UB fixes (#287)

Validating Cell construction with NockStack
Use the active fork, memmap2

Author: bitemyapp

Cargo.lock

@@ -212,6 +212,7 @@ mod tests {
     use rand::prelude::*;
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_fast_divide_small() {
         let mut rng = StdRng::seed_from_u64(1);
         for _ in 0..1000000 {
@@ -227,6 +228,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)]
     fn test_fast_divide_normalized() {
         let mut rng = StdRng::seed_from_u64(1);
         for _ in 0..1000000 {

rust/ibig/src/fast_divide.rs

@@ -21,7 +21,7 @@ intmap = "1.1.0"
 json = "0.12.4"
 lazy_static = "1.4.0"
 libc = "0.2.126"
-memmap = "0.7.0"
+memmap2 = "^0.9.5"
 num-derive = "0.3"
 num-traits = "0.2"
 rand = "0.8.5"

rust/sword/Cargo.toml

@@ -4,7 +4,7 @@ use crate::{assert_acyclic, assert_no_forwarding_pointers, assert_no_junior_poin
 use assert_no_alloc::permit_alloc;
 use either::Either::{self, Left, Right};
 use ibig::Stack;
-use memmap::MmapMut;
+use memmap2::MmapMut;
 use std::alloc::Layout;
 use std::panic::panic_any;
 use std::ptr::copy_nonoverlapping;
@@ -196,8 +196,8 @@ impl NockStack {
             return Err(NewStackError::StackTooSmall);
         }
         let free = size - (top_slots + RESERVED);
-        let memory = MmapMut::map_anon(size << 3)?;
-        let start = memory.as_ptr() as *const u64;
+        let mut memory = MmapMut::map_anon(size << 3)?;
+        let start = memory.as_mut_ptr() as *mut u64;
         // Here, frame_pointer < alloc_pointer, so the initial frame is West
         let frame_pointer = unsafe { start.add(RESERVED + top_slots) } as *mut u64;
         let stack_pointer = frame_pointer;
@@ -213,7 +213,7 @@ impl NockStack {
         );
         Ok((
             NockStack {
-                start,
+                start: start as *const u64,
                 size,
                 frame_pointer,
                 stack_pointer,

rust/sword/src/mem.rs

@@ -662,6 +662,7 @@ impl Cell {
 
     pub unsafe fn new_raw_mut<A: NounAllocator>(allocator: &mut A) -> (Cell, *mut CellMemory) {
         let memory = allocator.alloc_cell();
+        assert!(memory as usize % std::mem::align_of::<CellMemory>() == 0, "Memory is not aligned, {} {}", memory as usize, std::mem::align_of::<CellMemory>());
         (*memory).metadata = 0;
         (Self::from_raw_pointer(memory), memory)
     }

rust/sword/src/noun.rs

@@ -715,4 +715,11 @@ mod tests {
             println!("got expected error: {:?}", e);
         }
     }
+
+    #[test]
+    fn test_cell_construction() {
+        let mut stack = setup_stack();
+        let (cell, cell_mem_ptr) = unsafe { Cell::new_raw_mut(&mut stack) };
+        unsafe { assert!(cell_mem_ptr as *const CellMemory == cell.to_raw_pointer()) };
+    }
 }