Merged-in RISC-V memory support.

.vscode/settings.json

@@ -3,4 +3,5 @@
       "stddef.h": "c"
    },
    "rust-analyzer.checkOnSave.allTargets": false,
+   "rust-analyzer.cargo.target": "kernel/targets/riscv64-virt-ableos.json",
 }

Cargo.lock

@@ -179,6 +179,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "derive_more"
+version = "0.99.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4fb810d30a7c1953f91334de7244731fc3f3c10d7fe163338a35b9f640960321"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "env_logger"
 version = "0.10.0"
@@ -326,8 +337,10 @@ name = "kernel"
 version = "0.2.0"
 dependencies = [
  "crossbeam-queue",
+ "derive_more",
  "limine",
  "log",
+ "sbi",
  "slab",
  "spin",
  "uart_16550",
@@ -510,6 +523,12 @@ version = "1.0.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5583e89e108996506031660fe09baa5011b9dd0341b89029313006d1fb508d70"
 
+[[package]]
+name = "sbi"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29cb0870400aca7e4487e8ec1e93f9d4288da763cb1da2cedc5102e62b6522ad"
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"

kernel/Cargo.toml

@@ -8,14 +8,33 @@ slab = { version = "0.4", default-features = false }
 spin = "0.9"
 versioning = { git = "https://git.ablecorp.us/able/aos_userland" }
 log = "0.4"
+uart_16550 = "0.2"
 
 [dependencies.crossbeam-queue]
 version = "0.3"
 default-features = false
 features = ["alloc"]
 
+[dependencies.derive_more]
+version = "0.99"
+default-features = false
+features = [
+    "add",
+    "add_assign",
+    "constructor",
+    "display",
+    "from",
+    "into",
+    "mul",
+    "mul_assign",
+    "not",
+    "sum",
+]
+
 [target.'cfg(target_arch = "x86_64")'.dependencies]
 limine = { version = "0.1", git = "https://github.com/limine-bootloader/limine-rs" }
-uart_16550 = "0.2"
 x86_64 = "0.14"
 x2apic = "0.4"
+
+[target.'cfg(target_arch = "riscv64")'.dependencies]
+sbi = "0.2.0"

kernel/lds/riscv64-virt.ld

@@ -0,0 +1,66 @@
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+START_ADDRESS = 0x80200000;
+
+SECTIONS {
+    . = START_ADDRESS;
+
+    .text : {
+	    PROVIDE(_text_start = .);
+	    *(.text.entry)
+
+	    . = ALIGN(4K);
+
+	    *(.text .text.*)
+	    PROVIDE(_text_end = .);
+    }
+
+    . = ALIGN(4K);
+
+    .rodata : {
+	    PROVIDE(_rodata_start = .);
+	    *(.rodata .rodata.*)
+	    PROVIDE(_rodata_end = .);
+    }
+
+    . = ALIGN(4K);
+
+    .data : {
+        PROVIDE(_data_start = .);
+        *(.data .data.*)
+        PROVIDE(_data_end = .);
+    }
+	
+    . = ALIGN(4K);
+
+    .sdata : {
+	    PROVIDE(_sdata_start = .);
+	    *(.sdata)
+	    *(.sdata.*)
+	    *(.srodata.*)
+	    *(.gnu.linkonce.s.*)
+	    PROVIDE(_sdata_end = .);
+    }
+
+    . = ALIGN(4K);
+
+    .bss : {
+	    PROVIDE(_bss_start = .);
+	    *(.sbss*)
+	    *(.bss.stack)
+	    *(.bss .bss.*)
+	    PROVIDE(_initial_kernel_heap_start = .);
+	    PROVIDE(_initial_kernel_heap_size = 1024 * 1024);
+	    . += _initial_kernel_heap_size;
+	    PROVIDE(_bss_end = .);
+    }
+
+    /* FIXME: Currently this has to be aligned to PAGE_SIZE << MAX_ORDER */
+    PROVIDE(_usable_memory_start = ALIGN(4M));
+    PROVIDE(_usable_memory_size = 0x88000000 - _usable_memory_start);
+
+    /DISCARD/ : {
+        *(.comment)
+	    *(.eh_frame)
+    }
+}

kernel/src/allocator.rs

@@ -35,14 +35,6 @@ use core::{
 
 use spin::Mutex;
 
