feat: Application manager (#8)

* feat: map text area to kernel memory space, first application_manager
implementation

* feat: start application via application_manager

* feat: terminal, start app by ID

* feat: support CLI args, by applying System V ABI concepts

* refactor: rename terminal to console. Minor cleanup

* docs: README.md

.gitignore

@@ -6,3 +6,8 @@ settings.json
 .DS_Store
 .venv
 .nvimlog
+__pycache__
+.pytest_cache
+
+build/
+

.vscode/launch.json

@@ -3,7 +3,7 @@
   "compounds": [
     {
       "name": "Run QEMU + Attach LLDB",
-      "configurations": ["Attach LLDB"],
+      "configurations": ["LLDB"],
       "preLaunchTask": "Run QEMU"
     }
   ],
@@ -61,9 +61,21 @@
     {
       "name": "LLDB",
       "type": "lldb",
-      "request": "launch",
+      "request": "attach",
       "program": "${workspaceFolder}/target/aarch64-unknown-none/debug/nova",
-      "preLaunchTask": "Run QEMU wo window"
+      "preLaunchTask": "Run QEMU",
+      "stopOnEntry": true,
+      "processCreateCommands": ["gdb-remote localhost:1234"]
+    },
+
+    {
+      "name": "NVIM LLDB",
+      "type": "codelldb",
+      "request": "attach",
+      "program": "${workspaceFolder}/target/aarch64-unknown-none/debug/nova",
+      "preLaunchTask": "Run QEMU",
+      "stopOnEntry": true,
+      "processCreateCommands": ["gdb-remote localhost:1234"]
     }
   ]
 }

Cargo.lock

@@ -40,6 +40,15 @@ version = "0.2.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f9fbbcab51052fe104eb5e5d351cf728d30a5be1fe14d9be8a3b097481fb97de"
 
+[[package]]
+name = "lock_api"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "224399e74b87b5f3557511d98dff8b14089b3dadafcab6bb93eab67d3aace965"
+dependencies = [
+ "scopeguard",
+]
+
 [[package]]
 name = "log"
 version = "0.4.29"
@@ -55,6 +64,7 @@ dependencies = [
  "log",
  "nova_error",
  "paste",
+ "spin",
 ]
 
 [[package]]
@@ -129,6 +139,21 @@ dependencies = [
  "getrandom",
 ]
 
+[[package]]
+name = "scopeguard"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
+
+[[package]]
+name = "spin"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d5fe4ccb98d9c292d56fec89a5e07da7fc4cf0dc11e156b41793132775d3e591"
+dependencies = [
+ "lock_api",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.111"

Cargo.toml

@@ -18,6 +18,7 @@ heap = {path = "workspace/heap"}
 nova_error = {path = "workspace/nova_error"}
 paste = "1.0.15"
 log = "0.4.29"
+spin = "0.10.0"
 
 [workspace]
 

README.md

@@ -2,8 +2,6 @@
 
 NovaOS is a expository project where I build a kernel from scratch for a Raspberry PI 3 B+.
 
-[Technical write-up](https://leafnova.net/projects/pi3_kernel/)
-
 ## Features
 
 - Delay and sleep ✓
@@ -16,9 +14,9 @@ NovaOS is a expository project where I build a kernel from scratch for a Raspber
 - Heap Memory allocation ✓
 - MMU ✓
 - SVC instructions ~
+- Basic Console over UART ~
+- Multi Applications ~
 - Multi Core
-- Multi Applications
 - Dynamic clock speed
 - Kernel Independent Applications
 - Multiprocessing
-- Basic Terminal over UART

src/aarch64/mmu.rs

@@ -43,7 +43,8 @@ const L2_BLOCK_BITMAP_WORDS: usize = LEVEL2_BLOCK_SIZE / (64 * GRANULARITY);
 const MAX_PAGE_COUNT: usize = 1024 * 1024 * 1024 / GRANULARITY;
 
 const TRANSLATION_TABLE_BASE_ADDR: usize = 0xFFFF_FF82_0000_0000;
-pub const KERNEL_VIRTUAL_MEM_SPACE: usize = 0xFFFF_FF80_0000_0000;
+#[no_mangle]
+pub static KERNEL_VIRTUAL_MEM_SPACE: usize = 0xFFFF_FF80_0000_0000;
 
 pub const STACK_START_ADDR: usize = !KERNEL_VIRTUAL_MEM_SPACE & (!0xF);
 
