/*
    SPDX-FileCopyrightText: 2013-2014 Volker Krause <vkrause@kde.org>

    SPDX-License-Identifier: LGPL-2.0-or-later
*/

#include "elffileset.h"
#include "elfheader.h"
#include "elfgnudebuglinksection.h"

#include <QDebug>
#include <QDir>
#include <QFileInfo>

#include <cassert>

using namespace Qt::Literals;

ElfFileSet::ElfFileSet(QObject* parent) : QObject(parent)
{
    parseLdConf();
    for (const auto &path : qgetenv("LD_LIBRARY_PATH").split(':'))
        m_baseSearchPaths.push_back(path);

    m_globalDebugSearchPath.push_back(QStringLiteral("/usr/lib/debug")); // seems hardcoded?
}

ElfFileSet::~ElfFileSet()
{
    qDeleteAll(m_files);
}

void ElfFileSet::addFile(const QString& fileName)
{
    ElfFile* f = new ElfFile(fileName);
    if (!f->open(QIODevice::ReadOnly) || !f->isValid()) {
        delete f;
        return;
    }
    addFile(f);
}

static void resolvePlaceholder(QList<QByteArray> &paths, const QByteArray &originPath)
{
    for (auto it = paths.begin(); it != paths.end(); ++it)
        (*it).replace("$ORIGIN", originPath);
}

void ElfFileSet::addFile(ElfFile* file)
{
    assert(file);
    assert(file->isValid());

    findSeparateDebugFile(file);
    m_files.push_back(file);

    if (!file->dynamicSection())
        return;

    auto rpaths = file->dynamicSection()->rpaths();
    auto runpaths = file->dynamicSection()->runpaths();
    auto originPath = QFileInfo(file->fileName()).absolutePath().toUtf8();
    resolvePlaceholder(rpaths, originPath);
    resolvePlaceholder(runpaths, originPath);

    QList<QByteArray> searchPaths;
    searchPaths.reserve(rpaths.size() + m_ldLibraryPaths.size() + runpaths.size() + m_baseSearchPaths.size());
    if (runpaths.isEmpty()) // DT_RPATH is supposed to be ignored if DT_RUNPATH is present
        searchPaths += rpaths;
    searchPaths += m_ldLibraryPaths;
    searchPaths += runpaths;
    searchPaths += m_baseSearchPaths;

    for (const auto &lib : file->dynamicSection()->neededLibraries()) {
        if (std::find_if(m_files.cbegin(), m_files.cend(), [lib](ElfFile *file){ return file->dynamicSection()->soName() == lib; }) != m_files.cend())
            continue;
        bool dependencyFound = false;
        for (const auto &dir : searchPaths) {
            const auto fullPath = QString::fromUtf8(dir + '/' + lib);
            if (!QFile::exists(fullPath))
                continue;
            ElfFile *dep = new ElfFile(fullPath);
            ElfFile *firstFile = m_files.at(0);
            if (dep->open(QIODevice::ReadOnly) && dep->isValid() && dep->type() == firstFile->type() && dep->header()->machine() == firstFile->header()->machine()) {
                dependencyFound = true;
                addFile(dep);
                break;
            }
            delete dep;
        }

        // deal with NEEDED entries containing absolute paths
        if (!dependencyFound && lib.startsWith('/')) {
            const auto libFile = QString::fromUtf8(lib);
            if (std::find_if(m_files.cbegin(), m_files.cend(), [libFile](ElfFile *file){ return file->fileName() == libFile; }) != m_files.cend())
                continue;
            if (QFile::exists(libFile)) {
                ElfFile *dep = new ElfFile(libFile);
                ElfFile *firstFile = m_files.at(0);
                if (dep->open(QIODevice::ReadOnly) && dep->isValid() && dep->type() == firstFile->type() && dep->header()->machine() == firstFile->header()->machine()) {
                    dependencyFound = true;
                    addFile(dep);
                } else {
                    delete dep;
                }
            }
        }

        if (!dependencyFound)
            qWarning() << "Unable to locate dependency" << lib;
    }
}

int ElfFileSet::size() const
{
    return m_files.size();
}

ElfFile* ElfFileSet::file(int index) const
{
    return m_files.at(index);
}

static bool hasUnresolvedDependencies(ElfFile *file, const QList<ElfFile*> &resolved, int startIndex)
{
    if (!file->dynamicSection())
        return false;

    for (const auto &lib : file->dynamicSection()->neededLibraries()) {
        const auto it = std::find_if(resolved.constBegin() + startIndex, resolved.constEnd(), [lib](ElfFile *file){ return file->dynamicSection()->soName() == lib; });
        if (it == resolved.constEnd()) {
            return true;
        }
    }
    return false;
}

void ElfFileSet::topologicalSort()
{
    QList<ElfFile*> sorted;
    sorted.resize(m_files.size());

    QList<ElfFile*> remaining = m_files;

    for (int i = sorted.size() - 1; i >= 0; --i) {
        for (auto it = std::begin(remaining); it != std::end(remaining); ++it) {
            if (!hasUnresolvedDependencies(*it, sorted, i + 1)) {
                sorted[i] = *it;
                remaining.erase(it);
                break;
            }
        }

        // we did not find one with unresolved dependencies, shouldn't happen, unless there's a cycle
        // so just take one and see how far we get
        if (sorted.at(i) == nullptr)
            sorted[i] = remaining.takeFirst();
    }