-extern "C" {
-    fn _initial_kernel_heap_start();
-    fn _initial_kernel_heap_size();
-}
-
-const INITIAL_KERNEL_HEAP_START: *mut u8 = _initial_kernel_heap_start as _;
-const INITIAL_KERNEL_HEAP_SIZE: *const () = _initial_kernel_heap_size as _;
-
 struct Allocator(Mutex<Option<Heap>>);
 
 unsafe impl GlobalAlloc for Allocator {
@@ -66,10 +58,10 @@ unsafe impl GlobalAlloc for Allocator {
 #[global_allocator]
 static ALLOCATOR: Allocator = Allocator(Mutex::new(None));
 
-pub fn init() {
+// FIXME: umm is `memory` VirtualAddress or PhysicalAddress? both?
+pub fn init(memory: *mut u8, memory_size: usize) {
     log::info!("Initialising kernel heap allocator");
-    *ALLOCATOR.0.lock() =
+    *ALLOCATOR.0.lock() = Some(unsafe { Heap::new(memory, memory_size) });
-        Some(unsafe { Heap::new(INITIAL_KERNEL_HEAP_START, INITIAL_KERNEL_HEAP_SIZE as _) });
 }
 
 // FIXME: these are arch-specific
@@ -123,7 +115,6 @@ impl Heap {
         let size = size + mem::size_of::<Header>();
         let chunks_needed = (size + CHUNK_SIZE - 1) / CHUNK_SIZE;
         let chunk_alignment = (alignment + CHUNK_SIZE - 1) / CHUNK_SIZE;
-        log::debug!("size: {size} chunks: {chunks_needed} align: {chunk_alignment}");
 
         if chunks_needed + chunk_alignment > self.free_chunks() {
             return None;
@@ -137,11 +128,6 @@ impl Heap {
         // Align the starting address and verify that we haven't gone outside the calculated free area
         let addr =
             addr_unaligned + alignment - (addr_unaligned + mem::size_of::<Header>()) % alignment;
-        log::debug!(
-            "Addr unaligned: 0x{addr_unaligned:x} (offset: 0x{:x})",
-            addr_unaligned - chunks_addr
-        );
-        log::trace!("Addr: 0x{addr:x} (offset: 0x{:x})", addr - chunks_addr);
         let aligned_first_chunk = (addr - chunks_addr) / CHUNK_SIZE;
         assert!(first_chunk <= aligned_first_chunk);
         assert!(
@@ -158,7 +144,6 @@ impl Heap {
         self.allocated_chunks += chunks_needed;
 
         let ptr: *mut u8 = unsafe { mem::transmute(header.add(1)) };
-        log::trace!("{ptr:p}");
         // FIXME: zero or scrub memory?
         assert!(ptr.is_aligned_to(alignment));
         NonNull::new(ptr)

kernel/src/arch/riscv64/entry.s

@@ -0,0 +1,31 @@
+    .section .text.entry
+    .global _start
+_start: 
+    # load stack_top to sp register
+    la sp, stack_top
+
+    # The BSS section is expected to be zero
+    la 		a0, _bss_start
+	la		a1, _bss_end
+	bgeu	a0, a1, 2f
+1:
+    sd		zero, (a0)
+    addi	a0, a0, 8
+    bltu	a0, a1, 1b
+2:
+    call _kernel_start
+
+    .section .bss.stack
+    .global stack
+stack:
+    # alloc stack memory
+    .space 4096 * 16
+    .global stack_top
+stack_top:
+    .section .bss.heap
+    .global _initial_kernel_heap_start
+_initial_kernel_heap_start:
+    # alloc initial kmalloc memory
+    .space 4096 * 64
+    .global _initial_kernel_heap_end
+_initial_kernel_heap_end:

