Commit dfbdcda2 authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

gcc-plugins: arm-ssp: Prepare for THREAD_INFO_IN_TASK support 



We will be enabling THREAD_INFO_IN_TASK support for ARM, which means
that we can no longer load the stack canary value by masking the stack
pointer and taking the copy that lives in thread_info. Instead, we will
be able to load it from the task_struct directly, by using the TPIDRURO
register which will hold the current task pointer when
THREAD_INFO_IN_TASK is in effect. This is much more straight-forward,
and allows us to declutter this code a bit while at it.

Note that this means that ARMv6 (non-v6K) SMP systems can no longer use
this feature, but those are quite rare to begin with, so this is a
reasonable trade off.

Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Tested-by: default avatarAmit Daniel Kachhap <amit.kachhap@arm.com>
parent 6880fa6c

arch/arm/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -1600,7 +1600,7 @@ config XEN 


config STACKPROTECTOR_PER_TASK

	bool "Use a unique stack canary value for each task"

	depends on GCC_PLUGINS && STACKPROTECTOR && SMP && !XIP_DEFLATED_DATA

	depends on GCC_PLUGINS && STACKPROTECTOR && THREAD_INFO_IN_TASK && !XIP_DEFLATED_DATA

	select GCC_PLUGIN_ARM_SSP_PER_TASK

	default y

	help

arch/arm/Makefile

+1 −4
Original line number Diff line number Diff line
@@ -273,11 +273,8 @@ ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) 
prepare: stack_protector_prepare

stack_protector_prepare: prepare0

	$(eval SSP_PLUGIN_CFLAGS := \

		-fplugin-arg-arm_ssp_per_task_plugin-tso=$(shell	\

			awk '{if ($$2 == "THREAD_SZ_ORDER") print $$3;}'\

				include/generated/asm-offsets.h)	\

		-fplugin-arg-arm_ssp_per_task_plugin-offset=$(shell	\

			awk '{if ($$2 == "TI_STACK_CANARY") print $$3;}'\

			awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}'\

				include/generated/asm-offsets.h))

	$(eval KBUILD_CFLAGS += $(SSP_PLUGIN_CFLAGS))

	$(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS))

arch/arm/include/asm/stackprotector.h

+0 −2
Original line number Diff line number Diff line
@@ -39,8 +39,6 @@ static __always_inline void boot_init_stack_canary(void) 
	current->stack_canary = canary;

#ifndef CONFIG_STACKPROTECTOR_PER_TASK

	__stack_chk_guard = current->stack_canary;

#else

	current_thread_info()->stack_canary = current->stack_canary;

#endif

}

arch/arm/include/asm/thread_info.h

+0 −3
Original line number Diff line number Diff line
@@ -55,9 +55,6 @@ struct thread_info { 
	struct task_struct	*task;		/* main task structure */

	__u32			cpu;		/* cpu */

	__u32			cpu_domain;	/* cpu domain */

#ifdef CONFIG_STACKPROTECTOR_PER_TASK

	unsigned long		stack_canary;

#endif

	struct cpu_context_save	cpu_context;	/* cpu context */

	__u32			abi_syscall;	/* ABI type and syscall nr */

	__u8			used_cp[16];	/* thread used copro */

arch/arm/kernel/asm-offsets.c

+0 −4
Original line number Diff line number Diff line
@@ -63,10 +63,6 @@ int main(void) 
#ifdef CONFIG_IWMMXT

  DEFINE(TI_IWMMXT_STATE,	offsetof(struct thread_info, fpstate.iwmmxt));

#endif

#ifdef CONFIG_STACKPROTECTOR_PER_TASK

  DEFINE(TI_STACK_CANARY,	offsetof(struct thread_info, stack_canary));

#endif

  DEFINE(THREAD_SZ_ORDER,	THREAD_SIZE_ORDER);

  BLANK();

  DEFINE(S_R0,			offsetof(struct pt_regs, ARM_r0));

  DEFINE(S_R1,			offsetof(struct pt_regs, ARM_r1));