@@ -104,7 +105,7 @@ pub enum PhysSource {
 }
 
 #[repr(align(4096))]
-pub struct PageTable([TableEntry; TABLE_ENTRY_COUNT]);
+pub struct PageTable(pub [TableEntry; TABLE_ENTRY_COUNT]);
 
 impl Iterator for PageTable {
     type Item = VirtAddr;
@@ -203,7 +204,6 @@ fn map_range_dynamic(
         (virt, _) = virt.overflowing_add(GRANULARITY);
         remaining -= GRANULARITY;
     }
-
     Ok(())
 }
 
@@ -223,7 +223,7 @@ pub fn alloc_page(
 
 /// Allocate a singe page in one block.
 pub fn find_free_kerne_page_in_block(start: VirtAddr) -> Result<VirtAddr, NovaError> {
-    if !start.is_multiple_of(GRANULARITY) {
+    if !start.is_multiple_of(LEVEL2_BLOCK_SIZE) {
         return Err(NovaError::Misalignment);
     }
 
@@ -237,8 +237,8 @@ pub fn find_free_kerne_page_in_block(start: VirtAddr) -> Result<VirtAddr, NovaEr
         )?
     };
 
-    if let Some(virt_addr) = table.next() {
-        return Ok(virt_addr);
+    if let Some(offset) = table.next() {
+        return Ok(start + (offset * GRANULARITY));
     }
     Err(NovaError::OutOfMeomory)
 }
@@ -273,7 +273,7 @@ pub fn map_page(
     let table = unsafe { &mut *table_ptr };
 
     if !table.0[l3_off].is_invalid() {
-        return Err(NovaError::Paging);
+        return Err(NovaError::Paging("Page already occupied."));
     }
 
     table.0[l3_off] = TableEntry::page_descriptor(physical_address, additional_flags);
@@ -315,7 +315,7 @@ pub fn map_l2_block(
 
     // Verify virtual address is available.
     if !table.0[l2_off].is_invalid() {
-        return Err(NovaError::Paging);
+        return Err(NovaError::Paging("Block already occupied."));
     }
 
     let new_entry = TableEntry::block_descriptor(physical_address, additional_flags);
@@ -392,7 +392,7 @@ fn next_table(
     match table.0[offset].value & 0b11 {
         0 => {
             if !create_missing {
-                return Err(NovaError::Paging);
+                return Err(NovaError::Paging("No table defined."));
             }
             let new_phys_page_table_address = reserve_page();
 
@@ -406,7 +406,9 @@ fn next_table(
 
             Ok(resolve_table_addr(table.0[offset].address()) as *mut PageTable)
         }
-        1 => Err(NovaError::Paging),
+        1 => Err(NovaError::Paging(
+            "Can't navigate table due to block mapping.",
+        )),
         3 => Ok(resolve_table_addr(table.0[offset].address()) as *mut PageTable),
         _ => unreachable!(),
     }

src/aarch64/mmu/physical_mapping.rs

@@ -24,7 +24,7 @@ pub fn reserve_page_explicit(physical_address: usize) -> Result<PhysAddr, NovaEr
     let word_index = page / 64;
 
     if unsafe { PAGING_BITMAP.bitmap[word_index] } & (1 << (page % 64)) > 0 {
-        return Err(NovaError::Paging);
+        return Err(NovaError::Paging("Page PA already taken."));
     }
 
     unsafe { PAGING_BITMAP.bitmap[word_index] |= 1 << (page % 64) };
@@ -47,7 +47,7 @@ pub fn reserve_block_explicit(physical_address: usize) -> Result<(), NovaError>
     for i in 0..L2_BLOCK_BITMAP_WORDS {
         unsafe {
             if PAGING_BITMAP.bitmap[(page / 64) + i] != 0 {
-                return Err(NovaError::Paging);
+                return Err(NovaError::Paging("Block PA already taken."));
             }
         };
     }