kernel/src/arch/riscv64/memory.rs

@@ -0,0 +1,268 @@
+use core::num;
+
+use alloc::boxed::Box;
+use spin::{Mutex, Once};
+use crate::memory::{MemoryManager, PhysicalAddress, VirtualAddress};
+
+use super::PAGE_SIZE;
+
+pub enum PageSize {
+    Size4KiB,
+    Size2MiB,
+    Size1GiB,
+    // FIXME: SV48 support
+    // Size512GiB,
+    // FIXME: SV57 support
+    // Size256TiB,
+}
+
+impl PageSize {
+    fn level(&self) -> usize {
+        match self {
+            PageSize::Size4KiB => 0,
+            PageSize::Size2MiB => 1,
+            PageSize::Size1GiB => 2,
+            // FIXME: SV48 and SV57 support
+        }
+    }
+}
+
+pub struct PageTable {
+    entries: [PageEntry; 512]
+}
+
+impl PageTable {
+    /// Walk the page table to convert a virtual address to a physical address.
+    /// If a page fault would occur, this returns None. Otherwise, it returns the physical address.
+    pub fn virt_to_phys(&self, vaddr: VirtualAddress) -> Option<PhysicalAddress> {
+        let vpn = vaddr.vpns();
+
+        let mut v = &self.entries[vpn[2]];
+        for i in (0..=2).rev() {
+            if v.is_invalid() {
+                // This is an invalid entry, page fault.
+                break;
+            } else if v.is_leaf() {
+                // In RISC-V, a leaf can be at any level.
+
+                // The offset mask masks off the PPN. Each PPN is 9 bits and they start at bit #12.
+                // So, our formula 12 + i * 9
+                let off_mask = (1 << (12 + i * 9)) - 1;
+                let vaddr_pgoff = vaddr.as_addr() & off_mask;
+                let addr = ((v.entry() << 2) as usize) & !off_mask;
+                return Some((addr | vaddr_pgoff).into());
+            }
+            // Set v to the next entry which is pointed to by this entry.
+            // However, the address was shifted right by 2 places when stored in the page table
+            // entry, so we shift it left to get it back into place.
+            let entry = v.addr().as_ptr::<PageEntry>();
+            // We do i - 1 here, however we should get None or Some() above
+            // before we do 0 - 1 = -1.
+            v = unsafe { entry.add(vpn[i - 1]).as_ref().unwrap() };
+        }
+
+        // If we get here, we've exhausted all valid tables and haven't
+        // found a leaf.
+        None
+    }
+
+    /// Maps a virtual address to a physical address
+    /// flags should contain only the following:
+    ///   Read, Write, Execute, User, and/or Global
+    /// flags MUST include one or more of the following:
+    ///   Read, Write, Execute
+    /// The valid bit automatically gets added
+    pub fn map(&mut self, vaddr: VirtualAddress, paddr: PhysicalAddress, flags: PageEntryFlags, page_size: PageSize) {
+        assert!(flags as usize & 0xe != 0);
+
+        let vpn = vaddr.vpns();
+        let ppn = paddr.ppns();
+        let level = page_size.level();
+
+        let mut v = &mut self.entries[vpn[2]];
+
+        // Now, we're going to traverse the page table and set the bits properly. We expect the root
+        // to be valid, however we're required to create anything beyond the root
+        for i in (level..2).rev() {
+            if v.is_invalid() {
+                let mut mm = MEMORY_MANAGER.get().unwrap().lock();
+                let page = mm.zallocate_pages(1).unwrap().as_addr();
+                v.set_entry((page as usize >> 2) | PageEntryFlags::Valid as usize);
+            }
+
+            let entry = v.addr().as_mut_ptr::<PageEntry>();
+	        v = unsafe { entry.add(vpn[i]).as_mut().unwrap() };
+        }
+
+        // When we get here, we should be at VPN[0] and v should be pointing to our entry.
+        // The entry structure is Figure 4.18 in the RISC-V Privileged Specification
+        let entry = (ppn[2] << 28) as usize // PPN[2] = [53:28]
+            | (ppn[1] << 19) as usize // PPN[1] = [27:19]
+            | (ppn[0] << 10) as usize // PPN[0] = [18:10]
+            | flags as usize // Specified bits, such as User, Read, Write, etc.
+            | PageEntryFlags::Valid as usize;
+        v.set_entry(entry);
+    }
+
+    /// Identity maps a page of memory
+    pub fn identity_map(&mut self, addr: PhysicalAddress, flags: PageEntryFlags, page_size: PageSize) {
+        // log::debug!("identity mapped {addr}");
+        self.map(addr.as_addr().into(), addr, flags, page_size);
+    }
+
+    /// Identity maps a range of contiguous memory
+    /// This assumes that start <= end
+    pub fn identity_map_range(&mut self, start: PhysicalAddress, end: PhysicalAddress, flags: PageEntryFlags) {
+        log::debug!("start: {start}, end: {end}");
+        let mut mem_addr = start.as_addr() & !(PAGE_SIZE - 1);
