Allocate space and create new page table

src/kernel/arch/x86_64/paging.rs

@@ -5,12 +5,26 @@
 
 use crate::constants::KERNEL_BUILD_PROFILE;
 use crate::{LOGGER, LogLevel, format, log_info, log_trace, memory::HHDM_RESPONSE};
+use free_list::{PAGE_SIZE, PageLayout};
 use x86_64::{
     PhysAddr, VirtAddr,
     registers::control::*,
     structures::paging::{PageTable, PageTableFlags},
 };
 
+pub fn switch_ptable() {
+    let allocated_region = crate::memory::FREELIST
+        .lock()
+        .allocate(PageLayout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap())
+        .expect("Could not allocate pages for new page table!");
+    log_info!("Got region for new PML4: 0x{:x}", allocated_region.start());
+    let pml4_start_vaddr = allocated_region.start() + HHDM_RESPONSE.offset() as usize;
+    let pml4_ptr = pml4_start_vaddr as *mut PageTable;
+    let mut pml4 = unsafe { crate::memory::alloc::boxed::Box::from_raw(pml4_ptr) };
+    *pml4 = PageTable::new();
+    log_info!("Initialized page table at 0x{:p}", pml4);
+}
+
 pub fn get_mappings() {
     log_info!("Paging: {}", Cr0::read().contains(Cr0Flags::PAGING));
     log_info!(

src/kernel/arch/x86_64/serial.rs

@@ -161,7 +161,7 @@ impl SerialPort {
     }
 
     /// Create a new port-mapped serial port with the base address `port_addr`.
-    pub fn new(port_addr: u16) -> Self {
+    pub unsafe fn from_port_unchecked(port_addr: u16) -> Self {
         let mut port = SerialPort {
             base_port: Port::new(port_addr),
             interrupt_enable: Port::new(port_addr + 1),
@@ -180,6 +180,33 @@ impl SerialPort {
         port
     }
 
+    pub fn try_from_port(port_addr: u16) -> Option<Self> {
+        let mut port = unsafe { SerialPort::from_port_unchecked(port_addr) };
+
+        // Assert that port scratch register is writable
+        unsafe { port.scratch.write(192) };
+        if unsafe { port.scratch.read() } != 192 {
+            return None;
+        }
+
+        // Enable loopback mode
+        let mut port_modem = port.get_modem_control();
+        port_modem.insert(ModemControl::Loop);
+        port.set_modem_control(port_modem);
+        port.write_char(0xae as char);
+
+        // Assert that loopback mode worked
+        if port.read_char() != (0xae as u8) {
+            return None;
+        }
+
+        // Disable loopback mode
+        port_modem.remove(ModemControl::Loop);
+        port.set_modem_control(port_modem);
+
+        Some(port)
+    }
+
     fn get_line_control(&mut self) -> u8 {
         unsafe { self.line_control.read() }
     }

src/kernel/main.rs

@@ -37,18 +37,20 @@ use spin::mutex::Mutex;
 use crate::arch::x86_64::cpuid::{CPUID, virt_supported};
 
 lazy_static! {
-    pub static ref SERIAL_3F8: Mutex<SerialPort> =
-        Mutex::new(arch::x86_64::serial::SerialPort::new(0x3f8));
+    pub static ref SERIAL_3F8: Mutex<SerialPort> = Mutex::new(
+        arch::x86_64::serial::SerialPort::try_from_port(0x3f8).expect("Could not create port")
+    );
 }
 
 #[unsafe(no_mangle)]
 unsafe extern "C" fn main() -> ! {
+    // CRITICAL AREA
+    // Nothing non-essential should be done until we can initialize logging
+    // Otherwise it will fail silently
+
     // Assert supported bootloader version
     assert!(BASE_REVISION.is_supported());
 
-    // Ensure IDT exists
-    IDT.load();
-
     // Set up logging level from params
     // Nothing we can do here if this fails since no log subscribers are initialized yet
     if let Some(level) = PARAMS.get("-loglevel")
@@ -69,6 +71,13 @@ unsafe extern "C" fn main() -> ! {
         }
         log_trace!("Configured kernel logging devices");
     }
+
+    // END OF CRITICAL AREA
+    // Fallible code can be placed below this comment
+
+    // Ensure IDT exists
+    IDT.load();
+
     log_info!(
         "Kernel cmdline: {}",
         String::from_utf8_lossy(
@@ -150,5 +159,7 @@ unsafe extern "C" fn main() -> ! {
     }
     log_info!("Virtualization provider: {:?}", virt_supported());
 
+    arch::x86_64::paging::switch_ptable();
+
     panic!("Finished boot, but cannot start init because processes not implemented!");
 }

src/kernel/memory.rs

@@ -19,8 +19,8 @@ use talc::*;
 
 pub extern crate alloc;
 
-static FREELIST: Mutex<FreeList<32>> = Mutex::new(FreeList::<32>::new());
-static HW_FREELIST: Mutex<FreeList<32>> = Mutex::new(FreeList::<32>::new());
+pub static FREELIST: Mutex<FreeList<32>> = Mutex::new(FreeList::<32>::new());
+pub static HW_FREELIST: Mutex<FreeList<32>> = Mutex::new(FreeList::<32>::new());
 
 lazy_static! {
     pub static ref MEMMAP_RESPONSE: &'static MemoryMapResponse = MEMMAP_REQUEST

src/lib/syscall/mod.rs

@@ -1,33 +1,45 @@
+
 use num_derive::FromPrimitive;
 use num_traits::FromPrimitive;
 
 use crate::arch;
-
+#[repr(u32)]
 #[derive(FromPrimitive, Debug)]
 pub enum Syscall {
-    Exit,
-    Pid,
-    Message,
-    MemMap,
-    MemUnmap,
-    Resolve,
-    Spawn,
-    Version,
-    Yield,
+    /// Kill the calling process, and deallocate all
+    /// resources associated, including shared memory channels,
+    /// IPC sessions, handles, etc.
+    /// Arguments: 
+    ///     0 - Exit code
+    Exit = 0,
+    /// Get the current PID of the calling process.
+    Pid = 1,
+    /// Send a message to another process.
+    Message = 2,
+    MemMap = 3,
+    MemUnmap = 4,
+    Resolve = 5,
+    Spawn = 6,
+    Version = 7,
+    Yield = 8,
 }
 
+#[repr(u32)]
 #[derive(FromPrimitive, Debug)]
 pub enum SyscallStatus {
+    /// Syscall completed without any issues.
     Success,
+    /// Issued a system call with the wrong call ID.
     NoSuchCall,
     NoSuchProcess,
     NoSuchService,
-    NoPermission,
+    SecurityFailure,
     OutOfMemory,
     Aborted,
     Unspecified,
     Unknown,
     Unimplemented,
+    InvalidPage,
 }
 
 impl From<u64> for SyscallStatus {
@@ -35,3 +47,8 @@ impl From<u64> for SyscallStatus {
         SyscallStatus::from_u64(value).unwrap_or(Self::Unknown)
     }
 }
+
+pub fn exit(code: u32) -> ! {
+    arch::syscall_impl::caller_syscall_1(Syscall::Exit as u64, code as u64);
+    unreachable!();
+}