src/application_manager.rs

@@ -0,0 +1,145 @@
+use crate::{
+    aarch64::mmu::{
+        find_free_kerne_page_in_block, map_page, physical_mapping::reserve_page, PageTable,
+        TableEntry, VirtAddr, NORMAL_MEM, TRANSLATIONTABLE_TTBR0, TRANSLATIONTABLE_TTBR1, WRITABLE,
+    },
+    configuration::memory_mapping::{APPLICATION_TRANSLATION_TABLE_VA, EL0_STACK_TOP},
+};
+use alloc::vec::Vec;
+use core::{arch::asm, mem, ptr::write_volatile};
+use log::error;
+use nova_error::NovaError;
+use spin::Mutex;
+
+struct AppManager {
+    apps: Option<Vec<Application>>,
+}
+
+impl AppManager {
+    const fn new() -> Self {
+        Self { apps: None }
+    }
+}
+
+unsafe impl Send for AppManager {}
+
+pub struct Application {
+    pub table_ptr: *mut TableEntry,
+    pub start_addr: usize,
+    pub stack_pointer: usize,
+}
+
+impl Application {
+    pub fn new(start_addr: VirtAddr) -> Self {
+        let physical_addr = reserve_page();
+        let virtual_address =
+            find_free_kerne_page_in_block(APPLICATION_TRANSLATION_TABLE_VA).unwrap();
+
+        map_page(
+            virtual_address,
+            physical_addr,
+            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR1),
+            NORMAL_MEM | WRITABLE,
+        )
+        .unwrap();
+
+        // TODO: Temporary solution, while kernel and app share some memory regions
+        #[allow(static_mut_refs)]
+        unsafe {
+            let table = &mut *(virtual_address as *mut PageTable);
+            table.0 = TRANSLATIONTABLE_TTBR0.0;
+        }
+
+        Self {
+            table_ptr: physical_addr as *mut TableEntry,
+            start_addr,
+            stack_pointer: EL0_STACK_TOP,
+        }
+    }
+
+    pub unsafe fn configure_registers(&self) {
+        asm!("msr ELR_EL1, {}", in(reg) self.start_addr);
+        asm!("msr SPSR_EL1, {0:x}", in(reg) 0);
+        asm!("msr SP_EL0, {0:x}", in(reg) self.stack_pointer);
+        asm!("msr TTBR0_EL1, {}", in(reg) self.table_ptr as usize);
+    }
+
+    /// Starts an application.
+    ///
+    /// `ELR_EL1` ->  Exception Link Register (starting virtual address)
+    /// `SPSR_EL1` -> Saved Program State Register (settings for `eret` behaviour)
+    /// `SP_EL0` -> Stack Pointer Register (virtual_address of stack Pointer)
+    /// `TTBR0_EL1` -> Translation Table base Register Register
+    pub fn start(&mut self, args: Vec<&str>) {
+        let size = args.len();
+        let argv = self.construct_inital_stack(args);
+        unsafe {
+            self.configure_registers();
+            asm!("", in("x0") size, in("x1") argv);
+            asm!("eret");
+        }
+    }
+
+    /// Initializes the stack based on the System V ABI
+    fn construct_inital_stack(&mut self, args: Vec<&str>) -> usize {
+        let size = args.len();
+        let mut arg_addresses = Vec::with_capacity(size);
+
+        // Write strings into stack
+        for value in args {
+            self.stack_pointer -= value.len() * mem::size_of::<u8>();
+            let pointer = self.stack_pointer as *mut u8;
+            unsafe { core::ptr::copy(value.as_ptr(), pointer, value.len()) };
+            arg_addresses.push(pointer);
+        }
+        self.stack_pointer = align_down(self.stack_pointer, 16);
+
+        // TODO: Auxiliry vector entry
+        // TODO: Environment pointers
+
+        let argv = self.stack_pointer;
+
+        // Write argument pointers into stack
+        for addr in arg_addresses {
+            unsafe { write_volatile(self.stack_pointer as *mut *const u8, addr) };
+            self.stack_pointer -= mem::size_of::<*const u8>();
+        }
+
+        argv
+    }
+}
+
+fn align_down(sp: usize, align: usize) -> usize {
+    sp & !(align - 1)
+}
+
+static APP_MANAGER: Mutex<AppManager> = Mutex::new(AppManager::new());
+
+pub fn initialize_app_manager() {
+    let mut guard = APP_MANAGER.lock();
+    guard.apps = Some(Vec::new());
+}
+
+pub fn add_app(app: Application) -> Result<(), NovaError> {
+    if let Some(app_list) = APP_MANAGER.lock().apps.as_mut() {
+        app_list.push(app);
+        Ok(())
+    } else {
+        Err(NovaError::General("AppManager not initalized."))
+    }
+}
+
+pub fn start_app(index: usize, args: Vec<&str>) -> Result<(), NovaError> {
+    if let Some(app) = APP_MANAGER
+        .lock()
+        .apps
+        .as_mut()
+        .and_then(|am| am.get_mut(index))
+    {
+        app.start(args);
+        unreachable!()
+    } else {
+        error!("Unable to start app due to invalid App ID.");
+        Err(NovaError::General("Invalid app id."))
+    }
+}