+        let num_pages = (align_val(end.as_addr(), 12) - mem_addr - 1) / PAGE_SIZE + 1;
+
+        for _ in 0..num_pages {
+            // FIXME: we can merge these page entries if possible into Size2MiB or larger entries
+            self.identity_map(mem_addr.into(), flags, PageSize::Size4KiB);
+            mem_addr += 1 << 12;
+        }
+    }
+
+    /// Unmaps a page of memory at vaddr
+    pub fn unmap(&mut self, vaddr: VirtualAddress) {
+        let vpn = vaddr.vpns();
+
+        // Now, we're going to traverse the page table and clear the bits
+        let mut v = &mut self.entries[vpn[2]];
+        for i in (0..2).rev() {
+            if v.is_invalid() {
+                // This is an invalid entry, page is already unmapped
+                return;
+            } else if v.is_leaf() {
+                // This is a leaf, which can be at any level
+                // In order to make this page unmapped, we need to clear the entry
+                v.set_entry(0);
+                return;
+            }
+
+            let entry = v.addr().as_mut_ptr::<PageEntry>();
+	        v = unsafe { entry.add(vpn[i]).as_mut().unwrap() };
+        }
+
+        // If we're here this is an unmapped page
+        return;
+    }
+
+    /// Unmaps a range of contiguous memory
+    /// This assumes that start <= end
+    pub fn unmap_range(&mut self, start: VirtualAddress, end: VirtualAddress) {
+        let mut mem_addr = start.as_addr() & !(PAGE_SIZE - 1);
+        let num_pages = (align_val(end.as_addr(), 12) - mem_addr) / PAGE_SIZE;
+
+        for _ in 0..num_pages {
+            self.unmap(mem_addr.into());
+            mem_addr += 1 << 12;
+        }
+    }
+
+    /// Frees all memory associated with a table.
+    /// NOTE: This does NOT free the table directly. This must be freed manually.
+    fn destroy(&mut self) {
+        for entry in &mut self.entries {
+            entry.destroy()
+        }
+    }
+}
+
+#[repr(usize)]
+#[derive(Clone, Copy, Debug)]
+pub enum PageEntryFlags {
+    None = 0,
+    Valid = 1,
+    Read = 1 << 1,
+    Write = 1 << 2,
+    Execute = 1 << 3,
+    User = 1 << 4,
+    Global = 1 << 5,
+    Access = 1 << 6,
+    Dirty = 1 << 7,
+  
+    // for convenience
+    ReadWrite = Self::Read as usize | Self::Write as usize,
+    ReadExecute = Self::Read as usize | Self::Execute as usize,
+    ReadWriteExecute = Self::Read as usize | Self::Write as usize | Self::Execute as usize,
+    UserReadWrite = Self::User as usize | Self::ReadWrite as usize,
+    UserReadExecute = Self::User as usize | Self::ReadExecute as usize,
+    UserReadWriteExecute = Self::User as usize | Self::ReadWriteExecute as usize,
+}
+
+struct PageEntry(usize);
+
+impl PageEntry {
+    fn is_valid(&self) -> bool {
+        self.0 & PageEntryFlags::Valid as usize != 0
+    }
+
+    fn is_invalid(&self) -> bool {
+        !self.is_valid()
+    }
+
+    fn is_leaf(&self) -> bool {
+        self.0 & PageEntryFlags::ReadWriteExecute as usize != 0
+    }
+
+    fn is_branch(&self) -> bool {
+        !self.is_leaf()
+    }
+
+    fn entry(&self) -> usize {
+        self.0
+    }
+
+    fn set_entry(&mut self, entry: usize) {
+        self.0 = entry;
+    }
+
+    fn clear_flag(&mut self, flag: PageEntryFlags) {
+        self.0 &= !(flag as usize);
+    }
+
+    fn set_flag(&mut self, flag: PageEntryFlags) {
+        self.0 |= flag as usize;
+    }
+
+    fn addr(&self) -> PhysicalAddress {
+        ((self.entry() as usize & !0x3ff) << 2).into()
+    }
+
+    fn destroy(&mut self) {
+        if self.is_valid() && self.is_branch() {
+            // This is a valid entry so drill down and free
+            let memaddr = self.addr();
+            let table = memaddr.as_mut_ptr::<PageTable>();
+            unsafe {
+                (*table).destroy();
+                let mut mm = MEMORY_MANAGER.get().unwrap().lock();
+                mm.deallocate_pages(memaddr.into(), 0);
+            }
+        }
+    }
+}
+
+// FIXME: PageTable should be integrated into MemoryManager *somehow*
+pub static MEMORY_MANAGER: Once<Mutex<MemoryManager>> = Once::new();
+pub static PAGE_TABLE: Once<Mutex<PhysicalAddress>> = Once::new();
+
+pub fn init(start_addr: PhysicalAddress, page_count: usize) {
+    let mut memory_manager = MemoryManager::new();
+
+    unsafe {
+        memory_manager.add_range(start_addr, page_count);
+        PAGE_TABLE.call_once(|| Mutex::new(memory_manager.zallocate_pages(0).unwrap()));
+    }
+
+    MEMORY_MANAGER.call_once(|| Mutex::new(memory_manager));
+}
+
+/// Align (set to a multiple of some power of two)
+/// This function always rounds up.
+fn align_val(val: usize, order: usize) -> usize {
+    let o = (1 << order) - 1;
+    (val + o) & !o
+}

