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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* libc_init_dynamic.c
*
* This source files provides two important functions for dynamic
* executables:
*
* - a C runtime initializer (__libc_preinit), which is called by
* the dynamic linker when libc.so is loaded. This happens before
* any other initializer (e.g. static C++ constructors in other
* shared libraries the program depends on).
*
* - a program launch function (__libc_init), which is called after
* all dynamic linking has been performed. Technically, it is called
* from arch-$ARCH/bionic/crtbegin_dynamic.S which is itself called
* by the dynamic linker after all libraries have been loaded and
* initialized.
*/
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <elf.h>
#include "atexit.h"
#include "libc_init_common.h"
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
extern "C" {
extern void pthread_debug_init(void);
extern void malloc_debug_init(void);
extern void malloc_debug_fini(void);
};
// We flag the __libc_preinit function as a constructor to ensure
// that its address is listed in libc.so's .init_array section.
// This ensures that the function is called by the dynamic linker
// as soon as the shared library is loaded.
__attribute__((constructor)) static void __libc_preinit() {
// Read the kernel argument block pointer from TLS.
void** tls = __get_tls();
KernelArgumentBlock** args_slot = &reinterpret_cast<KernelArgumentBlock**>(tls)[TLS_SLOT_BIONIC_PREINIT];
KernelArgumentBlock* args = *args_slot;
// Clear the slot so no other initializer sees its value.
// __libc_init_common() will change the TLS area so the old one won't be accessible anyway.
*args_slot = NULL;
__libc_init_common(*args);
// Hooks for the debug malloc and pthread libraries to let them know that we're starting up.
pthread_debug_init();
malloc_debug_init();
}
__LIBC_HIDDEN__ void __libc_postfini() {
// A hook for the debug malloc library to let it know that we're shutting down.
malloc_debug_fini();
}
// This function is called from the executable's _start entry point
// (see arch-$ARCH/bionic/crtbegin_dynamic.S), which is itself
// called by the dynamic linker after it has loaded all shared
// libraries the executable depends on.
//
// Note that the dynamic linker has also run all constructors in the
// executable at this point.
__noreturn void __libc_init(void* raw_args,
void (*onexit)(void),
int (*slingshot)(int, char**, char**),
structors_array_t const * const structors) {
KernelArgumentBlock args(raw_args);
// Several Linux ABIs don't pass the onexit pointer, and the ones that
// do never use it. Therefore, we ignore it.
// The executable may have its own destructors listed in its .fini_array
// so we need to ensure that these are called when the program exits
// normally.
if (structors->fini_array) {
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
}
exit(slingshot(args.argc, args.argv, args.envp));
}
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