Commit dd523791 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: Kconfig: Make CONFIG_COMPAT a menuconfig entry 



Make CONFIG_COMPAT a menuconfig entry so that we can place
CONFIG_KUSER_HELPERS and CONFIG_ARMV8_DEPRECATED underneath it.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent af1b3cf2

arch/arm64/Kconfig

+58 −55
Original line number Diff line number Diff line
@@ -1082,9 +1082,65 @@ config RODATA_FULL_DEFAULT_ENABLED 
	  This requires the linear region to be mapped down to pages,

	  which may adversely affect performance in some cases.



config ARM64_SW_TTBR0_PAN

	bool "Emulate Privileged Access Never using TTBR0_EL1 switching"

	help

	  Enabling this option prevents the kernel from accessing

	  user-space memory directly by pointing TTBR0_EL1 to a reserved

	  zeroed area and reserved ASID. The user access routines

	  restore the valid TTBR0_EL1 temporarily.



menuconfig COMPAT

	bool "Kernel support for 32-bit EL0"

	depends on ARM64_4K_PAGES || EXPERT

	select COMPAT_BINFMT_ELF if BINFMT_ELF

	select HAVE_UID16

	select OLD_SIGSUSPEND3

	select COMPAT_OLD_SIGACTION

	help

	  This option enables support for a 32-bit EL0 running under a 64-bit

	  kernel at EL1. AArch32-specific components such as system calls,

	  the user helper functions, VFP support and the ptrace interface are

	  handled appropriately by the kernel.



	  If you use a page size other than 4KB (i.e, 16KB or 64KB), please be aware

	  that you will only be able to execute AArch32 binaries that were compiled

	  with page size aligned segments.



	  If you want to execute 32-bit userspace applications, say Y.



if COMPAT



config KUSER_HELPERS

	bool "Enable kuser helpers page for 32 bit applications"

	default y

	help

	  Warning: disabling this option may break 32-bit user programs.



	  Provide kuser helpers to compat tasks. The kernel provides

	  helper code to userspace in read only form at a fixed location

	  to allow userspace to be independent of the CPU type fitted to

	  the system. This permits binaries to be run on ARMv4 through

	  to ARMv8 without modification.



	  See Documentation/arm/kernel_user_helpers.txt for details.



	  However, the fixed address nature of these helpers can be used

	  by ROP (return orientated programming) authors when creating

	  exploits.



	  If all of the binaries and libraries which run on your platform

	  are built specifically for your platform, and make no use of

	  these helpers, then you can turn this option off to hinder

	  such exploits. However, in that case, if a binary or library

	  relying on those helpers is run, it will not function correctly.



	  Say N here only if you are absolutely certain that you do not

	  need these helpers; otherwise, the safe option is to say Y.





menuconfig ARMV8_DEPRECATED

	bool "Emulate deprecated/obsolete ARMv8 instructions"

	depends on COMPAT

	depends on SYSCTL

	help

	  Legacy software support may require certain instructions
@@ -1150,13 +1206,7 @@ config SETEND_EMULATION 
	  If unsure, say Y

endif



config ARM64_SW_TTBR0_PAN

	bool "Emulate Privileged Access Never using TTBR0_EL1 switching"

	help

	  Enabling this option prevents the kernel from accessing

	  user-space memory directly by pointing TTBR0_EL1 to a reserved

	  zeroed area and reserved ASID. The user access routines

	  restore the valid TTBR0_EL1 temporarily.

endif



menu "ARMv8.1 architectural features"
@@ -1479,53 +1529,6 @@ config DMI 


endmenu



config COMPAT

	bool "Kernel support for 32-bit EL0"

	depends on ARM64_4K_PAGES || EXPERT

	select COMPAT_BINFMT_ELF if BINFMT_ELF

	select HAVE_UID16

	select OLD_SIGSUSPEND3

	select COMPAT_OLD_SIGACTION

	help

	  This option enables support for a 32-bit EL0 running under a 64-bit

	  kernel at EL1. AArch32-specific components such as system calls,

	  the user helper functions, VFP support and the ptrace interface are

	  handled appropriately by the kernel.



	  If you use a page size other than 4KB (i.e, 16KB or 64KB), please be aware

	  that you will only be able to execute AArch32 binaries that were compiled

	  with page size aligned segments.



	  If you want to execute 32-bit userspace applications, say Y.



config KUSER_HELPERS

	bool "Enable kuser helpers page for 32 bit applications."

	depends on COMPAT

	default y

	help

	  Warning: disabling this option may break 32-bit user programs.



	  Provide kuser helpers to compat tasks. The kernel provides

	  helper code to userspace in read only form at a fixed location

	  to allow userspace to be independent of the CPU type fitted to

	  the system. This permits binaries to be run on ARMv4 through

	  to ARMv8 without modification.



	  See Documentation/arm/kernel_user_helpers.txt for details.



	  However, the fixed address nature of these helpers can be used

	  by ROP (return orientated programming) authors when creating

	  exploits.



	  If all of the binaries and libraries which run on your platform

	  are built specifically for your platform, and make no use of

	  these helpers, then you can turn this option off to hinder

	  such exploits. However, in that case, if a binary or library

	  relying on those helpers is run, it will not function correctly.



	  Say N here only if you are absolutely certain that you do not

	  need these helpers; otherwise, the safe option is to say Y.



config SYSVIPC_COMPAT

	def_bool y

	depends on COMPAT && SYSVIPC