Struct SimplePMP

pub struct SimplePMP<const AVAILABLE_ENTRIES: usize>;

A “simple” RISC-V PMP implementation.

The SimplePMP does not support locked regions, kernel memory protection, or any ePMP features (using the mseccfg CSR). It is generic over the number of hardware PMP regions available. AVAILABLE_ENTRIES is expected to be set to the number of available entries.

SimplePMP implements TORUserPMP to expose all of its regions as “top of range” (TOR) regions (each taking up two physical PMP entires) for use as a user-mode memory protection mechanism.

Notably, SimplePMP implements TORUserPMP<MPU_REGIONS> over a generic MPU_REGIONS where MPU_REGIONS <= (AVAILABLE_ENTRIES / 2). As PMP re-configuration can have a significiant runtime overhead, users are free to specify a small MPU_REGIONS const-generic parameter to reduce the runtime overhead induced through PMP configuration, at the cost of having less PMP regions available to use for userspace memory protection.

Implementations

impl<const AVAILABLE_ENTRIES: usize> SimplePMP<AVAILABLE_ENTRIES>

pub unsafe fn new() -> Result<Self, ()>

Trait Implementations

impl<const AVAILABLE_ENTRIES: usize> Display for SimplePMP<AVAILABLE_ENTRIES>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<const AVAILABLE_ENTRIES: usize, const MPU_REGIONS: usize> TORUserPMP<MPU_REGIONS> for SimplePMP<AVAILABLE_ENTRIES>

const CONST_ASSERT_CHECK: ()

A placeholder to define const-assertions which are evaluated in PMPUserMPU::new. This can be used to, for instance, assert that the number of userspace regions does not exceed the number of hardware regions.

fn available_regions(&self) -> usize

The number of TOR regions currently available for userspace memory protection. Within [0; MAX_REGIONS].

fn configure_pmp( &self, regions: &[(TORUserPMPCFG, *const u8, *const u8); MPU_REGIONS], ) -> Result<(), ()>

Configure the user-mode memory protection.

fn enable_user_pmp(&self) -> Result<(), ()>

Enable the user-mode memory protection.

fn disable_user_pmp(&self)

Disable the user-mode memory protection.