refactor: organize code

src/aarch64/mmu.rs

@@ -1,9 +1,12 @@
-use core::panic;
-
 use core::mem::size_of;
 use nova_error::NovaError;
 
-use crate::get_current_el;
+use crate::{
+    aarch64::mmu::physical_mapping::{
+        reserve_block, reserve_block_explicit, reserve_page, reserve_page_explicit,
+    },
+    get_current_el,
+};
 
 unsafe extern "C" {
     static mut __translation_table_l2_start: u64;
@@ -51,6 +54,16 @@ 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]);
 
@@ -59,122 +72,85 @@ pub static mut TRANSLATIONTABLE_TTBR0: PageTable = PageTable([0; 512]);
 #[no_mangle]
 pub static mut TRANSLATIONTABLE_TTBR1: PageTable = PageTable([0; 512]);
 
-static mut PAGING_BITMAP: [u64; MAX_PAGE_COUNT / 64] = [0; MAX_PAGE_COUNT / 64];
-
 /// Allocate a memory block of `size` starting at `virtual_address`.
 pub fn allocate_memory(
-    mut virtual_address: usize,
+    virtual_address: usize,
-    mut size: usize,
+    size_bytes: usize,
-    additional_flags: u64,
+    phys: PhysSource,
+    flags: u64,
 ) -> Result<(), NovaError> {
     if !virtual_address.is_multiple_of(GRANULARITY) {
         return Err(NovaError::Misalignment);
     }
-
+    if !size_bytes.is_multiple_of(GRANULARITY) {
-    let level1_blocks = size / LEVEL1_BLOCK_SIZE;
-    size %= LEVEL1_BLOCK_SIZE;
-    let level2_blocks = size / LEVEL2_BLOCK_SIZE;
-    size %= LEVEL2_BLOCK_SIZE;
-    let level3_pages = size / GRANULARITY;
-    if !size.is_multiple_of(GRANULARITY) {
         return Err(NovaError::InvalidGranularity);
     }
 
-    if level1_blocks > 0 {
-        todo!("Currently not supported");
-    }
-
     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)
     };
 
-    for _ in 0..level2_blocks {
+    match phys {
-        alloc_block_l2(virtual_address, base_table, additional_flags)?;
+        PhysSource::Any => map_range_dynamic(virtual_address, size_bytes, base_table, flags),
-        virtual_address += LEVEL2_BLOCK_SIZE;
+        PhysSource::Explicit(phys_addr) => {
+            map_range_explicit(virtual_address, phys_addr, size_bytes, base_table, flags)
         }
-    for _ in 0..level3_pages {
+    }
-        alloc_page(virtual_address, base_table, additional_flags)?;
+}
-        virtual_address += GRANULARITY;
+
+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 += GRANULARITY;
+        phys += GRANULARITY;
+        remaining -= GRANULARITY;
+    }
+
+    while remaining >= LEVEL2_BLOCK_SIZE {
+        map_l2_block(virt, phys, base, flags)?;
+        virt += LEVEL2_BLOCK_SIZE;
+        phys += LEVEL2_BLOCK_SIZE;
+        remaining -= LEVEL2_BLOCK_SIZE;
+    }
+
+    while remaining > 0 {
+        map_page(virt, phys, base, flags)?;
+        virt += GRANULARITY;
+        phys += GRANULARITY;
+        remaining -= GRANULARITY;
     }
 
     Ok(())
 }
 
-/// Allocate a memory block of `size` starting at `virtual_address`,
+fn map_range_dynamic(
-/// with explicit physical_address.
+    mut virt: PhysAddr,
-///
+    size_bytes: usize,
-/// Note: This can be used when mapping predefined regions.
+    base: *mut PageTable,
-pub fn allocate_memory_explicit(
+    flags: u64,
-    mut virtual_address: usize,
-    mut size: usize,
-    mut physical_address: usize,
-    additional_flags: u64,
 ) -> Result<(), NovaError> {
-    if !virtual_address.is_multiple_of(GRANULARITY) {
+    let mut remaining = size_bytes;
-        return Err(NovaError::Misalignment);
+
-    }
+    while remaining >= LEVEL2_BLOCK_SIZE {
-    if !physical_address.is_multiple_of(GRANULARITY) {
+        map_l2_block(virt, reserve_block(), base, flags)?;
-        return Err(NovaError::Misalignment);
+        virt += LEVEL2_BLOCK_SIZE;
+        remaining -= LEVEL2_BLOCK_SIZE;
     }
 
