register: add mconfigptr register

Adds the definition for the `mconfigptr` Machine configuration pointer
CSR.

Author: rmsyn

riscv/CHANGELOG.md

@@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Write utilities for `mcycle`, `minstret`
 - Add `senvcfg` CSR
 - Add `scontext` CSR
-- Add `mtinst` CSR
+- Add `mconfigptr` CSR
 
 ### Changed
 

riscv/src/register.rs

@@ -110,6 +110,9 @@ pub mod minstreth;
 mod mhpmeventx;
 pub use self::mhpmeventx::*;
 
+// Machine configuration
+pub mod mconfigptr;
+
 #[cfg(test)]
 mod tests;
 

riscv/src/register/mconfigptr.rs

@@ -0,0 +1,54 @@
+//! `mconfigptr` register.
+
+use crate::result::{Error, Result};
+
+const MASK: usize = usize::MAX;
+
+read_only_csr! {
+    /// `mconfigptr` register.
+    Mconfigptr: 0xf15,
+    mask: MASK,
+    sentinel: 0,
+}
+
+impl Mconfigptr {
+    /// Represents the bitshift for a properly aligned configuration pointer.
+    pub const ALIGN_SHIFT: usize = (usize::BITS / 8).ilog2() as usize;
+    /// Represents the bitmask for a properly aligned configuration pointer.
+    pub const ALIGN_MASK: usize = (1usize << Self::ALIGN_SHIFT) - 1;
+
+    /// Gets the pointer to the machine configuration structure.
+    ///
+    /// # Panics
+    ///
+    /// Panics if:
+    ///
+    /// - the value is `0`, indicating no configuration structure
+    /// - the pointer is not aligned to an MXLEN byte value
+    pub fn as_ptr(&self) -> *const u8 {
+        self.try_as_ptr().unwrap()
+    }
+
+    /// Attempts to get the pointer to the machine configuration structure.
+    ///
+    /// # Note
+    ///
+    /// Returns an error if:
+    ///
+    /// - the value is `0`, indicating no configuration structure
+    /// - the pointer is not aligned to an MXLEN byte value
+    pub const fn try_as_ptr(&self) -> Result<*const u8> {
+        match self.bits() {
+            0 => Err(Error::InvalidFieldVariant {
+                field: "mconfigptr",
+                value: 0,
+            }),
+            p if p & Self::ALIGN_MASK != 0 => Err(Error::InvalidFieldValue {
+                field: "mconfigptr",
+                value: p,
+                bitmask: !Self::ALIGN_MASK,
+            }),
+            p => Ok(p as *const _),
+        }
+    }
+}