linux-kernel - [tip:x86/cpu] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions

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Date:   Sat, 22 Jun 2019 03:06:54 -0700
From:   tip-bot for Andi Kleen <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, ak@...ux.intel.com, linux-kernel@...r.kernel.org,
        chang.seok.bae@...el.com, tglx@...utronix.de, hpa@...or.com,
        luto@...nel.org, ravi.v.shankar@...el.com
Subject: [tip:x86/cpu] x86/fsgsbase/64: Add intrinsics for FSGSBASE
 instructions

Commit-ID:  8b71340d702ec5d587443b38a852671c4fb6a723
Gitweb:     https://git.kernel.org/tip/8b71340d702ec5d587443b38a852671c4fb6a723
Author:     Andi Kleen <ak@...ux.intel.com>
AuthorDate: Wed, 8 May 2019 03:02:20 -0700
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sat, 22 Jun 2019 11:38:52 +0200

x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions

[ luto: Rename the variables from FS and GS to FSBASE and GSBASE and
  make <asm/fsgsbase.h> safe to include on 32-bit kernels. ]

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Cc: Ravi Shankar <ravi.v.shankar@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Link: https://lkml.kernel.org/r/1557309753-24073-6-git-send-email-chang.seok.bae@intel.com

---
 arch/x86/include/asm/fsgsbase.h | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index bca4c743de77..fdd1177499b4 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -19,6 +19,36 @@ extern unsigned long x86_gsbase_read_task(struct task_struct *task);
 extern void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase);
 extern void x86_gsbase_write_task(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("rdfsbase %0" : "=r" (fsbase) :: "memory");
+
+	return fsbase;
+}
+
+static __always_inline unsigned long rdgsbase(void)
+{
+	unsigned long gsbase;
+
+	asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");
+
+	return gsbase;
+}
+
+static __always_inline void wrfsbase(unsigned long fsbase)
+{
+	asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory");
+}
+
+static __always_inline void wrgsbase(unsigned long gsbase)
+{
+	asm volatile("wrgsbase %0" :: "r" (gsbase) : "memory");
+}
+
 /* Helper functions for reading/writing FS/GS base */
 
 static inline unsigned long x86_fsbase_read_cpu(void)