[PATCH v2 00/11] x86-64: Stack protector and percpu improvements

Brian Gerst
2023-10-26T16:01:31Z

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.

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 (11):
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/stackprotector/64: Convert stack protector to normal percpu
variable
x86/percpu/64: Remove fixed_percpu_data
x86/percpu/64: Use relative percpu offsets
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 | 7 +-
arch/x86/Makefile | 19 +--
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 | 37 ++----
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 | 10 +-
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 | 4 +-
arch/x86/tools/relocs.c | 136 +---------------------
arch/x86/xen/xen-head.S | 6 +-
include/asm-generic/vmlinux.lds.h | 1 -
include/linux/percpu-defs.h | 12 --
init/Kconfig | 11 +-
kernel/kallsyms.c | 12 +-
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 -
25 files changed, 61 insertions(+), 420 deletions(-)
delete mode 100755 scripts/gcc-x86_32-has-stack-protector.sh
delete mode 100755 scripts/gcc-x86_64-has-stack-protector.sh

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2.41.0