83 lines
3.2 KiB
C++
83 lines
3.2 KiB
C++
/*
|
|
* Copyright (C) 2017 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.
|
|
*/
|
|
|
|
#include "private/KernelArgumentBlock.h"
|
|
|
|
extern const char linker_offset;
|
|
|
|
// This will be replaced by host_bionic_inject, but must be non-zero
|
|
// here so that it's placed in the data section.
|
|
uintptr_t original_start = 42;
|
|
|
|
/* Find the load bias and base address of an executable or shared object loaded
|
|
* by the kernel. The ELF file's PHDR table must have a PT_PHDR entry.
|
|
*
|
|
* A VDSO doesn't have a PT_PHDR entry in its PHDR table.
|
|
*/
|
|
static void get_elf_base_from_phdr(const ElfW(Phdr)* phdr_table, size_t phdr_count,
|
|
ElfW(Addr)* base, ElfW(Addr)* load_bias) {
|
|
for (size_t i = 0; i < phdr_count; ++i) {
|
|
if (phdr_table[i].p_type == PT_PHDR) {
|
|
*load_bias = reinterpret_cast<ElfW(Addr)>(phdr_table) - phdr_table[i].p_vaddr;
|
|
*base = reinterpret_cast<ElfW(Addr)>(phdr_table) - phdr_table[i].p_offset;
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This is the entry point for the linker wrapper, which finds
|
|
* the real linker, then bootstraps into it.
|
|
*/
|
|
extern "C" ElfW(Addr) __linker_init(void* raw_args) {
|
|
KernelArgumentBlock args(raw_args);
|
|
|
|
ElfW(Addr) base_addr = 0;
|
|
ElfW(Addr) load_bias = 0;
|
|
get_elf_base_from_phdr(
|
|
reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR)), args.getauxval(AT_PHNUM),
|
|
&base_addr, &load_bias);
|
|
|
|
ElfW(Addr) linker_addr = base_addr + reinterpret_cast<uintptr_t>(&linker_offset);
|
|
ElfW(Addr) linker_entry_offset = reinterpret_cast<ElfW(Ehdr)*>(linker_addr)->e_entry;
|
|
|
|
for (ElfW(auxv_t)* v = args.auxv; v->a_type != AT_NULL; ++v) {
|
|
if (v->a_type == AT_BASE) {
|
|
// Set AT_BASE to the embedded linker
|
|
v->a_un.a_val = linker_addr;
|
|
}
|
|
if (v->a_type == AT_ENTRY) {
|
|
// Set AT_ENTRY to the proper entry point
|
|
v->a_un.a_val = base_addr + original_start;
|
|
}
|
|
}
|
|
|
|
// Return address of linker entry point
|
|
return linker_addr + linker_entry_offset;
|
|
}
|