kernel/src/arch/riscv64/memory_regions.s

@@ -0,0 +1,35 @@
+    .section .rodata
+    .global TEXT_START
+TEXT_START: .quad _text_start
+    .global TEXT_END
+TEXT_END: .quad _text_end
+
+    .global RODATA_START
+RODATA_START: .quad _rodata_start
+    .global RODATA_END
+RODATA_END: .quad _rodata_end
+
+    .global DATA_START
+DATA_START: .quad _data_start
+    .global DATA_END
+DATA_END: .quad _data_end
+
+    .global SDATA_START
+SDATA_START: .quad _sdata_start
+    .global SDATA_END
+SDATA_END: .quad _sdata_end
+
+    .global BSS_START
+BSS_START: .quad _bss_start
+    .global BSS_END
+BSS_END: .quad _bss_end
+
+    .global INITIAL_KERNEL_HEAP_START
+INITIAL_KERNEL_HEAP_START: .quad _initial_kernel_heap_start
+    .global INITIAL_KERNEL_HEAP_SIZE
+INITIAL_KERNEL_HEAP_SIZE: .quad _initial_kernel_heap_size
+
+    .global USABLE_MEMORY_START
+USABLE_MEMORY_START: .quad _usable_memory_start
+    .global USABLE_MEMORY_SIZE
+USABLE_MEMORY_SIZE: .quad _usable_memory_size

