[Minios-devel] [UNIKRAFT RFC PATCH 1/1] plat/common: Implement ffs/fls for non-x86 architectures

[Jianyong Wu <jianyong.wu@xxxxxxx>]

From: Jianyong Wu <Jianyong.Wu@xxxxxxx>

Some architectures like Arm64 don't have special instructions
like x86 to implement ffs/fls functions. So we use C code to
implement these functions for non-x86 architectures.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
 arch/arm/arm64/include/uk/asm/atomic.h |  32 ++++++++
 plat/common/bitops.c                   | 103 +++++++++++++++++++++++++
 2 files changed, 135 insertions(+)
 create mode 100644 plat/common/bitops.c

diff --git a/arch/arm/arm64/include/uk/asm/atomic.h 
b/arch/arm/arm64/include/uk/asm/atomic.h
index 7ee6667..8b5459f 100644
--- a/arch/arm/arm64/include/uk/asm/atomic.h
+++ b/arch/arm/arm64/include/uk/asm/atomic.h
@@ -68,3 +68,35 @@ static inline unsigned long ukarch_ffsl(unsigned long word)
 
        return 63 - clz;
 }
+
+/*
+ * ukarch_fls - find last (highest) set bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned int ukarch_fls(unsigned int word);
+
+/*
+ * ukarch_flsl - find last (highest) set bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned long ukarch_flsl(unsigned long word);
+
+/*
+ * ukarch_ffs - find first (lowest) set bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned long ukarch_ffs(unsigned int word);
+
+/*
+ * ukarch_ffsl - find first (lowest) set bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned long ukarch_ffsl(unsigned long word);
diff --git a/plat/common/bitops.c b/plat/common/bitops.c
new file mode 100644
index 0000000..6b8f767
--- /dev/null
+++ b/plat/common/bitops.c
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Code base on:
+ * https://github.com/freebsd/freebsd/tree/master/sys/libkern/
+ * fls.c/flsl.c/flsll.c/ffs.c/ffsl.c
+ *
+ * Authors: Wei Chen <wei.chen@xxxxxxx>
+ *
+ * Copyright (c) 2018, Arm Ltd., All rights reserved.
+ * Copyright (c) 1990, 1993
+ *     The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY.
+ */
+#define _FLSx(x)                       \
+({                                     \
+       int lsb;                        \
+       if (x == 0)                     \
+               return 0;               \
+       for (lsb = 1; x != 1; lsb++)    \
+               x = x >> 1;     \
+       lsb;                            \
+})
+
+#define _FFSx(x)                       \
+({                                     \
+       int fsb;                        \
+       if (x == 0)                     \
+               return 0;               \
+       for (fsb = 1; !(x & 1); fsb++)  \
+               x = x >> 1;             \
+       fsb;                            \
+})
+
+/**
+ * ukarch_fls - find last (highest) set bit in word for all architectures.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned int ukarch_fls(unsigned int word)
+{
+       return _FLSx(word);
+}
+
+/**
+ * ukarch_flsl - find last (highest) set bit in word for all architectures.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned int ukarch_flsl(unsigned long word)
+{
+       return _FLSx(word);
+}
+
+/**
+ * ukarch_ffs - find first (lowest) set bit in word for all architectures.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned long ukarch_ffs(unsigned int word)
+{
+       return _FFSx(word);
+}
+
+
+/**
+ * ukarch_ffsl - find first (lowest) set bit in word for all architectures.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+unsigned long ukarch_ffsl(unsigned long word)
+{
+       return _FFSx(word);
+}
-- 
2.17.1


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