-    let level1_blocks = size / LEVEL1_BLOCK_SIZE;
+    while remaining > 0 {
-    size %= LEVEL1_BLOCK_SIZE;
+        map_page(virt, reserve_page(), base, flags)?;
-    let mut level2_blocks = size / LEVEL2_BLOCK_SIZE;
+        virt += GRANULARITY;
-    size %= LEVEL2_BLOCK_SIZE;
+        remaining -= GRANULARITY;
-    let mut level3_pages = size / GRANULARITY;
-    if !size.is_multiple_of(GRANULARITY) {
-        return Err(NovaError::InvalidGranularity);
-    }
-
-    if level1_blocks > 0 {
-        todo!("Currently not supported");
-    }
-
-    let l2_alignment = (physical_address % LEVEL2_BLOCK_SIZE) / GRANULARITY;
-    if l2_alignment != 0 {
-        let l3_diff = LEVEL2_BLOCK_SIZE / GRANULARITY - l2_alignment;
-        if l3_diff > level3_pages {
-            level2_blocks -= 1;
-            level3_pages += TABLE_ENTRY_COUNT;
-        }
-
-        level3_pages -= l3_diff;
-
-        for _ in 0..l3_diff {
-            alloc_page_explicit(
-                virtual_address,
-                physical_address,
-                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
-                additional_flags,
-            )?;
-
-            virtual_address += GRANULARITY;
-            physical_address += GRANULARITY;
-        }
-    }
-
-    for _ in 0..level2_blocks {
-        alloc_block_l2_explicit(
-            virtual_address,
-            physical_address,
-            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
-            additional_flags,
-        )?;
-        virtual_address += LEVEL2_BLOCK_SIZE;
-        physical_address += LEVEL2_BLOCK_SIZE;
-    }
-
-    for _ in 0..level3_pages {
-        alloc_page_explicit(
-            virtual_address,
-            physical_address,
-            core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
-            additional_flags,
-        )?;
-        virtual_address += GRANULARITY;
-        physical_address += GRANULARITY;
     }
 
     Ok(())
@@ -232,20 +208,6 @@ fn map_page(
     Ok(())
 }
 
-// Allocate a level 2 block.
-pub fn alloc_block_l2(
-    virtual_addr: usize,
-    base_table_ptr: *mut PageTable,
-    additional_flags: u64,
-) -> Result<(), NovaError> {
-    map_l2_block(
-        virtual_addr,
-        reserve_block(),
-        base_table_ptr,
-        additional_flags,
-    )
-}
-
 // Allocate a level 2 block, at a explicit `physical_address`.
 pub fn alloc_block_l2_explicit(
     virtual_addr: usize,
@@ -290,10 +252,10 @@ pub fn map_l2_block(
     Ok(())
 }
 
-pub fn reserve_range_explicit(
+pub fn reserve_range(
-    start_physical_address: usize,
+    start_physical_address: PhysAddr,
-    end_physical_address: usize,
+    end_physical_address: PhysAddr,
-) -> Result<(), NovaError> {
+) -> Result<PhysAddr, NovaError> {
     let mut size = end_physical_address - start_physical_address;
     let l1_blocks = size / LEVEL1_BLOCK_SIZE;
     size %= LEVEL1_BLOCK_SIZE;
@@ -320,57 +282,7 @@ pub fn reserve_range_explicit(
         addr += GRANULARITY;
     }
 
