diff --git a/src/main.rs b/src/main.rs
index d970561..eb3b8d3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -108,8 +108,7 @@ impl MachineState {
         return Self::new_with_state(memory, pages);
     }
 
-    fn get_page_table_entry(&mut self, address: usize) -> PageTableEntry {
-        let page = address >> PAGE_BITS;
+    fn get_page_table_entry(&self, page: usize) -> PageTableEntry {
         if page < self.pages.len() {
             return self.pages[page];
         } else {
@@ -117,38 +116,37 @@ impl MachineState {
         }
     }
 
-    fn set_page_table_entry(&mut self, address: usize, entry: PageTableEntry) {
-        let page = address >> PAGE_BITS;
+    fn set_page_table_entry(&mut self, page: usize, entry: PageTableEntry) {
         if page < self.pages.len() {
-            self.pages[address >> 12] = entry;
+            self.pages[page] = entry;
         } else {
             panic!("@fixme: handle attempts to expand address space");
         }
     }
 
-    fn lb_physical(&mut self, address: usize) -> i64 {
+    fn lb_physical(&self, address: usize) -> i64 {
         return self.memory[address] as i8 as i64;
     }
 
-    fn lbu_physical(&mut self, address: usize) -> i64 {
+    fn lbu_physical(&self, address: usize) -> i64 {
         return self.memory[address] as u8 as i64;
     }
 
-    fn lh_physical(&mut self, address: usize) -> i64 {
+    fn lh_physical(&self, address: usize) -> i64 {
         return (
              (self.memory[address    ] as u16)       |
             ((self.memory[address + 1] as u16) << 8)
         ) as i16 as i64;
     }
 
-    fn lhu_physical(&mut self, address: usize) -> i64 {
+    fn lhu_physical(&self, address: usize) -> i64 {
         return (
              (self.memory[address    ] as u16)       |
             ((self.memory[address + 1] as u16) << 8)
         ) as i64;
     }
 
-    fn lw_physical(&mut self, address: usize) -> i64 {
+    fn lw_physical(&self, address: usize) -> i64 {
         return (
              (self.memory[address    ] as u32)        |
             ((self.memory[address + 1] as u32) <<  8) |
@@ -157,7 +155,7 @@ impl MachineState {
         ) as i32 as i64;
     }
 
-    fn lwu_physical(&mut self, address: usize) -> i64 {
+    fn lwu_physical(&self, address: usize) -> i64 {
         return (
              (self.memory[address    ] as u32)        |
             ((self.memory[address + 1] as u32) <<  8) |
@@ -166,7 +164,7 @@ impl MachineState {
         ) as u32 as i64;
     }
 
-    fn ld_physical(&mut self, address: usize) -> i64 {
+    fn ld_physical(&self, address: usize) -> i64 {
         return (
              (self.memory[address    ] as u64)        |
             ((self.memory[address + 1] as u64) <<  8) |
@@ -270,6 +268,122 @@ impl CoreState {
             dirty: vec![0u8; machine.memory.len()]
         }
     }
+
+    fn lb(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                return machine.lb_physical(address as usize);
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn lbu(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                return machine.lbu_physical(addr);
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn lh(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                let offset = addr & (PAGE_SIZE - 1);
+                if offset < (PAGE_SIZE - 2) || machine.get_page_table_entry(page + 1).is_readable() {
+                    return machine.lh_physical(addr);
+                } else {
+                    panic!("@fixme: trap on read failure on page + 1");
+                }
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn lhu(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                let offset = addr & (PAGE_SIZE - 1);
+                if offset < (PAGE_SIZE - 2) || machine.get_page_table_entry(page + 1).is_readable() {
+                    return machine.lhu_physical(addr);
+                } else {
+                    panic!("@fixme: trap on read failure on page + 1");
+                }
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn lw(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                let offset = addr & (PAGE_SIZE - 1);
+                if offset < (PAGE_SIZE - 4) || machine.get_page_table_entry(page + 1).is_readable() {
+                    return machine.lw_physical(addr);
+                } else {
+                    panic!("@fixme: trap on read failure on page + 1");
+                }
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn lwu(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                let offset = addr & (PAGE_SIZE - 1);
+                if offset < (PAGE_SIZE - 4) || machine.get_page_table_entry(page + 1).is_readable() {
+                    return machine.lwu_physical(addr);
+                } else {
+                    panic!("@fixme: trap on read failure on page + 1");
+                }
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
+
+    fn ld(&self, machine: &MachineState, address: i64) -> i64 {
+        let raw_page = (address as u64) >> PAGE_BITS;
+        if raw_page < machine.pages.len() as u64 {
+            let addr = address as usize;
+            let page = raw_page as usize;
+            let entry = machine.get_page_table_entry(page);
+            if entry.is_readable() {
+                let offset = addr & (PAGE_SIZE - 1);
+                if offset < (PAGE_SIZE - 8) || machine.get_page_table_entry(page + 1).is_readable() {
+                    return machine.ld_physical(addr);
+                } else {
+                    panic!("@fixme: trap on read failure on page + 1");
+                }
+            }
+        }
+        panic!("@fixme: trap on read failure on page");
+    }
 }