Commit 5287569a authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Will Deacon
Browse files

arm64: Implement Shadow Call Stack 



This change implements shadow stack switching, initial SCS set-up,
and interrupt shadow stacks for arm64.

Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 96547368

arch/arm64/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ config ARM64 
	select ARCH_USE_QUEUED_RWLOCKS

	select ARCH_USE_QUEUED_SPINLOCKS

	select ARCH_SUPPORTS_MEMORY_FAILURE

	select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK

	select ARCH_SUPPORTS_ATOMIC_RMW

	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG)

	select ARCH_SUPPORTS_NUMA_BALANCING
@@ -1025,6 +1026,10 @@ config ARCH_HAS_CACHE_LINE_SIZE 
config ARCH_ENABLE_SPLIT_PMD_PTLOCK

	def_bool y if PGTABLE_LEVELS > 2



# Supported by clang >= 7.0

config CC_HAVE_SHADOW_CALL_STACK

	def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)



config SECCOMP

	bool "Enable seccomp to safely compute untrusted bytecode"

	---help---

arch/arm64/include/asm/scs.h

0 → 100644
+46 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_SCS_H

#define _ASM_SCS_H



#ifdef __ASSEMBLY__



#ifdef CONFIG_SHADOW_CALL_STACK

	.macro scs_load tsk, tmp

	ldp	x18, \tmp, [\tsk, #TSK_TI_SCS_BASE]

	add	x18, x18, \tmp

	.endm



	.macro scs_save tsk, tmp

	ldr	\tmp, [\tsk, #TSK_TI_SCS_BASE]

	sub	\tmp, x18, \tmp

	str	\tmp, [\tsk, #TSK_TI_SCS_OFFSET]

	.endm

#else

	.macro scs_load tsk, tmp

	.endm



	.macro scs_save tsk, tmp

	.endm

#endif /* CONFIG_SHADOW_CALL_STACK */



#else /* __ASSEMBLY__ */



#include <linux/scs.h>



#ifdef CONFIG_SHADOW_CALL_STACK



static inline void scs_overflow_check(struct task_struct *tsk)

{

	if (unlikely(scs_corrupted(tsk)))

		panic("corrupted shadow stack detected inside scheduler\n");

}



#else /* CONFIG_SHADOW_CALL_STACK */



static inline void scs_overflow_check(struct task_struct *tsk) {}



#endif /* CONFIG_SHADOW_CALL_STACK */



#endif /* __ASSEMBLY __ */



#endif /* _ASM_SCS_H */

arch/arm64/include/asm/thread_info.h

+13 −0
Original line number Diff line number Diff line
@@ -41,6 +41,10 @@ struct thread_info { 
#endif

		} preempt;

	};

#ifdef CONFIG_SHADOW_CALL_STACK

	void			*scs_base;

	unsigned long		scs_offset;

#endif

};



#define thread_saved_pc(tsk)	\
@@ -100,11 +104,20 @@ void arch_release_task_struct(struct task_struct *tsk); 
				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \

				 _TIF_SYSCALL_EMU)



#ifdef CONFIG_SHADOW_CALL_STACK

#define INIT_SCS							\

	.scs_base	= init_shadow_call_stack,			\

	.scs_offset	= 0,

#else

#define INIT_SCS

#endif



#define INIT_THREAD_INFO(tsk)						\

{									\

	.flags		= _TIF_FOREIGN_FPSTATE,				\

	.preempt_count	= INIT_PREEMPT_COUNT,				\

	.addr_limit	= KERNEL_DS,					\

	INIT_SCS							\

}



#endif /* __ASM_THREAD_INFO_H */

arch/arm64/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o 
obj-$(CONFIG_ARM_SDE_INTERFACE)		+= sdei.o

obj-$(CONFIG_ARM64_SSBD)		+= ssbd.o

obj-$(CONFIG_ARM64_PTR_AUTH)		+= pointer_auth.o

obj-$(CONFIG_SHADOW_CALL_STACK)		+= scs.o



obj-y					+= vdso/ probes/

obj-$(CONFIG_COMPAT_VDSO)		+= vdso32/

arch/arm64/kernel/asm-offsets.c

+4 −0
Original line number Diff line number Diff line
@@ -33,6 +33,10 @@ int main(void) 
  DEFINE(TSK_TI_ADDR_LIMIT,	offsetof(struct task_struct, thread_info.addr_limit));

#ifdef CONFIG_ARM64_SW_TTBR0_PAN

  DEFINE(TSK_TI_TTBR0,		offsetof(struct task_struct, thread_info.ttbr0));

#endif

#ifdef CONFIG_SHADOW_CALL_STACK

  DEFINE(TSK_TI_SCS_BASE,	offsetof(struct task_struct, thread_info.scs_base));

  DEFINE(TSK_TI_SCS_OFFSET,	offsetof(struct task_struct, thread_info.scs_offset));

#endif

  DEFINE(TSK_STACK,		offsetof(struct task_struct, stack));

#ifdef CONFIG_STACKPROTECTOR