[PATCH v3 16/34] xen/lib: introduce generic find next bit operations

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

find-next-bit.c is common for Arm64 and RISC-V64 so it is moved
to xen/lib.

Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V3:
 - new patch.
---
 xen/arch/riscv/include/asm/fence.h |  11 +-
 xen/common/Kconfig                 |   3 +
 xen/lib/Makefile                   |   1 +
 xen/lib/find-next-bit.c            | 281 +++++++++++++++++++++++++++++
 4 files changed, 295 insertions(+), 1 deletion(-)
 create mode 100644 xen/lib/find-next-bit.c

diff --git a/xen/arch/riscv/include/asm/fence.h 
b/xen/arch/riscv/include/asm/fence.h
index b3f6b1c20a..5d9a851ae8 100644
--- a/xen/arch/riscv/include/asm/fence.h
+++ b/xen/arch/riscv/include/asm/fence.h
@@ -1,4 +1,4 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SPDX-License-Identifier: GPL-2.0-only */
 #ifndef _ASM_RISCV_FENCE_H
 #define _ASM_RISCV_FENCE_H
 
@@ -11,3 +11,12 @@
 #endif
 
 #endif /* _ASM_RISCV_FENCE_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 310ad4229c..56ce34ffd4 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -47,6 +47,9 @@ config ARCH_MAP_DOMAIN_PAGE
 config GENERIC_BUG_FRAME
        bool
 
+config GENERIC_FIND_NEXT_BIT
+       bool
+
 config HAS_ALTERNATIVE
        bool
 
