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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>
This commit is contained in:
Will Deacon 2019-04-23 14:37:24 +01:00
parent af1b3cf2c2
commit dd523791c9
1 changed files with 58 additions and 55 deletions
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113
arch/arm64/Kconfig
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@ -1082,9 +1082,65 @@ config RODATA_FULL_DEFAULT_ENABLED
This requires the linear region to be mapped down to pages, This requires the linear region to be mapped down to pages,
which may adversely affect performance in some cases. 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 menuconfig ARMV8_DEPRECATED
bool "Emulate deprecated/obsolete ARMv8 instructions" bool "Emulate deprecated/obsolete ARMv8 instructions"
depends on COMPAT
depends on SYSCTL depends on SYSCTL
help help
Legacy software support may require certain instructions Legacy software support may require certain instructions
@ -1150,13 +1206,7 @@ config SETEND_EMULATION
If unsure, say Y If unsure, say Y
endif endif
config ARM64_SW_TTBR0_PAN endif
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.
menu "ARMv8.1 architectural features" menu "ARMv8.1 architectural features"
@ -1479,53 +1529,6 @@ config DMI
endmenu 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 config SYSVIPC_COMPAT
def_bool y def_bool y
depends on COMPAT && SYSVIPC depends on COMPAT && SYSVIPC