[RFC PATCH v2 04/20] x86: Secure Memory Encryption (SME) support

[Tom Lendacky]

Provide support for Secure Memory Encryption (SME). This initial support
defines the memory encryption mask as a variable for quick access and an
accessor for retrieving the number of physical addressing bits lost if
SME is enabled.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/include/asm/mem_encrypt.h |   37 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/Makefile           |    2 ++
 arch/x86/kernel/mem_encrypt.S      |   29 ++++++++++++++++++++++++++++
 arch/x86/kernel/x8664_ksyms_64.c   |    6 ++++++
 4 files changed, 74 insertions(+)
 create mode 100644 arch/x86/include/asm/mem_encrypt.h
 create mode 100644 arch/x86/kernel/mem_encrypt.S

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
new file mode 100644
index 0000000..747fc52
--- /dev/null
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -0,0 +1,37 @@
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __X86_MEM_ENCRYPT_H__
+#define __X86_MEM_ENCRYPT_H__
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+
+extern unsigned long sme_me_mask;
+
+u8 sme_get_me_loss(void);
+
+#else	/* !CONFIG_AMD_MEM_ENCRYPT */
+
+#define sme_me_mask		0UL
+
+static inline u8 sme_get_me_loss(void)
+{
+	return 0;
+}
+
+#endif	/* CONFIG_AMD_MEM_ENCRYPT */
+
+#endif	/* __ASSEMBLY__ */
+
+#endif	/* __X86_MEM_ENCRYPT_H__ */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0503f5b..bda997f 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -125,6 +125,8 @@ obj-$(CONFIG_EFI)			+= sysfb_efi.o
 obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o
 obj-$(CONFIG_TRACING)			+= tracepoint.o
 
+obj-y					+= mem_encrypt.o
+
 ###
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/mem_encrypt.S b/arch/x86/kernel/mem_encrypt.S
new file mode 100644
index 0000000..ef7f325
--- /dev/null
+++ b/arch/x86/kernel/mem_encrypt.S
@@ -0,0 +1,29 @@
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/linkage.h>
+
+	.text
+	.code64
+ENTRY(sme_get_me_loss)
+	xor	%rax, %rax
+	mov	sme_me_loss(%rip), %al
+	ret
+ENDPROC(sme_get_me_loss)
+
+	.data
+	.align 16
+ENTRY(sme_me_mask)
+	.quad	0x0000000000000000
+sme_me_loss:
+	.byte	0x00
+	.align	8
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index 95e49f6..651c4c8 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -12,6 +12,7 @@
 #include <asm/uaccess.h>
 #include <asm/desc.h>
 #include <asm/ftrace.h>
+#include <asm/mem_encrypt.h>
 
 #ifdef CONFIG_FUNCTION_TRACER
 /* mcount and __fentry__ are defined in assembly */
@@ -83,3 +84,8 @@ EXPORT_SYMBOL(native_load_gs_index);
 EXPORT_SYMBOL(___preempt_schedule);
 EXPORT_SYMBOL(___preempt_schedule_notrace);
 #endif
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+EXPORT_SYMBOL_GPL(sme_me_mask);
+EXPORT_SYMBOL_GPL(sme_get_me_loss);
+#endif