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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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 HOLDER 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 "ELFLoader.h"
#include <AK/Demangle.h>
#include <AK/Memory.h>
#include <AK/QuickSort.h>
#ifdef KERNEL
# include <Kernel/VM/MemoryManager.h>
# define do_memcpy copy_to_user
#else
# define do_memcpy memcpy
#endif
//#define ELFLOADER_DEBUG
ELFLoader::ELFLoader(const u8* buffer, size_t size)
: m_image(buffer, size)
{
m_symbol_count = m_image.symbol_count();
}
ELFLoader::~ELFLoader()
{
}
bool ELFLoader::load()
{
#ifdef ELFLOADER_DEBUG
m_image.dump();
#endif
if (!m_image.is_valid())
return false;
if (!layout())
return false;
return true;
}
bool ELFLoader::layout()
{
bool failed = false;
m_image.for_each_program_header([&](const ELFImage::ProgramHeader& program_header) {
if (program_header.type() == PT_TLS) {
#ifdef KERNEL
auto* tls_image = tls_section_hook(program_header.size_in_memory(), program_header.alignment());
if (!tls_image) {
failed = true;
return;
}
if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbg() << "Shenanigans! ELF PT_TLS header sneaks outside of executable.";
failed = true;
return;
}
do_memcpy(tls_image, program_header.raw_data(), program_header.size_in_image());
#endif
return;
}
if (program_header.type() != PT_LOAD)
return;
#ifdef ELFLOADER_DEBUG
kprintf("PH: V%p %u r:%u w:%u\n", program_header.vaddr().get(), program_header.size_in_memory(), program_header.is_readable(), program_header.is_writable());
#endif
#ifdef KERNEL
if (program_header.is_writable()) {
auto* allocated_section = alloc_section_hook(
program_header.vaddr(),
program_header.size_in_memory(),
program_header.alignment(),
program_header.is_readable(),
program_header.is_writable(),
String::format("elf-alloc-%s%s", program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : ""));
if (!allocated_section) {
failed = true;
return;
}
if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbg() << "Shenanigans! Writable ELF PT_LOAD header sneaks outside of executable.";
failed = true;
return;
}
// It's not always the case with PIE executables (and very well shouldn't be) that the
// virtual address in the program header matches the one we end up giving the process.
// In order to copy the data image correctly into memory, we need to copy the data starting at
// the right initial page offset into the pages allocated for the elf_alloc-XX section.
// FIXME: There's an opportunity to munmap, or at least mprotect, the padding space between
// the .text and .data PT_LOAD sections of the executable.
// Accessing it would definitely be a bug.
auto page_offset = program_header.vaddr();
page_offset.mask(~PAGE_MASK);
do_memcpy((u8*)allocated_section + page_offset.get(), program_header.raw_data(), program_header.size_in_image());
} else {
auto* mapped_section = map_section_hook(
program_header.vaddr(),
program_header.size_in_memory(),
program_header.alignment(),
program_header.offset(),
program_header.is_readable(),
program_header.is_writable(),
program_header.is_executable(),
String::format("elf-map-%s%s%s", program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : "", program_header.is_executable() ? "x" : ""));
if (!mapped_section) {
failed = true;
}
}
#endif
});
return !failed;
}
char* ELFLoader::symbol_ptr(const char* name)
{
char* found_ptr = nullptr;
m_image.for_each_symbol([&](const ELFImage::Symbol symbol) {
if (symbol.type() != STT_FUNC)
return IterationDecision::Continue;
if (symbol.name() == name)
return IterationDecision::Continue;
if (m_image.is_executable())
found_ptr = (char*)(size_t)symbol.value();
else
ASSERT_NOT_REACHED();
return IterationDecision::Break;
});
return found_ptr;
}
String ELFLoader::symbolicate(u32 address, u32* out_offset) const
{
if (!m_symbol_count) {
if (out_offset)
*out_offset = 0;
return "??";
}
SortedSymbol* sorted_symbols = nullptr;
#ifdef KERNEL
if (!m_sorted_symbols_region) {
m_sorted_symbols_region = MM.allocate_kernel_region(PAGE_ROUND_UP(m_symbol_count * sizeof(SortedSymbol)), "Sorted symbols", Kernel::Region::Access::Read | Kernel::Region::Access::Write);
sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
size_t index = 0;
m_image.for_each_symbol([&](auto& symbol) {
sorted_symbols[index++] = { symbol.value(), symbol.name() };
return IterationDecision::Continue;
});
quick_sort(sorted_symbols, sorted_symbols + m_symbol_count, [](auto& a, auto& b) {
return a.address < b.address;
});
} else {
sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
}
#else
if (m_sorted_symbols.is_empty()) {
m_sorted_symbols.ensure_capacity(m_symbol_count);
m_image.for_each_symbol([this](auto& symbol) {
m_sorted_symbols.append({ symbol.value(), symbol.name(), {} });
return IterationDecision::Continue;
});
quick_sort(m_sorted_symbols, [](auto& a, auto& b) {
return a.address < b.address;
});
}
sorted_symbols = m_sorted_symbols.data();
#endif
for (size_t i = 0; i < m_symbol_count; ++i) {
if (sorted_symbols[i].address > address) {
if (i == 0) {
if (out_offset)
*out_offset = 0;
return "!!";
}
auto& symbol = sorted_symbols[i - 1];
#ifdef KERNEL
auto demangled_name = demangle(symbol.name);
#else
auto& demangled_name = symbol.demangled_name;
if (demangled_name.is_null())
demangled_name = demangle(symbol.name);
#endif
if (out_offset) {
*out_offset = address - symbol.address;
return demangled_name;
}
return String::format("%s +%u", demangled_name.characters(), address - symbol.address);
}
}
if (out_offset)
*out_offset = 0;
return "??";
}
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