src/config.S

@@ -10,8 +10,12 @@ el2_to_el1:
     msr SPSR_EL2, x0
 
     // Set return address to kernel_main
+    adrp x0, KERNEL_VIRTUAL_MEM_SPACE
+    ldr x1, [x0, :lo12:KERNEL_VIRTUAL_MEM_SPACE]
+
     adrp x0, kernel_main
     add  x0, x0, :lo12:kernel_main
+    orr  x0, x0, x1
     msr ELR_EL2, x0
 
     // Set SP_EL1 to stack base
@@ -74,25 +78,3 @@ configure_mmu_el1:
 
     ret
 
-.align 4
-.global el1_to_el0
-el1_to_el0:
-    mov x8, x0
-    // Set SPSR_EL1: return to EL0t
-    mov x0, #(0b0000)
-    msr SPSR_EL1, x0
-
-    // Set return address to el0
-    ldr x0, =el0
-    msr ELR_EL1, x0
-
-    // Set SP_EL1 to stack base
-    adrp x0, EL0_STACK_TOP
-    ldr  x1, [x0, :lo12:EL0_STACK_TOP]
-    msr SP_EL0, x1
-
-    isb
-
-    mov x0, x8
-    // Return to EL0
-    eret

src/configuration/memory_mapping.rs

@@ -1,10 +1,9 @@
 use crate::{
     aarch64::mmu::{
-        alloc_block_l2_explicit, allocate_memory, map_l2_block, map_page,
-        physical_mapping::reserve_page, reserve_range, PhysAddr, PhysSource, VirtAddr, DEVICE_MEM,
-        EL0_ACCESSIBLE, GRANULARITY, KERNEL_VIRTUAL_MEM_SPACE, LEVEL1_BLOCK_SIZE,
-        LEVEL2_BLOCK_SIZE, NORMAL_MEM, PXN, READ_ONLY, STACK_START_ADDR, TRANSLATIONTABLE_TTBR0,
-        UXN, WRITABLE,
+        alloc_block_l2_explicit, allocate_memory, map_page, physical_mapping::reserve_page,
+        reserve_range, PhysAddr, PhysSource, VirtAddr, DEVICE_MEM, EL0_ACCESSIBLE, GRANULARITY,
+        KERNEL_VIRTUAL_MEM_SPACE, LEVEL1_BLOCK_SIZE, LEVEL2_BLOCK_SIZE, NORMAL_MEM, PXN, READ_ONLY,
+        STACK_START_ADDR, TRANSLATIONTABLE_TTBR0, TRANSLATIONTABLE_TTBR1, UXN, WRITABLE,
     },
     PERIPHERAL_BASE,
 };
@@ -19,6 +18,8 @@ pub const EL0_STACK_SIZE: usize = LEVEL2_BLOCK_SIZE * 2;
 pub const MAILBOX_VIRTUAL_ADDRESS: VirtAddr = 0xFFFF_FF81_FFFF_E000;
 pub static mut MAILBOX_PHYSICAL_ADDRESS: Option<PhysAddr> = None;
 
+// TODO: Currently limited to 512 applications, more than enough, but has to be kept
+// in mind
 pub const APPLICATION_TRANSLATION_TABLE_VA: VirtAddr = 0xFFFF_FF81_FE00_0000;
 
 extern "C" {
@@ -44,6 +45,16 @@ pub fn initialize_mmu_translation_tables() {
         .unwrap();
     }
 
