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: Will Deacon <will.deacon@arm.com>
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Will Deacon
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dd523791c9
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@ -1082,9 +1082,65 @@ config RODATA_FULL_DEFAULT_ENABLED
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This requires the linear region to be mapped down to pages,
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which may adversely affect performance in some cases.
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config ARM64_SW_TTBR0_PAN
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bool "Emulate Privileged Access Never using TTBR0_EL1 switching"
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help
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Enabling this option prevents the kernel from accessing
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user-space memory directly by pointing TTBR0_EL1 to a reserved
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zeroed area and reserved ASID. The user access routines
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restore the valid TTBR0_EL1 temporarily.
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menuconfig COMPAT
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bool "Kernel support for 32-bit EL0"
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depends on ARM64_4K_PAGES || EXPERT
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select COMPAT_BINFMT_ELF if BINFMT_ELF
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select HAVE_UID16
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select OLD_SIGSUSPEND3
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select COMPAT_OLD_SIGACTION
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help
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This option enables support for a 32-bit EL0 running under a 64-bit
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kernel at EL1. AArch32-specific components such as system calls,
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the user helper functions, VFP support and the ptrace interface are
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handled appropriately by the kernel.
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If you use a page size other than 4KB (i.e, 16KB or 64KB), please be aware
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that you will only be able to execute AArch32 binaries that were compiled
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with page size aligned segments.
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If you want to execute 32-bit userspace applications, say Y.
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if COMPAT
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config KUSER_HELPERS
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bool "Enable kuser helpers page for 32 bit applications"
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default y
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help
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Warning: disabling this option may break 32-bit user programs.
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Provide kuser helpers to compat tasks. The kernel provides
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helper code to userspace in read only form at a fixed location
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to allow userspace to be independent of the CPU type fitted to
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the system. This permits binaries to be run on ARMv4 through
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to ARMv8 without modification.
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See Documentation/arm/kernel_user_helpers.txt for details.
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However, the fixed address nature of these helpers can be used
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by ROP (return orientated programming) authors when creating
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exploits.
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If all of the binaries and libraries which run on your platform
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are built specifically for your platform, and make no use of
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these helpers, then you can turn this option off to hinder
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such exploits. However, in that case, if a binary or library
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relying on those helpers is run, it will not function correctly.
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Say N here only if you are absolutely certain that you do not
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need these helpers; otherwise, the safe option is to say Y.
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menuconfig ARMV8_DEPRECATED
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bool "Emulate deprecated/obsolete ARMv8 instructions"
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depends on COMPAT
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depends on SYSCTL
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help
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Legacy software support may require certain instructions
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@ -1150,13 +1206,7 @@ config SETEND_EMULATION
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If unsure, say Y
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endif
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config ARM64_SW_TTBR0_PAN
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bool "Emulate Privileged Access Never using TTBR0_EL1 switching"
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help
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Enabling this option prevents the kernel from accessing
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user-space memory directly by pointing TTBR0_EL1 to a reserved
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zeroed area and reserved ASID. The user access routines
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restore the valid TTBR0_EL1 temporarily.
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endif
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menu "ARMv8.1 architectural features"
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@ -1479,53 +1529,6 @@ config DMI
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endmenu
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config COMPAT
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bool "Kernel support for 32-bit EL0"
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depends on ARM64_4K_PAGES || EXPERT
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select COMPAT_BINFMT_ELF if BINFMT_ELF
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select HAVE_UID16
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select OLD_SIGSUSPEND3
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select COMPAT_OLD_SIGACTION
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help
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This option enables support for a 32-bit EL0 running under a 64-bit
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kernel at EL1. AArch32-specific components such as system calls,
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the user helper functions, VFP support and the ptrace interface are
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handled appropriately by the kernel.
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If you use a page size other than 4KB (i.e, 16KB or 64KB), please be aware
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that you will only be able to execute AArch32 binaries that were compiled
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with page size aligned segments.
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If you want to execute 32-bit userspace applications, say Y.
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config KUSER_HELPERS
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bool "Enable kuser helpers page for 32 bit applications."
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depends on COMPAT
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default y
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help
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Warning: disabling this option may break 32-bit user programs.
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Provide kuser helpers to compat tasks. The kernel provides
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helper code to userspace in read only form at a fixed location
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to allow userspace to be independent of the CPU type fitted to
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the system. This permits binaries to be run on ARMv4 through
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to ARMv8 without modification.
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See Documentation/arm/kernel_user_helpers.txt for details.
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However, the fixed address nature of these helpers can be used
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by ROP (return orientated programming) authors when creating
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exploits.
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If all of the binaries and libraries which run on your platform
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are built specifically for your platform, and make no use of
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these helpers, then you can turn this option off to hinder
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such exploits. However, in that case, if a binary or library
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relying on those helpers is run, it will not function correctly.
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Say N here only if you are absolutely certain that you do not
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need these helpers; otherwise, the safe option is to say Y.
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config SYSVIPC_COMPAT
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def_bool y
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depends on COMPAT && SYSVIPC
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