7ccc50d2e4
The linux kernel requires that the ELF interpreter (runtime linker) that's referenced by PT_INTERP be either an absolute path, or a relative path from the current working directory. We'd prefer a relative path from the binary, similarly to how we handle looking up shared libraries, but that's not supported. Instead, extract the LOAD segments from the runtime linker ELF binary and embed them into each host bionic binary, omitting the PT_INTERP declaration. The kernel will treat it as a static binary, and we'll use a special entry point (linker_wrapper) to fix up the arguments passed by the kernel before jumping to the embedded linker. From the linker's point of view, it looks like the kernel loaded the linker like normal. Bug: 31559095 Test: Enable host bionic, build and run libdemangle_test Change-Id: I1753401ef91eecbf0ae3376faca31eec1c53842b
59 lines
2.4 KiB
C++
59 lines
2.4 KiB
C++
/*
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* Copyright (C) 2017 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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#include "private/KernelArgumentBlock.h"
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extern const char linker_code_start;
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extern const char original_start;
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extern const char linker_entry;
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/*
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* This is the entry point for the linker wrapper, which finds
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* the real linker, then bootstraps into it.
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*/
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extern "C" ElfW(Addr) __linker_init(void* raw_args) {
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KernelArgumentBlock args(raw_args);
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static uintptr_t linker_offset = reinterpret_cast<uintptr_t>(&linker_code_start);
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static uintptr_t linktime_addr = reinterpret_cast<uintptr_t>(&linktime_addr);
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ElfW(Addr) my_addr = reinterpret_cast<uintptr_t>(&linktime_addr) - linktime_addr;
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// Set AT_ENTRY to the proper entry point
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for (ElfW(auxv_t)* v = args.auxv; v->a_type != AT_NULL; ++v) {
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if (v->a_type == AT_BASE) {
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v->a_un.a_val = my_addr + linker_offset;
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}
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if (v->a_type == AT_ENTRY) {
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v->a_un.a_val = my_addr + reinterpret_cast<uintptr_t>(&original_start);
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}
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}
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// Return address of linker entry point -- may need to ensure that raw_args
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// was saved.
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return my_addr + linker_offset + reinterpret_cast<uintptr_t>(&linker_entry);
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}
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