[PATCH v2 4/4] x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR macro

[Uros Bizjak <ubizjak@xxxxxxxxx>]

Introduce x86_64 %rip-relative addressing to PER_CPU_VAR macro.
Instruction with %rip-relative address operand is one byte shorter than
its absolute address counterpart and is also compatible with position
independent executable (-fpie) build.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
---
 arch/x86/include/asm/percpu.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 83e6a4bcea38..c53c5a7f8e78 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -4,19 +4,21 @@
 
 #ifdef CONFIG_X86_64
 #define __percpu_seg           gs
+#define __percpu_rel           (%rip)
 #else
 #define __percpu_seg           fs
+#define __percpu_rel
 #endif
 
 #ifdef __ASSEMBLY__
 
 #ifdef CONFIG_SMP
 #define PER_CPU_ARG(arg)       %__percpu_seg:arg
-#define PER_CPU_VAR(var)       %__percpu_seg:var
+#define PER_CPU_VAR(var)       %__percpu_seg:(var)##__percpu_rel
 #else /* ! SMP */
 #define PER_CPU_ARG(arg)       arg
-#define PER_CPU_VAR(var)       var
-#endif /* SMP */
+#define PER_CPU_VAR(var)       (var)##__percpu_rel
+#endif /* SMP */
 
 #ifdef CONFIG_X86_64_SMP
 #define INIT_PER_CPU_VAR(var)  init_per_cpu__##var
-- 
2.41.0