Fix largefile tests on ARM and QEMU targets

- Test tst_LargeFile::mapFile fails on Qemu for files over 4Gb.
  Fixed by limiting maxSizeBits to 28 (must be n*4 and < 32).
- Bug QTBUG-21175 is also effective on ARM targets. Fixed by
  expecting failure also on ARM.

Change-Id: I9103727e618a17259b4785ec8c284f3bb60ebea7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

tests/auto/corelib/io/largefile/largefile.pro

@@ -2,3 +2,5 @@ CONFIG += testcase
 TARGET = tst_largefile
 QT = core testlib
 SOURCES = tst_largefile.cpp
+INCLUDEPATH += ../../../../shared/
+HEADERS += ../../../../shared/emulationdetector.h

tests/auto/corelib/io/largefile/tst_largefile.cpp

@@ -47,6 +47,8 @@
 #  endif
 #endif // Q_OS_WIN
 
+#include "emulationdetector.h"
+
 class tst_LargeFile
     : public QObject
 {
@@ -68,6 +70,10 @@ public:
     #else
         maxSizeBits = 24; // 16 MiB
     #endif
+
+        // QEMU only supports < 4GB files
+        if (EmulationDetector::isRunningArmOnX86())
+            maxSizeBits = qMin(maxSizeBits, 28);
     }
 
 private:

tests/shared/emulationdetector.h

@@ -0,0 +1,119 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef EMULATIONDETECTOR_H
+#define EMULATIONDETECTOR_H
+
+#if defined(Q_OS_LINUX) && defined(Q_PROCESSOR_ARM)
+#define SHOULD_CHECK_ARM_ON_X86
+
+#if QT_CONFIG(process) && !defined(QT_NO_REGULAREXPRESSION)
+#include <QProcess>
+#include <QRegularExpression>
+#endif
+
+#endif
+
+QT_BEGIN_NAMESPACE
+
+// Helper functions for detecting if running emulated
+namespace EmulationDetector {
+
+#ifdef SHOULD_CHECK_ARM_ON_X86
+static bool isX86SpecificFileAvailable(void);
+static bool isReportedArchitectureX86(void);
+#endif
+
+/*
+ * Check if we are running Arm binary on x86 machine.
+ *
+ * Currently this is only able to check on Linux. If not able to
+ * detect, return false.
+ */
+static bool isRunningArmOnX86()
+{
+#ifdef SHOULD_CHECK_ARM_ON_X86
+    if (isX86SpecificFileAvailable())
+        return true;
+
+    if (isReportedArchitectureX86())
+        return true;
+#endif
+    return false;
+}
+
+#ifdef SHOULD_CHECK_ARM_ON_X86
+/*
+ * Check if we can find a file that's only available on x86
+ */
+static bool isX86SpecificFileAvailable()
+{
+    // MTRR (Memory Type Range Registers) are a feature of the x86 architecture
+    // and /proc/mtrr is only present (on Linux) for that family.
+    // However, it's an optional kernel feature, so the absence of the file is
+    // not sufficient to conclude we're on real hardware.
+    QFileInfo mtrr("/proc/mtrr");
+    if (mtrr.exists())
+        return true;
+    return false;
+}
+
+/*
+ * Check if architecture reported by the OS is x86
+ */
+static bool isReportedArchitectureX86(void)
+{
+#if QT_CONFIG(process) && !defined(QT_NO_REGULAREXPRESSION)
+    QProcess unamer;
+    QString machineString;
+
+    // Using syscall "uname" is not possible since that would be captured by
+    // QEMU and result would be the architecture being emulated (e.g. armv7l).
+    // By using QProcess we get the architecture used by the host.
+    unamer.start("uname -a");
+    if (!unamer.waitForFinished()) {
+        return false;
+    }
+    machineString = unamer.readAll();
+
+    // Is our current host cpu x86?
+    if (machineString.contains(QRegularExpression("i386|i686|x86"))) {
+        return true;
+    }
+#endif
+
+    return false;
+}
+#endif // SHOULD_CHECK_ARM_ON_X86
+
+} // EmulationDetector namespace
+
+QT_END_NAMESPACE
+
+#endif
+