1 files changed, 70 insertions, 0 deletions
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
new file mode 100644
index 000000000..bab490379
--- /dev/null
+++ b/arch/x86/include/asm/smap.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Supervisor Mode Access Prevention support
+ *
+ * Copyright (C) 2012 Intel Corporation
+ * Author: H. Peter Anvin <hpa@linux.intel.com>
+ */
+
+#ifndef _ASM_X86_SMAP_H
+#define _ASM_X86_SMAP_H
+
+#include <asm/nops.h>
+#include <asm/cpufeatures.h>
+#include <asm/alternative.h>
+
+/* "Raw" instruction opcodes */
+#define __ASM_CLAC	".byte 0x0f,0x01,0xca"
+#define __ASM_STAC	".byte 0x0f,0x01,0xcb"
+
+#ifdef __ASSEMBLY__
+
+#define ASM_CLAC \
+	ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
+
+#define ASM_STAC \
+	ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
+
+#else /* __ASSEMBLY__ */
+
+static __always_inline void clac(void)
+{
+	/* Note: a barrier is implicit in alternative() */
+	alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
+}
+
+static __always_inline void stac(void)
+{
+	/* Note: a barrier is implicit in alternative() */
+	alternative("", __ASM_STAC, X86_FEATURE_SMAP);
+}
+
+static __always_inline unsigned long smap_save(void)
+{
+	unsigned long flags;
+
+	asm volatile ("# smap_save\n\t"
+		      ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC "\n\t",
+				  X86_FEATURE_SMAP)
+		      : "=rm" (flags) : : "memory", "cc");
+
+	return flags;
+}
+
+static __always_inline void smap_restore(unsigned long flags)
+{
+	asm volatile ("# smap_restore\n\t"
+		      ALTERNATIVE("", "push %0; popf\n\t",
+				  X86_FEATURE_SMAP)
+		      : : "g" (flags) : "memory", "cc");
+}
+
+/* These macros can be used in asm() statements */
+#define ASM_CLAC \
+	ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
+#define ASM_STAC \
+	ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_X86_SMAP_H */