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. Signed-off-by: Ard Biesheuvel <[email protected]> --- v3: add all 3 options to the Kconfig cc-option check, to avoid relying on implementation defined logic in the compiler regarding which options need to appear together. arch/arm64/Kconfig | 7 +++++++ arch/arm64/Makefile | 10 ++++++++++ arch/arm64/include/asm/stackprotector.h | 3 ++- arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/process.c | 2 +- 5 files changed, 23 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index ea2ab0330e3a..e355946cde97 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1272,6 +1272,13 @@ config RANDOMIZE_MODULE_REGION_FULL 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" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 6cb9fc7e9382..79d927542322 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -56,6 +56,16 @@ KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) +ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) +prepare: stack_protector_prepare +stack_protector_prepare: prepare0 + $(eval KBUILD_CFLAGS += -mstack-protector-guard=sysreg \ + -mstack-protector-guard-reg=sp_el0 \ + -mstack-protector-guard-offset=$(shell \ + awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \ + include/generated/asm-offsets.h)) +endif + ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) KBUILD_CPPFLAGS += -mbig-endian CHECKFLAGS += -D__AARCH64EB__ diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h index 58d15be11c4d..5884a2b02827 100644 --- a/arch/arm64/include/asm/stackprotector.h +++ b/arch/arm64/include/asm/stackprotector.h @@ -34,7 +34,8 @@ static __always_inline void boot_init_stack_canary(void) canary &= CANARY_MASK; current->stack_canary = canary; - __stack_chk_guard = current->stack_canary; + if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK)) + __stack_chk_guard = current->stack_canary; } #endif /* _ASM_STACKPROTECTOR_H */ diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 323aeb5f2fe6..65b8afc84466 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -46,6 +46,9 @@ int main(void) DEFINE(TSK_TI_TTBR0, offsetof(struct task_struct, thread_info.ttbr0)); #endif DEFINE(TSK_STACK, offsetof(struct task_struct, stack)); +#ifdef CONFIG_STACKPROTECTOR + DEFINE(TSK_STACK_CANARY, offsetof(struct task_struct, stack_canary)); +#endif BLANK(); DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context)); BLANK(); diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index d9a4c2d6dd8b..8a2d68f04e0d 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -59,7 +59,7 @@ #include <asm/processor.h> #include <asm/stacktrace.h> -#ifdef CONFIG_STACKPROTECTOR +#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK) #include <linux/stackprotector.h> unsigned long __stack_chk_guard __read_mostly; EXPORT_SYMBOL(__stack_chk_guard); -- 2.19.2 s
