Struct NAPOTRegionSpec

pub struct NAPOTRegionSpec { /* private fields */ }

A RISC-V PMP memory region specification, configured in NAPOT mode.

This type checks that the supplied start and size values meet the RISC-V NAPOT requirements, namely that

• the region is a power of two bytes in size
• the region’s start address is aligned to the region size
• the region is at least 8 bytes long

Finally, RISC-V restricts physical address spaces to 34 bit on RV32, and 56 bit on RV64 platforms. A NAPOTRegionSpec must not cover addresses exceeding this address space, respectively. In practice, this means that on RV64 platforms NAPOTRegionSpecs whose encoded pmpaddrX CSR contains any non-zero bits in the 10 most significant bits will be rejected.

By accepting this type, PMP implementations can rely on these requirements to be verified. Furthermore, they can use the NAPOTRegionSpec::pmpaddr convenience method to retrieve an pmpaddrX CSR value encoding this region’s address and length.

Implementations

impl NAPOTRegionSpec

pub fn from_pmpaddr_csr(pmpaddr: usize) -> Option<Self>

Construct a new NAPOTRegionSpec from a pmpaddr CSR value.

For an RV32 platform, every single integer in [0; usize::MAX] is a valid pmpaddrX CSR for a region configured in NAPOT mode, and this operation is thus effectively infallible.

For RV64 platforms, this operation checks if the range would include any address outside of the 56 bit physical address space and, in this case, rejects the pmpaddr (tests whether any of the 10 most significant bits are non-zero).

pub fn from_start_size(start: *const u8, size: usize) -> Option<Self>

Construct a new NAPOTRegionSpec from a start address and size.

This method accepts a start address and a region length. It returns Some(region) when all constraints specified in the NAPOTRegionSpec’s documentation are satisfied, otherwise None.

pub fn from_start_end(start: *const u8, end: *const u8) -> Option<Self>

Construct a new NAPOTRegionSpec from a start address and end address.

This method accepts a start address (inclusive) and end address (exclusive). It returns Some(region) when all constraints specified in the NAPOTRegionSpec’s documentation are satisfied, otherwise None.

pub fn pmpaddr(&self) -> usize

Retrieve a pmpaddrX-CSR compatible representation of this NAPOTRegionSpec’s address and length. For this value to be valid in a CSR register, the pmpcfgX octet’s A (address mode) value belonging to this pmpaddrX-CSR must be set to NAPOT (0b11).

pub fn address_range(&self) -> Range<u64>

Return the range of physical addresses covered by this PMP region.

This follows the regular Rust range semantics (start inclusive, end exclusive). It returns the addresses as u64-integers to ensure that all underlying pmpaddrX CSR values can be represented.

Trait Implementations

impl Clone for NAPOTRegionSpec

fn clone(&self) -> NAPOTRegionSpec

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NAPOTRegionSpec

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

Formats the value using the given formatter.

impl Copy for NAPOTRegionSpec