[PATCH v11 09/18] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions

From: Sasha Levin
Date: Sat May 09 2020 - 13:37:51 EST


From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Reviewed-by: Andy Lutomirski <luto@xxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
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 bca4c743de77c..fdd1177499b40 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)
--
2.20.1