diff options
| author | James Morse <james.morse@arm.com> | 2016-02-05 15:58:50 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-02-18 18:27:05 +0100 |
| commit | 705441960033e66b63524521f153fbb28c99ddbd (patch) | |
| tree | f24a8ab766c2e44e3aa5eaa49c852836023db055 /arch/arm64/kernel | |
| parent | arm64: cpufeature: Test 'matches' pointer to find the end of the list (diff) | |
| download | linux-705441960033e66b63524521f153fbb28c99ddbd.tar.xz linux-705441960033e66b63524521f153fbb28c99ddbd.zip | |
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/kernel')
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 9cc8186cd14b..7566cad9fa1d 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -67,6 +67,10 @@ DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS); .width = 0, \ } +/* meta feature for alternatives */ +static bool __maybe_unused +cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry); + static struct arm64_ftr_bits ftr_id_aa64isar0[] = { ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 32, 32, 0), ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, ID_AA64ISAR0_RDM_SHIFT, 4, 0), @@ -688,6 +692,12 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .enable = cpu_enable_uao, }, #endif /* CONFIG_ARM64_UAO */ +#ifdef CONFIG_ARM64_PAN + { + .capability = ARM64_ALT_PAN_NOT_UAO, + .matches = cpufeature_pan_not_uao, + }, +#endif /* CONFIG_ARM64_PAN */ {}, }; @@ -966,3 +976,9 @@ void __init setup_cpu_features(void) pr_warn("L1_CACHE_BYTES smaller than the Cache Writeback Granule (%d < %d)\n", L1_CACHE_BYTES, cls); } + +static bool __maybe_unused +cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry) +{ + return (cpus_have_cap(ARM64_HAS_PAN) && !cpus_have_cap(ARM64_HAS_UAO)); +} |