-    Ok(())
+    Ok(start_physical_address)
-}
-
-fn reserve_page() -> usize {
-    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!");
-}
-
-fn reserve_page_explicit(physical_address: usize) -> Result<(), 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(())
-}
-
-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!");
-}
-
-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 create_block_descriptor_entry(physical_address: usize, additional_flags: u64) -> u64 {
@@ -401,18 +313,6 @@ fn virtual_address_to_table_offset(virtual_addr: usize) -> (usize, usize, usize)
     (l1_off, l2_off, l3_off)
 }
 
-/// Debugging function to navigate the translation tables.
-#[allow(unused_variables)]
-pub fn sim_l3_access(addr: usize) {
-    unsafe {
-        let entry1 = TRANSLATIONTABLE_TTBR0.0[addr / LEVEL1_BLOCK_SIZE];
-        let table2 = &mut *(entry_phys(entry1 as usize) as *mut PageTable);
-        let entry2 = table2.0[(addr % LEVEL1_BLOCK_SIZE) / LEVEL2_BLOCK_SIZE];
-        let table3 = &mut *(entry_phys(entry2 as usize) as *mut PageTable);
-        let _entry3 = table3.0[(addr % LEVEL2_BLOCK_SIZE) / GRANULARITY];
-    }
-}
-
 /// Navigate the table tree, by following given offsets. This function
 /// allocates new tables if required.
 fn navigate_table(
@@ -451,49 +351,14 @@ fn next_table(table_ptr: *mut PageTable, offset: usize) -> Result<*mut PageTable
     }
 }
 
-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
-}
-
 /// Extracts the physical address out of an table entry.
 #[inline]
-fn entry_phys(entry: usize) -> usize {
+fn entry_phys(entry: usize) -> PhysAddr {
     entry & 0x0000_FFFF_FFFF_F000
 }
 
 #[inline]
-fn entry_table_addr(entry: usize) -> usize {
+fn entry_table_addr(entry: usize) -> VirtAddr {
     if get_current_el() == 1 {
         phys_table_to_kernel_space(entry_phys(entry))
     } else {
@@ -503,6 +368,6 @@ fn entry_table_addr(entry: usize) -> usize {
 
 /// Extracts the physical address out of an table entry.
 #[inline]
-fn phys_table_to_kernel_space(entry: usize) -> usize {
+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/configuration.rs

@@ -32,20 +32,19 @@ const AS: u64 = 0b1 << 36; // configure an ASID size of 16 bits
 pub static TCR_EL1_CONF: u64 = IPS | TG0 | TG1 | T0SZ | T1SZ | SH0 | SH1 | AS;
 
 pub mod mmu {
-
     use crate::{
         aarch64::mmu::{
-            alloc_block_l2, alloc_block_l2_explicit, map_l2_block, reserve_range_explicit,
+            alloc_block_l2_explicit, allocate_memory, map_l2_block, reserve_range, PhysSource,
             DEVICE_MEM, EL0_ACCESSIBLE, KERNEL_VIRTUAL_MEM_SPACE, LEVEL1_BLOCK_SIZE,
             LEVEL2_BLOCK_SIZE, NORMAL_MEM, PXN, READ_ONLY, STACK_START_ADDR,
-            TRANSLATIONTABLE_TTBR0, TRANSLATIONTABLE_TTBR1, UXN, WRITABLE,
+            TRANSLATIONTABLE_TTBR0, UXN, WRITABLE,
         },
         PERIPHERAL_BASE,
     };
 
     #[no_mangle]
     static EL1_STACK_TOP: usize = STACK_START_ADDR | KERNEL_VIRTUAL_MEM_SPACE;
-    const EL1_STACK_BOTTOM: usize = EL1_STACK_TOP - LEVEL2_BLOCK_SIZE * 2;
+    const EL1_STACK_SIZE: usize = LEVEL2_BLOCK_SIZE * 2;
 
     extern "C" {
         static _data: u64;
@@ -58,53 +57,54 @@ pub mod mmu {
         let kernel_end = unsafe { &__kernel_end } as *const _ as usize;
         let user_space_end = unsafe { &_end } as *const _ as usize;
 
