Commit 68c76ad4 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64: unwind: add asynchronous unwind tables to kernel and modules 



Enable asynchronous unwind table generation for both the core kernel as
well as modules, and emit the resulting .eh_frame sections as init code
so we can use the unwind directives for code patching at boot or module
load time.

This will be used by dynamic shadow call stack support, which will rely
on code patching rather than compiler codegen to emit the shadow call
stack push and pop instructions.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: default avatarSami Tolvanen <samitolvanen@google.com>
Tested-by: default avatarSami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20221027155908.1940624-2-ardb@kernel.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent f0c4d9fc

arch/arm64/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -370,6 +370,9 @@ config KASAN_SHADOW_OFFSET 
	default 0xeffffff800000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS

	default 0xffffffffffffffff



config UNWIND_TABLES

	bool



source "arch/arm64/Kconfig.platforms"



menu "Kernel Features"

arch/arm64/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -45,8 +45,13 @@ KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) 
KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)



# Avoid generating .eh_frame* sections.

ifneq ($(CONFIG_UNWIND_TABLES),y)

KBUILD_CFLAGS	+= -fno-asynchronous-unwind-tables -fno-unwind-tables

KBUILD_AFLAGS	+= -fno-asynchronous-unwind-tables -fno-unwind-tables

else

KBUILD_CFLAGS	+= -fasynchronous-unwind-tables

KBUILD_AFLAGS	+= -fasynchronous-unwind-tables

endif



ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)

prepare: stack_protector_prepare

arch/arm64/include/asm/module.lds.h

+8 −0
Original line number Diff line number Diff line
@@ -17,4 +17,12 @@ SECTIONS { 
	 */

	.text.hot : { *(.text.hot) }

#endif



#ifdef CONFIG_UNWIND_TABLES

	/*

	 * Currently, we only use unwind info at module load time, so we can

	 * put it into the .init allocation.

	 */

	.init.eh_frame : { *(.eh_frame) }

#endif

}

arch/arm64/kernel/pi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \ 
		   -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \

		   -include $(srctree)/include/linux/hidden.h \

		   -D__DISABLE_EXPORTS -ffreestanding -D__NO_FORTIFY \

		   -fno-asynchronous-unwind-tables -fno-unwind-tables \

		   $(call cc-option,-fno-addrsig)



# remove SCS flags from all objects in this directory

arch/arm64/kernel/vmlinux.lds.S

+13 −0
Original line number Diff line number Diff line
@@ -121,6 +121,17 @@ jiffies = jiffies_64; 
#define TRAMP_TEXT

#endif



#ifdef CONFIG_UNWIND_TABLES

#define UNWIND_DATA_SECTIONS				\

	.eh_frame : {					\

		__eh_frame_start = .;			\

		*(.eh_frame)				\

		__eh_frame_end = .;			\

	}

#else

#define UNWIND_DATA_SECTIONS

#endif



/*

 * The size of the PE/COFF section that covers the kernel image, which

 * runs from _stext to _edata, must be a round multiple of the PE/COFF
@@ -231,6 +242,8 @@ SECTIONS 
		__alt_instructions_end = .;

	}



	UNWIND_DATA_SECTIONS



	. = ALIGN(SEGMENT_ALIGN);

	__inittext_end = .;

	__initdata_begin = .;