize TLS: %s", strerror(errno)); 76 77 // Tell the kernel to clear our tid field when we exit, so we're like any other pthread. 78 // As a side-effect, this tells us our pid (which is the same as the main thread's tid). 79 main_thread.tid = __set_tid_address(&main_thread.tid); 80 main_thread.set_cached_pid(main_thread.tid); 81 82 // We don't want to free the main thread's stack even when the main thread exits 83 // because things like environment variables with global scope live on it. 84 // We also can't free the pthread_internal_t itself, since that lives on the main 85 // thread's stack rather than on the heap. 86 // The main thread has no mmap allocated space for stack or pthread_internal_t. 87 main_thread.mmap_size = 0; 88 89 pthread_attr_init(&main_thread.attr); 90 // We don't want to explicitly set the main thread's scheduler attributes (http://b/68328561). 91 pthread_attr_setinheritsched(&main_thread.attr, PTHREAD_INHERIT_SCHED); 92 // The main thread has no guard page. 93 pthread_attr_setguardsize(&main_thread.attr, 0); 94 // User code should never see this; we'll compute it when asked. 95 pthread_attr_setstacksize(&main_thread.attr, 0); 96 97 // The TLS stack guard is set from the global, so ensure that we've initialized the global 98 // before we initialize the TLS. Dynamic executables will initialize their copy of the global 99 // stack protector from the one in the main thread's TLS. 100 __libc_init_global_stack_chk_guard(args); 101 __init_thread_stack_guard(&main_thread); 102 103 __init_thread(&main_thread); 104 105 // Store a pointer to the kernel argument block in a TLS slot to be 106 // picked up by the libc constructor. 107 main_thread.tls[TLS_SLOT_BIONIC_PREINIT] = &args; 108 109 __init_alternate_signal_stack(&main_thread); 110 } 111
