From 80fded75892e4fd25cb29a5a3f102c2d9f8ccb03 Mon Sep 17 00:00:00 2001
From: bunnie <bunnie@kosagi.com>
Date: Mon, 11 Mar 2024 18:44:17 +0800
Subject: [PATCH] add functions to allow low-level access from outside the
 crate

and also make the internal functions use the same conventions
---
 .../src/backend/serial/u32e/mod.rs            | 20 ++++++++---
 curve25519-dalek/src/montgomery.rs            | 36 +++++--------------
 2 files changed, 25 insertions(+), 31 deletions(-)

diff --git a/curve25519-dalek/src/backend/serial/u32e/mod.rs b/curve25519-dalek/src/backend/serial/u32e/mod.rs
index c295a90f2..11b86b54c 100644
--- a/curve25519-dalek/src/backend/serial/u32e/mod.rs
+++ b/curve25519-dalek/src/backend/serial/u32e/mod.rs
@@ -72,7 +72,19 @@ pub fn ensure_engine() {
     }
 }
 
-pub(crate) fn copy_to_rf(bytes: [u8; 32], register: usize, rf: &mut [u32], window: usize) {
+/// Safety: must be called after ensure_engine()
+pub unsafe fn get_ucode() -> &'static mut [u32] {
+    core::slice::from_raw_parts_mut(ENGINE_MEM.unwrap().as_mut_ptr() as *mut u32, 1024)
+}
+/// Safety: must be called after ensure_engine()
+pub unsafe fn get_rf() -> &'static mut [u32] {
+    core::slice::from_raw_parts_mut(
+        (ENGINE_MEM.unwrap().as_mut_ptr() as usize + RF_U8_BASE) as *mut u32,
+        TOTAL_RF_SIZE_IN_U32,
+    )
+}
+
+pub fn copy_to_rf(bytes: [u8; 32], register: usize, rf: &mut [u32], window: usize) {
     use core::convert::TryInto;
     for (byte, rf_dst) in bytes.chunks_exact(4).zip(
         rf[window * RF_SIZE_IN_U32 + register * 8..window * RF_SIZE_IN_U32 + (register + 1) * 8]
@@ -82,7 +94,7 @@ pub(crate) fn copy_to_rf(bytes: [u8; 32], register: usize, rf: &mut [u32], windo
     }
 }
 
-pub(crate) fn copy_from_rf(register: usize, rf: &[u32], window: usize) -> [u8; 32] {
+pub fn copy_from_rf(register: usize, rf: &[u32], window: usize) -> [u8; 32] {
     let mut ret: [u8; 32] = [0; 32];
 
     for (src, dst) in rf
@@ -98,7 +110,7 @@ pub(crate) fn copy_from_rf(register: usize, rf: &[u32], window: usize) -> [u8; 3
     ret
 }
 
-pub(crate) fn get_single_result(rf_hw: &[u32], window: usize, r: usize) -> [u8; 32] {
+pub fn get_single_result(rf_hw: &[u32], window: usize, r: usize) -> [u8; 32] {
     // TODO: put handlers for illegal opcodes, suspend/resume catch
 
     let mut ret_r: [u8; 32] = [0; 32];
@@ -115,7 +127,7 @@ pub(crate) fn get_single_result(rf_hw: &[u32], window: usize, r: usize) -> [u8;
 
 /// This assumes that arguments have been loaded in appropriate locations for the microcode
 /// and that the result is always in r31.
-pub(crate) fn run_job(
+pub fn run_job(
     ucode_hw: &mut [u32],
     rf_hw: &[u32],
     mcode: &[i32],
diff --git a/curve25519-dalek/src/montgomery.rs b/curve25519-dalek/src/montgomery.rs
index 7f901d1e2..c78bea385 100644
--- a/curve25519-dalek/src/montgomery.rs
+++ b/curve25519-dalek/src/montgomery.rs
@@ -466,15 +466,9 @@ impl ProjectivePoint {
 
         use crate::backend::serial::u32e::*;
         ensure_engine();
-        let mut ucode_hw: &'static mut [u32] = unsafe {
-            core::slice::from_raw_parts_mut(ENGINE_MEM.unwrap().as_mut_ptr() as *mut u32, 1024)
-        };
-        let rf_hw: &mut [u32] = unsafe {
-            core::slice::from_raw_parts_mut(
-                (ENGINE_MEM.unwrap().as_mut_ptr() as usize + RF_U8_BASE) as *mut u32,
-                TOTAL_RF_SIZE_IN_U32,
-            )
-        };
+        // safety: these were called after ensure_engine()
+        let mut ucode_hw = unsafe { get_ucode() };
+        let rf_hw = unsafe { get_rf() };
 
         copy_to_rf(self.U.as_bytes(), 29, rf_hw, 0);
         copy_to_rf(self.W.as_bytes(), 30, rf_hw, 0);
@@ -629,15 +623,9 @@ pub(crate) fn differential_add_and_double(
     );
     use crate::backend::serial::u32e::*;
     ensure_engine();
-    let mut ucode_hw: &'static mut [u32] = unsafe {
-        core::slice::from_raw_parts_mut(ENGINE_MEM.unwrap().as_mut_ptr() as *mut u32, 1024)
-    };
-    let rf_hw: &mut [u32] = unsafe {
-        core::slice::from_raw_parts_mut(
-            (ENGINE_MEM.unwrap().as_mut_ptr() as usize + RF_U8_BASE) as *mut u32,
-            TOTAL_RF_SIZE_IN_U32,
-        )
-    };
+    // safety: these were called after ensure_engine()
+    let mut ucode_hw = unsafe { get_ucode() };
+    let rf_hw = unsafe { get_rf() };
 
     // P.U in %20
     // P.W in %21
@@ -958,15 +946,9 @@ impl Mul<&Scalar> for &MontgomeryPoint {
 
         let window = 0;
         ensure_engine();
-        let mut ucode_hw: &'static mut [u32] = unsafe {
-            core::slice::from_raw_parts_mut(ENGINE_MEM.unwrap().as_mut_ptr() as *mut u32, 1024)
-        };
-        let mut rf_hw: &mut [u32] = unsafe {
-            core::slice::from_raw_parts_mut(
-                (ENGINE_MEM.unwrap().as_mut_ptr() as usize + RF_U8_BASE) as *mut u32,
-                TOTAL_RF_SIZE_IN_U32,
-            )
-        };
+        // safety: these were called after ensure_engine()
+        let mut ucode_hw = unsafe { get_ucode() };
+        let mut rf_hw = unsafe { get_rf() };
 
         copy_to_rf(x0.U.as_bytes(), 25, &mut rf_hw, window);
         copy_to_rf(x0.W.as_bytes(), 26, &mut rf_hw, window);