feat: move EL0 stack to virtual space

* feat: Implement a basic MMU configuration

* feat: Enhance MMU by separating sections and configuring permissions

* feat: Update MMU configuration and memory allocation functions

* fix: Level 3 translation fault

* docs: add code documentation

* fix: linter

* feat: map translation tables to kernel space

* feat: move el1 stack to kernel VA space

* feat: use virtual memory for heap allocation

* docs: update Readme

.cargo/config.toml

@@ -1,5 +1,2 @@
-[build]
-target = "aarch64-unknown-none"
-
 [target.aarch64-unknown-none]
 rustflags = ["-C", "link-arg=-Tlink.ld"]

.github/workflows/rust.yml

@@ -21,8 +21,7 @@ jobs:
       - name: Run format check
         run: cargo fmt --check
       - name: Run lint
-        run: cargo clippy -- -D warnings
-
+        run: cargo clippy --target aarch64-unknown-none -- -D warnings
   build:
     runs-on: ubuntu-latest
 
@@ -33,4 +32,16 @@ jobs:
       - name: Add AArch64 Target
         run: rustup target add aarch64-unknown-none
       - name: Build
-        run: cargo build --verbose
+        run: cargo build --verbose --target aarch64-unknown-none
+
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install rustfmt for nightly
+        run: rustup component add --toolchain nightly-x86_64-unknown-linux-gnu rustfmt clippy
+      - name: Add AArch64 Target
+        run: rustup target add aarch64-unknown-none
+      - name: Heap Workspace Test
+        run: cargo test -p heap

.gitignore

@@ -3,3 +3,5 @@ kernel8.img
 .env
 sd.img
 settings.json
+.DS_Store
+.venv

.vscode/launch.json

@@ -33,6 +33,31 @@
       ],
       "preLaunchTask": "Run QEMU"
     },
+    {
+      "name": "Attach to QEMU (AArch64) wo. window",
+      "type": "cppdbg",
+      "request": "launch",
+      "program": "${workspaceFolder}/target/aarch64-unknown-none/debug/nova",
+      "miDebuggerServerAddress": "localhost:1234",
+      "miDebuggerPath": "gdb",
+      "cwd": "${workspaceFolder}",
+      "stopAtEntry": true,
+      "externalConsole": false,
+      "MIMode": "gdb",
+      "setupCommands": [
+        {
+          "description": "Enable pretty-printing for gdb",
+          "text": "-enable-pretty-printing",
+          "ignoreFailures": true
+        },
+        {
+          "description": "Show assembly on stop",
+          "text": "set disassemble-next-line on",
+          "ignoreFailures": true
+        }
+      ],
+      "preLaunchTask": "Run QEMU wo window"
+    },
 
     {
       "name": "Attach LLDB",

.vscode/tasks.json

@@ -14,9 +14,38 @@
     {
       "label": "Run QEMU",
       "type": "shell",
-      "command": "llvm-objcopy -O binary target/aarch64-unknown-none/debug/nova target/aarch64-unknown-none/debug/kernel8.img && qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -serial stdio -sd sd.img -kernel ${workspaceFolder}/target/aarch64-unknown-none/debug/kernel8.img -S -s -m 1024",
+      "command": "llvm-objcopy -O binary target/aarch64-unknown-none/debug/nova target/aarch64-unknown-none/debug/kernel8.img && echo Starting QEMU&qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -serial stdio -sd sd.img -kernel ${workspaceFolder}/target/aarch64-unknown-none/debug/kernel8.img -S -s -m 1024",
       "isBackground": true,
-      "dependsOn": ["Build"]
+      "dependsOn": ["Build"],
+      "problemMatcher": {
+                "pattern": {
+                    "regexp": "^(Starting QEMU)",
+                    "line": 1,
+                },
+                "background": {
+                    "activeOnStart": true,
+                    "beginsPattern": "^(Starting QEMU)",
+                    "endsPattern": "^(Starting QEMU)"
+                }
+            }
+    },
+        {
+      "label": "Run QEMU wo window",
+      "type": "shell",
+      "command": "llvm-objcopy -O binary target/aarch64-unknown-none/debug/nova target/aarch64-unknown-none/debug/kernel8.img && echo Starting QEMU&qemu-system-aarch64 -M raspi3b -cpu cortex-a53 -display none -serial stdio -sd sd.img -kernel ${workspaceFolder}/target/aarch64-unknown-none/debug/kernel8.img -S -s -m 1024",
+      "isBackground": true,
+      "dependsOn": ["Build"],
+      "problemMatcher": {
+                "pattern": {
+                    "regexp": "^(Starting QEMU)",
+                    "line": 1,
+                },
+                "background": {
+                    "activeOnStart": true,
+                    "beginsPattern": "^(Starting QEMU)",
+                    "endsPattern": "^(Starting QEMU)"
+                }
+            }
     }
   ]
 }

Cargo.lock

@@ -2,6 +2,38 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "cfg-if"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
+
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasip2",
+]
+
+[[package]]
+name = "heap"
+version = "0.1.0"
+dependencies = [
+ "nova_error",
+ "rand",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.178"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37c93d8daa9d8a012fd8ab92f088405fb202ea0b6ab73ee2482ae66af4f42091"
+
 [[package]]
 name = "libm"
 version = "0.2.15"
@@ -12,5 +44,132 @@ checksum = "f9fbbcab51052fe104eb5e5d351cf728d30a5be1fe14d9be8a3b097481fb97de"
 name = "nova"
 version = "0.1.0"
 dependencies = [
+ "heap",
  "libm",
+ "nova_error",
+ "paste",
+]
+
+[[package]]
+name = "nova_error"
+version = "0.1.0"
+
+[[package]]
+name = "paste"
+version = "1.0.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57c0d7b74b563b49d38dae00a0c37d4d6de9b432382b2892f0574ddcae73fd0a"
+
+[[package]]
+name = "ppv-lite86"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
+dependencies = [
+ "zerocopy",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.103"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ee95bc4ef87b8d5ba32e8b7714ccc834865276eab0aed5c9958d00ec45f49e8"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a338cc41d27e6cc6dce6cefc13a0729dfbb81c262b1f519331575dd80ef3067f"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.111"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "390cc9a294ab71bdb1aa2e99d13be9c753cd2d7bd6560c77118597410c4d2e87"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"
+
+[[package]]
+name = "wasip2"
+version = "1.0.1+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0562428422c63773dad2c345a1882263bbf4d65cf3f42e90921f787ef5ad58e7"
+dependencies = [
+ "wit-bindgen",
+]
+
+[[package]]
+name = "wit-bindgen"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f17a85883d4e6d00e8a97c586de764dabcc06133f7f1d55dce5cdc070ad7fe59"
+
+[[package]]
+name = "zerocopy"
+version = "0.8.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd74ec98b9250adb3ca554bdde269adf631549f51d8a8f8f0a10b50f1cb298c3"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8a8d209fdf45cf5138cbb5a506f6b52522a25afccc534d1475dad8e31105c6a"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
 ]

Cargo.toml

@@ -14,3 +14,13 @@ panic = "abort"
 
 [dependencies]
 libm = "0.2.15"
+heap = {path = "workspace/heap"}
+nova_error = {path = "workspace/nova_error"}
+paste = "1.0.15"
+
+[workspace]
+
+members = [
+    "workspace/nova_error",
+    "workspace/heap",
+]

README.md

@@ -14,8 +14,10 @@ NovaOS is a expository project where I build a kernel from scratch for a Raspber
 - Communicate with peripherals via mailboxes ✓
 - Frame Buffer ✓
 - Heap Memory allocation ✓
+- MMU ✓
+- SVC instructions
+- Kernel Independent Applications
 - Multi Core
 - Dynamic clock speed
-- MMU
 - Multiprocessing
 - Basic Terminal over UART

link.ld

@@ -4,6 +4,8 @@ SECTIONS {
     .text ALIGN(4) : {
         KEEP(*(.text._start))
         *(.text .text.*)
+        . = ALIGN(4K);
+        __text_end = .;
     }
 
     .rodata : {
@@ -11,38 +13,34 @@ SECTIONS {
     }
 
     .data  : {
-        _data = .;
         *(.data .data.*)
     }
 
-    .bss (NOLOAD) : {
-        . = ALIGN(16);
+    .bss ALIGN(16) (NOLOAD) : {
         __bss_start = .;
         *(.bss .bss.*)
-        *(COMMON)
         __bss_end = .;
     }
 
-    .vector_table ALIGN(2048) : {
+    . = ALIGN(2M);
+
+    __share_end = .;
+
+    .vector_table ALIGN(2K) : {
         KEEP(*(.vector_table))
     }
 
-    .heap 0x8000000 : ALIGN(16)
-    {
-    __heap_start = .;
-    . += 0x10000; #10kB
-    __heap_end = .;
-    }
-
-    .stack : ALIGN(16)
-    {
+    # EL2 Stack
+    .stack ALIGN(16): {
     __stack_start = .;
-    . += 0x10000; #10kB stack
+    . += 100K; #100kB stack
+    . = ALIGN(16);
     __stack_end = .;
     }
 
+    . = ALIGN(2M);
 
