Commit 92b6919d authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64: Kconfig: force ARM64_PAN=y when enabling TTBR0 sw PAN 



There are a couple of instances of Kconfig constraints where PAN must be
enabled too if TTBR0 sw PAN is enabled, primarily to avoid dealing with
the modified TTBR0_EL1 sysreg format that is used when 52-bit physical
addressing and/or CnP are enabled (support for either implies support
for hardware PAN as well, which will supersede PAN emulation if both are
available)

Let's simplify this, and always enable ARM64_PAN when enabling TTBR0 sw
PAN. This decouples the PAN configuration from the VA size selection,
permitting us to simplify the latter in subsequent patches. (Note that
PAN and TTBR0 sw PAN can still be disabled after this patch, but not
independently)

To avoid a convoluted circular Kconfig dependency involving KCSAN, make
ARM64_MTE select ARM64_PAN too, instead of depending on it.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241212081841.2168124-13-ardb+git@google.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 9d86c3c9

arch/arm64/Kconfig

+2 −4
Original line number Diff line number Diff line
@@ -1379,7 +1379,6 @@ config ARM64_VA_BITS_48 


config ARM64_VA_BITS_52

	bool "52-bit"

	depends on ARM64_PAN || !ARM64_SW_TTBR0_PAN

	help

	  Enable 52-bit virtual addressing for userspace when explicitly

	  requested via a hint to mmap(). The kernel will also use 52-bit
@@ -1431,7 +1430,6 @@ config ARM64_PA_BITS_48 
config ARM64_PA_BITS_52

	bool "52-bit"

	depends on ARM64_64K_PAGES || ARM64_VA_BITS_52

	depends on ARM64_PAN || !ARM64_SW_TTBR0_PAN

	help

	  Enable support for a 52-bit physical address space, introduced as

	  part of the ARMv8.2-LPA extension.
@@ -1681,6 +1679,7 @@ config RODATA_FULL_DEFAULT_ENABLED 
config ARM64_SW_TTBR0_PAN

	bool "Emulate Privileged Access Never using TTBR0_EL1 switching"

	depends on !KCSAN

	select ARM64_PAN

	help

	  Enabling this option prevents the kernel from accessing

	  user-space memory directly by pointing TTBR0_EL1 to a reserved
@@ -1937,7 +1936,6 @@ config ARM64_RAS_EXTN 
config ARM64_CNP

	bool "Enable support for Common Not Private (CNP) translations"

	default y

	depends on ARM64_PAN || !ARM64_SW_TTBR0_PAN

	help

	  Common Not Private (CNP) allows translation table entries to

	  be shared between different PEs in the same inner shareable
@@ -2132,7 +2130,7 @@ config ARM64_MTE 
	depends on AS_HAS_ARMV8_5

	depends on AS_HAS_LSE_ATOMICS

	# Required for tag checking in the uaccess routines

	depends on ARM64_PAN

	select ARM64_PAN

	select ARCH_HAS_SUBPAGE_FAULTS

	select ARCH_USES_HIGH_VMA_FLAGS

	select ARCH_USES_PG_ARCH_2