+    for addr in (0..text_end).step_by(GRANULARITY) {
+        map_page(
+            addr | KERNEL_VIRTUAL_MEM_SPACE,
+            addr,
+            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR1),
+            READ_ONLY | NORMAL_MEM,
+        )
+        .unwrap();
+    }
+
     for addr in (text_end..shared_segment_end).step_by(GRANULARITY) {
         map_page(
             addr,
@@ -54,12 +65,12 @@ pub fn initialize_mmu_translation_tables() {
         .unwrap();
     }
 
-    for addr in (shared_segment_end..kernel_end).step_by(LEVEL2_BLOCK_SIZE) {
-        map_l2_block(
+    for addr in (text_end..shared_segment_end).step_by(GRANULARITY) {
+        map_page(
+            addr | KERNEL_VIRTUAL_MEM_SPACE,
             addr,
-            addr,
-            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
-            WRITABLE | UXN | NORMAL_MEM,
+            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR1),
+            EL0_ACCESSIBLE | WRITABLE | NORMAL_MEM,
         )
         .unwrap();
     }

src/console.rs

@@ -1,8 +1,7 @@
-use core::arch::asm;
-
 use alloc::string::String;
 
 use crate::{
+    application_manager::start_app,
     interrupt_handlers::irq::{register_interrupt_handler, IRQSource},
     peripherals::uart::read_uart_data,
     pi3::mailbox::read_soc_temp,
@@ -15,10 +14,6 @@ pub struct Terminal {
     input: String,
 }
 
-extern "C" {
-    fn el1_to_el0();
-}
-
 impl Default for Terminal {
     fn default() -> Self {
         Self::new()
@@ -41,15 +36,20 @@ impl Terminal {
         let val = self.input.clone();
         self.input.clear();
 
-        match val.as_str() {
+        let mut parts = val.split(" ");
+
+        match parts.next().unwrap() {
             "temp" => {
                 println!("{}", read_soc_temp([0]).unwrap()[1]);
             }
-            "el0" => unsafe {
-                let i = 69;
-                asm!("", in("x0") i);
-                el1_to_el0();
-            },
+            "app" => {
+                if let Some(app_id) = parts.next().and_then(|a| a.parse::<usize>().ok()) {
+                    let args = parts.collect();
+                    let _ = start_app(app_id, args);
+                } else {
+                    println!("App ID not set.");
+                }
+            }
             _ => {
                 println!("Unknown command: \"{}\"", self.input);
             }

src/interrupt_handlers/synchronous.rs

@@ -20,12 +20,16 @@ unsafe extern "C" fn rust_synchronous_interrupt_imm_lower_aarch64(frame: &mut Tr
     log_sync_exception();
     match esr.ec {
         0b100100 => {
-            warn!("Cause: Data Abort from a lower Exception level");
+            error!("Data Abort from a lower Exception level");
+            error!("Cause: {}", decode_data_abort(esr.iss as usize));
         }
         0b010101 => {
-            debug!("Cause: SVC instruction execution in AArch64");
+            debug!("SVC instruction execution in AArch64");
             return handle_svc(frame);
         }
+        0b100010 => {
+            error!("PC alignment fault.");
+        }
         _ => {
             error!("Synchronous interrupt: Unknown Error Code: {:b}", esr.ec);
         }
@@ -36,8 +40,62 @@ unsafe extern "C" fn rust_synchronous_interrupt_imm_lower_aarch64(frame: &mut Tr
     0
 }
 
