arm64: enable per-task stack canaries
This enables the use of per-task stack canary values if GCC has
support for emitting the stack canary reference relative to the
value of sp_el0, which holds the task struct pointer in the arm64
kernel.
The $(eval) extends KBUILD_CFLAGS at the moment the make rule is
applied, which means asm-offsets.o (which we rely on for the offset
value) is built without the arguments, and everything built afterwards
has the options set.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index e9af113..0b3aa2a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1344,6 +1344,13 @@
a limited range that contains the [_stext, _etext] interval of the
core kernel, so branch relocations are always in range.
+config CC_HAVE_STACKPROTECTOR_SYSREG
+ def_bool $(cc-option,-mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=0)
+
+config STACKPROTECTOR_PER_TASK
+ def_bool y
+ depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_SYSREG
+
endmenu
menu "Boot options"