[PATCH v2 0/4] Introduce %rip-relative addressing to PER_CPU_VAR macro

Uros Bizjak
2023-10-12T20:18:02Z

The following patch series introduces %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.

The first three patches are cleanups that fix various inconsistencies
throughout the assembly code.

The last patch introduces (%rip) suffix and uses it for x86_64 target,
resulting in a small code size decrease:

text data bss dec hex filename
25510677 4386685 808388 30705750 1d48856 vmlinux-new.o
25510629 4386685 808388 30705702 1d48826 vmlinux-old.o

Patch series is against current mainline and can be applied independently
of ongoing percpu work.

v2: Introduce PER_CPU_ARG macro to conditionally enable
segment registers in cmpxchg{8,16}b_emu.S for CONFIG_SMP.

Cc: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>

Uros Bizjak (4):
x86/percpu: Introduce PER_CPU_ARG and use it in cmpxchg{8,16}b_emu.S
x86/percpu: Correct PER_CPU_VAR usage to include symbol and its addend
x86/percpu, xen: Correct PER_CPU_VAR usage to include symbol and its
addend
x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR macro

arch/x86/entry/calling.h | 2 +-
arch/x86/entry/entry_32.S | 2 +-
arch/x86/entry/entry_64.S | 2 +-
arch/x86/include/asm/percpu.h | 10 +++++++---
arch/x86/kernel/head_64.S | 2 +-
arch/x86/lib/cmpxchg16b_emu.S | 12 ++++++------
arch/x86/lib/cmpxchg8b_emu.S | 24 ++++++++++++++++++------
arch/x86/xen/xen-asm.S | 10 +++++-----
8 files changed, 40 insertions(+), 24 deletions(-)

--
2.41.0