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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_static.c
*
* The program startup function __libc_init() defined here is
* used for static executables only (i.e. those that don't depend
* on shared libraries). It is called from arch-$ARCH/bionic/crtbegin_static.S
* which is directly invoked by the kernel when the program is launched.
*
* The 'structors' parameter contains pointers to various initializer
* arrays that must be run before the program's 'main' routine is launched.
*/
#include <elf.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/auxv.h>
#include <sys/mman.h>
#include "atexit.h"
#include "libc_init_common.h"
#include "pthread_internal.h"
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
// Returns the address of the page containing address 'x'.
#define PAGE_START(x) ((x) & PAGE_MASK)
// Returns the address of the next page after address 'x', unless 'x' is
// itself at the start of a page.
#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))
static void call_array(void(**list)()) {
// First element is -1, list is null-terminated
while (*++list) {
(*list)();
}
}
static void apply_gnu_relro() {
Elf_Phdr* phdr_start = reinterpret_cast<Elf_Phdr*>(getauxval(AT_PHDR));
unsigned long int phdr_ct = getauxval(AT_PHNUM);
for (Elf_Phdr* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
if (phdr->p_type != PT_GNU_RELRO) {
continue;
}
Elf_Addr seg_page_start = PAGE_START(phdr->p_vaddr);
Elf_Addr seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
// Check return value here? What do we do if we fail?
mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
}
}
__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);
__libc_init_tls(args);
__libc_init_common(args);
apply_gnu_relro();
// Several Linux ABIs don't pass the onexit pointer, and the ones that
// do never use it. Therefore, we ignore it.
call_array(structors->preinit_array);
call_array(structors->init_array);
// 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 != NULL) {
__cxa_atexit(__libc_fini,structors->fini_array,NULL);
}
exit(slingshot(args.argc, args.argv, args.envp));
}
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