Fix many issues relating to paging, split page fault into 2 vectors

src/main.rs

@@ -7,6 +7,7 @@ pub mod cpu;
 pub mod keyboard;
 pub mod mouse;
 pub mod disk;
+pub mod setjmp;
 
 use audio::AudioChannel;
 use bus::Bus;
@@ -158,6 +159,9 @@ fn main() {
     builder.spawn({
         move || {
             loop {
+                if let Some(exception) = unsafe { cpu.setjmp() } {
+                    cpu.interrupt(Interrupt::Exception(exception));
+                }
                 while !cpu.halted {
                     if let Ok(exception) = exception_receiver.try_recv() {
                         cpu.interrupt(Interrupt::Exception(exception));

src/memory.rs

@@ -2,6 +2,7 @@
 
 use crate::error;
 use crate::cpu::Exception;
+use crate::setjmp::{JumpEnv, longjmp};
 
 use std::cell::UnsafeCell;
 use std::collections::HashMap;
@@ -111,11 +112,15 @@ impl Memory {
         let old_state = *self.mmu_enabled();
         *self.mmu_enabled() = false;
         let directory_address = *self.paging_directory_address();
-        let directory = self.read_32(directory_address + (page_directory_index * 4));
+        let directory = self.read_opt_32(directory_address + (page_directory_index * 4));
+        match directory {
+            Some(directory) => {
                 let dir_present = directory & 0b1 != 0;
                 let dir_address = directory & 0xFFFFF000;
                 if dir_present {
-            let table = self.read_32(dir_address + (page_table_index * 4));
+                    let table = self.read_opt_32(dir_address + (page_table_index * 4));
+                    match table {
+                        Some(table) => {
                             let table_present = table & 0b01 != 0;
                             let table_rw = table & 0b10 != 0;
                             let table_address = table & 0xFFFFF000;
@@ -128,9 +133,18 @@ impl Memory {
                                 };
                                 self.tlb().entry((page_directory_index << 22) | (page_table_index << 12)).or_insert(tlb_entry);
                             }
+                        },
+                        None => {}
+                    }
                 }
                 *self.mmu_enabled() = old_state;
                 dir_present
+            },
+            None => {
+                *self.mmu_enabled() = old_state;
+                false
+            }
+        }
     }
 
     pub fn virtual_to_physical(&mut self, virtual_address: u32) -> Option<(u32, bool)> {
@@ -170,47 +184,53 @@ impl Memory {
         physical_address
     }
 
-    pub fn read_8(&mut self, mut address: u32) -> u8 {
+    pub fn read_opt_8(&mut self, mut address: u32) -> Option<u8> {
         if *self.mmu_enabled() {
-            (address, _) = self.virtual_to_physical(address as u32).unwrap_or_else(|| {
-                self.exception_sender().send(Exception::PageFault(address)).unwrap();
-                (0, false)
-            });
+            let address_maybe = self.virtual_to_physical(address as u32);
+            match address_maybe {
+                Some(addr) => address = addr.0,
+                None => return None,
+            }
         }
 
         let address = address as usize;
 
-        let result = if address >= MEMORY_ROM_START && address < MEMORY_ROM_START + MEMORY_ROM_SIZE {
-            self.rom().get(address - MEMORY_ROM_START)
+        if address >= MEMORY_ROM_START && address < MEMORY_ROM_START + MEMORY_ROM_SIZE {
+            self.rom().get(address - MEMORY_ROM_START).map(|value| *value)
         } else {
-            self.ram().get(address - MEMORY_RAM_START)
-        };
+            self.ram().get(address - MEMORY_RAM_START).map(|value| *value)
+        }
+    }
+    pub fn read_opt_16(&mut self, address: u32) -> Option<u16> {
+        Some(
+            (self.read_opt_8(address)? as u16) |
+            (self.read_opt_8(address + 1)? as u16) << 8
+        )
+    }
+    pub fn read_opt_32(&mut self, address: u32) -> Option<u32> {
+        Some(
+            (self.read_opt_8(address)? as u32) |
+            (self.read_opt_8(address + 1)? as u32) <<  8 |
+            (self.read_opt_8(address + 2)? as u32) << 16 |
+            (self.read_opt_8(address + 3)? as u32) << 24
+        )
+    }
 