diff --git a/xen/lib/Makefile b/xen/lib/Makefile
index 2d9ebb945f..66237a45c5 100644
--- a/xen/lib/Makefile
+++ b/xen/lib/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_X86) += x86/
 lib-y += bsearch.o
 lib-y += ctors.o
 lib-y += ctype.o
+lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find-next-bit.o
 lib-y += list-sort.o
 lib-y += memchr.o
 lib-y += memchr_inv.o
diff --git a/xen/lib/find-next-bit.c b/xen/lib/find-next-bit.c
new file mode 100644
index 0000000000..ca6f82277e
--- /dev/null
+++ b/xen/lib/find-next-bit.c
@@ -0,0 +1,281 @@
+/* find_next_bit.c: fallback find next bit implementation
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+#include <xen/bitops.h>
+
+#include <asm/byteorder.h>
+
+#ifndef find_next_bit
+/*
+ * Find the next set bit in a memory region.
+ */
+unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+                           unsigned long offset)
+{
+       const unsigned long *p = addr + BIT_WORD(offset);
+       unsigned long result = offset & ~(BITS_PER_LONG-1);
+       unsigned long tmp;
+
+       if (offset >= size)
+               return size;
+       size -= result;
+       offset %= BITS_PER_LONG;
+       if (offset) {
+               tmp = *(p++);
+               tmp &= (~0UL << offset);
+               if (size < BITS_PER_LONG)
+                       goto found_first;
+               if (tmp)
+                       goto found_middle;
+               size -= BITS_PER_LONG;
+               result += BITS_PER_LONG;
+       }
+       while (size & ~(BITS_PER_LONG-1)) {
+               if ((tmp = *(p++)))
+                       goto found_middle;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+       tmp = *p;
+
+found_first:
+       tmp &= (~0UL >> (BITS_PER_LONG - size));
+       if (tmp == 0UL)         /* Are any bits set? */
+               return result + size;   /* Nope. */
+found_middle:
+       return result + __ffs(tmp);
+}
+EXPORT_SYMBOL(find_next_bit);
+#endif
+
+#ifndef find_next_zero_bit
+/*
+ * This implementation of find_{first,next}_zero_bit was stolen from
+ * Linus' asm-alpha/bitops.h.
+ */
+unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
+                                unsigned long offset)
+{
+       const unsigned long *p = addr + BIT_WORD(offset);
+       unsigned long result = offset & ~(BITS_PER_LONG-1);
+       unsigned long tmp;
+
+       if (offset >= size)
+               return size;
+       size -= result;
+       offset %= BITS_PER_LONG;
+       if (offset) {
+               tmp = *(p++);
+               tmp |= ~0UL >> (BITS_PER_LONG - offset);
+               if (size < BITS_PER_LONG)
+                       goto found_first;
+               if (~tmp)
+                       goto found_middle;
+               size -= BITS_PER_LONG;
+               result += BITS_PER_LONG;
+       }
+       while (size & ~(BITS_PER_LONG-1)) {
+               if (~(tmp = *(p++)))
+                       goto found_middle;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+       tmp = *p;
+
+found_first:
+       tmp |= ~0UL << size;
+       if (tmp == ~0UL)        /* Are any bits zero? */
+               return result + size;   /* Nope. */
+found_middle:
+       return result + ffz(tmp);
+}
+EXPORT_SYMBOL(find_next_zero_bit);
+#endif
+
+#ifndef find_first_bit
+/*
+ * Find the first set bit in a memory region.
+ */
+unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
+{
+       const unsigned long *p = addr;
+       unsigned long result = 0;
+       unsigned long tmp;
+
+       while (size & ~(BITS_PER_LONG-1)) {
+               if ((tmp = *(p++)))
+                       goto found;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+
+       tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
+       if (tmp == 0UL)         /* Are any bits set? */
+               return result + size;   /* Nope. */
+found:
+       return result + __ffs(tmp);
+}
+EXPORT_SYMBOL(find_first_bit);
+#endif
+
+#ifndef find_first_zero_bit
+/*
+ * Find the first cleared bit in a memory region.
+ */
+unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long 
size)
+{
+       const unsigned long *p = addr;
+       unsigned long result = 0;
+       unsigned long tmp;
+
+       while (size & ~(BITS_PER_LONG-1)) {
+               if (~(tmp = *(p++)))
+                       goto found;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+
+       tmp = (*p) | (~0UL << size);
+       if (tmp == ~0UL)        /* Are any bits zero? */
+               return result + size;   /* Nope. */
+found:
+       return result + ffz(tmp);
+}
+EXPORT_SYMBOL(find_first_zero_bit);
+#endif
+
+#ifdef __BIG_ENDIAN
+
+/* include/linux/byteorder does not support "unsigned long" type */
+static inline unsigned long ext2_swabp(const unsigned long * x)
+{
+#if BITS_PER_LONG == 64
+       return (unsigned long) __swab64p((u64 *) x);
+#elif BITS_PER_LONG == 32
+       return (unsigned long) __swab32p((u32 *) x);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+/* include/linux/byteorder doesn't support "unsigned long" type */
+static inline unsigned long ext2_swab(const unsigned long y)
+{
+#if BITS_PER_LONG == 64
+       return (unsigned long) __swab64((u64) y);
+#elif BITS_PER_LONG == 32
+       return (unsigned long) __swab32((u32) y);
+#else
+#error BITS_PER_LONG not defined
+#endif
+}
+
+#ifndef find_next_zero_bit_le
+unsigned long find_next_zero_bit_le(const void *addr, unsigned
+               long size, unsigned long offset)
+{
+       const unsigned long *p = addr;
+       unsigned long result = offset & ~(BITS_PER_LONG - 1);
+       unsigned long tmp;
+
+       if (offset >= size)
+               return size;
+       p += BIT_WORD(offset);
+       size -= result;
+       offset &= (BITS_PER_LONG - 1UL);
+       if (offset) {
+               tmp = ext2_swabp(p++);
+               tmp |= (~0UL >> (BITS_PER_LONG - offset));
+               if (size < BITS_PER_LONG)
+                       goto found_first;
+               if (~tmp)
+                       goto found_middle;
+               size -= BITS_PER_LONG;
+               result += BITS_PER_LONG;
+       }
+
+       while (size & ~(BITS_PER_LONG - 1)) {
+               if (~(tmp = *(p++)))
+                       goto found_middle_swap;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+       tmp = ext2_swabp(p);
+found_first:
+       tmp |= ~0UL << size;
+       if (tmp == ~0UL)        /* Are any bits zero? */
+               return result + size; /* Nope. Skip ffz */
+found_middle:
+       return result + ffz(tmp);
+
+found_middle_swap:
+       return result + ffz(ext2_swab(tmp));
+}
+EXPORT_SYMBOL(find_next_zero_bit_le);
+#endif
+
+#ifndef find_next_bit_le
+unsigned long find_next_bit_le(const void *addr, unsigned
+               long size, unsigned long offset)
+{
+       const unsigned long *p = addr;
+       unsigned long result = offset & ~(BITS_PER_LONG - 1);
+       unsigned long tmp;
+
+       if (offset >= size)
+               return size;
+       p += BIT_WORD(offset);
+       size -= result;
+       offset &= (BITS_PER_LONG - 1UL);
+       if (offset) {
+               tmp = ext2_swabp(p++);
+               tmp &= (~0UL << offset);
+               if (size < BITS_PER_LONG)
+                       goto found_first;
+               if (tmp)
+                       goto found_middle;
+               size -= BITS_PER_LONG;
+               result += BITS_PER_LONG;
+       }
+
+       while (size & ~(BITS_PER_LONG - 1)) {
+               tmp = *(p++);
+               if (tmp)
+                       goto found_middle_swap;
+               result += BITS_PER_LONG;
+               size -= BITS_PER_LONG;
+       }
+       if (!size)
+               return result;
+       tmp = ext2_swabp(p);
+found_first:
+       tmp &= (~0UL >> (BITS_PER_LONG - size));
+       if (tmp == 0UL)         /* Are any bits set? */
+               return result + size; /* Nope. */
+found_middle:
+       return result + __ffs(tmp);
+
+found_middle_swap:
+       return result + __ffs(ext2_swab(tmp));
+}
+EXPORT_SYMBOL(find_next_bit_le);
+#endif
+
+#endif /* __BIG_ENDIAN */
-- 
2.43.0