-    _end = .;
+    __kernel_end = .;
 }
 
 __bss_size = (__bss_end - __bss_start) >> 3;

src/aarch64/mmu.rs

@@ -0,0 +1,366 @@
+use core::mem::size_of;
+use nova_error::NovaError;
+
+use crate::{
+    aarch64::mmu::physical_mapping::{
+        reserve_block, reserve_block_explicit, reserve_page, reserve_page_explicit,
+    },
+    get_current_el,
+};
+
+const BLOCK: u64 = 0b01;
+const TABLE: u64 = 0b11;
+const PAGE: u64 = 0b11;
+
+/// Allow EL0 to access this section
+pub const EL0_ACCESSIBLE: u64 = 1 << 6;
+
+/// Allow a page or block to be written.
+pub const WRITABLE: u64 = 0 << 7;
+/// Disallow a page or block to be written.
+pub const READ_ONLY: u64 = 1 << 7;
+
+const ACCESS_FLAG: u64 = 1 << 10;
+const INNER_SHAREABILITY: u64 = 0b11 << 8;
+
+pub const NORMAL_MEM: u64 = 0 << 2;
+pub const DEVICE_MEM: u64 = 1 << 2;
+
+/// Disallow EL1 Execution.
+pub const PXN: u64 = 1 << 53;
+
+/// Disallow EL0 Execution.
+pub const UXN: u64 = 1 << 54;
+
+pub const GRANULARITY: usize = 4 * 1024;
+const TABLE_ENTRY_COUNT: usize = GRANULARITY / size_of::<u64>(); // 2MiB
+
+pub const LEVEL1_BLOCK_SIZE: usize = TABLE_ENTRY_COUNT * TABLE_ENTRY_COUNT * GRANULARITY;
+pub const LEVEL2_BLOCK_SIZE: usize = TABLE_ENTRY_COUNT * GRANULARITY;
+
+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;
+
+pub const STACK_START_ADDR: usize = !KERNEL_VIRTUAL_MEM_SPACE & (!0xF);
+
+mod physical_mapping;
+
+type VirtAddr = usize;
+type PhysAddr = usize;
+
+pub enum PhysSource {
+    Any,
+    Explicit(PhysAddr),
+}
+
+#[repr(align(4096))]
+pub struct PageTable([u64; TABLE_ENTRY_COUNT]);
+
+#[no_mangle]
+pub static mut TRANSLATIONTABLE_TTBR0: PageTable = PageTable([0; 512]);
+#[no_mangle]
+pub static mut TRANSLATIONTABLE_TTBR1: PageTable = PageTable([0; 512]);
+
+/// Allocate a memory block of `size` starting at `virtual_address`.
+pub fn allocate_memory(
+    virtual_address: usize,
+    size_bytes: usize,
+    phys: PhysSource,
+    flags: u64,
+) -> Result<(), NovaError> {
+    if !virtual_address.is_multiple_of(GRANULARITY) {
+        return Err(NovaError::Misalignment);
+    }
+    if !size_bytes.is_multiple_of(GRANULARITY) {
+        return Err(NovaError::InvalidGranularity);
+    }
+
+    let base_table = if virtual_address & KERNEL_VIRTUAL_MEM_SPACE > 0 {
+        core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR1)
+    } else {
+        core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0)
+    };
+
+    match phys {
+        PhysSource::Any => map_range_dynamic(virtual_address, size_bytes, base_table, flags),
+        PhysSource::Explicit(phys_addr) => {
+            map_range_explicit(virtual_address, phys_addr, size_bytes, base_table, flags)
+        }
+    }
+}
+
+fn map_range_explicit(
+    mut virt: VirtAddr,
+    mut phys: PhysAddr,
+    size_bytes: usize,
+    base: *mut PageTable,
+    flags: u64,
+) -> Result<(), NovaError> {
+    let mut remaining = size_bytes;
+
+    while virt % LEVEL2_BLOCK_SIZE != 0 {
+        map_page(virt, phys, base, flags)?;
+        (virt, _) = virt.overflowing_add(GRANULARITY);
+        phys += GRANULARITY;
+        remaining -= GRANULARITY;
+    }
+
+    while remaining >= LEVEL2_BLOCK_SIZE {
+        map_l2_block(virt, phys, base, flags)?;
+        (virt, _) = virt.overflowing_add(LEVEL2_BLOCK_SIZE);
+        phys += LEVEL2_BLOCK_SIZE;
+        remaining -= LEVEL2_BLOCK_SIZE;
+    }
+
+    while remaining > 0 {
+        map_page(virt, phys, base, flags)?;
+        (virt, _) = virt.overflowing_add(GRANULARITY);
+        phys += GRANULARITY;
+        remaining -= GRANULARITY;
+    }
+
+    Ok(())
+}
+
+fn map_range_dynamic(
+    mut virt: PhysAddr,
+    size_bytes: usize,
+    base: *mut PageTable,
+    flags: u64,
+) -> Result<(), NovaError> {
+    let mut remaining = size_bytes;
+
+    while remaining >= LEVEL2_BLOCK_SIZE {
+        map_l2_block(virt, reserve_block(), base, flags)?;
+        (virt, _) = virt.overflowing_add(LEVEL2_BLOCK_SIZE);
+        remaining -= LEVEL2_BLOCK_SIZE;
+    }
+
+    while remaining > 0 {
+        map_page(virt, reserve_page(), base, flags)?;
+        (virt, _) = virt.overflowing_add(GRANULARITY);
+        remaining -= GRANULARITY;
+    }
+
+    Ok(())
+}
+
+/// Allocate a singe page.
+pub fn alloc_page(
+    virtual_address: usize,
+    base_table: *mut PageTable,
+    additional_flags: u64,
+) -> Result<(), NovaError> {
+    map_page(
+        virtual_address,
+        reserve_page(),
+        base_table,
+        additional_flags,
+    )
+}
+
+/// Allocate a single page at an explicit `physical_address`.
+pub fn alloc_page_explicit(
+    virtual_address: usize,
+    physical_address: usize,
+    base_table: *mut PageTable,
+    additional_flags: u64,
+) -> Result<(), NovaError> {
+    reserve_page_explicit(physical_address)?;
+    map_page(
+        virtual_address,
+        physical_address,
+        base_table,
+        additional_flags,
+    )
+}
+
+pub fn map_page(
+    virtual_address: usize,
+    physical_address: usize,
+    base_table_ptr: *mut PageTable,
+    additional_flags: u64,
+) -> Result<(), NovaError> {
+    let (l1_off, l2_off, l3_off) = virtual_address_to_table_offset(virtual_address);
+
+    let offsets = [l1_off, l2_off];
+
+    let table_ptr = navigate_table(base_table_ptr, &offsets)?;
+    let table = unsafe { &mut *table_ptr };
+
+    if table.0[l3_off] & 0b11 > 0 {
+        return Err(NovaError::Paging);
+    }
+
+    table.0[l3_off] = create_page_descriptor_entry(physical_address, additional_flags);
+
+    Ok(())
+}
+
+// Allocate a level 2 block, at a explicit `physical_address`.
+pub fn alloc_block_l2_explicit(
+    virtual_addr: usize,
+    physical_address: usize,
+    base_table_ptr: *mut PageTable,
+    additional_flags: u64,
+) -> Result<(), NovaError> {
+    if !physical_address.is_multiple_of(LEVEL2_BLOCK_SIZE) {
+        return Err(NovaError::Misalignment);
+    }
+
+    reserve_block_explicit(physical_address)?;
+    map_l2_block(
+        virtual_addr,
+        physical_address,
+        base_table_ptr,
+        additional_flags,
+    )
+}
+
+pub fn map_l2_block(
+    virtual_addr: usize,
+    physical_address: usize,
+    base_table_ptr: *mut PageTable,
+    additional_flags: u64,
+) -> Result<(), NovaError> {
+    let (l1_off, l2_off, _) = virtual_address_to_table_offset(virtual_addr);
+    let offsets = [l1_off];
+    let table_ptr = navigate_table(base_table_ptr, &offsets)?;
+
+    let table = unsafe { &mut *table_ptr };
+
+    // Verify virtual address is available.
+    if table.0[l2_off] & 0b11 != 0 {
+        return Err(NovaError::Paging);
+    }
+
+    let new_entry = create_block_descriptor_entry(physical_address, additional_flags);
+
+    table.0[l2_off] = new_entry;
+
+    Ok(())
+}
+
+pub fn reserve_range(
+    start_physical_address: PhysAddr,
+    end_physical_address: PhysAddr,
+) -> Result<PhysAddr, NovaError> {
+    let mut size = end_physical_address - start_physical_address;
+    let l1_blocks = size / LEVEL1_BLOCK_SIZE;
+    size %= LEVEL1_BLOCK_SIZE;
+    let l2_blocks = size / LEVEL2_BLOCK_SIZE;
+    size %= LEVEL2_BLOCK_SIZE;
+    let l3_pages = size / GRANULARITY;
+
+    if !size.is_multiple_of(GRANULARITY) {
+        return Err(NovaError::Misalignment);
+    }
+
+    if l1_blocks > 0 {
+        todo!();
+    }
+
+    let mut addr = start_physical_address;
+    for _ in 0..l2_blocks {
+        reserve_block_explicit(addr)?;
+        addr += LEVEL2_BLOCK_SIZE;
+    }
+
+    for _ in 0..l3_pages {
+        reserve_page_explicit(addr)?;
+        addr += GRANULARITY;
+    }
+
+    Ok(start_physical_address)
+}
+
+fn create_block_descriptor_entry(physical_address: usize, additional_flags: u64) -> u64 {
+    (physical_address as u64 & 0x0000_FFFF_FFFF_F000)
+        | BLOCK
+        | ACCESS_FLAG
+        | INNER_SHAREABILITY
+        | additional_flags
+}
+
+fn create_page_descriptor_entry(physical_address: usize, additional_flags: u64) -> u64 {
+    (physical_address as u64 & 0x0000_FFFF_FFFF_F000)
+        | PAGE
+        | ACCESS_FLAG
+        | INNER_SHAREABILITY
+        | additional_flags
+}
+
+fn create_table_descriptor_entry(addr: usize) -> u64 {
+    (addr as u64 & 0x0000_FFFF_FFFF_F000) | TABLE
+}
+
+fn virtual_address_to_table_offset(virtual_addr: usize) -> (usize, usize, usize) {
+    let absolute_page_off = (virtual_addr & !KERNEL_VIRTUAL_MEM_SPACE) / GRANULARITY;
+    let l3_off = absolute_page_off % TABLE_ENTRY_COUNT;
+    let l2_off = (absolute_page_off / TABLE_ENTRY_COUNT) % TABLE_ENTRY_COUNT;
+    let l1_off = (absolute_page_off / TABLE_ENTRY_COUNT / TABLE_ENTRY_COUNT) % TABLE_ENTRY_COUNT;
+    (l1_off, l2_off, l3_off)
+}
+
+/// Navigate the table tree, by following given offsets. This function
+/// allocates new tables if required.
+fn navigate_table(
+    initial_table_ptr: *mut PageTable,
+    offsets: &[usize],
+) -> Result<*mut PageTable, NovaError> {
+    let mut table = initial_table_ptr;
+    for offset in offsets {
+        table = next_table(table, *offset)?;
+    }
+    Ok(table)
+}
+
+/// Get the next table one level down.
+///
+/// If table doesn't exit a page will be allocated for it.
+fn next_table(table_ptr: *mut PageTable, offset: usize) -> Result<*mut PageTable, NovaError> {
+    let table = unsafe { &mut *table_ptr };
+    match table.0[offset] & 0b11 {
+        0 => {
+            let new_phys_page_table_address = reserve_page();
+
+            table.0[offset] = create_table_descriptor_entry(new_phys_page_table_address);
+            map_page(
+                phys_table_to_kernel_space(new_phys_page_table_address),
+                new_phys_page_table_address,
+                &raw mut TRANSLATIONTABLE_TTBR1,
+                NORMAL_MEM | WRITABLE | PXN | UXN,
+            )?;
+
+            Ok(entry_table_addr(table.0[offset] as usize) as *mut PageTable)
+        }
+        1 => Err(NovaError::Paging),
+        3 => Ok(entry_table_addr(table.0[offset] as usize) as *mut PageTable),
+        _ => unreachable!(),
+    }
+}
+
+/// Extracts the physical address out of an table entry.
+#[inline]
+fn entry_phys(entry: usize) -> PhysAddr {
+    entry & 0x0000_FFFF_FFFF_F000
+}
+
+#[inline]
+fn entry_table_addr(entry: usize) -> VirtAddr {
+    if get_current_el() == 1 {
+        phys_table_to_kernel_space(entry_phys(entry))
+    } else {
+        entry_phys(entry)
+    }
+}
+
+/// Extracts the physical address out of an table entry.
+#[inline]
+fn phys_table_to_kernel_space(entry: usize) -> VirtAddr {
+    entry | TRANSLATION_TABLE_BASE_ADDR
+}

src/aarch64/mmu/physical_mapping.rs

@@ -0,0 +1,89 @@
+use crate::aarch64::mmu::{PhysAddr, GRANULARITY, L2_BLOCK_BITMAP_WORDS, MAX_PAGE_COUNT};
+use nova_error::NovaError;
+
+static mut PAGING_BITMAP: [u64; MAX_PAGE_COUNT / 64] = [0; MAX_PAGE_COUNT / 64];
+
+pub fn reserve_page() -> PhysAddr {
+    if let Some(address) = find_unallocated_page() {
+        let page = address / GRANULARITY;
+        let word_index = page / 64;
+        unsafe { PAGING_BITMAP[word_index] |= 1 << (page % 64) };
+        return address;
+    }
+    panic!("Out of Memory!");
+}
+
+pub fn reserve_page_explicit(physical_address: usize) -> Result<PhysAddr, NovaError> {
+    let page = physical_address / GRANULARITY;
+    let word_index = page / 64;
+
+    if unsafe { PAGING_BITMAP[word_index] } & (1 << (page % 64)) > 0 {
+        return Err(NovaError::Paging);
+    }
+
+    unsafe { PAGING_BITMAP[word_index] |= 1 << (page % 64) };
+    Ok(physical_address)
+}
+
+pub fn reserve_block() -> usize {
+    if let Some(start) = find_contiguous_free_bitmap_words(L2_BLOCK_BITMAP_WORDS) {
+        for j in 0..L2_BLOCK_BITMAP_WORDS {
+            unsafe { PAGING_BITMAP[start + j] = u64::MAX };
+        }
+        return start * 64 * GRANULARITY;
+    }
+
+    panic!("Out of Memory!");
+}
+
+pub fn reserve_block_explicit(physical_address: usize) -> Result<(), NovaError> {
+    let page = physical_address / GRANULARITY;
+    for i in 0..L2_BLOCK_BITMAP_WORDS {
+        unsafe {
+            if PAGING_BITMAP[(page / 64) + i] != 0 {
+                return Err(NovaError::Paging);
+            }
+        };
+    }
+    for i in 0..L2_BLOCK_BITMAP_WORDS {
+        unsafe {
+            PAGING_BITMAP[(page / 64) + i] = u64::MAX;
+        };
+    }
+    Ok(())
+}
+
+fn find_unallocated_page() -> Option<usize> {
+    for (i, entry) in unsafe { PAGING_BITMAP }.iter().enumerate() {
+        if *entry != u64::MAX {
+            for offset in 0..64 {
+                if entry >> offset & 0b1 == 0 {
+                    return Some((i * 64 + offset) * GRANULARITY);
+                }
+            }
+        }
+    }
+    None
+}
+
+fn find_contiguous_free_bitmap_words(required_words: usize) -> Option<usize> {
+    let mut run_start = 0;
+    let mut run_len = 0;
+
+    for (i, entry) in unsafe { PAGING_BITMAP }.iter().enumerate() {
+        if *entry == 0 {
+            if run_len == 0 {
+                run_start = i;
+            }
+            run_len += 1;
+
+            if run_len == required_words {
+                return Some(run_start);
+            }
+        } else {
+            run_len = 0;
+        }
+    }
+
+    None
+}

src/aarch64/mod.rs

@@ -0,0 +1,2 @@
+pub mod mmu;
+pub mod registers;

src/aarch64/registers.rs

@@ -0,0 +1,59 @@
+use core::arch::asm;
+
+pub mod daif {
+    use core::arch::asm;
+
+    #[inline(always)]
+    pub fn mask_all() {
+        unsafe { asm!("msr DAIFSet, #0xf", options(nomem, nostack)) }
+    }
+
+    #[inline(always)]
+    pub fn unmask_all() {
+        unsafe { asm!("msr DAIFClr, #0xf", options(nomem, nostack)) }
+    }
+
+    #[inline(always)]
+    pub fn mask_irq() {
+        unsafe { asm!("msr DAIFSet, #0x2", options(nomem, nostack)) }
+    }
+
+    #[inline(always)]
+    pub fn unmask_irq() {
+        unsafe { asm!("msr DAIFClr, #0x2", options(nomem, nostack)) }
+    }
+}
+
+#[macro_export]
+macro_rules! psr {
+    ($name:ident, $t:tt) => {
+        paste::item! {
+            pub fn [<read_ $name:lower>]() -> $t {
+                let buf: $t;
+                unsafe {
+                    asm!(
+                        concat!("mrs {0:x}, ", stringify!($name)),
+                        out(reg) buf
+                    );
+                }
+                buf
+            }
+        }
+    };
+}
+
+psr!(TCR_EL1, u64);
+
+psr!(ID_AA64MMFR0_EL1, u64);
+
+psr!(ESR_EL1, u32);
+
+psr!(SPSR_EL1, u32);
+
+psr!(ELR_EL1, u64);
+
+psr!(SCTLR_EL1, u64);
+
+pub fn read_exception_source_el() -> u32 {
+    read_spsr_el1() & 0b1111
+}