-        match result {
-            Some(value) => {
-                *value
+    pub fn read_8(&mut self, onfault: &JumpEnv<Exception>, address: u32) -> u8 {
+        self.read_opt_8(address).unwrap_or_else(|| unsafe { longjmp(onfault, Exception::PageFaultRead(address)) })
     }
-            None => {
-                error(&format!("attempting to read from unmapped physical memory address: {:#010X}", address));
+    pub fn read_16(&mut self, onfault: &JumpEnv<Exception>, address: u32) -> u16 {
+        self.read_opt_16(address).unwrap_or_else(|| unsafe { longjmp(onfault, Exception::PageFaultRead(address)) })
     }
-        }
-    }
-    pub fn read_16(&mut self, address: u32) -> u16 {
-        (self.read_8(address) as u16) |
-        (self.read_8(address + 1) as u16) << 8
-    }
-    pub fn read_32(&mut self, address: u32) -> u32 {
-        (self.read_8(address) as u32) |
-        (self.read_8(address + 1) as u32) <<  8 |
-        (self.read_8(address + 2) as u32) << 16 |
-        (self.read_8(address + 3) as u32) << 24
+    pub fn read_32(&mut self, onfault: &JumpEnv<Exception>, address: u32) -> u32 {
+        self.read_opt_32(address).unwrap_or_else(|| unsafe { longjmp(onfault, Exception::PageFaultRead(address)) })
     }
 
     pub fn write_8(&mut self, mut address: u32, byte: u8) {
         let mut writable = true;
         if *self.mmu_enabled() {
             (address, writable) = self.virtual_to_physical(address as u32).unwrap_or_else(|| {
-                self.exception_sender().send(Exception::PageFault(address)).unwrap();
+                self.exception_sender().send(Exception::PageFaultWrite(address)).unwrap();
                 (0, false)
             });
         }
@@ -231,7 +251,7 @@ impl Memory {
                 }
             }
         } else {
-            self.exception_sender().send(Exception::PageFault(address)).unwrap();
+            self.exception_sender().send(Exception::PageFaultWrite(address)).unwrap();
         }
     }
     pub fn write_16(&mut self, address: u32, half: u16) {

src/setjmp.rs

@@ -0,0 +1,56 @@
+// setjmp.rs
+
+use std::os::raw::*;
+
+mod internal {
+    use std::os::raw::*;
+    use std::cell::*;
+
+    extern "C" {
+        pub fn setjmp(env: *mut c_void) -> c_int;
+        pub fn longjmp(env: *mut c_void, status: c_int) -> !;
+    }
+
+    pub type JumpBuf = [u8; 512];
+
+    pub struct JumpEnv<T>{
+        buffer: Box<RefCell<JumpBuf>>,
+        value: Cell<Option<T>>,
+    }
+
+    impl<T> JumpEnv<T> {
+        pub fn new() -> Self {
+            Self {
+                buffer: Box::new(RefCell::new([0u8; 512])),
+                value: Cell::default(),
+            }
+        }
+
+        pub fn buffer(&self) -> RefMut<JumpBuf> {
+            self.buffer.borrow_mut()
+        }
+
+        pub fn value_set(&self, value: T) {
+            self.value.set(Some(value));
+        }
+
+        pub fn value_take(&self) -> Option<T> {
+            self.value.take()
+        }
+    }
+}
+
+pub use internal::JumpEnv;
+
+pub unsafe fn setjmp<T>(env: &JumpEnv<T>) -> Option<T> {
+    if internal::setjmp(env.buffer().as_mut_ptr() as *mut c_void) != 0 {
+        env.value_take()
+    } else {
+        None
+    }
+}
+
+pub unsafe fn longjmp<T>(env: &JumpEnv<T>, value: T) -> ! {
+    env.value_set(value);
+    internal::longjmp(env.buffer().as_mut_ptr() as *mut c_void, 1)
+}