mirror of https://github.com/OpenIPC/firmware.git
76 lines
2.4 KiB
Diff
76 lines
2.4 KiB
Diff
--- linux-4.9.37/include/linux/nospec.h 1970-01-01 03:00:00.000000000 +0300
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+++ linux-4.9.y/include/linux/nospec.h 2021-06-07 13:01:34.000000000 +0300
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@@ -0,0 +1,72 @@
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+// SPDX-License-Identifier: GPL-2.0
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+// Copyright(c) 2018 Linus Torvalds. All rights reserved.
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+// Copyright(c) 2018 Alexei Starovoitov. All rights reserved.
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+// Copyright(c) 2018 Intel Corporation. All rights reserved.
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+
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+#ifndef _LINUX_NOSPEC_H
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+#define _LINUX_NOSPEC_H
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+
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+/**
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+ * array_index_mask_nospec() - generate a ~0 mask when index < size, 0 otherwise
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+ * @index: array element index
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+ * @size: number of elements in array
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+ *
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+ * When @index is out of bounds (@index >= @size), the sign bit will be
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+ * set. Extend the sign bit to all bits and invert, giving a result of
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+ * zero for an out of bounds index, or ~0 if within bounds [0, @size).
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+ */
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+#ifndef array_index_mask_nospec
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+static inline unsigned long array_index_mask_nospec(unsigned long index,
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+ unsigned long size)
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+{
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+ /*
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+ * Warn developers about inappropriate array_index_nospec() usage.
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+ *
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+ * Even if the CPU speculates past the WARN_ONCE branch, the
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+ * sign bit of @index is taken into account when generating the
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+ * mask.
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+ *
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+ * This warning is compiled out when the compiler can infer that
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+ * @index and @size are less than LONG_MAX.
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+ */
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+ if (WARN_ONCE(index > LONG_MAX || size > LONG_MAX,
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+ "array_index_nospec() limited to range of [0, LONG_MAX]\n"))
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+ return 0;
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+
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+ /*
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+ * Always calculate and emit the mask even if the compiler
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+ * thinks the mask is not needed. The compiler does not take
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+ * into account the value of @index under speculation.
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+ */
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+ OPTIMIZER_HIDE_VAR(index);
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+ return ~(long)(index | (size - 1UL - index)) >> (BITS_PER_LONG - 1);
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+}
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+#endif
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+
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+/*
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+ * array_index_nospec - sanitize an array index after a bounds check
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+ *
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+ * For a code sequence like:
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+ *
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+ * if (index < size) {
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+ * index = array_index_nospec(index, size);
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+ * val = array[index];
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+ * }
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+ *
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+ * ...if the CPU speculates past the bounds check then
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+ * array_index_nospec() will clamp the index within the range of [0,
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+ * size).
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+ */
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+#define array_index_nospec(index, size) \
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+ ({ \
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+ typeof(index) _i = (index); \
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+ typeof(size) _s = (size); \
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+ unsigned long _mask = array_index_mask_nospec(_i, _s); \
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+ \
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+ BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
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+ BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
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+ \
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+ _i &= _mask; \
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+ _i; \
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+ })
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+#endif /* _LINUX_NOSPEC_H */
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