kernel/src/arch/riscv64/mod.rs

@@ -1 +1,93 @@
-//! 
+mod memory;
+
+use core::{arch::{asm, global_asm}, fmt::Write};
+use alloc::boxed::Box;
+use sbi::system_reset::{ResetType, ResetReason, system_reset};
+use spin::{Mutex, Once};
+use uart_16550::MmioSerialPort;
+
+use crate::{allocator, memory::PhysicalAddress, arch::riscv64::memory::{PAGE_TABLE, PageEntryFlags, PageSize, PageTable}};
+
+global_asm!(include_str!("entry.s"));
+global_asm!(include_str!("memory_regions.s"));
+
+pub const PAGE_SIZE: usize = 4096;
+
+extern {
+    static TEXT_START: PhysicalAddress;
+    static TEXT_END: PhysicalAddress;
+
+    static RODATA_START: PhysicalAddress;
+    static RODATA_END: PhysicalAddress;
+    
+    static DATA_START: PhysicalAddress;
+    static DATA_END: PhysicalAddress;
+
+    static SDATA_START: PhysicalAddress;
+    static SDATA_END: PhysicalAddress;
+    
+    static BSS_START: PhysicalAddress;
+    static BSS_END: PhysicalAddress;
+    
+    static INITIAL_KERNEL_HEAP_START: PhysicalAddress;
+    static INITIAL_KERNEL_HEAP_SIZE: usize;
+    
+    static USABLE_MEMORY_START: PhysicalAddress;
+    static USABLE_MEMORY_SIZE: usize;
+}
+
+static SERIAL_CONSOLE: Once<Mutex<MmioSerialPort>> = Once::new();
+
+#[no_mangle]
+unsafe extern fn _kernel_start() -> ! {
+    SERIAL_CONSOLE.call_once(|| Mutex::new(unsafe { MmioSerialPort::new(0x1000_0000) }));
+    crate::logger::init().expect("failed to set logger");
+    log::info!("Initialising AKern {}", crate::VERSION);
+
+    allocator::init(INITIAL_KERNEL_HEAP_START.as_mut_ptr::<u8>(), INITIAL_KERNEL_HEAP_SIZE);
+    memory::init(USABLE_MEMORY_START.into(), USABLE_MEMORY_SIZE / PAGE_SIZE);
+
+    let mut page_table_addr = PAGE_TABLE.get().unwrap().lock();
+    let mut page_table = page_table_addr.as_mut_ptr::<PageTable>().as_mut().unwrap();
+
+    // Map text (executable) section
+    page_table.identity_map_range(TEXT_START, TEXT_END, PageEntryFlags::ReadExecute);
+    // Map rodata section
+    page_table.identity_map_range(RODATA_START, RODATA_END, PageEntryFlags::Read);
+    // Map data section
+    page_table.identity_map_range(DATA_START, DATA_END, PageEntryFlags::ReadWrite);
+    // Map sdata section
+    page_table.identity_map_range(SDATA_START, SDATA_END, PageEntryFlags::ReadWrite);
+    // Map bss section (includes stack and initial kernel heap)
+    page_table.identity_map_range(BSS_START, BSS_END, PageEntryFlags::ReadWrite);
+    // Map usable memory range (as rw so not executable)
+    page_table.identity_map_range(USABLE_MEMORY_START, USABLE_MEMORY_START + USABLE_MEMORY_SIZE.into(), PageEntryFlags::ReadWrite);
+    // Map Uart so we can continue using serial
+    page_table.identity_map(0x1000_0000_usize.into(), PageEntryFlags::ReadWrite, PageSize::Size4KiB);
+
+    let table_ppn = page_table_addr.as_addr() as usize >> 12;
+    let satp_value = 8 << 60 | table_ppn;
+    log::info!("Enabling the MMU...");
+
+    asm!(
+        "csrw satp, {}",
+        "sfence.vma",
+        in(reg) satp_value,
+    );
+
+    log::info!("We're in PAGING LAND!");
+
+    #[allow(unreachable_code)]
+    match system_reset(ResetType::Shutdown, ResetReason::NoReason).unwrap() {}
+}
+
+/// Spin loop
+pub fn sloop() -> ! {
+    loop {
+        unsafe { asm!("wfi") }
+    }
+}
+
+pub fn log(args: core::fmt::Arguments<'_>) -> core::fmt::Result {
+    SERIAL_CONSOLE.get().unwrap().lock().write_fmt(args)
+}

kernel/src/arch/x86_64/memory.rs

@@ -1,14 +1,14 @@
 use core::sync::atomic::AtomicU64;
 use limine::{LimineMemmapEntry, LimineMemoryMapEntryType, NonNullPtr};
 use spin::{Mutex, Once};
-use x86_64::{
+use x86_64::{structures::paging::OffsetPageTable, VirtAddr};
-    structures::paging::{FrameAllocator, FrameDeallocator, OffsetPageTable, PhysFrame, Size4KiB},
+use crate::memory::{MemoryManager, MAX_ORDER};
-    PhysAddr, VirtAddr,
-};
 
