diff options
| author | James Morse <james.morse@arm.com> | 2016-02-05 14:58:50 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-02-18 17:27:05 +0000 |
| commit | 705441960033e66b63524521f153fbb28c99ddbd (patch) | |
| tree | f24a8ab766c2e44e3aa5eaa49c852836023db055 /arch/arm64/include/asm/cpufeature.h | |
| parent | 644c2ae198412c956700e55a2acf80b2541f6aa5 (diff) | |
arm64: kernel: Don't toggle PAN on systems with UAO
If a CPU supports both Privileged Access Never (PAN) and User Access
Override (UAO), we don't need to disable/re-enable PAN round all
copy_to_user() like calls.
UAO alternatives cause these calls to use the 'unprivileged' load/store
instructions, which are overridden to be the privileged kind when
fs==KERNEL_DS.
This patch changes the copy_to_user() calls to have their PAN toggling
depend on a new composite 'feature' ARM64_ALT_PAN_NOT_UAO.
If both features are detected, PAN will be enabled, but the copy_to_user()
alternatives will not be applied. This means PAN will be enabled all the
time for these functions. If only PAN is detected, the toggling will be
enabled as normal.
This will save the time taken to disable/re-enable PAN, and allow us to
catch copy_to_user() accesses that occur with fs==KERNEL_DS.
Futex and swp-emulation code continue to hang their PAN toggling code on
ARM64_HAS_PAN.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/cpufeature.h')
| -rw-r--r-- | arch/arm64/include/asm/cpufeature.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index a5df7cde616b..37a53fc6b384 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -32,8 +32,9 @@ #define ARM64_WORKAROUND_834220 7 #define ARM64_HAS_NO_HW_PREFETCH 8 #define ARM64_HAS_UAO 9 +#define ARM64_ALT_PAN_NOT_UAO 10 -#define ARM64_NCAPS 10 +#define ARM64_NCAPS 11 #ifndef __ASSEMBLY__ |