x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()

x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()

Introduce x86_64 %rip-relative addressing to the PER_CPU_VAR() macro.
Instructions using %rip-relative address operand are one byte shorter
than their absolute address counterparts and are also compatible with
position independent executable (-fpie) builds. The patch reduces
code size of a test kernel build by 150 bytes.

The PER_CPU_VAR() macro is intended to be applied to a symbol and should
not be used with register operands. Introduce the new __percpu macro and
use it in cmpxchg{8,16}b_emu.S instead.

Also add a missing function comment to this_cpu_cmpxchg8b_emu().

No functional changes intended.

Signed-off-by: Uros Bizjak <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: Brian Gerst <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Sean Christopherson <[email protected]>