1 files changed, 115 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
new file mode 100644
index 000000000..1a2eafca7
--- /dev/null
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_CMPXCHG_32_H
+#define _ASM_X86_CMPXCHG_32_H
+
+/*
+ * Note: if you use set64_bit(), __cmpxchg64(), or their variants, you
+ *       you need to test for the feature in boot_cpu_data.
+ */
+
+/*
+ * CMPXCHG8B only writes to the target if we had the previous
+ * value in registers, otherwise it acts as a read and gives us the
+ * "new previous" value.  That is why there is a loop.  Preloading
+ * EDX:EAX is a performance optimization: in the common case it means
+ * we need only one locked operation.
+ *
+ * A SIMD/3DNOW!/MMX/FPU 64-bit store here would require at the very
+ * least an FPU save and/or %cr0.ts manipulation.
+ *
+ * cmpxchg8b must be used with the lock prefix here to allow the
+ * instruction to be executed atomically.  We need to have the reader
+ * side to see the coherent 64bit value.
+ */
+static inline void set_64bit(volatile u64 *ptr, u64 value)
+{
+	u32 low  = value;
+	u32 high = value >> 32;
+	u64 prev = *ptr;
+
+	asm volatile("\n1:\t"
+		     LOCK_PREFIX "cmpxchg8b %0\n\t"
+		     "jnz 1b"
+		     : "=m" (*ptr), "+A" (prev)
+		     : "b" (low), "c" (high)
+		     : "memory");
+}
+
+#ifdef CONFIG_X86_CMPXCHG64
+#define arch_cmpxchg64(ptr, o, n)					\
+	((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
+					 (unsigned long long)(n)))
+#define arch_cmpxchg64_local(ptr, o, n)					\
+	((__typeof__(*(ptr)))__cmpxchg64_local((ptr), (unsigned long long)(o), \
+					       (unsigned long long)(n)))
+#endif
+
+static inline u64 __cmpxchg64(volatile u64 *ptr, u64 old, u64 new)
+{
+	u64 prev;
+	asm volatile(LOCK_PREFIX "cmpxchg8b %1"
+		     : "=A" (prev),
+		       "+m" (*ptr)
+		     : "b" ((u32)new),
+		       "c" ((u32)(new >> 32)),
+		       "0" (old)
+		     : "memory");
+	return prev;
+}
+
+static inline u64 __cmpxchg64_local(volatile u64 *ptr, u64 old, u64 new)
+{
+	u64 prev;
+	asm volatile("cmpxchg8b %1"
+		     : "=A" (prev),
+		       "+m" (*ptr)
+		     : "b" ((u32)new),
+		       "c" ((u32)(new >> 32)),
+		       "0" (old)
+		     : "memory");
+	return prev;
+}
+
+#ifndef CONFIG_X86_CMPXCHG64
+/*
+ * Building a kernel capable running on 80386 and 80486. It may be necessary
+ * to simulate the cmpxchg8b on the 80386 and 80486 CPU.
+ */
+
+#define arch_cmpxchg64(ptr, o, n)				\
+({								\
+	__typeof__(*(ptr)) __ret;				\
+	__typeof__(*(ptr)) __old = (o);				\
+	__typeof__(*(ptr)) __new = (n);				\
+	alternative_io(LOCK_PREFIX_HERE				\
+			"call cmpxchg8b_emu",			\
+			"lock; cmpxchg8b (%%esi)" ,		\
+		       X86_FEATURE_CX8,				\
+		       "=A" (__ret),				\
+		       "S" ((ptr)), "0" (__old),		\
+		       "b" ((unsigned int)__new),		\
+		       "c" ((unsigned int)(__new>>32))		\
+		       : "memory");				\
+	__ret; })
+
+
+#define arch_cmpxchg64_local(ptr, o, n)				\
+({								\
+	__typeof__(*(ptr)) __ret;				\
+	__typeof__(*(ptr)) __old = (o);				\
+	__typeof__(*(ptr)) __new = (n);				\
+	alternative_io("call cmpxchg8b_emu",			\
+		       "cmpxchg8b (%%esi)" ,			\
+		       X86_FEATURE_CX8,				\
+		       "=A" (__ret),				\
+		       "S" ((ptr)), "0" (__old),		\
+		       "b" ((unsigned int)__new),		\
+		       "c" ((unsigned int)(__new>>32))		\
+		       : "memory");				\
+	__ret; })
+
+#endif
+
+#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
+
+#endif /* _ASM_X86_CMPXCHG_32_H */