src/config.S

@@ -0,0 +1,194 @@
+.section .text.config
+.align 4
+.global el2_to_el1
+el2_to_el1:
+    mov x0, #(1 << 31)
+    msr HCR_EL2, x0
+
+    // Set SPSR_EL2: return to EL1h
+    mov x0, #(0b0101)
+    msr SPSR_EL2, x0
+
+    // Set return address to kernel_main
+    adrp x0, kernel_main
+    add  x0, x0, :lo12:kernel_main
+    msr ELR_EL2, x0
+
+    // Set SP_EL1 to stack base
+    adrp x0, EL1_STACK_TOP
+    ldr  x1, [x0, :lo12:EL1_STACK_TOP]
+    msr SP_EL1, x1
+
+    // Set VBAR_EL1 to vector table
+    adrp x0, vector_table
+    add  x0, x0, :lo12:vector_table
+    msr VBAR_EL1, x0
+
+    isb
+
+    adrp x0, SCTLR_EL1_CONF
+    ldr  x1, [x0, :lo12:SCTLR_EL1_CONF]
+    msr SCTLR_EL1, x1
+
+    isb
+
+    // SIMD should not be trapped
+    mrs x0, CPACR_EL1
+    mov x1, #(0b11<<20)
+    orr x0,x0, x1
+    msr CPACR_EL1,x0
+
+    isb
+
+    // Return to EL1
+    eret
+
+.section .text.config
+.align 4
+.global configure_mmu_el1
+configure_mmu_el1:
+    // Configure MMU
+    adrp x0, TCR_EL1_CONF
+    ldr  x1, [x0, :lo12:TCR_EL1_CONF]
+    msr TCR_EL1, x1
+    isb
+
+    // MAIR0: Normal Mem.
+    // MAIR1: Device Mem.
+    mov x0, #0x04FF
+    msr MAIR_EL1, x0
+    isb
+
+    // Configure translation table
+    adrp x0, TRANSLATIONTABLE_TTBR0
+    add  x1, x0, :lo12:TRANSLATIONTABLE_TTBR0
+    msr TTBR0_EL1, x1
+
+    adrp x0, TRANSLATIONTABLE_TTBR1
+    add  x1, x0, :lo12:TRANSLATIONTABLE_TTBR1
+    msr TTBR1_EL1, x1
+
+    tlbi vmalle1
+    dsb ish
+    isb
+
+    ret
+
+.align 4
+.global el1_to_el0
+el1_to_el0:
+
+    // 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
+
+    // Return to EL0
+    eret
+
+
+.align 4
+irq_handler:
+    sub sp, sp, #176
+    stp x0, x1, [sp, #0]
+    stp x2, x3, [sp, #16]
+    stp x4, x5, [sp, #32]
+    stp x6, x7, [sp, #48]
+    stp x8, x9, [sp, #64]
+    stp x10, x11, [sp, #80]
+    stp x12, x13, [sp, #96]
+    stp x14, x15, [sp, #112]
+    stp x16, x17, [sp, #128]
+    stp x18, x29, [sp, #144]
+    stp x30, xzr, [sp, #160]
+
+    bl rust_irq_handler
+
+    ldp x0, x1, [sp, #0]
+    ldp x2, x3, [sp, #16]
+    ldp x4, x5, [sp, #32]
+    ldp x6, x7, [sp, #48]
+    ldp x8, x9, [sp, #64]
+    ldp x10, x11, [sp, #80]
+    ldp x12, x13, [sp, #96]
+    ldp x14, x15, [sp, #112]
+    ldp x16, x17, [sp, #128]
+    ldp x18, x29, [sp, #144]
+    ldp x30, xzr, [sp, #160]
+    add sp, sp, #176
+
+    eret
+
+.align 4
+synchronous_interrupt_imm_lower_aarch64:
+    sub sp, sp, #176
+    stp x0, x1, [sp, #0]
+    stp x2, x3, [sp, #16]
+    stp x4, x5, [sp, #32]
+    stp x6, x7, [sp, #48]
+    stp x8, x9, [sp, #64]
+    stp x10, x11, [sp, #80]
+    stp x12, x13, [sp, #96]
+    stp x14, x15, [sp, #112]
+    stp x16, x17, [sp, #128]
+    stp x18, x29, [sp, #144]
+    stp x30, xzr, [sp, #160]
+
+    bl rust_synchronous_interrupt_imm_lower_aarch64
+
+    ldp x0, x1, [sp, #0]
+    ldp x2, x3, [sp, #16]
+    ldp x4, x5, [sp, #32]
+    ldp x6, x7, [sp, #48]
+    ldp x8, x9, [sp, #64]
+    ldp x10, x11, [sp, #80]
+    ldp x12, x13, [sp, #96]
+    ldp x14, x15, [sp, #112]
+    ldp x16, x17, [sp, #128]
+    ldp x18, x29, [sp, #144]
+    ldp x30, xzr, [sp, #160]
+    add sp, sp, #176
+
+    eret
+
+.align 4
+synchronous_interrupt_no_el_change:
+    sub sp, sp, #176
+    stp x0, x1, [sp, #0]
+    stp x2, x3, [sp, #16]
+    stp x4, x5, [sp, #32]
+    stp x6, x7, [sp, #48]
+    stp x8, x9, [sp, #64]
+    stp x10, x11, [sp, #80]
+    stp x12, x13, [sp, #96]
+    stp x14, x15, [sp, #112]
+    stp x16, x17, [sp, #128]
+    stp x18, x29, [sp, #144]
+    stp x30, xzr, [sp, #160]
+
+    bl rust_synchronous_interrupt_no_el_change
+
+    ldp x0, x1, [sp, #0]
+    ldp x2, x3, [sp, #16]
+    ldp x4, x5, [sp, #32]
+    ldp x6, x7, [sp, #48]
+    ldp x8, x9, [sp, #64]
+    ldp x10, x11, [sp, #80]
+    ldp x12, x13, [sp, #96]
+    ldp x14, x15, [sp, #112]
+    ldp x16, x17, [sp, #128]
+    ldp x18, x29, [sp, #144]
+    ldp x30, xzr, [sp, #160]
+    add sp, sp, #176
+
+    eret

src/configuration.rs

@@ -1,15 +1,129 @@
-static SCTLR_EL1_MMU_DISABLED: u64 = 0 << 0; //M
-static SCTLR_EL1_DATA_CACHE_DISABLED: u64 = 0 << 2; //C
-static SCTLR_EL1_INSTRUCTION_CACHE_DISABLED: u64 = 0 << 12; //I
-static SCTLR_EL1_LITTLE_ENDIAN_EL0: u64 = 0 << 24; //E0E
-static SCTLR_EL1_LITTLE_ENDIAN_EL1: u64 = 0 << 25; //EE
+const SCTLR_EL1_MMU_ENABLED: u64 = 1; //M
+const SCTLR_EL1_DATA_CACHE_DISABLED: u64 = 0 << 2; //C
+const SCTLR_EL1_INSTRUCTION_CACHE_DISABLED: u64 = 0 << 12; //I
+const SCTLR_EL1_LITTLE_ENDIAN_EL0: u64 = 0 << 24; //E0E
+const SCTLR_EL1_LITTLE_ENDIAN_EL1: u64 = 0 << 25; //EE
+const SCTLR_EL1_SPAN: u64 = 1 << 23; //SPAN
 
-static SCTLR_EL1_RES: u64 = (0 << 6) | (1 << 11) | (0 << 17) | (1 << 20) | (1 << 22); //Res0 & Res1
+#[allow(clippy::identity_op)]
+const SCTLR_EL1_RES: u64 = (0 << 6) | (1 << 11) | (0 << 17) | (1 << 20) | (1 << 22); //Res0 & Res1
 
 #[no_mangle]
-pub static SCTLR_EL1_CONF: u64 = SCTLR_EL1_MMU_DISABLED
+pub static SCTLR_EL1_CONF: u64 = SCTLR_EL1_MMU_ENABLED
     | SCTLR_EL1_DATA_CACHE_DISABLED
     | SCTLR_EL1_INSTRUCTION_CACHE_DISABLED
     | SCTLR_EL1_LITTLE_ENDIAN_EL0
     | SCTLR_EL1_LITTLE_ENDIAN_EL1
-    | SCTLR_EL1_RES;
+    | SCTLR_EL1_RES
+    | SCTLR_EL1_SPAN;
+
+const TG0: u64 = 0b00 << 14; // 4KB granularity EL0
+const T0SZ: u64 = 25; // 25 Bits of TTBR select -> 39 Bits of VA
+const SH0: u64 = 0b11 << 12; // Inner shareable
+
+const TG1: u64 = 0b10 << 30; // 4KB granularity EL1
+const T1SZ: u64 = 25 << 16; // 25 Bits of TTBR select -> 39 Bits of VA
+const SH1: u64 = 0b11 << 28; // Inner sharable
+
+const IPS: u64 = 0b000 << 32; // 32 bits of PA space -> up to 4GiB
+const AS: u64 = 0b1 << 36; // configure an ASID size of 16 bits
+
+#[no_mangle]
+pub static TCR_EL1_CONF: u64 = IPS | TG0 | TG1 | T0SZ | T1SZ | SH0 | SH1 | AS;
+
+pub mod mmu {
+    use crate::{
+        aarch64::mmu::{
+            alloc_block_l2_explicit, allocate_memory, map_l2_block, map_page, reserve_range,
+            PhysSource, 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,
+        },
+        PERIPHERAL_BASE,
+    };
+
+    #[no_mangle]
+    static EL1_STACK_TOP: usize = STACK_START_ADDR | KERNEL_VIRTUAL_MEM_SPACE;
+    const EL1_STACK_SIZE: usize = LEVEL2_BLOCK_SIZE * 2;
+    #[no_mangle]
+    static EL0_STACK_TOP: usize = STACK_START_ADDR;
+    const EL0_STACK_SIZE: usize = LEVEL2_BLOCK_SIZE * 2;
+    extern "C" {
+        static __text_end: u64;
+        static __share_end: u64;
+        static __kernel_end: u64;
+    }
+
+    pub fn initialize_mmu_translation_tables() {
+        let text_end = unsafe { &__text_end } as *const _ as usize;
+        let shared_segment_end = unsafe { &__share_end } as *const _ as usize;
+        let kernel_end = unsafe { &__kernel_end } as *const _ as usize;
+
+        reserve_range(0x0, kernel_end).unwrap();
+
+        for addr in (0..text_end).step_by(GRANULARITY) {
+            map_page(
+                addr,
+                addr,
+                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
+                EL0_ACCESSIBLE | READ_ONLY | NORMAL_MEM,
+            )
+            .unwrap();
+        }
+
+        for addr in (text_end..shared_segment_end).step_by(GRANULARITY) {
+            map_page(
+                addr,
+                addr,
+                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
+                EL0_ACCESSIBLE | WRITABLE | NORMAL_MEM,
+            )
+            .unwrap();
+        }
+
+        for addr in (shared_segment_end..kernel_end).step_by(LEVEL2_BLOCK_SIZE) {
+            map_l2_block(
+                addr,
+                addr,
+                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
+                WRITABLE | UXN | NORMAL_MEM,
+            )
+            .unwrap();
+        }
+
+        for addr in (PERIPHERAL_BASE..LEVEL1_BLOCK_SIZE).step_by(LEVEL2_BLOCK_SIZE) {
+            alloc_block_l2_explicit(
+                addr,
+                addr,
+                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
+                EL0_ACCESSIBLE | WRITABLE | UXN | PXN | DEVICE_MEM,
+            )
+            .unwrap();
+        }
+
+        // Frame Buffer memory range
+        allocate_memory(
+            0x3c100000,
+            1080 * 1920 * 4,
+            PhysSource::Explicit(0x3c100000),
+            NORMAL_MEM | PXN | UXN | WRITABLE | EL0_ACCESSIBLE,
+        )
+        .unwrap();
+
+        allocate_memory(
+            EL1_STACK_TOP - EL1_STACK_SIZE + 0x10,
+            EL1_STACK_SIZE,
+            PhysSource::Any,
+            WRITABLE | NORMAL_MEM,
+        )
+        .unwrap();
+
+        allocate_memory(
+            EL0_STACK_TOP - EL0_STACK_SIZE + 0x10,
+            EL0_STACK_SIZE,
+            PhysSource::Any,
+            WRITABLE | EL0_ACCESSIBLE | NORMAL_MEM,
+        )
+        .unwrap();
+    }
+}

src/framebuffer.rs

@@ -4,7 +4,10 @@ mod bitmaps;
 
 use bitmaps::BASIC_LEGACY;
 
-use crate::mailbox::{read_mailbox, write_mailbox};
+use crate::{
+    pi3::mailbox::{read_mailbox, write_mailbox},
+    println,
+};
 #[repr(align(16))]
 struct Mailbox([u32; 36]);
 
@@ -16,12 +19,13 @@ const SET_PIXEL_ORDER: u32 = 0x0004_8006;
 const GET_PITCH: u32 = 0x000_40008;
 const SET_FB_OFFSET: u32 = 0x0004_8009;
 
+#[allow(dead_code)]
 pub struct FrameBuffer {
     pixel_depth: u32, // Bits per pixel
     pitch: u32,       // Pixel per row
     rows: u32,        // Rows
-    start_addr: *mut u32,
-    size: u32, //Bytes
+    pub start_addr: *mut u32,
+    pub size: u32, //Bytes
 }
 
 pub const RED: u32 = 0x00FF0000;
@@ -31,76 +35,11 @@ pub const ORANGE: u32 = 0x00FFA500;
 pub const YELLOW: u32 = 0x00FFFF00;
 
 impl FrameBuffer {
-    pub fn new() -> Self {
-        let mut mailbox = Mailbox([0; 36]);
-        mailbox.0[0] = 35 * 4;
-        mailbox.0[1] = 0;
-
-        mailbox.0[2] = SET_PHYSICAL_DISPLAY_WH;
-        mailbox.0[3] = 8;
-        mailbox.0[4] = 8;
-        mailbox.0[5] = 1920;
-        mailbox.0[6] = 1080;
-
-        mailbox.0[7] = SET_VIRTUAL_DISPLAY_WH;
-        mailbox.0[8] = 8;
-        mailbox.0[9] = 8;
-        mailbox.0[10] = 1920;
-        mailbox.0[11] = 1080;
-
-        mailbox.0[12] = SET_PIXEL_DEPTH;
-        mailbox.0[13] = 4;
-        mailbox.0[14] = 4;
-        mailbox.0[15] = 32; // 32 bit per pixel
-
-        mailbox.0[16] = SET_PIXEL_ORDER;
-        mailbox.0[17] = 4;
-        mailbox.0[18] = 4;
-        mailbox.0[19] = 0x0; // RGB
-
-        mailbox.0[20] = SET_FB_OFFSET;
-        mailbox.0[21] = 8;
-        mailbox.0[22] = 8;
-        mailbox.0[23] = 0; // X in pixels
-        mailbox.0[24] = 0; // Y in pixels
-
-        mailbox.0[25] = ALLOCATE_BUFFER;
-        mailbox.0[26] = 8;
-        mailbox.0[27] = 4;
-        mailbox.0[28] = 4096; // Alignment
-        mailbox.0[29] = 0;
-
-        mailbox.0[30] = GET_PITCH;
-        mailbox.0[31] = 4;
-        mailbox.0[32] = 0;
-        mailbox.0[33] = 0;
-
-        mailbox.0[34] = 0; // End tag
-
-        // TODO: validate responses
-
-        let addr = core::ptr::addr_of!(mailbox.0[0]) as u32;
-
-        write_mailbox(8, addr);
-
-        let _ = read_mailbox(8);
-        if mailbox.0[1] == 0 {
-            println!("Failed");
-        }
-
-        mailbox.0[28] &= 0x3FFFFFFF;
-
-        Self {
-            pixel_depth: mailbox.0[15],
-            pitch: mailbox.0[33] / (mailbox.0[15] / 8),
-            rows: mailbox.0[29] / mailbox.0[33],
-            start_addr: mailbox.0[28] as *mut u32,
-            size: mailbox.0[29],
-        }
-    }
-
     pub fn draw_pixel(&self, x: u32, y: u32, color: u32) {
         let offset = x + y * self.pitch;
+        if x >= self.pitch || y >= self.rows {
+            return;
+        }
         unsafe {
             write_volatile(self.start_addr.add(offset as usize), color);
         }
@@ -109,6 +48,7 @@ impl FrameBuffer {
     /*Bresenham's line algorithm
     TODO: check if its possible to optimize y1==y2 case (ARM neon?)
     */
+    #[allow(clippy::collapsible_else_if)]
     pub fn draw_line(&self, x1: u32, y1: u32, x2: u32, y2: u32, color: u32) {
         if x1 == x2 {
             for y in y1..=y2 {
@@ -218,7 +158,7 @@ impl FrameBuffer {
     }
 
