citra/src/core/loader/nso.cpp

// Copyright 2017 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <vector>
#include <lz4.h>

#include "common/logging/log.h"
#include "common/swap.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/resource_limit.h"
#include "core/loader/nso.h"
#include "core/memory.h"

namespace Loader {

struct NsoSegmentHeader {
    u32_le offset;
    u32_le location;
    u32_le size;
    u32_le alignment;
};
static_assert(sizeof(NsoSegmentHeader) == 0x10, "NsoSegmentHeader has incorrect size.");

struct NsoHeader {
    u32_le magic;
    INSERT_PADDING_BYTES(0xc);
    std::array<NsoSegmentHeader, 3> segments; // Text, RoData, Data (in that order)
    u32_le bss_size;
    INSERT_PADDING_BYTES(0x1c);
    std::array<u32_le, 3> segments_compressed_size;
};
static_assert(sizeof(NsoHeader) == 0x6c, "NsoHeader has incorrect size.");

struct ModHeader {
    u32_le magic;
    u32_le dynamic_offset;
    u32_le bss_start_offset;
    u32_le bss_end_offset;
    u32_le eh_frame_hdr_start_offset;
    u32_le eh_frame_hdr_end_offset;
    u32_le module_offset; // Offset to runtime-generated module object. typically equal to .bss base
};
static_assert(sizeof(ModHeader) == 0x1c, "ModHeader has incorrect size.");

FileType AppLoader_NSO::IdentifyType(FileUtil::IOFile& file) {
    u32 magic = 0;
    file.Seek(0, SEEK_SET);
    if (1 != file.ReadArray<u32>(&magic, 1)) {
        return FileType::Error;
    }

    if (MakeMagic('N', 'S', 'O', '0') == magic) {
        return FileType::NSO;
    }

    return FileType::Error;
}

static std::vector<u8> ReadSegment(FileUtil::IOFile& file, const NsoSegmentHeader& header,
                                   int compressed_size) {
    std::vector<u8> compressed_data;
    compressed_data.resize(compressed_size);

    file.Seek(header.offset, SEEK_SET);
    if (compressed_size != file.ReadBytes(compressed_data.data(), compressed_size)) {
        LOG_CRITICAL(Loader, "Failed to read %d NSO LZ4 compressed bytes", compressed_size);
        return {};
    }

    std::vector<u8> uncompressed_data;
    uncompressed_data.resize(header.size);
    const int bytes_uncompressed =
        LZ4_decompress_safe_partial(reinterpret_cast<const char*>(compressed_data.data()),
                                    reinterpret_cast<char*>(uncompressed_data.data()),
                                    compressed_size, header.size, header.size);

    ASSERT_MSG(bytes_uncompressed == header.size, "%d != %d", bytes_uncompressed, header.size);

    return uncompressed_data;
}

VAddr AppLoader_NSO::GetEntryPoint(VAddr load_base) const {
    // Find nnMain function, set entrypoint to that address
    const auto& search = exports.find("nnMain");
    if (search != exports.end()) {
        return search->second;
    }
    LOG_ERROR(Loader, "Unable to find entrypoint, defaulting to: 0x%llx", load_base);
    return load_base;
}

static constexpr u32 PageAlignSize(u32 size) {
    return (size + Memory::PAGE_MASK) & ~Memory::PAGE_MASK;
}

bool AppLoader_NSO::LoadNso(const std::string& path, VAddr load_base) {
    FileUtil::IOFile file(path, "rb");
    if (!file.IsOpen()) {
        return {};
    }

    // Read NSO header
    NsoHeader nso_header{};
    file.Seek(0, SEEK_SET);
    if (sizeof(NsoHeader) != file.ReadBytes(&nso_header, sizeof(NsoHeader))) {
        return {};
    }
    if (nso_header.magic != MakeMagic('N', 'S', 'O', '0')) {
        return {};
    }

    // Build program image
    Kernel::SharedPtr<Kernel::CodeSet> codeset = Kernel::CodeSet::Create("", 0);
    std::vector<u8> program_image;
    for (int i = 0; i < nso_header.segments.size(); ++i) {
        std::vector<u8> data =
            ReadSegment(file, nso_header.segments[i], nso_header.segments_compressed_size[i]);
        program_image.resize(nso_header.segments[i].location);
        program_image.insert(program_image.end(), data.begin(), data.end());
        codeset->segments[i].addr = nso_header.segments[i].location;
        codeset->segments[i].offset = nso_header.segments[i].location;
        codeset->segments[i].size = PageAlignSize(static_cast<u32>(data.size()));
    }

    // MOD header pointer is at .text offset + 4
    u32 module_offset;
    std::memcpy(&module_offset, program_image.data() + 4, sizeof(u32));

    // Read MOD header
    ModHeader mod_header{};
    u32 bss_size{Memory::PAGE_SIZE}; // Default .bss to page size if MOD0 section doesn't exist
    std::memcpy(&mod_header, program_image.data() + module_offset, sizeof(ModHeader));
    const bool has_mod_header{mod_header.magic == MakeMagic('M', 'O', 'D', '0')};
    if (has_mod_header) {
        // Resize program image to include .bss section and page align each section
        bss_size = PageAlignSize(mod_header.bss_end_offset - mod_header.bss_start_offset);
        codeset->data.size += bss_size;
    }
    program_image.resize(PageAlignSize(static_cast<u32>(program_image.size()) + bss_size));

    // Relocate symbols if there was a proper MOD header - This must happen after the image has been
    // loaded into memory
    if (has_mod_header) {
        Relocate(program_image, module_offset + mod_header.dynamic_offset, load_base);
    }

    // Load codeset for current process
    codeset->name = path;
    codeset->memory = std::make_shared<std::vector<u8>>(std::move(program_image));
    Kernel::g_current_process->LoadModule(codeset, load_base);

    return true;
}

ResultStatus AppLoader_NSO::Load() {
    if (is_loaded) {
        return ResultStatus::ErrorAlreadyLoaded;
    }
    if (!file.IsOpen()) {
        return ResultStatus::Error;
    }

    // Load and relocate "main" and "sdk" NSO
    static constexpr VAddr main_base{0x710000000};
    Kernel::g_current_process = Kernel::Process::Create("main");
    if (!LoadNso(filepath, main_base)) {
        return ResultStatus::ErrorInvalidFormat;
    }
    const std::string sdkpath = filepath.substr(0, filepath.find_last_of("/\\")) + "/sdk";
    if (!LoadNso(sdkpath, 0x720000000)) {
        LOG_WARNING(Loader, "failed to find SDK NSO");
    }

    Kernel::g_current_process->svc_access_mask.set();
    Kernel::g_current_process->address_mappings = default_address_mappings;
    Kernel::g_current_process->resource_limit =
        Kernel::ResourceLimit::GetForCategory(Kernel::ResourceLimitCategory::APPLICATION);
    Kernel::g_current_process->Run(GetEntryPoint(main_base), 48, Kernel::DEFAULT_STACK_SIZE);

    ResolveImports();

    is_loaded = true;
    return ResultStatus::Success;
}

} // namespace Loader