From: Andi Kleen <a...@linux.intel.com>
Add C intrinsics and assembler macros for the new FSBASE and GSBASE
instructions.
Very straight forward. Used in followon patches.
[ luto: Rename the variables from FS and GS to FSBASE and GSBASE and
make <asm/fsgsbase.h> safe to include on 32-bit kernels. ]
v2: Use __always_inline
[ chang: Revise the changelog. Place them in <asm/fsgsbase.h>. Replace
the macros with GAS-compatible ones. ]
If GCC supports it, we can add -mfsgsbase to CFLAGS and use the builtins
here for extra performance.
[ chang: Use FSGSBASE instructions directly ]
Signed-off-by: Andi Kleen <a...@linux.intel.com>
Signed-off-by: Andy Lutomirski <l...@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok....@intel.com>
Reviewed-by: Andy Lutomirski <l...@kernel.org>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@kernel.org>
---
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)
--
2.19.1
