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.
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>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Dave Hansen <dave.han...@linux.intel.com>
---
arch/x86/include/asm/fsgsbase.h | 72 +++++++++++++++++++++++++++++++++
1 file changed, 72 insertions(+)
diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index eb377b6e9eed..b4d4509b786c 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -19,6 +19,44 @@ extern unsigned long x86_gsbase_read_task(struct task_struct
*task);
extern int x86_fsbase_write_task(struct task_struct *task, unsigned long
fsbase);
extern int 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(".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 */
static inline unsigned long x86_fsbase_read_cpu(void)
@@ -44,6 +82,40 @@ extern void x86_gsbase_write_cpu_inactive(unsigned long
gsbase);
#endif /* CONFIG_X86_64 */
+#else /* __ASSEMBLY__ */
+
+#ifdef CONFIG_X86_64
+
+#include <asm/inst.h>
+
+.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
+ .error "RDGSBASE: only for 64-bit value"
+ .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
+ .error "WRGSBASE: only for 64-bit value"
+ .endif
+ .byte 0xf, 0xae
+ MODRM 0xd0 wrgsbase_opd 1
+.endm
+
+#endif /* CONFIG_X86_64 */
+
#endif /* __ASSEMBLY__ */
#endif /* _ASM_FSGSBASE_H */
--
2.19.1
