110 lines
3.9 KiB
C++
110 lines
3.9 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* libc_init_static.c
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*
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* The program startup function __libc_init() defined here is
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* used for static executables only (i.e. those that don't depend
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* on shared libraries). It is called from arch-$ARCH/bionic/crtbegin_static.S
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* which is directly invoked by the kernel when the program is launched.
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*
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* The 'structors' parameter contains pointers to various initializer
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* arrays that must be run before the program's 'main' routine is launched.
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*/
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#include <elf.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/auxv.h>
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#include <sys/mman.h>
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#include "atexit.h"
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#include "bionic_tls.h"
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#include "KernelArgumentBlock.h"
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#include "libc_init_common.h"
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#include "pthread_internal.h"
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// Returns the address of the page containing address 'x'.
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#define PAGE_START(x) ((x) & PAGE_MASK)
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// Returns the address of the next page after address 'x', unless 'x' is
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// itself at the start of a page.
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#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))
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static void call_array(void(**list)()) {
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// First element is -1, list is null-terminated
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while (*++list) {
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(*list)();
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}
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}
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static void apply_gnu_relro() {
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Elf32_Phdr* phdr_start = reinterpret_cast<Elf32_Phdr*>(getauxval(AT_PHDR));
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unsigned long int phdr_ct = getauxval(AT_PHNUM);
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for (Elf32_Phdr* phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
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if (phdr->p_type != PT_GNU_RELRO) {
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continue;
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}
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Elf32_Addr seg_page_start = PAGE_START(phdr->p_vaddr);
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Elf32_Addr seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz);
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// Check return value here? What do we do if we fail?
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mprotect(reinterpret_cast<void*>(seg_page_start), seg_page_end - seg_page_start, PROT_READ);
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}
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}
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__noreturn void __libc_init(void* raw_args,
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void (*onexit)(void),
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int (*slingshot)(int, char**, char**),
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structors_array_t const * const structors) {
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KernelArgumentBlock args(raw_args);
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__libc_init_tls(args);
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__libc_init_common(args);
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apply_gnu_relro();
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// Several Linux ABIs don't pass the onexit pointer, and the ones that
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// do never use it. Therefore, we ignore it.
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call_array(structors->preinit_array);
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call_array(structors->init_array);
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// The executable may have its own destructors listed in its .fini_array
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// so we need to ensure that these are called when the program exits
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// normally.
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if (structors->fini_array != NULL) {
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__cxa_atexit(__libc_fini,structors->fini_array,NULL);
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}
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exit(slingshot(args.argc, args.argv, args.envp));
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}
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