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| author | Catalin Marinas <catalin.marinas@arm.com> | 2022-04-23 11:07:49 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2022-04-25 10:25:43 +0100 |
| commit | da32b5817253697671af961715517bfbb308a592 (patch) | |
| tree | 561dd2cd02bda257eb1e50dfee2adb56b3545b43 /arch/Kconfig | |
| parent | b2d229d4ddb17db541098b83524d901257e93845 (diff) | |
| download | lwn-da32b5817253697671af961715517bfbb308a592.tar.gz lwn-da32b5817253697671af961715517bfbb308a592.zip | |
mm: Add fault_in_subpage_writeable() to probe at sub-page granularity
On hardware with features like arm64 MTE or SPARC ADI, an access fault
can be triggered at sub-page granularity. Depending on how the
fault_in_writeable() function is used, the caller can get into a
live-lock by continuously retrying the fault-in on an address different
from the one where the uaccess failed.
In the majority of cases progress is ensured by the following
conditions:
1. copy_to_user_nofault() guarantees at least one byte access if the
user address is not faulting.
2. The fault_in_writeable() loop is resumed from the first address that
could not be accessed by copy_to_user_nofault().
If the loop iteration is restarted from an earlier (initial) point, the
loop is repeated with the same conditions and it would live-lock.
Introduce an arch-specific probe_subpage_writeable() and call it from
the newly added fault_in_subpage_writeable() function. The arch code
with sub-page faults will have to implement the specific probing
functionality.
Note that no other fault_in_subpage_*() functions are added since they
have no callers currently susceptible to a live-lock.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20220423100751.1870771-2-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/Kconfig')
| -rw-r--r-- | arch/Kconfig | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 29b0167c088b..b34032279926 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -24,6 +24,13 @@ config KEXEC_ELF config HAVE_IMA_KEXEC bool +config ARCH_HAS_SUBPAGE_FAULTS + bool + help + Select if the architecture can check permissions at sub-page + granularity (e.g. arm64 MTE). The probe_user_*() functions + must be implemented. + config HOTPLUG_SMT bool |