-        reserve_range_explicit(0x0, user_space_end).unwrap();
+        reserve_range(0x0, user_space_end).unwrap();
 
         for addr in (0..shared_segment_end).step_by(LEVEL2_BLOCK_SIZE) {
-            let _ = map_l2_block(
+            map_l2_block(
                 addr,
                 addr,
                 core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
                 EL0_ACCESSIBLE | READ_ONLY | NORMAL_MEM,
-            );
+            )
+            .unwrap();
         }
 
         for addr in (shared_segment_end..kernel_end).step_by(LEVEL2_BLOCK_SIZE) {
-            let _ = map_l2_block(
+            map_l2_block(
                 addr,
                 addr,
                 core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
                 WRITABLE | UXN | NORMAL_MEM,
-            );
+            )
+            .unwrap();
         }
 
         for addr in (kernel_end..user_space_end).step_by(LEVEL2_BLOCK_SIZE) {
-            let _ = map_l2_block(
+            map_l2_block(
                 addr,
                 addr,
                 core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
                 EL0_ACCESSIBLE | WRITABLE | PXN | NORMAL_MEM,
-            );
+            )
+            .unwrap();
         }
 
         for addr in (PERIPHERAL_BASE..LEVEL1_BLOCK_SIZE).step_by(LEVEL2_BLOCK_SIZE) {
-            let _ = alloc_block_l2_explicit(
+            alloc_block_l2_explicit(
                 addr,
                 addr,
                 core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR0),
                 EL0_ACCESSIBLE | WRITABLE | UXN | PXN | DEVICE_MEM,
-            );
+            )
+            .unwrap();
         }
 
-        for addr in (EL1_STACK_BOTTOM..EL1_STACK_TOP)
+        allocate_memory(
-            .rev()
+            EL1_STACK_TOP - EL1_STACK_SIZE + 0x10,
-            .step_by(LEVEL2_BLOCK_SIZE)
+            EL1_STACK_SIZE,
-        {
+            PhysSource::Any,
-            let _ = alloc_block_l2(
-                addr,
-                core::ptr::addr_of_mut!(TRANSLATIONTABLE_TTBR1),
             WRITABLE | NORMAL_MEM,
-            );
+        )
-        }
+        .unwrap();
     }
 }

src/lib.rs

@@ -14,7 +14,8 @@ use heap::Heap;
 
 use crate::{
     aarch64::mmu::{
-        allocate_memory, KERNEL_VIRTUAL_MEM_SPACE, LEVEL2_BLOCK_SIZE, NORMAL_MEM, UXN, WRITABLE,
+        allocate_memory, PhysSource, KERNEL_VIRTUAL_MEM_SPACE, LEVEL2_BLOCK_SIZE, NORMAL_MEM, UXN,
+        WRITABLE,
     },
     interrupt_handlers::initialize_interrupt_handler,
     logger::DefaultLogger,
@@ -33,7 +34,7 @@ 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, NORMAL_MEM | UXN | WRITABLE).unwrap();
+    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);
 }

src/main.rs

@@ -12,7 +12,7 @@ extern crate alloc;
 use alloc::vec::Vec;
 use nova::{
     aarch64::{
-        mmu::{allocate_memory_explicit, EL0_ACCESSIBLE, NORMAL_MEM, PXN, UXN, WRITABLE},
+        mmu::{allocate_memory, PhysSource, EL0_ACCESSIBLE, NORMAL_MEM, PXN, UXN, WRITABLE},
         registers::{daif, read_id_aa64mmfr0_el1},
     },
     configuration::mmu::initialize_mmu_translation_tables,
@@ -102,10 +102,10 @@ pub extern "C" fn kernel_main() -> ! {
 
     // Frame Buffer memory range
     // TODO: this is just temporary
-    allocate_memory_explicit(
+    allocate_memory(
         0x3c100000,
         1080 * 1920 * 4,
-        0x3c100000,
+        PhysSource::Explicit(0x3c100000),
         NORMAL_MEM | PXN | UXN | WRITABLE | EL0_ACCESSIBLE,
     )
     .unwrap();