bybrooklyn/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-04-18 06:44:00 -04:00
Code Issues Packages Projects Releases Wiki Activity

x86/stackprotector/64: Convert to normal per-CPU variable

Browse Source 
Older versions of GCC fixed the location of the stack protector canary
at %gs:40.  This constraint forced the percpu section to be linked at
absolute address 0 so that the canary could be the first data object in
the percpu section.  Supporting the zero-based percpu section requires
additional code to handle relocations for RIP-relative references to
percpu data, extra complexity to kallsyms, and workarounds for linker
bugs due to the use of absolute symbols.

GCC 8.1 supports redefining where the canary is located, allowing it to
become a normal percpu variable instead of at a fixed location.  This
removes the constraint that the percpu section must be zero-based.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-8-brgerst@gmail.com
This commit is contained in:
Brian Gerst
2025-01-23 14:07:39 -05:00
committed by Ingo Molnar
parent 78c4374ef8
commit 80d47defdd
9 changed files with 23 additions and 70 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
arch/x86/Makefile
View File

@@ -140,14 +140,7 @@ ifeq ($(CONFIG_X86_32),y)
# temporary until string.h is fixed
KBUILD_CFLAGS += -ffreestanding
ifeq ($(CONFIG_STACKPROTECTOR),y)
ifeq ($(CONFIG_SMP),y)
KBUILD_CFLAGS += -mstack-protector-guard-reg=fs \
-mstack-protector-guard-symbol=__ref_stack_chk_guard
else
KBUILD_CFLAGS += -mstack-protector-guard=global
endif
endif
percpu_seg := fs
else
BITS := 64
UTS_MACHINE := x86_64
@@ -197,6 +190,17 @@ else
KBUILD_CFLAGS += -mcmodel=kernel
KBUILD_RUSTFLAGS += -Cno-redzone=y
KBUILD_RUSTFLAGS += -Ccode-model=kernel
percpu_seg := gs
endif
ifeq ($(CONFIG_STACKPROTECTOR),y)
ifeq ($(CONFIG_SMP),y)
KBUILD_CFLAGS += -mstack-protector-guard-reg=$(percpu_seg)
KBUILD_CFLAGS += -mstack-protector-guard-symbol=__ref_stack_chk_guard
else
KBUILD_CFLAGS += -mstack-protector-guard=global
endif
endif
#