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