     fn draw_ascii(&self, x: u32, y: u32, char: usize, scale: u32, color: u32) {
-        for (y_offset, row) in (&BASIC_LEGACY[char]).iter().enumerate() {
+        for (y_offset, row) in BASIC_LEGACY[char].iter().enumerate() {
             for bit in 0..8 {
                 match row & (1 << bit) {
                     0 => {}
@@ -241,3 +181,73 @@ impl FrameBuffer {
         }
     }
 }
+
+impl Default for FrameBuffer {
+    fn default() -> Self {
+        let mut mailbox = Mailbox([0; 36]);
+        mailbox.0[0] = 35 * 4;
+        mailbox.0[1] = 0;
+
+        mailbox.0[2] = SET_PHYSICAL_DISPLAY_WH;
+        mailbox.0[3] = 8;
+        mailbox.0[4] = 8;
+        mailbox.0[5] = 1920;
+        mailbox.0[6] = 1080;
+
+        mailbox.0[7] = SET_VIRTUAL_DISPLAY_WH;
+        mailbox.0[8] = 8;
+        mailbox.0[9] = 8;
+        mailbox.0[10] = 1920;
+        mailbox.0[11] = 1080;
+
+        mailbox.0[12] = SET_PIXEL_DEPTH;
+        mailbox.0[13] = 4;
+        mailbox.0[14] = 4;
+        mailbox.0[15] = 32; // 32 bit per pixel
+
+        mailbox.0[16] = SET_PIXEL_ORDER;
+        mailbox.0[17] = 4;
+        mailbox.0[18] = 4;
+        mailbox.0[19] = 0x0; // RGB
+
+        mailbox.0[20] = SET_FB_OFFSET;
+        mailbox.0[21] = 8;
+        mailbox.0[22] = 8;
+        mailbox.0[23] = 0; // X in pixels
+        mailbox.0[24] = 0; // Y in pixels
+
+        mailbox.0[25] = ALLOCATE_BUFFER;
+        mailbox.0[26] = 8;
+        mailbox.0[27] = 4;
+        mailbox.0[28] = 4096; // Alignment
+        mailbox.0[29] = 0;
+
+        mailbox.0[30] = GET_PITCH;
+        mailbox.0[31] = 4;
+        mailbox.0[32] = 0;
+        mailbox.0[33] = 0;
+
+        mailbox.0[34] = 0; // End tag
+
+        // TODO: validate responses
+
+        let addr = core::ptr::addr_of!(mailbox.0[0]) as u32;
+
+        write_mailbox(8, addr);
+
+        let _ = read_mailbox(8);
+        if mailbox.0[1] == 0 {
+            println!("Failed");
+        }
+
+        mailbox.0[28] &= 0x3FFFFFFF;
+
+        Self {
+            pixel_depth: mailbox.0[15],
+            pitch: mailbox.0[33] / (mailbox.0[15] / 8),
+            rows: mailbox.0[29] / mailbox.0[33],
+            start_addr: mailbox.0[28] as *mut u32,
+            size: mailbox.0[29],
+        }
+    }
+}

src/heap.rs

@@ -1,216 +0,0 @@
-#![allow(static_mut_refs)]
-
-use core::{
-    alloc::GlobalAlloc,
-    ptr::{self, null_mut, read_volatile},
-};
-
-use crate::NovaError;
-extern crate alloc;
-
-extern "C" {
-    static mut __heap_start: u8;
-    static mut __heap_end: u8;
-}
-
-#[repr(C, align(16))]
-pub struct HeapHeader {
-    pub next: *mut HeapHeader,
-    before: *mut HeapHeader,
-    pub size: usize,
-    free: bool,
-}
-
-const HEAP_HEADER_SIZE: usize = size_of::<HeapHeader>();
-const MIN_BLOCK_SIZE: usize = 16;
-
-// TODO: This implementation has to be reevaluated when implementing multiprocessing
-// Spinlock could be a solution but has its issues:
-// https://matklad.github.io/2020/01/02/spinlocks-considered-harmful.html
-pub static mut HEAP: Heap = Heap {
-    start_address: &raw mut __heap_start as *mut HeapHeader,
-    end_address: &raw mut __heap_end as *mut HeapHeader,
-    raw_size: 0,
-};
-
-// TODO: investigate if there is a better alternative to this
-pub unsafe fn init_global_heap() {
-    HEAP.init();
-}
-
-#[derive(Default)]
-pub struct Novalloc;
-
-unsafe impl GlobalAlloc for Novalloc {
-    unsafe fn alloc(&self, layout: core::alloc::Layout) -> *mut u8 {
-        HEAP.malloc(layout.size()).unwrap()
-    }
-
-    unsafe fn dealloc(&self, ptr: *mut u8, _: core::alloc::Layout) {
-        HEAP.free(ptr).unwrap();
-    }
-}
-
-#[global_allocator]
-static GLOBAL_ALLOCATOR: Novalloc = Novalloc;
-
-pub struct Heap {
-    start_address: *mut HeapHeader,
-    end_address: *mut HeapHeader,
-    raw_size: usize,
-}
-impl Heap {
-    pub fn new(heap_start: usize, heap_end: usize) -> Self {
-        let mut instance = Self {
-            start_address: &raw const heap_start as *mut HeapHeader,
-            end_address: &raw const heap_end as *mut HeapHeader,
-            raw_size: heap_end - heap_start,
-        };
-        instance.init();
-        instance
-    }
-
-    fn init(&mut self) {
-        self.raw_size = self.end_address as usize - self.start_address as usize;
-
-        unsafe {
-            ptr::write(
-                self.start_address,
-                HeapHeader {
-                    next: null_mut(),
-                    before: null_mut(),
-                    size: self.raw_size - HEAP_HEADER_SIZE,
-                    free: true,
-                },
-            );
-        }
-    }
-
-    unsafe fn find_first_fit(&self, size: usize) -> Result<*mut HeapHeader, NovaError> {
-        let mut current = self.start_address;
-        while !fits(size, current) {
-            if (*self.start_address).next.is_null() {
-                return Err(NovaError::HeapFull);
-            }
-            current = (*current).next;
-        }
-        Ok(current)
-    }
-
-    pub fn malloc(&self, mut size: usize) -> Result<*mut u8, NovaError> {
-        if size == 0 {
-            return Err(NovaError::EmptyHeapSegmentNotAllowed);
-        }
-
-        if size < MIN_BLOCK_SIZE {
-            size = MIN_BLOCK_SIZE;
-        }
-
-        // Align size to the next 16 bytes
-        size += (16 - (size % 16)) % 16;
-
-        unsafe {
-            // Find First-Fit memory segment
-            let current = self.find_first_fit(size)?;
-
-            // Return entire block WITHOUT generating a new header
-            // if the current block doesn't have enough space to hold: requested size + HEAP_HEADER_SIZE + MIN_BLOCK_SIZE
-            if (*current).size < size + HEAP_HEADER_SIZE + MIN_BLOCK_SIZE {
-                (*current).free = false;
-                return Ok(current.byte_add(HEAP_HEADER_SIZE) as *mut u8);
-            }
-
-            Self::fragment_segment(current, size);
-
-            let data_start_address = current.byte_add(HEAP_HEADER_SIZE);
-
-            Ok(data_start_address as *mut u8)
-        }
-    }
-
-    unsafe fn fragment_segment(current: *mut HeapHeader, size: usize) {
-        let byte_offset = HEAP_HEADER_SIZE + size;
-        let new_address = current.byte_add(byte_offset);
-
-        // Handle case where fragmenting center free space
-        let next = (*current).next;
-        if !(*current).next.is_null() {
-            (*next).before = new_address;
-        }
-
-        ptr::write(
-            new_address as *mut HeapHeader,
-            HeapHeader {
-                next,
-                before: current,
-                size: (*current).size - size - HEAP_HEADER_SIZE,
-                free: true,
-            },
-        );
-        (*current).next = new_address;
-        (*current).free = false;
-        (*current).size = size;
-    }
-
-    pub fn free(&self, pointer: *mut u8) -> Result<(), NovaError> {
-        let mut segment = unsafe { pointer.sub(HEAP_HEADER_SIZE) as *mut HeapHeader };
-        unsafe {
-            // IF prev is free:
-            // Delete header, add size to previous and fix pointers.
-            // Move Head left
-            if !(*segment).before.is_null() && (*(*segment).before).free {
-                let before_head = (*segment).before;
-                (*before_head).size += (*segment).size + HEAP_HEADER_SIZE;
-                delete_header(segment);
-                segment = before_head;
-            }
-            // IF next is free:
-            // Delete next header and merge size, fix pointers
-            if !(*segment).next.is_null() && (*(*segment).next).free {
-                let next_head = (*segment).next;
-                (*segment).size += (*next_head).size + HEAP_HEADER_SIZE;
-                delete_header(next_head);
-            }
-
-            // Neither: Set free
-            (*segment).free = true;
-        }
-
-        Ok(())
-    }
-
-    pub fn traverse_heap(&self) {
-        let mut pointer_address = self.start_address;
-        loop {
-            let head = unsafe { read_volatile(pointer_address) };
-            println!("Header {:#x}", pointer_address as u32);
-            println!("free: {}", head.free);
-            println!("size: {}", head.size);
-            println!("hasNext: {}", !head.next.is_null());
-            println!("");
-            if !head.next.is_null() {
-                pointer_address = head.next;
-            } else {
-                println!("---------------");
-                return;
-            }
-        }
-    }
-}
-
-unsafe fn fits(size: usize, header: *mut HeapHeader) -> bool {
-    (*header).free && size <= (*header).size
-}
-
-unsafe fn delete_header(header: *mut HeapHeader) {
-    let before = (*header).before;
-    let next = (*header).next;
-
-    if !before.is_null() {
-        (*before).next = next;
-    }
-
-    if !next.is_null() {
-        (*next).before = before;
-    }
-}

