diff options
| author | Will Deacon <will.deacon@arm.com> | 2018-12-10 17:15:15 +0300 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2018-12-10 21:42:18 +0300 |
| commit | 68d23da4373aba76f5300017c4746440f276698e (patch) | |
| tree | 138b93b628cf77727970417690693f18eddf7c40 /arch/arm64/Kconfig | |
| parent | b9567720a1b8e739380e0241413606c056c57859 (diff) | |
| download | linux-68d23da4373aba76f5300017c4746440f276698e.tar.xz | |
arm64: Kconfig: Re-jig CONFIG options for 52-bit VA
Enabling 52-bit VAs for userspace is pretty confusing, since it requires
you to select "48-bit" virtual addressing in the Kconfig.
Rework the logic so that 52-bit user virtual addressing is advertised in
the "Virtual address space size" choice, along with some help text to
describe its interaction with Pointer Authentication. The EXPERT-only
option to force all user mappings to the 52-bit range is then made
available immediately below the VA size selection.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/Kconfig')
| -rw-r--r-- | arch/arm64/Kconfig | 47 |
1 files changed, 29 insertions, 18 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index ca1f93233b22..905ce1653e82 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -682,15 +682,43 @@ config ARM64_VA_BITS_47 config ARM64_VA_BITS_48 bool "48-bit" +config ARM64_USER_VA_BITS_52 + bool "52-bit (user)" + depends on ARM64_64K_PAGES && (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 continue to + use 48-bit virtual addresses for its own mappings. + + NOTE: Enabling 52-bit virtual addressing in conjunction with + ARMv8.3 Pointer Authentication will result in the PAC being + reduced from 7 bits to 3 bits, which may have a significant + impact on its susceptibility to brute-force attacks. + + If unsure, select 48-bit virtual addressing instead. + endchoice +config ARM64_FORCE_52BIT + bool "Force 52-bit virtual addresses for userspace" + depends on ARM64_USER_VA_BITS_52 && EXPERT + help + For systems with 52-bit userspace VAs enabled, the kernel will attempt + to maintain compatibility with older software by providing 48-bit VAs + unless a hint is supplied to mmap. + + This configuration option disables the 48-bit compatibility logic, and + forces all userspace addresses to be 52-bit on HW that supports it. One + should only enable this configuration option for stress testing userspace + memory management code. If unsure say N here. + config ARM64_VA_BITS int default 36 if ARM64_VA_BITS_36 default 39 if ARM64_VA_BITS_39 default 42 if ARM64_VA_BITS_42 default 47 if ARM64_VA_BITS_47 - default 48 if ARM64_VA_BITS_48 + default 48 if ARM64_VA_BITS_48 || ARM64_USER_VA_BITS_52 choice prompt "Physical address space size" @@ -716,10 +744,6 @@ config ARM64_PA_BITS_52 endchoice -config ARM64_52BIT_VA - def_bool y - depends on ARM64_VA_BITS_48 && ARM64_64K_PAGES && (ARM64_PAN || !ARM64_SW_TTBR0_PAN) - config ARM64_PA_BITS int default 48 if ARM64_PA_BITS_48 @@ -1186,19 +1210,6 @@ config ARM64_CNP at runtime, and does not affect PEs that do not implement this feature. -config ARM64_FORCE_52BIT - bool "Force 52-bit virtual addresses for userspace" - depends on ARM64_52BIT_VA && EXPERT - help - For systems with 52-bit userspace VAs enabled, the kernel will attempt - to maintain compatibility with older software by providing 48-bit VAs - unless a hint is supplied to mmap. - - This configuration option disables the 48-bit compatibility logic, and - forces all userspace addresses to be 52-bit on HW that supports it. One - should only enable this configuration option for stress testing userspace - memory management code. If unsure say N here. - endmenu config ARM64_SVE |