+fn decode_data_abort(iss: usize) -> &'static str {
+    match iss & 0b111111 {
+        0b000000 => "Address size fault, level 0",
+        0b000001 => "Address size fault, level 1",
+        0b000010 => "Address size fault, level 2",
+        0b000011 => "Address size fault, level 3",
+
+        0b000100 => "Translation fault, level 0",
+        0b000101 => "Translation fault, level 1",
+        0b000110 => "Translation fault, level 2",
+        0b000111 => "Translation fault, level 3",
+
+        0b001001 => "Access flag fault, level 1",
+        0b001010 => "Access flag fault, level 2",
+        0b001011 => "Access flag fault, level 3",
+
+        0b001101 => "Permission fault, level 1",
+        0b001110 => "Permission fault, level 2",
+        0b001111 => "Permission fault, level 3",
+
+        0b010000 => "Synchronous External abort, not on translation table walk",
+        0b011000 => {
+            "Synchronous parity or ECC error on memory access, not on translation table walk"
+        }
+
+        0b010100 => "Synchronous External abort, on translation table walk, level 0",
+        0b010101 => "Synchronous External abort, on translation table walk, level 1",
+        0b010110 => "Synchronous External abort, on translation table walk, level 2",
+        0b010111 => "Synchronous External abort, on translation table walk, level 3",
+
+        0b011100 => "Synchronous parity or ECC error on translation table walk, level 0",
+        0b011101 => "Synchronous parity or ECC error on translation table walk, level 1",
+        0b011110 => "Synchronous parity or ECC error on translation table walk, level 2",
+        0b011111 => "Synchronous parity or ECC error on translation table walk, level 3",
+
+        0b100001 => "Alignment fault",
+        0b110000 => "TLB conflict abort",
+        0b110001 => "Unsupported atomic hardware update fault",
+
+        0b110100 => "IMPLEMENTATION DEFINED fault (Lockdown)",
+        0b110101 => "IMPLEMENTATION DEFINED fault (Unsupported Exclusive or Atomic access)",
+
+        0b111101 => "Section Domain Fault",
+        0b111110 => "Page Domain Fault",
+
+        _ => "Reserved / Unknown",
+    }
+}
+
 fn handle_svc(frame: &mut TrapFrame) -> usize {
     match frame.x8 {
+        0 => {
+            debug!("Program exited!");
+            set_return_to_kernel_loop();
+            0
+        }
         67 => {
             let response = mailbox::read_soc_temp([0]).unwrap();
             response[1] as usize

src/lib.rs

@@ -18,9 +18,10 @@ use crate::{
         allocate_memory, PhysSource, KERNEL_VIRTUAL_MEM_SPACE, LEVEL2_BLOCK_SIZE, NORMAL_MEM, UXN,
         WRITABLE,
     },
+    application_manager::initialize_app_manager,
+    console::{flush_terminal, init_terminal},
     interrupt_handlers::irq::initialize_interrupt_handler,
     pi3::timer::sleep_s,
-    terminal::{flush_terminal, init_terminal},
 };
 
 static LOGGER: UartLogger = UartLogger;
@@ -57,8 +58,9 @@ pub mod configuration;
 pub mod framebuffer;
 pub mod interrupt_handlers;
 
+pub mod application_manager;
+pub mod console;
 pub mod pi3;
-pub mod terminal;
 
 #[inline(always)]
 pub unsafe fn read_address(address: u32) -> u32 {
@@ -85,6 +87,7 @@ pub fn get_current_el() -> u64 {
 pub fn initialize_kernel() {
     unsafe { initialize_kernel_heap() };
     initialize_interrupt_handler();
+    initialize_app_manager();
     init_terminal();
 }
 

src/main.rs

@@ -10,9 +10,10 @@ use log::{debug, info};
 
 extern crate alloc;
 
-use alloc::vec::Vec;
+use alloc::{slice, vec::Vec};
 use nova::{
     aarch64::registers::{daif, read_id_aa64mmfr0_el1},
+    application_manager::{add_app, Application},
     configuration::memory_mapping::initialize_mmu_translation_tables,
     framebuffer::{FrameBuffer, BLUE, GREEN, RED},
     get_current_el, init_logger,
@@ -24,6 +25,7 @@ use nova::{
         },
         uart::uart_init,
     },
+    pi3::timer::sleep_s,
     print, println,
 };
 
@@ -77,7 +79,6 @@ pub extern "C" fn main() -> ! {
     unsafe {
         el2_to_el1();
     }
-
     #[allow(clippy::empty_loop)]
     loop {}
 }
@@ -101,23 +102,40 @@ pub extern "C" fn kernel_main() {
         test_vector.push(i);
     }
     debug!("heap allocation test: {:?}", test_vector);
-
     enable_irq_source(IRQSource::UartInt);
 
