qv4functiontable_unix.cpp

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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant
 
#include "qv4functiontable_p.h"
#include "qv4function_p.h"
 
#include <assembler/MacroAssemblerCodeRef.h>
 
#include <QtCore/qfile.h>
#include <QtCore/qcoreapplication.h>
 
QT_BEGIN_NAMESPACE
 
namespace QV4 {
 
void generateFunctionTable(Function *function, JSC::MacroAssemblerCodeRef *codeRef)
{
    // This implements writing of JIT'd addresses so that perf can find the
    // symbol names.
    //
    // Perf expects the mapping to be in a certain place and have certain
    // content, for more information, see:
    // https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt
    static bool doProfile = !qEnvironmentVariableIsEmpty("QV4_PROFILE_WRITE_PERF_MAP");
    if (Q_UNLIKELY(doProfile)) {
        static QFile perfMapFile(QString::fromLatin1("/tmp/perf-%1.map")
                                 .arg(QCoreApplication::applicationPid()));
        static const bool isOpen = perfMapFile.open(QIODevice::WriteOnly);
        if (!isOpen) {
            qWarning("QV4::JIT::Assembler: Cannot write perf map file.");
            doProfile = false;
        } else {
            const void *address = codeRef->code().executableAddress();
            perfMapFile.write(QByteArray::number(reinterpret_cast<quintptr>(address), 16));
            perfMapFile.putChar(' ');
            perfMapFile.write(QByteArray::number(static_cast<qsizetype>(codeRef->size()), 16));
            perfMapFile.putChar(' ');
            perfMapFile.write(Function::prettyName(function, address).toUtf8());
            perfMapFile.putChar('\n');
            perfMapFile.flush();
        }
    }
}
 
void destroyFunctionTable(Function *function, JSC::MacroAssemblerCodeRef *codeRef)
{
    Q_UNUSED(function);
    Q_UNUSED(codeRef);
 
    // It's not advisable to remove things from the perf map file, as it's primarily used to analyze
    // a trace after the application has terminated. We want to know about all functions that were
    // ever jitted then. If the memory ranges overlap, we will have a problem when analyzing the
    // trace. The JIT should try to avoid this.
}
 
size_t exceptionHandlerSize()
{
    return 0;
}
 
} // QV4
 
QT_END_NAMESPACE