1 files changed, 83 insertions, 0 deletions
diff --git a/src/qml/jsruntime/qv4compilationunitmapper_unix.cpp b/src/qml/jsruntime/qv4compilationunitmapper_unix.cpp
new file mode 100644
index 0000000000..204e222121
--- /dev/null
+++ b/src/qml/jsruntime/qv4compilationunitmapper_unix.cpp
@@ -0,0 +1,83 @@
+// Copyright (C) 2016 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
+
+#include "qv4compilationunitmapper_p.h"
+
+#include <private/qcore_unix_p.h>
+#include <private/qv4compileddata_p.h>
+
+#include <QtCore/qscopeguard.h>
+#include <QtCore/qdatetime.h>
+
+#include <functional>
+#include <sys/mman.h>
+
+QT_BEGIN_NAMESPACE
+
+using namespace QV4;
+
+CompiledData::Unit *CompilationUnitMapper::open(const QString &cacheFileName, const QDateTime &sourceTimeStamp, QString *errorString)
+{
+    close();
+
+    int fd = qt_safe_open(QFile::encodeName(cacheFileName).constData(), O_RDONLY);
+    if (fd == -1) {
+        *errorString = qt_error_string(errno);
+        return nullptr;
+    }
+
+    auto cleanup = qScopeGuard([fd]{
+       qt_safe_close(fd) ;
+    });
+
+    CompiledData::Unit header;
+    qint64 bytesRead = qt_safe_read(fd, reinterpret_cast<char *>(&header), sizeof(header));
+
+    if (bytesRead != sizeof(header)) {
+        *errorString = QStringLiteral("File too small for the header fields");
+        return nullptr;
+    }
+
+    if (!header.verifyHeader(sourceTimeStamp, errorString))
+        return nullptr;
+
+    // Data structure and qt version matched, so now we can access the rest of the file safely.
+
+    length = static_cast<size_t>(lseek(fd, 0, SEEK_END));
+    /* Error out early on file corruption. We assume we can read header.unitSize bytes
+       later (even before verifying the checksum), potentially causing out-of-bound
+       reads
+       Also, no need to wait until checksum verification if we know beforehand
+       that the cached unit is bogus
+    */
+    if (length != header.unitSize) {
+        *errorString = QStringLiteral("Potential file corruption, file too small");
+        return nullptr;
+    }
+
+    void *ptr = mmap(nullptr, length, PROT_READ, MAP_SHARED, fd, /*offset*/0);
+    if (ptr == MAP_FAILED) {
+        *errorString = qt_error_string(errno);
+        return nullptr;
+    }
+    dataPtr = ptr;
+
+    return reinterpret_cast<CompiledData::Unit*>(dataPtr);
+}
+
+void CompilationUnitMapper::close()
+{
+    // Do not unmap the data here.
+    if (dataPtr != nullptr) {
+        // Do not unmap cache files that are built with the StaticData flag. That's the majority of
+        // them and it's necessary to benefit from the QString literal optimization. There might
+        // still be QString instances around that point into that memory area. The memory is backed
+        // on the disk, so the kernel is free to release the pages and all that remains is the
+        // address space allocation.
+        if (!(reinterpret_cast<CompiledData::Unit*>(dataPtr)->flags & CompiledData::Unit::StaticData))
+            munmap(dataPtr, length);
+    }
+    dataPtr = nullptr;
+}
+
+QT_END_NAMESPACE