+    let app = Application::new(el0 as *const () as usize);
+    add_app(app).unwrap();
+
     kernel_loop();
 }
-
 #[no_mangle]
 pub extern "C" fn kernel_loop() {
     daif::unmask_all();
-
     #[allow(clippy::empty_loop)]
     loop {}
 }
-
 #[no_mangle]
-pub extern "C" fn el0(input: usize) {
+pub unsafe extern "C" fn el0(argc: usize, argv: *const *const u8) {
     println!("Jumped into EL0");
+    println!("num: {}", argc);
+    println!("argv: {:?}", argv);
+
+    let raw_args = unsafe { slice::from_raw_parts(argv, argc) };
+    let first_arg = raw_args
+        .iter()
+        .map(|&arg_ptr| {
+            if arg_ptr.is_null() {
+                return "";
+            }
+
+            let c_str = unsafe { core::ffi::CStr::from_ptr(arg_ptr) };
+            let str_slice = c_str.to_str().unwrap();
+            str_slice
+        })
+        .next();
+
+    sleep_s(1);
 
     // Set GPIO 26 to Input
     enable_irq_source(IRQSource::GpioInt0); //26 is on the first GPIO bank
@@ -140,25 +158,30 @@ pub extern "C" fn el0(input: usize) {
 
     let _temp = syscall(67);
 
-    println!("Calculting prime to: {}", input);
+    if let Some(num) = first_arg.and_then(|val| val.parse::<usize>().ok()) {
+        println!("Calculting prime to: {}", num);
 
-    for i in 3..input {
-        let mut is_prime = true;
-        for j in 3..i {
-            if i == j {
-                continue;
+        for i in 3..num {
+            let mut is_prime = true;
+            for j in 3..i {
+                if i == j {
+                    continue;
+                }
+                if i % j == 0 {
+                    is_prime = false;
+                }
             }
-            if i % j == 0 {
-                is_prime = false;
+            if is_prime {
+                print!("{} ", i);
             }
         }
-        if is_prime {
-            print!("{} ", i);
-        }
+        println!("");
+    } else {
+        println!("Input NaN");
     }
-    println!("");
 
     blink_gpio(SpecificGpio::OnboardLed as u8, 500);
+    syscall(0);
 }
 
 fn cos(x: u32) -> f64 {

tools/start_simulator_debug.sh

@@ -11,4 +11,4 @@ qemu-system-aarch64 \
   -cpu cortex-a53 \
   -serial stdio \
   -sd ../sd.img \
-  -kernel ../target/aarch64-unknown-none/debug/kernel8.img \
+  -kernel ../target/aarch64-unknown-none/debug/kernel8.img -S -s

workspace/heap/src/tests.rs

@@ -29,7 +29,7 @@ fn test_heap_allocation() {
         assert_eq!(actual_alloc_size % MIN_BLOCK_SIZE, 0);
 
         // Verify section is occupied
-        assert!((*malloc_header).free == false);
+        assert!(!(*malloc_header).free);
 
         // Verify next header has been created
         let next = (*malloc_header).next.unwrap();
@@ -55,7 +55,7 @@ fn test_full_heap() {
     let malloc = heap.malloc(malloc_size).unwrap();
     let malloc_header = Heap::get_header_ref_from_data_pointer(malloc);
     unsafe {
-        assert_eq!((*malloc_header).free, false);
+        assert!(!(*malloc_header).free);
         assert!((*malloc_header).next.is_none());
     }
 
@@ -79,7 +79,7 @@ fn test_freeing_root() {
     let malloc = heap.malloc(malloc_size).unwrap();
     let malloc_header = Heap::get_header_ref_from_data_pointer(malloc);
     unsafe {
-        assert_eq!((*malloc_header).free, false);
+        assert!(!(*malloc_header).free);
         assert!((*malloc_header).size >= malloc_size);
         assert!((*root_header).next.is_some());
 

workspace/nova_error/src/lib.rs

@@ -5,11 +5,12 @@ use core::prelude::rust_2024::derive;
 
 #[derive(Debug)]
 pub enum NovaError {
+    General(&'static str),
     Mailbox,
     HeapFull,
     EmptyHeapSegmentNotAllowed,
     Misalignment,
     InvalidGranularity,
-    Paging,
+    Paging(&'static str),
     OutOfMeomory,
 }