#if 0
    qDebug() << "input";
    for(const auto f : m_files)
        qDebug() << f->displayName() << f->fileName();
    qDebug() << "sorted";
    for(const auto f : sorted)
        qDebug() << f->displayName();
    qDebug() << "remaining";
    for(const auto f : remaining)
        qDebug() << f->displayName();
#endif

    Q_ASSERT(remaining.isEmpty());
    if (sorted.first() != m_files.first()) {
        qWarning() << "FILE SET ORDER IS MESSED UP\nThis mostly happens due to missing dependencies. Let's try to ignore it for now...";
    }

    m_files = sorted;
}

void ElfFileSet::parseLdConf()
{
    parseLdConf(QStringLiteral("/etc/ld.so.conf"));

    // built-in defaults
    m_baseSearchPaths.push_back("/lib64");
    m_baseSearchPaths.push_back("/lib");
    m_baseSearchPaths.push_back("/usr/lib64");
    m_baseSearchPaths.push_back("/usr/lib");
}

void ElfFileSet::parseLdConf(const QString& fileName)
{
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly)) {
        qWarning() << file.errorString();
        return;
    }

    while (!file.atEnd()) {
        const auto line = file.readLine().trimmed();
        if (line.isEmpty())
            continue;
        if (line.startsWith('#'))
            continue;
        if (line.startsWith("include")) {
            const auto fileGlob = QString::fromUtf8(line.mid(8));
            if (QFileInfo::exists(fileGlob)) {
                parseLdConf(fileGlob);
            } else {
                const auto idx = fileGlob.lastIndexOf('/'_L1);
                assert(idx >= 0);
                QDir dir(fileGlob.left(idx));
                for (const auto &file : dir.entryList(QStringList() << fileGlob.mid(idx + 1)))
                    parseLdConf(dir.absolutePath() + '/'_L1 + file);
            }
            continue;
        }
        if (line.startsWith('/')) {
            if (QFileInfo::exists(QString::fromUtf8(line)))
                m_baseSearchPaths.push_back(line);
            continue;
        }
        qWarning() << "unable to handle ld.so.conf line:" << line;
    }
}

void ElfFileSet::findSeparateDebugFile(ElfFile* file) const
{
    // (1) via build id
    const auto buildId = file->buildId().toHex();
    for (const auto &debugDir : m_globalDebugSearchPath) {
        QString debugFile = debugDir + "/.build-id/"_L1 + QString::fromUtf8(buildId.left(2)) + "/"_L1 + QString::fromUtf8(buildId.mid(2)) + ".debug"_L1;
        if (QFile::exists(debugFile)) {
            file->setSeparateDebugFile(debugFile);
            return;
        }
    }

    // (2) via debug link
    const auto debugLinkIndex = file->indexOfSection(".gnu_debuglink");
    if (debugLinkIndex < 0)
        return;
    const auto debugLinkSection = file->section<ElfGnuDebugLinkSection>(debugLinkIndex);
    assert(debugLinkSection);
    if (debugLinkSection->fileName().isEmpty())
        return;
    const auto dir = QFileInfo(file->fileName()).absolutePath();

    // (2a) next to file
    QString debugFile = dir + "/"_L1 + QString::fromUtf8(debugLinkSection->fileName());
    if (isValidDebugLinkFile(debugFile, debugLinkSection->crc())) {
        file->setSeparateDebugFile(debugFile);
        return;
    }

    // (2b) in .debug sub-folder next to file
    debugFile = dir + "/.debug/"_L1 + QString::fromUtf8(debugLinkSection->fileName());
    if (isValidDebugLinkFile(debugFile, debugLinkSection->crc())) {
        file->setSeparateDebugFile(debugFile);
        return;
    }

    // (2c) in global debug directories
    for (const auto &debugDir : m_globalDebugSearchPath) {
        debugFile = debugDir + dir + "/"_L1 + QString::fromUtf8(debugLinkSection->fileName());
        if (isValidDebugLinkFile(debugFile, debugLinkSection->crc())) {
            file->setSeparateDebugFile(debugFile);
            return;
        }
    }
}

// from GDB manual
static uint32_t gnu_debuglink_crc32 (uint32_t crc, unsigned char *buf, size_t len)
{
    static const unsigned long crc32_table[256] =
    {
        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
        0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
        0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
        0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
        0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
        0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
        0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
        0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
        0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
        0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
        0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
        0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
        0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
        0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
        0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
        0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
        0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
        0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
        0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
        0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
        0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
        0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
        0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
        0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
        0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
        0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
        0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
        0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
        0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
        0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
        0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
        0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
        0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
        0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
        0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
        0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
        0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
        0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
        0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
        0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
        0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
        0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
        0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
        0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
        0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
        0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
        0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
        0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
        0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
        0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
        0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
        0x2d02ef8d
    };
    unsigned char *end;

    crc = ~crc & 0xffffffff;
    for (end = buf + len; buf < end; ++buf)
        crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
    return ~crc & 0xffffffff;
}

bool ElfFileSet::isValidDebugLinkFile(const QString& fileName, uint32_t expectedCrc)
{
    if (!QFile::exists(fileName))
        return false;

    QFile f(fileName);
    if (!f.open(QFile::ReadOnly))
        return false;

    auto data = f.map(0, f.size());
    if (!data)
        return false;

    auto actualCrc = gnu_debuglink_crc32(0, data, f.size());
    qDebug() << fileName << expectedCrc << actualCrc;
    return actualCrc == expectedCrc;
}