src/interrupt_handlers.rs

@@ -0,0 +1,228 @@
+use core::arch::asm;
+
+use alloc::vec::Vec;
+
+use crate::{
+    aarch64::registers::{
+        daif::{mask_all, unmask_irq},
+        read_elr_el1, read_esr_el1, read_exception_source_el,
+    },
+    get_current_el,
+    peripherals::{
+        gpio::{read_gpio_event_detect_status, reset_gpio_event_detect_status},
+        uart::clear_uart_interrupt_state,
+    },
+    println, read_address, write_address,
+};
+
+const INTERRUPT_BASE: u32 = 0x3F00_B000;
+const IRQ_PENDING_BASE: u32 = INTERRUPT_BASE + 0x204;
+const ENABLE_IRQ_BASE: u32 = INTERRUPT_BASE + 0x210;
+const DISABLE_IRQ_BASE: u32 = INTERRUPT_BASE + 0x21C;
+
+const GPIO_PENDING_BIT_OFFSET: u64 = 0b1111 << 49;
+
+struct InterruptHandlers {
+    source: IRQSource,
+    function: fn(),
+}
+
+// TODO: replace with hashmap and check for better alternatives for option
+static mut INTERRUPT_HANDLERS: Option<Vec<InterruptHandlers>> = None;
+
+#[derive(Clone)]
+#[repr(u32)]
+pub enum IRQSource {
+    AuxInt = 29,
+    I2cSpiSlvInt = 44,
+    Pwa0 = 45,
+    Pwa1 = 46,
+    Smi = 48,
+    GpioInt0 = 49,
+    GpioInt1 = 50,
+    GpioInt2 = 51,
+    GpioInt3 = 52,
+    I2cInt = 53,
+    SpiInt = 54,
+    PcmInt = 55,
+    UartInt = 57,
+}
+
+/// Representation of the ESR_ELx registers
+///
+///  Reference: D1.10.4
+#[derive(Debug, Clone, Copy)]
+#[allow(dead_code)]
+struct EsrElX {
+    ec: u32,
+    il: u32,
+    iss: u32,
+}
+
+impl From<u32> for EsrElX {
+    fn from(value: u32) -> Self {
+        Self {
+            ec: value >> 26,
+            il: (value >> 25) & 0b1,
+            iss: value & 0x1FFFFFF,
+        }
+    }
+}
+
+#[no_mangle]
+unsafe extern "C" fn rust_irq_handler() {
+    mask_all();
+    let pending_irqs = get_irq_pending_sources();
+
+    if pending_irqs & GPIO_PENDING_BIT_OFFSET != 0 {
+        handle_gpio_interrupt();
+        let source_el = read_exception_source_el() >> 2;
+        println!("Source EL: {}", source_el);
+        println!("Current EL: {}", get_current_el());
+        println!("Return register address: {:#x}", read_esr_el1());
+    }
+
+    if let Some(handler_vec) = unsafe { &*core::ptr::addr_of_mut!(INTERRUPT_HANDLERS) } {
+        for handler in handler_vec {
+            if (pending_irqs & (1 << (handler.source.clone() as u32))) != 0 {
+                (handler.function)();
+                clear_interrupt_for_source(handler.source.clone());
+            }
+        }
+    }
+}
+
+#[no_mangle]
+unsafe extern "C" fn rust_synchronous_interrupt_no_el_change() {
+    mask_all();
+
+    let source_el = read_exception_source_el() >> 2;
+    println!("--------Sync Exception in EL{}--------", source_el);
+    println!("No EL change");
+    println!("Current EL: {}", get_current_el());
+    println!("{:?}", EsrElX::from(read_esr_el1()));
+    println!("Return register address: {:#x}", read_esr_el1());
+    println!("-------------------------------------");
+}
+
+/// Synchronous Exception Handler
+///
+/// Lower Exception level, where the implemented level
+/// immediately lower than the target level is using
+/// AArch64.
+#[no_mangle]
+unsafe extern "C" fn rust_synchronous_interrupt_imm_lower_aarch64() {
+    mask_all();
+
+    let source_el = read_exception_source_el() >> 2;
+    println!("--------Sync Exception in EL{}--------", source_el);
+    println!("Exception escalated to EL {}", get_current_el());
+    println!("Current EL: {}", get_current_el());
+    let esr: EsrElX = EsrElX::from(read_esr_el1());
+    println!("{:?}", esr);
+    println!("Return address: {:#x}", read_elr_el1());
+
+    match esr.ec {
+        0b100100 => {
+            println!("Cause: Data Abort from a lower Exception level");
+        }
+        _ => {
+            println!("Unknown Error Code: {:b}", esr.ec);
+        }
+    }
+    println!("-------------------------------------");
+
+    set_return_to_kernel_main();
+}
+
+fn clear_interrupt_for_source(source: IRQSource) {
+    match source {
+        IRQSource::UartInt => clear_uart_interrupt_state(),
+        _ => {
+            todo!()
+        }
+    }
+}
+
+fn set_return_to_kernel_main() {
+    unsafe {
+        asm!("ldr x0, =kernel_main", "msr ELR_EL1, x0");
+        asm!("mov x0, #(0b0101)", "msr SPSR_EL1, x0");
+    }
+}
+
+fn handle_gpio_interrupt() {
+    println!("Interrupt");
+    for i in 0..=53u32 {
+        let val = read_gpio_event_detect_status(i);
+
+        if val {
+            #[allow(clippy::single_match)]
+            match i {
+                26 => {
+                    println!("Button Pressed");
+                }
+                _ => {}
+            }
+            // Reset GPIO Interrupt handler by writing a 1
+            reset_gpio_event_detect_status(i);
+        }
+    }
+    unmask_irq();
+}
+
+/// Enables IRQ Source
+pub fn enable_irq_source(state: IRQSource) {
+    let nr = state as u32;
+    let register = ENABLE_IRQ_BASE + 4 * (nr / 32);
+    let register_offset = nr % 32;
+    let current = unsafe { read_address(register) };
+    let mask = 0b1 << register_offset;
+    let new_val = current | mask;
+    unsafe { write_address(register, new_val) };
+}
+
+/// Disable IRQ Source
+pub fn disable_irq_source(state: IRQSource) {
+    let nr = state as u32;
+    let register = DISABLE_IRQ_BASE + 4 * (nr / 32);
+    let register_offset = nr % 32;
+    let current = unsafe { read_address(register) };
+    let mask = 0b1 << register_offset;
+    let new_val = current | mask;
+    unsafe { write_address(register, new_val) };
+}
+
+/// Read current IRQ Source status
+pub fn read_irq_source_status(state: IRQSource) -> u32 {
+    let nr = state as u32;
+    let register = ENABLE_IRQ_BASE + 4 * (nr / 32);
+    let register_offset = nr % 32;
+    (unsafe { read_address(register) } >> register_offset) & 0b1
+}
+
+/// Status if a IRQ Source is pending
+pub fn is_irq_source_pending(state: IRQSource) -> bool {
+    let nr = state as u32;
+    let register = IRQ_PENDING_BASE + 4 * (nr / 32);
+    let register_offset = nr % 32;
+    ((unsafe { read_address(register) } >> register_offset) & 0b1) != 0
+}
+
+/// Status if a IRQ Source is pending
+pub fn get_irq_pending_sources() -> u64 {
+    let mut pending = unsafe { read_address(IRQ_PENDING_BASE + 4) as u64 } << 32;
+    pending |= unsafe { read_address(IRQ_PENDING_BASE) as u64 };
+    pending
+}
+
+#[inline(always)]
+pub fn initialize_interrupt_handler() {
+    unsafe { INTERRUPT_HANDLERS = Some(Vec::new()) };
+}
+
+pub fn register_interrupt_handler(source: IRQSource, function: fn()) {
+    if let Some(handler_vec) = unsafe { &mut *core::ptr::addr_of_mut!(INTERRUPT_HANDLERS) } {
+        handler_vec.push(InterruptHandlers { source, function });
+    }
+}

src/irq_interrupt.rs

@@ -1,162 +0,0 @@
-use core::{
-    arch::asm,
-    sync::atomic::{compiler_fence, Ordering},
-};
-
-use crate::{
-    mmio_read, mmio_write,
-    peripherals::gpio::{blink_gpio, SpecificGpio},
-    print,
-    timer::sleep_s,
-};
-
-const INTERRUPT_BASE: u32 = 0x3F00_B000;
-const IRQ_PENDING_BASE: u32 = INTERRUPT_BASE + 0x204;
-const ENABLE_IRQ_BASE: u32 = INTERRUPT_BASE + 0x210;
-const DISABLE_IRQ_BASE: u32 = INTERRUPT_BASE + 0x21C;
-
-// GPIO
-const GPEDS_BASE: u32 = 0x3F20_0040;
-
-#[repr(u32)]
-pub enum IRQState {
-    AuxInt = 29,
-    I2cSpiSlvInt = 44,
-    Pwa0 = 45,
-    Pwa1 = 46,
-    Smi = 48,
-    GpioInt0 = 49,
-    GpioInt1 = 50,
-    GpioInt2 = 51,
-    GpioInt3 = 52,
-    I2cInt = 53,
-    SpiInt = 54,
-    PcmInt = 55,
-    UartInt = 57,
-}
-
-#[no_mangle]
-unsafe extern "C" fn irq_handler() {
-    handle_gpio_interrupt();
-}
-
-#[no_mangle]
-unsafe extern "C" fn synchronous_interrupt() {
-    loop {
-        println!("Sync Exception");
-        blink_gpio(SpecificGpio::OnboardLed as u8, 100);
-        esr_uart_dump();
-        sleep_s(200);
-    }
-}
-
-fn esr_uart_dump() {
-    let esr: u32;
-    unsafe {
-        asm!(
-            "mrs {esr}, ESR_EL1",
-            esr = out(reg) esr
-        );
-    }
-    for i in (0..32).rev() {
-        if ((esr >> i) & 1) == 0 {
-            print!("0");
-        } else {
-            print!("1");
-        }
-        if i % 4 == 0 && i > 0 {
-            print!("_");
-        }
-
-        if i == 26 || i == 25 || i == 0 {
-            print!("\n\r");
-        }
-    }
-}
-
-fn handle_gpio_interrupt() {
-    println!("Interrupt");
-    for i in 0..=53u32 {
-        let val = read_gpio_event_detect_status(i);
-
-        if val {
-            match i {
-                26 => print!("Button Pressed"),
-                _ => {}
-            }
-            // Reset GPIO Interrupt handler by writing a 1
-            reset_gpio_event_detect_status(i);
-        }
-    }
-    enable_irq();
-}
-
-/// Get current interrupt status of a GPIO pin
-pub fn read_gpio_event_detect_status(id: u32) -> bool {
-    let register = GPEDS_BASE + (id / 32) * 4;
-    let register_offset = id % 32;
-
-    let val = mmio_read(register) >> register_offset;
-    (val & 0b1) != 0
-}
-
-/// Resets current interrupt status of a GPIO pin
-pub fn reset_gpio_event_detect_status(id: u32) {
-    let register = GPEDS_BASE + (id / 32) * 4;
-    let register_offset = id % 32;
-
-    mmio_write(register, 0b1 << register_offset);
-    compiler_fence(Ordering::SeqCst);
-}
-
-/// Enables IRQ Source
-pub fn enable_irq_source(state: IRQState) {
-    let nr = state as u32;
-    let register = ENABLE_IRQ_BASE + 4 * (nr / 32);
-    let register_offset = nr % 32;
-    let current = mmio_read(register);
-    let mask = 0b1 << register_offset;
-    let new_val = current | mask;
-    mmio_write(register, new_val);
-}
-
-/// Disable IRQ Source
-pub fn disable_irq_source(state: IRQState) {
-    let nr = state as u32;
-    let register = DISABLE_IRQ_BASE + 4 * (nr / 32);
-    let register_offset = nr % 32;
-    let current = mmio_read(register);
-    let mask = 0b1 << register_offset;
-    let new_val = current | mask;
-    mmio_write(register, new_val);
-}
-
-/// Read current IRQ Source status
-pub fn read_irq_source_status(state: IRQState) -> u32 {
-    let nr = state as u32;
-    let register = ENABLE_IRQ_BASE + 4 * (nr / 32);
-    let register_offset = nr % 32;
-    (mmio_read(register) >> register_offset) & 0b1
-}
-
-/// Status if a IRQ Source is enabled
-pub fn read_irq_pending(state: IRQState) -> bool {
-    let nr = state as u32;
-    let register = IRQ_PENDING_BASE + 4 * (nr / 32);
-    let register_offset = nr % 32;
-    ((mmio_read(register) >> register_offset) & 0b1) != 0
-}
-
-/// Clears the IRQ DAIF Mask
-///
-/// Enables IRQ interrupts
-pub fn enable_irq() {
-    unsafe { asm!("msr DAIFClr, #0x2") }
-}
-
-/// Clears the IRQ DAIF Mask
-///
-/// Disable IRQ interrupts
-pub fn disable_irq() {
-    unsafe { asm!("msr DAIFSet, #0x2") }
-}

src/lib.rs

@@ -1,44 +1,85 @@
 #![no_std]
+#![allow(clippy::missing_safety_doc)]
 
-use core::ptr::{read_volatile, write_volatile};
+extern crate alloc;
 
-#[macro_export]
-macro_rules! print {
-    () => {};
-    ($($arg:tt)*) => {
-        $crate::peripherals::uart::_print(format_args!($($arg)*))
+use alloc::boxed::Box;
+use core::{
+    arch::asm,
+    panic::PanicInfo,
+    ptr::{read_volatile, write_volatile},
 };
+
+use heap::Heap;
+
+use crate::{
+    aarch64::mmu::{
+        allocate_memory, PhysSource, KERNEL_VIRTUAL_MEM_SPACE, LEVEL2_BLOCK_SIZE, NORMAL_MEM, UXN,
+        WRITABLE,
+    },
+    interrupt_handlers::initialize_interrupt_handler,
+    logger::DefaultLogger,
+};
+
+static PERIPHERAL_BASE: usize = 0x3F00_0000;
+
+unsafe extern "C" {
+    unsafe static mut __kernel_end: u8;
 }
 
-#[macro_export]
-macro_rules! println {
-    () => {};
-    ($($arg:tt)*) => {
-        print!($($arg)*);
-        print!("\r\n");
-    };
+#[global_allocator]
+pub static mut GLOBAL_ALLOCATOR: Heap = Heap::empty();
+
+pub unsafe fn init_kernel_heap() {
+    let start = core::ptr::addr_of_mut!(__kernel_end) as usize | KERNEL_VIRTUAL_MEM_SPACE;
+    let size = LEVEL2_BLOCK_SIZE * 2;
+
+    allocate_memory(start, size, PhysSource::Any, NORMAL_MEM | UXN | WRITABLE).unwrap();
+    let heap = core::ptr::addr_of_mut!(GLOBAL_ALLOCATOR);
+    (*heap).init(start, start + size);
+}
+
+#[panic_handler]
+fn panic(_panic: &PanicInfo) -> ! {
+    loop {
+        println!("Panic: {}", _panic.message());
+    }
 }
 
 pub mod peripherals;
 
+pub mod aarch64;
 pub mod configuration;
 pub mod framebuffer;
-pub mod heap;
-pub mod irq_interrupt;
-pub mod mailbox;
-pub mod timer;
+pub mod interrupt_handlers;
+pub mod logger;
 
-pub fn mmio_read(address: u32) -> u32 {
+pub mod pi3;
+
+#[inline(always)]
+pub unsafe fn read_address(address: u32) -> u32 {
     unsafe { read_volatile(address as *const u32) }
 }
 
-pub fn mmio_write(address: u32, data: u32) {
+#[inline(always)]
+pub unsafe fn write_address(address: u32, data: u32) {
     unsafe { write_volatile(address as *mut u32, data) }
 }
 
-#[derive(Debug)]
-pub enum NovaError {
-    Mailbox,
-    HeapFull,
-    EmptyHeapSegmentNotAllowed,
+pub fn get_current_el() -> u64 {
+    let el: u64;
+    unsafe {
+        asm!(
+            "mrs {el}, CurrentEL",
+            el = out(reg) el,
+            options(nomem, nostack, preserves_flags)
+        );
+    }
+    el >> 2
+}
+
+pub fn initialize_kernel() {
+    unsafe { init_kernel_heap() };
+    logger::set_logger(Box::new(DefaultLogger));
+    initialize_interrupt_handler();
 }

src/logger.rs

@@ -0,0 +1,45 @@
+use core::fmt::Write;
+
+use alloc::{boxed::Box, fmt};
+
+use crate::peripherals::uart;
+
+static mut LOGGER: Option<Box<dyn Logger>> = None;
+
+pub trait Logger: Write + Sync {
+    fn flush(&mut self);
+}
+
+pub struct DefaultLogger;
+
+impl Logger for DefaultLogger {
+    fn flush(&mut self) {}
+}
+
+impl Write for DefaultLogger {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        uart::Uart.write_str(s)
+    }
+}
+
+#[macro_export]
+macro_rules! log {
+    () => {};
+    ($($arg:tt)*) => {
+        $crate::logger::log(format_args!($($arg)*))
+    };
+}
+
+pub fn log(args: fmt::Arguments) {
+    if let Some(logger) = unsafe { &mut *core::ptr::addr_of_mut!(LOGGER) } {
+        logger.write_str("\n").unwrap();
+        logger.write_fmt(args).unwrap();
+        logger.flush();
+    }
+}
+
+pub fn set_logger(logger: Box<dyn Logger>) {
+    unsafe {
+        LOGGER = Some(logger);
+    }
+}

src/main.rs

@@ -1,20 +1,21 @@
 #![no_main]
 #![no_std]
-#![feature(asm_experimental_arch)]
 #![allow(static_mut_refs)]
+#![allow(clippy::missing_safety_doc)]
 use core::{
     arch::{asm, global_asm},
-    panic::PanicInfo,
     ptr::write_volatile,
 };
 
 extern crate alloc;
 
