linux-kernel - [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base instructions

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Date:	Mon, 28 Apr 2014 15:12:37 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 3/7] x86: Add C intrinsics for new rd/wr fs/gs base instructions

From: Andi Kleen <ak@...ux.intel.com>

Plus for swapgs.

Very straight forward. Used in followon patch.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/include/asm/fsgs.h | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 arch/x86/include/asm/fsgs.h

diff --git a/arch/x86/include/asm/fsgs.h b/arch/x86/include/asm/fsgs.h
new file mode 100644
index 0000000..a3a5cd3
--- /dev/null
+++ b/arch/x86/include/asm/fsgs.h
@@ -0,0 +1,43 @@
+#ifndef _ASM_FSGS_H
+#define _ASM_FSGS_H 1
+
+static inline void swapgs(void)
+{
+	asm volatile("swapgs" ::: "memory");
+}
+
+/* Must be protected by X86_FEATURE_FSGSBASE check. */
+
+static inline unsigned long rdgsbase(void)
+{
+	unsigned long gs;
+	asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xc8 # rdgsbaseq %%rax"
+			: "=a" (gs)
+			:: "memory");
+	return gs;
+}
+
+static inline unsigned long rdfsbase(void)
+{
+	unsigned long fs;
+	asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xc0 # rdfsbaseq %%rax"
+			: "=a" (fs)
+			:: "memory");
+	return fs;
+}
+
+static inline void wrgsbase(unsigned long gs)
+{
+	asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xd8 # wrgsbaseq %%rax"
+			:: "a" (gs)
+			: "memory");
+}
+
+static inline void wrfsbase(unsigned long fs)
+{
+	asm volatile(".byte 0xf3,0x48,0x0f,0xae,0xd0 # wrfsbaseq %%rax"
+			:: "a" (fs)
+			: "memory");
+}
+
+#endif
-- 
1.9.0

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