[PATCH v5 08/23] xen/asm-generic: introduce generic non-atomic test_*bit()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

The patch introduces the following generic functions:
* test_bit
* generic___test_and_set_bit
* generic___test_and_clear_bit
* generic___test_and_change_bit

Also, the patch introduces the following generics which are
used by the functions mentioned above:
* BITOP_BITS_PER_WORD
* BITOP_MASK
* BITOP_WORD
* BITOP_TYPE

These functions and macros can be useful for architectures
that don't have corresponding arch-specific instructions.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
 Changes in V5:
   - new patch
---
 xen/include/asm-generic/bitops/bitops-bits.h  | 21 +++++
 .../asm-generic/bitops/generic-non-atomic.h   | 89 +++++++++++++++++++
 xen/include/asm-generic/bitops/test-bit.h     | 18 ++++
 3 files changed, 128 insertions(+)
 create mode 100644 xen/include/asm-generic/bitops/bitops-bits.h
 create mode 100644 xen/include/asm-generic/bitops/generic-non-atomic.h
 create mode 100644 xen/include/asm-generic/bitops/test-bit.h

diff --git a/xen/include/asm-generic/bitops/bitops-bits.h 
b/xen/include/asm-generic/bitops/bitops-bits.h
new file mode 100644
index 0000000000..4ece2affd6
--- /dev/null
+++ b/xen/include/asm-generic/bitops/bitops-bits.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_BITS_H_
+#define _ASM_GENERIC_BITOPS_BITS_H_
+
+#ifndef BITOP_BITS_PER_WORD
+#define BITOP_BITS_PER_WORD     32
+#endif
+
+#ifndef BITOP_MASK
+#define BITOP_MASK(nr)          (1U << ((nr) % BITOP_BITS_PER_WORD))
+#endif
+
+#ifndef BITOP_WORD
+#define BITOP_WORD(nr)          ((nr) / BITOP_BITS_PER_WORD)
+#endif
+
+#ifndef BITOP_TYPE
+typedef uint32_t bitops_uint_t;
+#endif
+
+#endif /* _ASM_GENERIC_BITOPS_BITS_H_ */
diff --git a/xen/include/asm-generic/bitops/generic-non-atomic.h 
b/xen/include/asm-generic/bitops/generic-non-atomic.h
new file mode 100644
index 0000000000..42569d0d7c
--- /dev/null
+++ b/xen/include/asm-generic/bitops/generic-non-atomic.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * The file is based on Linux ( 6.4.0 ) header:
+ *   include/asm-generic/bitops/generic-non-atomic.h
+ * 
+ * Only functions that can be reused in Xen were left; others were removed.
+ * 
+ * Also, the following changes were done:
+ *  - it was updated the message inside #ifndef ... #endif.
+ *  - __always_inline -> always_inline to be align with definition in
+ *    xen/compiler.h.
+ *  - update function prototypes from
+ *    generic___test_and_*(unsigned long nr nr, volatile unsigned long *addr) 
to
+ *    generic___test_and_*(unsigned long nr, volatile void *addr) to be
+ *    consistent with other related macros/defines.
+ *  - convert identations from tabs to spaces.
+ *  - inside generic__test_and_* use 'bitops_uint_t' instead of 'unsigned long'
+ *    to be generic.
+ */
+
+#ifndef __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
+#define __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H
+
+#include <xen/compiler.h>
+
+#include <asm-generic/bitops/bitops-bits.h>
+
+#ifndef _LINUX_BITOPS_H
+#error only <xen/bitops.h> can be included directly
+#endif
+
+/*
+ * Generic definitions for bit operations, should not be used in regular code
+ * directly.
+ */
+
+/**
+ * generic___test_and_set_bit - Set a bit and return its old value
+ * @nr: Bit to set
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail.  You must protect multiple accesses with a lock.
+ */
+static always_inline bool
+generic___test_and_set_bit(unsigned long nr, volatile void *addr)
+{
+    bitops_uint_t mask = BITOP_MASK(nr);
+    bitops_uint_t *p = ((bitops_uint_t *)addr) + BITOP_WORD(nr);
+    bitops_uint_t old = *p;
+
+    *p = old | mask;
+    return (old & mask) != 0;
+}
+
+/**
+ * generic___test_and_clear_bit - Clear a bit and return its old value
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail.  You must protect multiple accesses with a lock.
+ */
+static always_inline bool
+generic___test_and_clear_bit(bitops_uint_t nr, volatile void *addr)
+{
+    bitops_uint_t mask = BITOP_MASK(nr);
+    bitops_uint_t *p = ((bitops_uint_t *)addr) + BITOP_WORD(nr);
+    bitops_uint_t old = *p;
+
+    *p = old & ~mask;
+    return (old & mask) != 0;
+}
+
+/* WARNING: non atomic and it can be reordered! */
+static always_inline bool
+generic___test_and_change_bit(unsigned long nr, volatile void *addr)
+{
+    bitops_uint_t mask = BITOP_MASK(nr);
+    bitops_uint_t *p = ((bitops_uint_t *)addr) + BITOP_WORD(nr);
+    bitops_uint_t old = *p;
+
+    *p = old ^ mask;
+    return (old & mask) != 0;
+}
+
+#endif /* __ASM_GENERIC_BITOPS_GENERIC_NON_ATOMIC_H */
diff --git a/xen/include/asm-generic/bitops/test-bit.h 
b/xen/include/asm-generic/bitops/test-bit.h
new file mode 100644
index 0000000000..6fb414d808
--- /dev/null
+++ b/xen/include/asm-generic/bitops/test-bit.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_TESTBIT_H_
+#define _ASM_GENERIC_BITOPS_TESTBIT_H_
+
+#include <asm-generic/bitops/bitops-bits.h>
+
+/**
+ * test_bit - Determine whether a bit is set
+ * @nr: bit number to test
+ * @addr: Address to start counting from
+ */
+static inline int test_bit(int nr, const volatile void *addr)
+{
+    const volatile bitops_uint_t *p = addr;
+    return 1 & (p[BITOP_WORD(nr)] >> (nr & (BITOP_BITS_PER_WORD - 1)));
+}
+
+#endif /* _ASM_GENERIC_BITOPS_TESTBIT_H_ */
-- 
2.43.0