+use alloc::vec::Vec;
 use nova::{
+    aarch64::registers::{daif, read_id_aa64mmfr0_el1},
+    configuration::mmu::initialize_mmu_translation_tables,
     framebuffer::{FrameBuffer, BLUE, GREEN, RED},
-    heap::{init_global_heap, HEAP},
-    irq_interrupt::enable_irq_source,
-    mailbox::mb_read_soc_temp,
+    get_current_el,
+    interrupt_handlers::{enable_irq_source, IRQSource},
     peripherals::{
         gpio::{
             blink_gpio, gpio_pull_up, set_falling_edge_detect, set_gpio_function, GPIOFunction,
@@ -22,27 +23,24 @@ use nova::{
         },
         uart::uart_init,
     },
-    print, println,
-    timer::{delay_nops, sleep_us},
+    println,
 };
 
 global_asm!(include_str!("vector.S"));
+global_asm!(include_str!("config.S"));
+
+static mut FRAMEBUFFER: Option<FrameBuffer> = None;
 
 extern "C" {
     fn el2_to_el1();
+    fn el1_to_el0();
+    fn configure_mmu_el1();
     static mut __bss_start: u32;
     static mut __bss_end: u32;
 }
 
-#[panic_handler]
-fn panic(_panic: &PanicInfo) -> ! {
-    loop {
-        println!("Panic");
-    }
-}
-
 #[no_mangle]
-#[link_section = ".text._start"]
+#[cfg_attr(not(test), link_section = ".text._start")]
 pub unsafe extern "C" fn _start() {
     // Set the stack pointer
     asm!(
@@ -63,12 +61,20 @@ pub extern "C" fn main() -> ! {
     // Set ACT Led to Outout
     let _ = set_gpio_function(21, GPIOFunction::Output);
 
-    // Delay so clock speed can stabilize
-    delay_nops(50000);
     println!("Hello World!");
+    println!("Exception level: {}", get_current_el());
+
+    unsafe {
+        initialize_mmu_translation_tables();
+        configure_mmu_el1();
+        println!("MMU initialized...");
+    };
+
+    println!("Register: AA64MMFR0_EL1: {:064b}", read_id_aa64mmfr0_el1());
+    println!("Moving El2->EL1");
+    unsafe { FRAMEBUFFER = Some(FrameBuffer::default()) };
 
     unsafe {
-        asm!("mrs x0, SCTLR_EL1");
         el2_to_el1();
     }
 
@@ -86,72 +92,68 @@ unsafe fn zero_bss() {
 
 #[no_mangle]
 pub extern "C" fn kernel_main() -> ! {
-    println!("EL: {}", get_current_el());
+    println!("Kernel Start...");
+    nova::initialize_kernel();
+    let mut test_vector = Vec::new();
+    for i in 0..20 {
+        test_vector.push(i);
+    }
+    println!("heap allocation test: {:?}", test_vector);
 
-    heap_test();
+    println!("Exception Level: {}", get_current_el());
+    daif::unmask_all();
 
-    sleep_us(500_000);
+    unsafe {
+        el1_to_el0();
+    };
+
+    #[allow(clippy::empty_loop)]
+    loop {}
+}
+
+#[no_mangle]
+pub extern "C" fn el0() -> ! {
+    println!("Jumped into EL0");
 
     // Set GPIO 26 to Input
-    enable_irq_source(nova::irq_interrupt::IRQState::GpioInt0); //26 is on the first GPIO bank
+    enable_irq_source(IRQSource::GpioInt0); //26 is on the first GPIO bank
     let _ = set_gpio_function(26, GPIOFunction::Input);
     gpio_pull_up(26);
     set_falling_edge_detect(26, true);
 
-    let fb = FrameBuffer::new();
+    enable_irq_source(IRQSource::UartInt);
 
+    if let Some(fb) = unsafe { FRAMEBUFFER.as_mut() } {
+        for i in 0..1080 {
+            fb.draw_pixel(50, i, BLUE);
+        }
         fb.draw_square(500, 500, 600, 700, RED);
         fb.draw_square_fill(800, 800, 900, 900, GREEN);
         fb.draw_square_fill(1000, 800, 1200, 700, BLUE);
         fb.draw_square_fill(900, 100, 800, 150, RED | BLUE);
         fb.draw_string("Hello World! :D\nTest next Line", 500, 5, 3, BLUE);
 
-    fb.draw_function(cos, 100, 101, RED);
+        fb.draw_function(cos, 0, 101, RED);
+    }
 
     loop {
-        let temp = mb_read_soc_temp([0]).unwrap();
-        println!("{} °C", temp[1] / 1000);
+        // TODO: Mailbox requires a physical address. The stack is now in VA space causing an issue.
+        // Fix with SVCs ?
+
+        // let temp = mailbox::read_soc_temp([0]).unwrap();
+        // println!("{} °C", temp[1] / 1000);
 
         blink_gpio(SpecificGpio::OnboardLed as u8, 500);
     }
 }
 
-fn heap_test() {
-    unsafe {
-        init_global_heap();
-        let a = HEAP.malloc(32).unwrap();
-        let b = HEAP.malloc(64).unwrap();
-        let c = HEAP.malloc(128).unwrap();
-        let _ = HEAP.malloc(256).unwrap();
-        HEAP.traverse_heap();
-        HEAP.free(b).unwrap();
-        HEAP.traverse_heap();
-        HEAP.free(a).unwrap();
-        HEAP.traverse_heap();
-        HEAP.free(c).unwrap();
-        HEAP.traverse_heap();
-    }
-}
-
 fn cos(x: u32) -> f64 {
     libm::cos(x as f64 * 0.1) * 20.0
 }
 
-fn get_current_el() -> u64 {
-    let el: u64;
-    unsafe {
-        asm!(
-            "mrs {el}, CurrentEL",
-            el = out(reg) el,
-            options(nomem, nostack, preserves_flags)
-        );
-    }
-    el >> 2
-}
-
 fn enable_uart() {
-    uart_init();
     // Set GPIO Pins to UART
     let _ = set_gpio_function(14, GPIOFunction::Alternative0);
     let _ = set_gpio_function(15, GPIOFunction::Alternative0);
+    uart_init();
 }

src/peripherals/gpio.rs

@@ -1,17 +1,19 @@
 use core::result::Result;
 use core::result::Result::Ok;
+use core::sync::atomic::{compiler_fence, Ordering};
 
-use crate::timer::{delay_nops, sleep_ms};
-use crate::{mmio_read, mmio_write};
+use crate::pi3::timer::{delay_nops, sleep_ms};
+use crate::{read_address, write_address};
 
 const GPFSEL_BASE: u32 = 0x3F20_0000;
 const GPSET_BASE: u32 = 0x3F20_001C;
 const GPCLR_BASE: u32 = 0x3F20_0028;
 const GPLEV_BASE: u32 = 0x3F20_0034;
+const GPEDS_BASE: u32 = 0x3F20_0040;
+const GPFEN_BASE: u32 = 0x3F20_0058;
 const GPPUD: u32 = 0x3F20_0094;
 const GPPUDCLK_BASE: u32 = 0x3F20_0098;
 const GPREN_BASE: u32 = 0x3F20_004C;
-const GPFEN_BASE: u32 = 0x3F20_0058;
 
 #[repr(u8)]
 pub enum SpecificGpio {
@@ -35,26 +37,27 @@ pub fn set_gpio_function(gpio: u8, state: GPIOFunction) -> Result<(), &'static s
     let register_index = gpio / 10;
     let register_offset = (gpio % 10) * 3;
     let register_addr = GPFSEL_BASE + (register_index as u32 * 4);
-    let current = mmio_read(register_addr);
+    let current = unsafe { read_address(register_addr) };
 
     let mask = !(0b111 << register_offset);
     let cleared = current & mask;
 
     let new_val = cleared | ((state as u32) << register_offset);
 
-    mmio_write(register_addr, new_val);
+    unsafe { write_address(register_addr, new_val) };
     Ok(())
 }
 
 /// Set the GPIO to high
 ///
-/// Should be used when GPIO function is set to `OUTPUT` via `set_gpio_function`
+/// Should be used when GPIO function is set to `OUTPUT` via `set_gpio_function`,
+/// otherwise setting is ignored
 pub fn gpio_high(gpio: u8) -> Result<(), &'static str> {
     let register_index = gpio / 32;
     let register_offset = gpio % 32;
     let register_addr = GPSET_BASE + (register_index as u32 * 4);
 
-    mmio_write(register_addr, 1 << register_offset);
+    unsafe { write_address(register_addr, 1 << register_offset) };
     Ok(())
 }
 
@@ -66,7 +69,7 @@ pub fn gpio_low(gpio: u8) -> Result<(), &'static str> {
     let register_offset = gpio % 32;
     let register_addr = GPCLR_BASE + (register_index as u32 * 4);
 
-    mmio_write(register_addr, 1 << register_offset);
+    unsafe { write_address(register_addr, 1 << register_offset) };
     Ok(())
 }
 
@@ -76,7 +79,7 @@ pub fn gpio_get_state(gpio: u8) -> u8 {
     let register_offset = gpio % 32;
     let register_addr = GPLEV_BASE + (register_index as u32 * 4);
 
-    let state = mmio_read(register_addr);
+    let state = unsafe { read_address(register_addr) };
     ((state >> register_offset) & 0b1) as u8
 }
 
@@ -100,40 +103,40 @@ fn gpio_pull_up_down(gpio: u8, val: u32) {
     let register_offset = gpio % 32;
 
     // 1. Write Pull up
-    mmio_write(GPPUD, val);
+    unsafe { write_address(GPPUD, val) };
 
     // 2. Delay 150 cycles
     delay_nops(150);
 
     // 3. Write to clock
     let new_val = 0b1 << register_offset;
-    mmio_write(register_addr, new_val);
+    unsafe { write_address(register_addr, new_val) };
 
     // 4. Delay 150 cycles
     delay_nops(150);
 
     // 5. reset GPPUD
-    mmio_write(GPPUD, 0);
+    unsafe { write_address(GPPUD, 0) };
 
     // 6. reset clock
-    mmio_write(register_addr, 0);
+    unsafe { write_address(register_addr, 0) };
 }
 
-/// Get the current status if falling edge detection is set
+/// Get the current status of the falling edge detection
 pub fn read_falling_edge_detect(gpio: u8) -> bool {
     let register_addr = GPFEN_BASE + 4 * (gpio as u32 / 32);
     let register_offset = gpio % 32;
 
-    let current = mmio_read(register_addr);
+    let current = unsafe { read_address(register_addr) };
     ((current >> register_offset) & 0b1) != 0
 }
 
-/// Get the current status if falling edge detection is set
+/// Get the current status of the rising edge detection
 pub fn read_rising_edge_detect(gpio: u8) -> bool {
     let register_addr = GPREN_BASE + 4 * (gpio as u32 / 32);
     let register_offset = gpio % 32;
 
-    let current = mmio_read(register_addr);
+    let current = unsafe { read_address(register_addr) };
     ((current >> register_offset) & 0b1) != 0
 }
 
@@ -142,7 +145,7 @@ pub fn set_falling_edge_detect(gpio: u8, enable: bool) {
     let register_addr = GPFEN_BASE + 4 * (gpio as u32 / 32);
     let register_offset = gpio % 32;
 
-    let current = mmio_read(register_addr);
+    let current = unsafe { read_address(register_addr) };
     let mask = 0b1 << register_offset;
     let new_val = if enable {
         current | mask
@@ -150,7 +153,7 @@ pub fn set_falling_edge_detect(gpio: u8, enable: bool) {
         current & !mask
     };
 
-    mmio_write(register_addr, new_val);
+    unsafe { write_address(register_addr, new_val) };
 }
 
 /// Enables rising edge detection
@@ -158,7 +161,7 @@ pub fn set_rising_edge_detect(gpio: u8, enable: bool) {
     let register_addr = GPREN_BASE + 4 * (gpio as u32 / 32);
     let register_offset = gpio % 32;
 
-    let current = mmio_read(register_addr);
+    let current = unsafe { read_address(register_addr) };
 
     let mask = 0b1 << register_offset;
     let new_val = if enable {
@@ -167,10 +170,33 @@ pub fn set_rising_edge_detect(gpio: u8, enable: bool) {
         current & !mask
     };
 
-    mmio_write(register_addr, new_val);
+    unsafe { write_address(register_addr, new_val) };
 }
 
-pub fn blink_gpio(gpio: u8, duration_ms: u32) {
+/// Returns with the interrupt status of an GPIO.
+///
+/// GPEDS register is used to record level and edge events on the GPIO pins.
+/// When an event is triggered by the GPIO, the corresponding bit will be set to 1.
+pub fn read_gpio_event_detect_status(id: u32) -> bool {
+    let register = GPEDS_BASE + (id / 32) * 4;
+    let register_offset = id % 32;
+
+    let val = unsafe { read_address(register) } >> register_offset;
+    (val & 0b1) != 0
+}
+
+/// Resets current interrupt status of a GPIO pin.
+pub fn reset_gpio_event_detect_status(id: u32) {
+    let register = GPEDS_BASE + (id / 32) * 4;
+    let register_offset = id % 32;
+
+    unsafe { write_address(register, 0b1 << register_offset) };
+    compiler_fence(Ordering::SeqCst);
+}
+
+// TODO: GPHEN,GPLEN,GPAREN,GPAFEN
+
+pub fn blink_gpio(gpio: u8, duration_ms: u64) {
     let _ = gpio_high(gpio);
 
     sleep_ms(duration_ms);

src/peripherals/uart.rs

@@ -3,7 +3,7 @@ use core::{
     fmt::{self, Write},
 };
 
-use crate::{mmio_read, mmio_write};
+use crate::{read_address, write_address};
 
 const BAUD: u32 = 115200;
 const UART_CLK: u32 = 48_000_000;
@@ -18,33 +18,53 @@ const UART0_FBRD: u32 = 0x3F20_1028;
 
 const UART0_CR: u32 = 0x3F20_1030;
 const UART0_CR_UARTEN: u32 = 1 << 0;
+
 const UART0_CR_TXE: u32 = 1 << 8;
+const UART0_CR_RXE: u32 = 1 << 9;
 
 const UART0_LCRH: u32 = 0x3F20_102C;
 const UART0_LCRH_FEN: u32 = 1 << 4;
 
