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-rw-r--r--src/corelib/tools/qsimd.cpp103
1 files changed, 63 insertions, 40 deletions
diff --git a/src/corelib/tools/qsimd.cpp b/src/corelib/tools/qsimd.cpp
index 6e3b0f9faf..d7c1d8c4a9 100644
--- a/src/corelib/tools/qsimd.cpp
+++ b/src/corelib/tools/qsimd.cpp
@@ -1,7 +1,7 @@
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
-** Copyright (C) 2018 Intel Corporation.
+** Copyright (C) 2019 Intel Corporation.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
@@ -188,6 +188,8 @@ static inline quint64 detectProcessorFeatures()
# define PICreg "%%rbx"
#endif
+static bool checkRdrndWorks() noexcept;
+
static int maxBasicCpuidSupported()
{
#if defined(Q_CC_EMSCRIPTEN)
@@ -376,37 +378,8 @@ static quint64 detectProcessorFeatures()
features &= ~AllAVX512;
}
-#if defined(Q_PROCESSOR_X86) && QT_COMPILER_SUPPORTS_HERE(RDRND)
- /**
- * Some AMD CPUs (e.g. AMD A4-6250J and AMD Ryzen 3000-series) have a
- * failing random generation instruction, which always returns
- * 0xffffffff, even when generation was "successful".
- *
- * This code checks if hardware random generator generates four consecutive
- * equal numbers. If it does, then we probably have a failing one and
- * should disable it completely.
- *
- * https://bugreports.qt.io/browse/QTBUG-69423
- */
- if (features & CpuFeatureRDRND) {
- const qsizetype testBufferSize = 4;
- unsigned testBuffer[4] = {};
-
- const qsizetype generated = qRandomCpu(testBuffer, testBufferSize);
-
- if (Q_UNLIKELY(generated == testBufferSize &&
- testBuffer[0] == testBuffer[1] &&
- testBuffer[1] == testBuffer[2] &&
- testBuffer[2] == testBuffer[3])) {
-
- fprintf(stderr, "WARNING: CPU random generator seem to be failing, disable hardware random number generation\n");
- fprintf(stderr, "WARNING: RDRND generated: 0x%x 0x%x 0x%x 0x%x\n",
- testBuffer[0], testBuffer[1], testBuffer[2], testBuffer[3]);
-
- features &= ~CpuFeatureRDRND;
- }
- }
-#endif
+ if (features & CpuFeatureRDRND && !checkRdrndWorks())
+ features &= ~(CpuFeatureRDRND | CpuFeatureRDSEED);
return features;
}
@@ -662,15 +635,9 @@ static unsigned *qt_random_rdseed(unsigned *ptr, unsigned *)
}
# endif
-QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) noexcept
+static QT_FUNCTION_TARGET(RDRND) unsigned *qt_random_rdrnd(unsigned *ptr, unsigned *end) noexcept
{
- unsigned *ptr = reinterpret_cast<unsigned *>(buffer);
- unsigned *end = ptr + count;
int retries = 10;
-
- if (qCpuHasFeature(RDSEED))
- ptr = qt_random_rdseed(ptr, end);
-
while (ptr + sizeof(qregisteruint)/sizeof(*ptr) <= end) {
if (_rdrandXX_step(reinterpret_cast<qregisteruint *>(ptr)))
ptr += sizeof(qregisteruint)/sizeof(*ptr);
@@ -688,8 +655,64 @@ QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) no
}
out:
+ return ptr;
+}
+
+static QT_FUNCTION_TARGET(RDRND) Q_DECL_COLD_FUNCTION bool checkRdrndWorks() noexcept
+{
+ /*
+ * Some AMD CPUs (e.g. AMD A4-6250J and AMD Ryzen 3000-series) have a
+ * failing random generation instruction, which always returns
+ * 0xffffffff, even when generation was "successful".
+ *
+ * This code checks if hardware random generator generates four consecutive
+ * equal numbers. If it does, then we probably have a failing one and
+ * should disable it completely.
+ *
+ * https://bugreports.qt.io/browse/QTBUG-69423
+ */
+ constexpr qsizetype TestBufferSize = 4;
+ unsigned testBuffer[TestBufferSize] = {};
+
+ unsigned *end = qt_random_rdrnd(testBuffer, testBuffer + TestBufferSize);
+ if (end < testBuffer + 3) {
+ // Random generation didn't produce enough data for us to make a
+ // determination whether it's working or not. Assume it isn't, but
+ // don't print a warning.
+ return false;
+ }
+
+ // Check the results for equality
+ if (testBuffer[0] == testBuffer[1]
+ && testBuffer[0] == testBuffer[2]
+ && end == testBuffer + TestBufferSize && testBuffer[0] == testBuffer[3]) {
+ fprintf(stderr, "WARNING: CPU random generator seem to be failing, "
+ "disabling hardware random number generation\n"
+ "WARNING: RDRND generated:");
+ for (unsigned *ptr = testBuffer; ptr < end; ++ptr)
+ fprintf(stderr, " 0x%x", *ptr);
+ fprintf(stderr, "\n");
+ return false;
+ }
+
+ // We're good
+ return true;
+}
+
+QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) noexcept
+{
+ unsigned *ptr = reinterpret_cast<unsigned *>(buffer);
+ unsigned *end = ptr + count;
+
+ if (qCpuHasFeature(RDSEED))
+ ptr = qt_random_rdseed(ptr, end);
+
+ // fill the buffer with RDRND if RDSEED didn't
+ ptr = qt_random_rdrnd(ptr, end);
return ptr - reinterpret_cast<unsigned *>(buffer);
}
-#endif
+#elif defined(Q_PROCESSOR_X86) && !defined(Q_OS_NACL) && !defined(Q_PROCESSOR_ARM)
+static bool checkRdrndWorks() noexcept { return false; }
+#endif // Q_PROCESSOR_X86 && RDRND
QT_END_NAMESPACE