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From:   Brian Gerst <brgerst@gmail.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org
Cc:     Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Uros Bizjak <ubizjak@gmail.com>, David.Laight@aculab.com,
        Brian Gerst <brgerst@gmail.com>
Subject: [PATCH v3 00/14] x86-64: Stack protector and percpu improvements
Date:   Wed, 15 Nov 2023 12:36:54 -0500
Message-ID: <20231115173708.108316-1-brgerst@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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 most other architectures.  In turn, this allows removal
of code that was needed to support the zero-based percpu section.

The major change with this iteration is adding support to objtool for
older compilers that can't change the location of the stackprotector
canary value.

v3:
- Add objtool suport to convert stackprotector code from older compilers.
- Handle R_X86_64_REX_GOTPCRELX relocations from clang
 
v2:
- Include PVH boot in GSBASE changes.
- Split out removal of 64-bit test script to give full context on why
  it's not needed anymore.
- Formatting and comment cleanups.

Brian Gerst (14):
  x86/stackprotector/32: Remove stack protector test script
  x86/stackprotector/64: Remove stack protector test script
  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
  objtool: Allow adding relocations to an existing section
  objtool: Convert fixed location stack protector accesses
  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
  kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU

 arch/x86/Kconfig                          |  16 +--
 arch/x86/Makefile                         |  21 ++--
 arch/x86/boot/compressed/misc.c           |  14 +--
 arch/x86/entry/entry_64.S                 |   2 +-
 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              |   8 +-
 arch/x86/kernel/head_64.S                 |  20 ++-
 arch/x86/kernel/irq_64.c                  |   1 -
 arch/x86/kernel/setup_percpu.c            |  12 +-
 arch/x86/kernel/vmlinux.lds.S             |  35 ------
 arch/x86/platform/pvh/head.S              |  10 +-
 arch/x86/tools/relocs.c                   | 143 ++--------------------
 arch/x86/xen/xen-head.S                   |  10 +-
 include/asm-generic/vmlinux.lds.h         |   1 -
 include/linux/percpu-defs.h               |  12 --
 init/Kconfig                              |  11 +-
 kernel/kallsyms.c                         |  12 +-
 scripts/Makefile.lib                      |   2 +
 scripts/gcc-x86_32-has-stack-protector.sh |   8 --
 scripts/gcc-x86_64-has-stack-protector.sh |   4 -
 scripts/kallsyms.c                        |  80 +++---------
 scripts/link-vmlinux.sh                   |   4 -
 tools/objtool/arch/x86/decode.c           |  46 +++++++
 tools/objtool/arch/x86/special.c          |  88 +++++++++++++
 tools/objtool/builtin-check.c             |   9 +-
 tools/objtool/check.c                     |  14 ++-
 tools/objtool/elf.c                       | 133 ++++++++++++++++----
 tools/objtool/include/objtool/arch.h      |   3 +
 tools/objtool/include/objtool/builtin.h   |   2 +
 tools/objtool/include/objtool/elf.h       |  90 +++++++++++---
 34 files changed, 433 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

-- 
2.41.0