+const UART0_IMSC: u32 = 0x3F20_1038;
+const UART0_IMSC_RXIM: u32 = 1 << 4;
+
+const UART0_ICR: u32 = 0x3F20_1044;
+
 pub struct Uart;
 
 impl Write for Uart {
     fn write_str(&mut self, s: &str) -> core::fmt::Result {
         for byte in s.bytes() {
-            while (mmio_read(UART0_FR) & UART0_FR_TXFF) != 0 {
+            while (unsafe { read_address(UART0_FR) } & UART0_FR_TXFF) != 0 {
                 unsafe { asm!("nop") }
             }
-            mmio_write(UART0_DR, byte as u32);
+            unsafe { write_address(UART0_DR, byte as u32) };
         }
         // wait till uart is not busy anymore
-        while ((mmio_read(UART0_FR) >> 3) & 0b1) != 0 {}
+        while ((unsafe { read_address(UART0_FR) } >> 3) & 0b1) != 0 {}
         Ok(())
     }
 }
 
-pub fn _print(args: fmt::Arguments) {
-    let _ = Uart.write_fmt(args);
+#[macro_export]
+macro_rules! print {
+    () => {};
+    ($($arg:tt)*) => {
+        $crate::peripherals::uart::_print(format_args!($($arg)*))
+    };
 }
 
-pub fn _print_str(st: &str) {
-    let _ = Uart.write_str(st);
+#[macro_export]
+macro_rules! println {
+    () => {};
+    ($($arg:tt)*) => {
+        $crate::print!($($arg)*);
+        $crate::print!("\r\n");
+    };
+}
+
+pub fn _print(args: fmt::Arguments) {
+    let _ = Uart.write_fmt(args);
 }
 
 /// Initialize UART peripheral
@@ -55,23 +75,26 @@ pub fn uart_init() {
     let fbrd = baud_div_times_64 % 64;
 
     uart_enable(false);
-    uart_fifo_enable(false);
+    uart_fifo_enable(true);
 
-    mmio_write(UART0_IBRD, ibrd);
-    mmio_write(UART0_FBRD, fbrd);
+    unsafe {
+        write_address(UART0_IBRD, ibrd);
+        write_address(UART0_FBRD, fbrd);
+    }
 
+    uart_enable_rx_interrupt();
     uart_set_lcrh(0b11, true);
 
-    // Enable transmit and uart
-    let mut cr = mmio_read(UART0_CR);
-    cr |= UART0_CR_UARTEN | UART0_CR_TXE;
+    // Enable transmit, receive and uart
+    let mut cr = unsafe { read_address(UART0_CR) };
+    cr |= UART0_CR_UARTEN | UART0_CR_TXE | UART0_CR_RXE;
 
-    mmio_write(UART0_CR, cr);
+    unsafe { write_address(UART0_CR, cr) };
 }
 
 /// Enable UARTEN
 fn uart_enable(enable: bool) {
-    let mut cr = mmio_read(UART0_CR);
+    let mut cr = unsafe { read_address(UART0_CR) };
 
     if enable {
         cr |= UART0_CR_UARTEN;
@@ -79,12 +102,12 @@ fn uart_enable(enable: bool) {
         cr &= !UART0_CR_UARTEN;
     }
 
-    mmio_write(UART0_CR, cr);
+    unsafe { write_address(UART0_CR, cr) };
 }
 
 /// Enable UART FIFO
 fn uart_fifo_enable(enable: bool) {
-    let mut lcrh = mmio_read(UART0_LCRH);
+    let mut lcrh = unsafe { read_address(UART0_LCRH) };
 
     if enable {
         lcrh |= UART0_LCRH_FEN;
@@ -92,14 +115,32 @@ fn uart_fifo_enable(enable: bool) {
         lcrh &= !UART0_LCRH_FEN;
     }
 
-    mmio_write(UART0_LCRH, lcrh);
+    unsafe { write_address(UART0_LCRH, lcrh) };
+}
+
+#[inline(always)]
+fn uart_enable_rx_interrupt() {
+    unsafe { write_address(UART0_IMSC, UART0_IMSC_RXIM) };
 }
 
 /// Set UART word length and set FIFO status
+#[inline(always)]
 fn uart_set_lcrh(wlen: u32, enable_fifo: bool) {
     let mut value = (wlen & 0b11) << 5;
     if enable_fifo {
         value |= UART0_LCRH_FEN;
     }
-    mmio_write(UART0_LCRH, value);
+    unsafe { write_address(UART0_LCRH, value) };
+}
+
+#[inline(always)]
+pub fn read_uart_data() -> char {
+    (unsafe { read_address(UART0_DR) } & 0xFF) as u8 as char
+}
+
+#[inline(always)]
+pub fn clear_uart_interrupt_state() {
+    unsafe {
+        write_address(UART0_ICR, 1 << 4);
+    }
 }

src/pi3/mailbox.rs

@@ -1,9 +1,10 @@
-use crate::{mmio_read, mmio_write, NovaError};
+use crate::{read_address, write_address};
+use nova_error::NovaError;
 
 const MBOX_BASE: u32 = 0x3F00_0000 + 0xB880;
 
 // MB0
-const MBOX_READ: u32 = MBOX_BASE + 0x00;
+const MBOX_READ: u32 = MBOX_BASE;
 const MBOX_STATUS: u32 = MBOX_BASE + 0x18;
 
 // MB1
@@ -26,7 +27,7 @@ macro_rules! max {
 #[macro_export]
 macro_rules! mailbox_command {
     ($name:ident, $tag:expr, $request_len:expr,$response_len:expr) => {
-        /// More information at: https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface
+        /// More information at: <https://github.com/raspberrypi/firmware/wiki/Mailbox-property-interface>
         pub fn $name(
             request_data: [u32; $request_len / 4],
         ) -> Result<[u32; $response_len / 4], NovaError> {
@@ -51,23 +52,23 @@ macro_rules! mailbox_command {
                 return Err(NovaError::Mailbox);
             }
 
-            let mut out = [0u32; $response_len / 4]; // TODO: Can this be improved?
+            let mut out = [0u32; $response_len / 4];
             out.copy_from_slice(&mailbox[5..(5 + $response_len / 4)]);
             Ok(out)
         }
     };
 }
 
-mailbox_command!(mb_read_soc_temp, 0x0003_0006, 4, 8);
+mailbox_command!(read_soc_temp, 0x0003_0006, 4, 8);
 
 // Framebuffer
-mailbox_command!(mb_get_display_resolution, 0x0004_0003, 0, 8);
+mailbox_command!(get_display_resolution, 0x0004_0003, 0, 8);
 
 pub fn read_mailbox(channel: u32) -> u32 {
     // Wait until mailbox is not empty
     loop {
-        while mmio_read(MBOX_STATUS) & MAIL_EMPTY != 0 {}
-        let mut data = mmio_read(MBOX_READ);
+        while unsafe { read_address(MBOX_STATUS) } & MAIL_EMPTY != 0 {}
+        let mut data = unsafe { read_address(MBOX_READ) };
         let read_channel = data & 0xF;
 
         data >>= 4;
@@ -79,6 +80,6 @@ pub fn read_mailbox(channel: u32) -> u32 {
 }
 
 pub fn write_mailbox(channel: u32, data: u32) {
-    while mmio_read(MBOX_STATUS) & MAIL_FULL != 0 {}
-    mmio_write(MBOX_WRITE, (data & !0xF) | (channel & 0xF));
+    while unsafe { read_address(MBOX_STATUS) } & MAIL_FULL != 0 {}
+    unsafe { write_address(MBOX_WRITE, (data & !0xF) | (channel & 0xF)) };
 }

src/pi3/mod.rs

@@ -0,0 +1,3 @@
+pub mod mailbox;
+pub mod power_management;
+pub mod timer;

src/pi3/power_management.rs

@@ -0,0 +1,28 @@
+use core::ptr::{read_volatile, write_volatile};
+
+use crate::PERIPHERAL_BASE;
+
+/// Power Management Base
+static PM_BASE: u32 = PERIPHERAL_BASE as u32 + 0x10_0000;
+static PM_RSTC: u32 = PM_BASE + 0x1c;
+static PM_WDOG: u32 = PM_BASE + 0x24;
+
+static PM_PASSWORD: u32 = 0x5a000000;
+static PM_WDOG_TIMER_MASK: u32 = 0x000fffff;
+static PM_RSTC_WRCFG_CLR: u32 = 0xffffffcf;
+static PM_RSTC_WRCFG_FULL_RESET: u32 = 0x00000020;
+
+pub fn reboot_system() {
+    unsafe {
+        let pm_rstc_val = read_volatile(PM_RSTC as *mut u32);
+        // (31:16) bits -> password
+        // (11:0) bits -> value
+        write_volatile(PM_WDOG as *mut u32, PM_PASSWORD | (1 & PM_WDOG_TIMER_MASK));
+        write_volatile(
+            PM_RSTC as *mut u32,
+            PM_PASSWORD | (pm_rstc_val & PM_RSTC_WRCFG_CLR) | PM_RSTC_WRCFG_FULL_RESET,
+        );
+    }
+    #[allow(clippy::empty_loop)]
+    loop {}
+}

src/pi3/timer.rs

@@ -0,0 +1,61 @@
+use core::{hint::spin_loop, ptr::read_volatile};
+
+const TIMER_CLOCK_LO: u32 = 0x3F00_3004;
+const TIMER_CLOCK_HI: u32 = 0x3F00_3008;
+
+fn read_timer_32() -> u32 {
+    unsafe { read_volatile(TIMER_CLOCK_LO as *const u32) }
+}
+
+fn read_timer_64() -> u64 {
+    loop {
+        let clock_hi1 = unsafe { read_volatile(TIMER_CLOCK_HI as *const u32) };
+        let clock_lo = unsafe { read_volatile(TIMER_CLOCK_LO as *const u32) };
+        let clock_hi2 = unsafe { read_volatile(TIMER_CLOCK_HI as *const u32) };
+
+        // account for roll over during read
+        if clock_hi1 == clock_hi2 {
+            return ((clock_hi1 as u64) << 32) | clock_lo as u64;
+        }
+    }
+}
+
+/// Sleep for `us` microseconds
+pub fn sleep_us(us: u64) {
+    if us < u32::MAX as u64 {
+        sleep_us_u32(us as u32);
+    } else {
+        sleep_us_u64(us);
+    }
+}
+
+fn sleep_us_u32(us: u32) {
+    let start = read_timer_32();
+    while read_timer_32().wrapping_sub(start) < us {
+        spin_loop();
+    }
+}
+
+fn sleep_us_u64(us: u64) {
+    let start = read_timer_64();
+    while read_timer_64().wrapping_sub(start) < us {
+        spin_loop();
+    }
+}
+
+/// Sleep for `ms` milliseconds
+pub fn sleep_ms(ms: u64) {
+    sleep_us(ms * 1_000);
+}
+
+/// Sleep for `s` seconds
+pub fn sleep_s(s: u64) {
+    sleep_ms(s * 1_000);
+}
+
+/// Wait for `count` operations to pass
+pub fn delay_nops(count: u32) {
+    for _ in 0..count {
+        spin_loop()
+    }
+}

src/terminal.rs

@@ -0,0 +1,53 @@
+use core::fmt::Write;
+
+use alloc::string::String;
+use nova::{
+    interrupt_handlers::register_interrupt_handler, logger::Logger,
+    peripherals::uart::read_uart_data, print, println,
+};
+
+pub struct Terminal {
+    buffer: String,
+    input: String,
+}
+
+impl Terminal {
+    pub fn new() -> Self {
+        Self {
+            buffer: String::new(),
+            input: String::new(),
+        }
+    }
+
+    fn flush(&mut self) {
+        println!("{}", self.buffer);
+        print!("> {}", self.input);
+        self.buffer.clear();
+    }
+}
+
+impl Write for Terminal {
+    fn write_str(&mut self, s: &str) -> core::fmt::Result {
+        self.buffer.push_str(s);
+        Ok(())
+    }
+}
+
+impl Logger for Terminal {
+    fn flush(&mut self) {
+        println!("{}", self.buffer);
+        print!("> {}", self.input);
+        self.buffer.clear();
+    }
+}
+
+fn terminal_uart_rx_interrupt_handler() {
+    print!("{}", read_uart_data());
+}
+
+pub fn register_terminal_interrupt_handler() {
+    register_interrupt_handler(
+        nova::interrupt_handlers::IRQSource::UartInt,
+        terminal_uart_rx_interrupt_handler,
+    );
+}

src/timer.rs

@@ -1,32 +0,0 @@
-use crate::mmio_read;
-
-const TIMER_CLO: u32 = 0x3F00_3004;
-
-fn read_clo() -> u32 {
-    mmio_read(TIMER_CLO)
-}
-
-/// Sleep for `us` microseconds
-pub fn sleep_us(us: u32) {
-    let start = read_clo();
-    while read_clo() - start < us {
-        unsafe { core::arch::asm!("nop") }
-    }
-}
-
-/// Sleep for `ms` milliseconds
-pub fn sleep_ms(ms: u32) {
-    sleep_us(ms * 1000);
-}
-
-/// Sleep for `s` seconds
-pub fn sleep_s(s: u32) {
-    sleep_us(s * 1000);
-}
-
-/// Wait for `count` operations to pass
-pub fn delay_nops(count: u32) {
-    for _ in 0..count {
-        unsafe { core::arch::asm!("nop") }
-    }
-}

src/vector.S

@@ -1,59 +1,29 @@
-
-.global vector_table
+.section .vector_table  , "ax"
 .extern irq_handler
 
 .macro    ventry    label
-.align    7
+.align    11
 b    \label
 .endm
 
-.section .vector_table, "ax"
+.global vector_table
 vector_table:
     ventry .
     ventry .
     ventry .
     ventry .
 
-    ventry synchronous_interrupt      // Synchronous Exception  0x200
+    ventry synchronous_interrupt_no_el_change  // Synchronous Exception  0x200
     ventry irq_handler                // IRQ(Interrupt Request) 0x280
     ventry .
     ventry .
 
+    ventry synchronous_interrupt_imm_lower_aarch64
+    ventry irq_handler
+    ventry .
+    ventry .
 
