[PATCH 09/15] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions

[Chang S. Bae]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Add C intrinsics and assembler macros for the new RD/WR FS/GS BASE
instructions.

Very straight forward. Used in followon patch.

[luto: rename the variables from fs and gs to fsbase and gsbase and
 make fsgs.h safe to include on 32-bit kernels.]

v2: Use __always_inline

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
[chang: Replace new instruction macros with GAS-compatible and
 renaming]
Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
---
 arch/x86/include/asm/fsgsbase.h | 102 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index 29249f6..cad2831 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -18,6 +18,44 @@ int write_task_fsbase(struct task_struct *task, unsigned long fsbase);
 int write_task_gsbase(struct task_struct *task, unsigned long gsbase);
 
 /*
+ * Must be protected by X86_FEATURE_FSGSBASE check.
+ */
+
+static __always_inline unsigned long rdfsbase(void)
+{
+	unsigned long fsbase;
+
+	asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xc0 # rdfsbaseq %%rax"
+			: "=a" (fsbase)
+			:: "memory");
+	return fsbase;
+}
+
+static __always_inline unsigned long rdgsbase(void)
+{
+	unsigned long gsbase;
+
+	asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xc8 # rdgsbaseq %%rax;"
+			: "=a" (gsbase)
+			:: "memory");
+	return gsbase;
+}
+
+static __always_inline void wrfsbase(unsigned long fsbase)
+{
+	asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xd0 # wrfsbaseq %%rax"
+			:: "a" (fsbase)
+			: "memory");
+}
+
+static __always_inline void wrgsbase(unsigned long gsbase)
+{
+	asm volatile(".byte 0xf3, 0x48, 0x0f, 0xae, 0xd8 # wrgsbaseq %%rax;"
+			:: "a" (gsbase)
+			: "memory");
+}
+
+/*
  * Helper functions for reading/writing FS/GS base
  */
 
@@ -43,6 +81,70 @@ void  write_shadow_gsbase(unsigned long gsbase);
 
 #endif /* CONFIG_X86_64 */
 
+#else /* __ASSEMBLY__ */
+
+#ifdef CONFIG_X86_64
+
+#include <asm/inst.h>
+
+.macro RDFSBASE opd
+	REG_TYPE rdfsbase_opd_type \opd
+	.if rdfsbase_opd_type == REG_TYPE_R64
+	R64_NUM rdfsbase_opd \opd
+	.byte 0xf3
+	PFX_REX rdfsbase_opd 0 W = 1
+	.else
+	R32_NUM rdfsbase_opd \opd
+	.byte 0xf3
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xc0 rdfsbase_opd 0
+.endm
+
+.macro WRFSBASE opd
+	REG_TYPE wrfsbase_opd_type \opd
+	.if wrfsbase_opd_type == REG_TYPE_R64
+	R64_NUM wrfsbase_opd \opd
+	.byte 0xf3
+	PFX_REX wrfsbase_opd 0 W = 1
+	.else
+	R32_NUM wrfsbase_opd \opd
+	.byte 0xf3
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xd0 wrfsbase_opd 0
+.endm
+
+.macro RDGSBASE opd
+	REG_TYPE rdgsbase_opd_type \opd
+	.if rdgsbase_opd_type == REG_TYPE_R64
+	R64_NUM rdgsbase_opd \opd
+	.byte 0xf3
+	PFX_REX rdgsbase_opd 0 W = 1
+	.else
+	R32_NUM rdgsbase_opd \opd
+	.byte 0xf3
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xc0 rdgsbase_opd 1
+.endm
+
+.macro WRGSBASE opd
+	REG_TYPE wrgsbase_opd_type \opd
+	.if wrgsbase_opd_type == REG_TYPE_R64
+	R64_NUM wrgsbase_opd \opd
+	.byte 0xf3
+	PFX_REX wrgsbase_opd 0 W = 1
+	.else
+	R32_NUM wrgsbase_opd \opd
+	.byte 0xf3
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xd0 wrgsbase_opd 1
+.endm
+
+#endif /* CONFIG_X86_64 */
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_FSGSBASE_H */
-- 
2.7.4