linux-kernel - [PATCH v5 00/16] x86-64: Stack protector and percpu improvements

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Message-ID: <20241105155801.1779119-1-brgerst@gmail.com>
Date: Tue,  5 Nov 2024 10:57:45 -0500
From: Brian Gerst <brgerst@...il.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Uros Bizjak <ubizjak@...il.com>,
	Brian Gerst <brgerst@...il.com>
Subject: [PATCH v5 00/16] x86-64: Stack protector and percpu improvements

Currently, x86-64 uses an unusual percpu 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 how the percpu
section is linked.  This allows the percpu section to be linked normally,
like other architectures.  In turn, this allows removal of code that was
needed to support the zero-based percpu section.

v5:
- Added two patches from Ard Biesheuvel to make stack protector work
  properly when compiling with clang.
- Raise minimum GCC version to 8.1 for x86.
- Drop objtool conversion code.

Ard Biesheuvel (2):
  x86/stackprotector: Work around strict Clang TLS symbol requirements
  x86/module: Deal with GOT based stack cookie load on Clang < 17

Brian Gerst (14):
  x86: Raise minimum GCC version to 8.1
  x86/stackprotector: Remove stack protector test scripts
  x86/boot: Disable stack protector for early boot code
  x86/pvh: Use fixed_percpu_data for early boot GSBASE
  x86/relocs: Handle R_X86_64_REX_GOTPCRELX relocations
  x86/stackprotector/64: Convert to normal percpu variable
  x86/percpu/64: Use relative percpu offsets
  x86/percpu/64: Remove fixed_percpu_data
  x86/boot/64: Remove inverse relocations
  x86/percpu/64: Remove INIT_PER_CPU macros
  percpu: Remove PER_CPU_FIRST_SECTION
  percpu: Remove PERCPU_VADDR()
  percpu: Remove __per_cpu_load
  kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU

 arch/x86/Kconfig                          |  11 +-
 arch/x86/Makefile                         |  19 +--
 arch/x86/boot/compressed/misc.c           |  14 +--
 arch/x86/entry/entry.S                    |  14 +++
 arch/x86/entry/entry_64.S                 |   2 +-
 arch/x86/include/asm/asm-prototypes.h     |   3 +
 arch/x86/include/asm/desc.h               |   1 -
 arch/x86/include/asm/elf.h                |   3 +-
 arch/x86/include/asm/percpu.h             |  22 ----
 arch/x86/include/asm/processor.h          |  28 +----
 arch/x86/include/asm/stackprotector.h     |  36 +-----
 arch/x86/kernel/Makefile                  |   2 +
 arch/x86/kernel/asm-offsets_64.c          |   6 -
 arch/x86/kernel/cpu/common.c              |  11 +-
 arch/x86/kernel/head64.c                  |   2 +-
 arch/x86/kernel/head_64.S                 |  20 ++-
 arch/x86/kernel/irq_64.c                  |   1 -
 arch/x86/kernel/module.c                  |  15 +++
 arch/x86/kernel/setup_percpu.c            |  12 +-
 arch/x86/kernel/vmlinux.lds.S             |  38 +-----
 arch/x86/platform/pvh/head.S              |  14 ++-
 arch/x86/tools/relocs.c                   | 147 ++--------------------
 arch/x86/xen/xen-head.S                   |  10 +-
 include/asm-generic/sections.h            |   2 +-
 include/asm-generic/vmlinux.lds.h         |  38 +-----
 include/linux/percpu-defs.h               |  12 --
 init/Kconfig                              |   5 -
 kernel/kallsyms.c                         |  12 +-
 mm/percpu.c                               |   4 +-
 scripts/gcc-x86_32-has-stack-protector.sh |   8 --
 scripts/gcc-x86_64-has-stack-protector.sh |   4 -
 scripts/kallsyms.c                        |  72 ++---------
 scripts/link-vmlinux.sh                   |   4 -
 scripts/min-tool-version.sh               |   2 +
 34 files changed, 122 insertions(+), 472 deletions(-)
 delete mode 100755 scripts/gcc-x86_32-has-stack-protector.sh
 delete mode 100755 scripts/gcc-x86_64-has-stack-protector.sh


base-commit: 4b9984799820b5b32b0ae1f3d8074886895a44e1
-- 
2.47.0