[PATCH v4 00/16] x86-64: Stack protector and percpu improvements

Brian Gerst
2024-03-22T16:52:46Z

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.

v4:
- Updated to current tip tree
- Added two new cleanups made possible by the removal of IA-64.
- Small improvements to the objtool conversion code.

Brian Gerst (16):
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
percpu: Remove PERCPU_VADDR()
percpu: Remove __per_cpu_load
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/desc.h | 1 -
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 | 9 +-
arch/x86/kernel/head64.c | 2 +-
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/sections.h | 2 +-
include/asm-generic/vmlinux.lds.h | 43 +------
include/linux/percpu-defs.h | 12 --
init/Kconfig | 11 +-
kernel/kallsyms.c | 12 +-
mm/percpu.c | 4 +-
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 | 91 ++++++++++++++
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 +++++++++++---
38 files changed, 442 insertions(+), 518 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: 30052fd948a3b43506c83590eaaada12d1f2dd09
--
2.44.0