Commit da64e9d1 authored Apr 27, 2020 by Sami Tolvanen Committed by Will Deacon May 15, 2020

arm64: Reserve register x18 from general allocation with SCS



Reserve the x18 register from general allocation when SCS is enabled,
because the compiler uses the register to store the current task's
shadow stack pointer. Note that all external kernel modules must also be
compiled with -ffixed-x18 if the kernel has SCS enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

parent ddc9863e

arch/arm64/Makefile

+4 −0

Original line number	Diff line number	Diff line
		@@ -81,6 +81,10 @@ endif

		KBUILD_CFLAGS += $(branch-prot-flags-y)

		ifeq ($(CONFIG_SHADOW_CALL_STACK), y)
		KBUILD_CFLAGS += -ffixed-x18
		endif

		ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
		KBUILD_CPPFLAGS += -mbig-endian
		CHECKFLAGS += -D__AARCH64EB__

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