linux-kernel - [PATCH 0/3] x86-64: Stack protector and percpu improvements

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Date:   Sat, 13 Nov 2021 07:40:32 -0500
From:   Brian Gerst <brgerst@...il.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
        Brian Gerst <brgerst@...il.com>
Subject: [PATCH 0/3] x86-64: Stack protector and percpu improvements

Currently, x86-64 uses an unusual per-cpu layout, where the percpu section
is linked at absolute address 0.  The reason behind this is that older GCC
versions placed the stack protector (if enabled) at a fixed offset from the
GS segment base.  Since the GS segement is also used for percpu variables,
this forced the current layout.

GCC since version 8.1 supports a configurable location for the stack
protector value, which allows removal of the restriction on where the percpu
data is linked.  Compatibility with older compilers is maintained until
the minimum compiler version is raised.

Brian Gerst (3):
  x86-64: Use per-cpu stack canary if supported by compiler
  x86/relocs: Make absolute percpu relocations conditional
  x86_64: Use relative per-cpu offsets

 arch/x86/Kconfig                      |  9 +++++++++
 arch/x86/Makefile                     | 21 ++++++++++++++-------
 arch/x86/boot/compressed/Makefile     |  3 ++-
 arch/x86/entry/entry_64.S             |  6 +++++-
 arch/x86/include/asm/percpu.h         |  4 ++--
 arch/x86/include/asm/processor.h      | 14 +++++++++++---
 arch/x86/include/asm/stackprotector.h | 17 ++++++-----------
 arch/x86/kernel/asm-offsets_64.c      |  2 +-
 arch/x86/kernel/cpu/common.c          | 14 ++++++++------
 arch/x86/kernel/head_64.S             | 12 ++++++++----
 arch/x86/kernel/setup_percpu.c        |  2 +-
 arch/x86/kernel/vmlinux.lds.S         | 16 +++++++---------
 arch/x86/tools/relocs.c               |  4 ++--
 arch/x86/tools/relocs.h               |  4 ++--
 arch/x86/tools/relocs_common.c        | 11 ++++++++---
 arch/x86/xen/xen-head.S               | 10 ++++------
 init/Kconfig                          |  1 -
 17 files changed, 90 insertions(+), 60 deletions(-)

-- 
2.31.1