-.align 4
-.global el2_to_el1
-el2_to_el1:
-
-    mov x0, #(1 << 31)
-    msr HCR_EL2, x0
-
-    // Set SPSR_EL2: return to EL1h
-    mov x0, #(0b0101)
-    msr SPSR_EL2, x0
-
-    // Set return address to ELR_EL2
-    ldr x0, =kernel_main
-    msr ELR_EL2, x0
-
-    // Set SP_EL1 to stack base
-    ldr x0, =__stack_end
-    msr SP_EL1, x0
-
-    // Set VBAR_EL1 to vector table
-    adr x0, vector_table
-    msr VBAR_EL1, x0
-
-    // Disable MMU
-    ldr x0, =SCTLR_EL1_CONF
-    msr sctlr_el1, x0
-
-    // SIMD should not be trapped
-    mrs x0, CPACR_EL1
-    mov x1, #(0b11<<20)
-    orr x0,x0, x1
-    msr CPACR_EL1,x0
-
-    isb
-
-    // Return to EL1
-    eret
+    ventry .
+    ventry .
+    ventry .
+    ventry .

tools/deply_to_hw.sh

@@ -15,7 +15,7 @@ REMOTE_DIR="$TFTP_PATH"
 
 # BUILD
 echo "[*] Building kernel..."
-cargo build --release
+cargo build --release --target aarch64-unknown-none
 
 # CONVERT TO IMG
 echo "[*] Convert kernel elf to img..."

tools/start_simulator.sh

@@ -1,3 +1,5 @@
+set -e
+
 cargo build --target aarch64-unknown-none --release
 cd "$(dirname "$0")"
 

tools/start_simulator_debug.sh

@@ -1,3 +1,5 @@
+set -e
+
 cargo build --target aarch64-unknown-none
 
 cd "$(dirname "$0")"
@@ -9,6 +11,4 @@ qemu-system-aarch64 \
   -cpu cortex-a53 \
   -serial stdio \
   -sd ../sd.img \
-  -display none \
   -kernel ../target/aarch64-unknown-none/debug/kernel8.img \
-  -s -S

workspace/heap/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "heap"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+nova_error = {path = "../nova_error"}
+
+[dev-dependencies]
+rand = "0.9.2"

workspace/heap/src/lib.rs

@@ -0,0 +1,200 @@
+#![allow(static_mut_refs)]
+#![cfg_attr(not(test), no_std)]
+
+use core::{
+    alloc::GlobalAlloc,
+    mem::size_of,
+    prelude::v1::*,
+    ptr::{self, null_mut},
+    result::Result,
+};
+
+use nova_error::NovaError;
+
+extern crate alloc;
+
+#[repr(C, align(16))]
+#[derive(Clone, Copy)]
+struct HeapHeader {
+    next: Option<*mut HeapHeader>,
+    before: Option<*mut HeapHeader>,
+    size: usize,
+    free: bool,
+}
+
+const HEAP_HEADER_SIZE: usize = size_of::<HeapHeader>();
+const MIN_BLOCK_SIZE: usize = 16;
+
+pub struct Heap {
+    start_address: *mut HeapHeader,
+    end_address: *mut HeapHeader,
+    raw_size: usize,
+}
+impl Heap {
+    pub const fn empty() -> Self {
+        Self {
+            start_address: null_mut(),
+            end_address: null_mut(),
+            raw_size: 0,
+        }
+    }
+
+    pub fn init(&mut self, heap_start: usize, heap_end: usize) {
+        self.start_address = heap_start as *mut HeapHeader;
+        self.end_address = heap_end as *mut HeapHeader;
+
+        self.raw_size = heap_end - heap_start + 1;
+
+        unsafe {
+            ptr::write(
+                self.start_address,
+                HeapHeader {
+                    next: None,
+                    before: None,
+                    size: self.raw_size - HEAP_HEADER_SIZE,
+                    free: true,
+                },
+            );
+        }
+    }
+
+    unsafe fn find_first_fit(&self, size: usize) -> Result<*mut HeapHeader, NovaError> {
+        let mut current = self.start_address;
+        unsafe {
+            while !fits(size, current) {
+                if let Some(next) = (*current).next {
+                    current = next;
+                } else {
+                    return Err(NovaError::HeapFull);
+                }
+            }
+        }
+        Ok(current)
+    }
+
+    fn malloc(&self, mut size: usize) -> Result<*mut u8, NovaError> {
+        if size == 0 {
+            return Err(NovaError::EmptyHeapSegmentNotAllowed);
+        }
+
+        if size < MIN_BLOCK_SIZE {
+            size = MIN_BLOCK_SIZE;
+        }
+
+        // Align size to the next 16 bytes
+        size += (16 - (size % 16)) % 16;
+
+        unsafe {
+            // Find First-Fit memory segment
+            let current = self.find_first_fit(size)?;
+
+            // Return entire block WITHOUT generating a new header
+            // if the current block doesn't have enough space to hold: requested size + HEAP_HEADER_SIZE + MIN_BLOCK_SIZE
+            if (*current).size < size + HEAP_HEADER_SIZE + MIN_BLOCK_SIZE {
+                (*current).free = false;
+                return Ok(current.byte_add(HEAP_HEADER_SIZE) as *mut u8);
+            }
+
+            Self::fragment_segment(current, size);
+
+            let data_start_address = current.byte_add(HEAP_HEADER_SIZE);
+
+            Ok(data_start_address as *mut u8)
+        }
+    }
+
+    unsafe fn fragment_segment(current: *mut HeapHeader, size: usize) {
+        let byte_offset = HEAP_HEADER_SIZE + size;
+        let new_address = unsafe { current.byte_add(byte_offset) };
+
+        // Handle case where fragmenting center free space
+        unsafe {
+            let next = (*current).next;
+            if let Some(next) = next {
+                (*next).before = Some(new_address);
+            }
+
+            ptr::write(
+                new_address,
+                HeapHeader {
+                    next,
+                    before: Some(current),
+                    size: (*current).size - byte_offset,
+                    free: true,
+                },
+            );
+
+            (*current).next = Some(new_address);
+            (*current).free = false;
+            (*current).size = size;
+        }
+    }
+
+    fn free(&self, pointer: *mut u8) -> Result<(), NovaError> {
+        let mut segment = Self::get_header_ref_from_data_pointer(pointer);
+        unsafe {
+            // IF prev is free:
+            // Delete header, add size to previous and fix pointers.
+            // Move Head left
+            if let Some(before_head) = (*segment).before
+                && (*before_head).free
+            {
+                (*before_head).size += (*segment).size + HEAP_HEADER_SIZE;
+                delete_header(segment);
+                segment = before_head;
+            }
+
+            // IF next is free:
+            // Delete next header and merge size, fix pointers
+            if let Some(next_head) = (*segment).next
+                && (*next_head).free
+            {
+                (*segment).size += (*next_head).size + HEAP_HEADER_SIZE;
+                delete_header(next_head);
+            }
+
+            // Neither: Set free
+            (*segment).free = true;
+        }
+
+        Ok(())
+    }
+
+    const fn get_header_ref_from_data_pointer(pointer: *mut u8) -> *mut HeapHeader {
+        unsafe { pointer.sub(HEAP_HEADER_SIZE) as *mut HeapHeader }
+    }
+}
+
+unsafe impl GlobalAlloc for Heap {
+    unsafe fn alloc(&self, layout: core::alloc::Layout) -> *mut u8 {
+        self.malloc(layout.size()).unwrap()
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, _: core::alloc::Layout) {
+        self.free(ptr).unwrap();
+    }
+}
+
+unsafe impl Sync for Heap {}
+
+unsafe fn fits(size: usize, header: *mut HeapHeader) -> bool {
+    unsafe { (*header).free && size <= (*header).size }
+}
+
+unsafe fn delete_header(header: *mut HeapHeader) {
+    unsafe {
+        let before_opt = (*header).before;
+        let next_opt = (*header).next;
+
+        if let Some(before) = before_opt {
+            (*before).next = next_opt;
+        }
+
+        if let Some(next) = next_opt {
+            (*next).before = before_opt;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;

workspace/heap/src/tests.rs

@@ -0,0 +1,163 @@
+use super::*;
+use rand::{self, random_range};
+extern crate std;
+
+static HEAP_SIZE: usize = 1024;
+
+#[test]
+fn test_heap_allocation() {
+    let heap_vector = Box::new([0u8; HEAP_SIZE]);
+    let mut heap = Heap::empty();
+    heap.init(
+        &heap_vector[0] as *const u8 as usize,
+        &heap_vector[HEAP_SIZE - 1] as *const u8 as usize,
+    );
+
+    let root_header = heap.start_address;
+
+    let malloc_size = random_range(0..(HEAP_SIZE - HEAP_HEADER_SIZE));
+    let malloc = heap.malloc(malloc_size).unwrap();
+    let malloc_header = Heap::get_header_ref_from_data_pointer(malloc);
+
+    assert_eq!(root_header, malloc_header);
+
+    unsafe {
+        let actual_alloc_size = (*malloc_header).size;
+        let actual_raw_size = actual_alloc_size + HEAP_HEADER_SIZE;
+        // Verify sizing
+        assert!(actual_alloc_size >= malloc_size);
+        assert_eq!(actual_alloc_size % MIN_BLOCK_SIZE, 0);
+
+        // Verify section is occupied
+        assert!((*malloc_header).free == false);
+
+        // Verify next header has been created
+        let next = (*malloc_header).next.unwrap();
+
+        assert_eq!(malloc_header.byte_add(actual_raw_size), next);
+        assert!((*next).free);
+        assert_eq!((*malloc_header).next.unwrap(), next);
+        assert_eq!((*next).before.unwrap(), malloc_header);
+        assert_eq!((*next).size, HEAP_SIZE - actual_raw_size - HEAP_HEADER_SIZE)
+    }
+}
+
+#[test]
+fn test_full_heap() {
+    let heap_vector = Box::new([0u8; HEAP_SIZE]);
+    let mut heap = Heap::empty();
+    heap.init(
+        &heap_vector[0] as *const u8 as usize,
+        &heap_vector[HEAP_SIZE - 1] as *const u8 as usize,
+    );
+
+    let malloc_size = HEAP_SIZE - HEAP_HEADER_SIZE;
+    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).next.is_none());
+    }
+
+    let malloc2 = heap.malloc(MIN_BLOCK_SIZE);
+    assert!(malloc2.is_err());
+}
+
+#[test]
+fn test_freeing_root() {
+    let heap_vector = Box::new([0u8; HEAP_SIZE]);
+    let mut heap = Heap::empty();
+    heap.init(
+        &heap_vector[0] as *const u8 as usize,
+        &heap_vector[HEAP_SIZE - 1] as *const u8 as usize,
+    );
+
+    let root_header = heap.start_address;
+    let root_header_start_size = unsafe { (*root_header).size };
+
+    let malloc_size = random_range(0..((HEAP_SIZE - HEAP_HEADER_SIZE) / 2));
+    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).size >= malloc_size);
+        assert!((*root_header).next.is_some());
+
+        assert!(heap.free(malloc).is_ok());
+
+        assert_eq!((*root_header).size, root_header_start_size);
+        assert!((*root_header).next.is_none());
+    }
+}
+
+#[test]
+fn test_merging_free_sections() {
+    let heap_vector = Box::new([0u8; HEAP_SIZE]);
+    let mut heap = Heap::empty();
+    heap.init(
+        &heap_vector[0] as *const u8 as usize,
+        &heap_vector[HEAP_SIZE - 1] as *const u8 as usize,
+    );
+
+    let root_header = heap.start_address;
+    let _root_header_start_size = unsafe { (*root_header).size };
+
+    let malloc1 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+    let malloc_header_before = unsafe { *Heap::get_header_ref_from_data_pointer(malloc1) };
+    let malloc2 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+    let _ = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+
+    unsafe {
+        assert!(heap.free(malloc1).is_ok());
+
+        let malloc_header_free = *Heap::get_header_ref_from_data_pointer(malloc1);
+        assert_ne!(malloc_header_before.free, malloc_header_free.free);
+        assert_eq!(malloc_header_before.size, malloc_header_free.size);
+
+        assert!(heap.free(malloc2).is_ok());
+        let malloc_header_merge = *Heap::get_header_ref_from_data_pointer(malloc1);
+
+        assert!(malloc_header_merge.free);
+        assert_eq!(
+            malloc_header_merge.size,
+            malloc_header_free.size + MIN_BLOCK_SIZE + HEAP_HEADER_SIZE
+        );
+    }
+}
+
+#[test]
+fn test_first_fit() {
+    let heap_vector = Box::new([0u8; HEAP_SIZE]);
+    let mut heap = Heap::empty();
+    heap.init(
+        &heap_vector[0] as *const u8 as usize,
+        &heap_vector[HEAP_SIZE - 1] as *const u8 as usize,
+    );
+
+    let root_header = heap.start_address;
+    let _root_header_start_size = unsafe { (*root_header).size };
+
+    let malloc1 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+    let _malloc2 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+    let malloc3 = heap.malloc(MIN_BLOCK_SIZE * 3).unwrap();
+    let malloc4 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+
+    assert!(heap.free(malloc1).is_ok());
+    assert!(heap.free(malloc3).is_ok());
+    let malloc5 = heap.malloc(MIN_BLOCK_SIZE * 2).unwrap();
+    let malloc1_header = unsafe { *Heap::get_header_ref_from_data_pointer(malloc1) };
+
+    // First free block stays empty
+    assert!(malloc1_header.free);
+
+    // New allocation takes the first fit aka. malloc3
+    assert_eq!(malloc5, malloc3);
+
+    // If no free slot could be found, append to the end
+    let malloc6 = heap.malloc(MIN_BLOCK_SIZE * 2).unwrap();
+    assert!(malloc6 > malloc4);
+
+    // Malloc7 takes slot of Malloc1
+    let malloc7 = heap.malloc(MIN_BLOCK_SIZE).unwrap();
+    assert_eq!(malloc1, malloc7);
+}

workspace/nova_error/Cargo.toml

@@ -0,0 +1,4 @@
+[package]
+name = "nova_error"
+version = "0.1.0"
+edition = "2024"

workspace/nova_error/src/lib.rs

@@ -0,0 +1,14 @@
+#![no_std]
+
+use core::fmt::Debug;
+use core::prelude::rust_2024::derive;
+
+#[derive(Debug)]
+pub enum NovaError {
+    Mailbox,
+    HeapFull,
+    EmptyHeapSegmentNotAllowed,
+    Misalignment,
+    InvalidGranularity,
+    Paging,
+}