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c8d9f1b9c9
Since the CPU already does almost all necessary validation steps for us, we don't really need to attempt to do this. Doing it ourselves doesn't really work very reliably, because we'd have to account for other processors modifying virtual memory, and we'd have to account for e.g. pages not being able to be allocated due to insufficient resources. So change the copy_to/from_user (and associated helper functions) to use the new safe_memcpy, which will return whether it succeeded or not. The only manual validation step needed (which the CPU can't perform for us) is making sure the pointers provided by user mode aren't pointing to kernel mappings. To make it easier to read/write from/to either kernel or user mode data add the UserOrKernelBuffer helper class, which will internally either use copy_from/to_user or directly memcpy, or pass the data through directly using a temporary buffer on the stack. Last but not least we need to keep syscall params trivial as we need to copy them from/to user mode using copy_from/to_user.
281 lines
10 KiB
C++
281 lines
10 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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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 are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED 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 OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "Loader.h"
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#include <AK/Demangle.h>
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#include <AK/Memory.h>
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#include <AK/QuickSort.h>
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#ifdef KERNEL
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# include <Kernel/VM/MemoryManager.h>
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# define do_memcpy copy_to_user
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#else
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# define do_memcpy memcpy
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#endif
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//#define Loader_DEBUG
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namespace ELF {
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Loader::Loader(const u8* buffer, size_t size, bool verbose_logging)
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: m_image(buffer, size, verbose_logging)
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{
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if (m_image.is_valid())
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m_symbol_count = m_image.symbol_count();
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}
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Loader::~Loader()
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{
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}
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bool Loader::load()
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{
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#ifdef Loader_DEBUG
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m_image.dump();
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#endif
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if (!m_image.is_valid())
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return false;
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if (!layout())
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return false;
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return true;
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}
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bool Loader::layout()
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{
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bool failed = false;
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m_image.for_each_program_header([&](const Image::ProgramHeader& program_header) {
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if (program_header.type() == PT_TLS) {
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#ifdef KERNEL
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auto* tls_image = tls_section_hook(program_header.size_in_memory(), program_header.alignment());
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if (!tls_image) {
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failed = true;
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return;
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}
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if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
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dbg() << "Shenanigans! ELF PT_TLS header sneaks outside of executable.";
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failed = true;
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return;
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}
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if (!do_memcpy(tls_image, program_header.raw_data(), program_header.size_in_image())) {
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failed = false;
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return;
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}
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#endif
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return;
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}
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if (program_header.type() != PT_LOAD)
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return;
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#ifdef KERNEL
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# ifdef Loader_DEBUG
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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());
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# endif
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if (program_header.is_writable()) {
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auto* allocated_section = alloc_section_hook(
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program_header.vaddr(),
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program_header.size_in_memory(),
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program_header.alignment(),
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program_header.is_readable(),
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program_header.is_writable(),
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String::format("elf-alloc-%s%s", program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : ""));
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if (!allocated_section) {
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failed = true;
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return;
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}
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if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
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dbg() << "Shenanigans! Writable ELF PT_LOAD header sneaks outside of executable.";
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failed = true;
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return;
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}
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// It's not always the case with PIE executables (and very well shouldn't be) that the
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// virtual address in the program header matches the one we end up giving the process.
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// In order to copy the data image correctly into memory, we need to copy the data starting at
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// the right initial page offset into the pages allocated for the elf_alloc-XX section.
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// FIXME: There's an opportunity to munmap, or at least mprotect, the padding space between
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// the .text and .data PT_LOAD sections of the executable.
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// Accessing it would definitely be a bug.
