linux-kernel - [PATCH v2 0/4] Introduce %rip-relative addressing to PER_CPU

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Message-ID: <20231012201743.292149-1-ubizjak@gmail.com>
Date:   Thu, 12 Oct 2023 22:12:03 +0200
From:   Uros Bizjak <ubizjak@...il.com>
To:     x86@...nel.org, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org
Cc:     Uros Bizjak <ubizjak@...il.com>, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v2 0/4]  Introduce %rip-relative addressing to PER_CPU_VAR macro

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@...e.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.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