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auto page_offset = program_header.vaddr();
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page_offset.mask(~PAGE_MASK);
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if (!do_memcpy((u8*)allocated_section + page_offset.get(), program_header.raw_data(), program_header.size_in_image())) {
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failed = false;
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return;
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}
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} else {
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auto* mapped_section = map_section_hook(
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program_header.vaddr(),
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program_header.size_in_memory(),
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program_header.alignment(),
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program_header.offset(),
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program_header.is_readable(),
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program_header.is_writable(),
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program_header.is_executable(),
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String::format("elf-map-%s%s%s", program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : "", program_header.is_executable() ? "x" : ""));
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if (!mapped_section) {
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failed = true;
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}
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}
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#endif
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});
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return !failed;
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}
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Optional<Image::Symbol> Loader::find_demangled_function(const String& name) const
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{
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Optional<Image::Symbol> found;
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m_image.for_each_symbol([&](const Image::Symbol symbol) {
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if (symbol.type() != STT_FUNC)
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return IterationDecision::Continue;
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auto demangled = demangle(symbol.name());
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auto index_of_paren = demangled.index_of("(");
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if (index_of_paren.has_value()) {
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demangled = demangled.substring(0, index_of_paren.value());
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}
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if (demangled != name)
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return IterationDecision::Continue;
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found = symbol;
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return IterationDecision::Break;
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});
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return found;
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}
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#ifndef KERNEL
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Optional<Image::Symbol> Loader::find_symbol(u32 address, u32* out_offset) const
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{
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if (!m_symbol_count)
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return {};
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SortedSymbol* sorted_symbols = nullptr;
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# ifdef KERNEL
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if (!m_sorted_symbols_region) {
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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);
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sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
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size_t index = 0;
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m_image.for_each_symbol([&](auto& symbol) {
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sorted_symbols[index++] = { symbol.value(), symbol.name() };
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return IterationDecision::Continue;
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});
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quick_sort(sorted_symbols, sorted_symbols + m_symbol_count, [](auto& a, auto& b) {
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return a.address < b.address;
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});
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} else {
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sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
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}
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# else
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if (m_sorted_symbols.is_empty()) {
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m_sorted_symbols.ensure_capacity(m_symbol_count);
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m_image.for_each_symbol([this](auto& symbol) {
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m_sorted_symbols.append({ symbol.value(), symbol.name(), {}, symbol });
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return IterationDecision::Continue;
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});
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quick_sort(m_sorted_symbols, [](auto& a, auto& b) {
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return a.address < b.address;
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});
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}
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sorted_symbols = m_sorted_symbols.data();
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# endif
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for (size_t i = 0; i < m_symbol_count; ++i) {
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if (sorted_symbols[i].address > address) {
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if (i == 0)
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return {};
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auto& symbol = sorted_symbols[i - 1];
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if (out_offset)
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*out_offset = address - symbol.address;
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return symbol.symbol;
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}
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}
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return {};
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}
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#endif
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String Loader::symbolicate(u32 address, u32* out_offset) const
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{
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if (!m_symbol_count) {
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if (out_offset)
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*out_offset = 0;
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return "??";
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}
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SortedSymbol* sorted_symbols = nullptr;
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#ifdef KERNEL
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if (!m_sorted_symbols_region) {
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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);
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sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
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size_t index = 0;
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m_image.for_each_symbol([&](auto& symbol) {
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sorted_symbols[index++] = { symbol.value(), symbol.name() };
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return IterationDecision::Continue;
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});
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quick_sort(sorted_symbols, sorted_symbols + m_symbol_count, [](auto& a, auto& b) {
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return a.address < b.address;
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});
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} else {
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sorted_symbols = (SortedSymbol*)m_sorted_symbols_region->vaddr().as_ptr();
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}
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#else
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if (m_sorted_symbols.is_empty()) {
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m_sorted_symbols.ensure_capacity(m_symbol_count);
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m_image.for_each_symbol([this](auto& symbol) {
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m_sorted_symbols.append({ symbol.value(), symbol.name(), {}, {} });
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return IterationDecision::Continue;
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});
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quick_sort(m_sorted_symbols, [](auto& a, auto& b) {
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return a.address < b.address;
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});
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}
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sorted_symbols = m_sorted_symbols.data();
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#endif
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for (size_t i = 0; i < m_symbol_count; ++i) {
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if (sorted_symbols[i].address > address) {
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if (i == 0) {
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if (out_offset)
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*out_offset = 0;
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return "!!";
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}
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auto& symbol = sorted_symbols[i - 1];
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#ifdef KERNEL
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auto demangled_name = demangle(symbol.name);
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#else
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auto& demangled_name = symbol.demangled_name;
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if (demangled_name.is_null())
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demangled_name = demangle(symbol.name);
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#endif
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if (out_offset) {
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*out_offset = address - symbol.address;
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return demangled_name;
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}
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return String::format("%s +%u", demangled_name.characters(), address - symbol.address);
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}
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}
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if (out_offset)
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*out_offset = 0;
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return "??";
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}
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} // end namespace ELF
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