-pub static PAGE_TABLE: Once<Mutex<OffsetPageTable>> = Once::new();
+pub const PAGE_SIZE: usize = 4096;
-pub static FRAME_ALLOC: Once<Mutex<FrameAlloc>> = Once::new();
+
+pub static MEMORY_MANAGER: Once<Mutex<MemoryManager>> = Once::new();
 pub static HHDM_OFFSET: AtomicU64 = AtomicU64::new(0);
+static PAGE_TABLE: Once<Mutex<OffsetPageTable>> = Once::new();
 
 /// Initialise page table
 pub unsafe fn init_pt(phys_base: VirtAddr) {
@@ -27,45 +27,28 @@ pub unsafe fn init_pt(phys_base: VirtAddr) {
     });
 }
 
-/// Initialise page frame allocator
+/// Initialise memory manager
-pub unsafe fn init_falloc(mmap: &'static [NonNullPtr<LimineMemmapEntry>]) {
+pub fn initialize(mmap: &'static [NonNullPtr<LimineMemmapEntry>]) {
-    log::info!("Initialising frame allocator");
+    let mut memory_manager = MemoryManager::new();
-    FRAME_ALLOC.call_once(|| Mutex::new(FrameAlloc::new(mmap)));
-}
 
-pub struct FrameAlloc {
+    for entry in mmap {
-    mmap: &'static [NonNullPtr<LimineMemmapEntry>],
+        if entry.typ != LimineMemoryMapEntryType::Usable {
-    next: usize,
+            continue;
-}
-
-unsafe impl Send for FrameAlloc {}
-
-impl FrameAlloc {
-    pub unsafe fn new(mmap: &'static [NonNullPtr<LimineMemmapEntry>]) -> Self {
-        Self { mmap, next: 0 }
         }
 
-    fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
+        let alignment = PAGE_SIZE << MAX_ORDER;
-        self.mmap
+        let start_addr_unaligned = entry.base as usize;
-            .iter()
+        let diff = alignment - start_addr_unaligned % alignment;
-            .filter(|e| e.typ == LimineMemoryMapEntryType::Usable)
+        if diff > entry.len as usize {
-            .map(|e| e.base..e.base + e.len)
+            continue;
-            .flat_map(|r| r.step_by(4096))
-            .map(PhysAddr::new)
-            .map(PhysFrame::containing_address)
         }
-}
+        let start_addr = start_addr_unaligned + diff;
+        let page_count = (entry.len as usize - diff) / PAGE_SIZE;
 
-unsafe impl FrameAllocator<Size4KiB> for FrameAlloc {
+        unsafe {
-    fn allocate_frame(&mut self) -> Option<PhysFrame<Size4KiB>> {
+            memory_manager.add_range(start_addr.into(), page_count);
-        let f = self.usable_frames().nth(self.next);
+        }
-        self.next += 1;
-        f
     }
-}
 
-impl FrameDeallocator<Size4KiB> for FrameAlloc {
+    MEMORY_MANAGER.call_once(|| Mutex::new(memory_manager));
-    unsafe fn deallocate_frame(&mut self, frame: PhysFrame<Size4KiB>) {
-        // TODO
-    }
 }

kernel/src/arch/x86_64/mod.rs

@@ -1,16 +1,26 @@
+pub mod memory;
 mod gdt;
 mod interrupts;
 mod logging;
-mod memory;
 
 pub use logging::log;
+pub use memory::PAGE_SIZE;
 
 use crate::allocator;
+use memory::MEMORY_MANAGER;
 use limine::{
     LimineHhdmRequest, LimineKernelFileRequest, LimineMemmapRequest, LimineModuleRequest,
 };
 use x86_64::VirtAddr;
 
+extern "C" {
+    fn _initial_kernel_heap_start();
+    fn _initial_kernel_heap_size();
+}
+
+const INITIAL_KERNEL_HEAP_START: *mut u8 = _initial_kernel_heap_start as _;
+const INITIAL_KERNEL_HEAP_SIZE: *const () = _initial_kernel_heap_size as _;
+
 #[no_mangle]
 unsafe extern "C" fn _kernel_start() -> ! {
     logging::init();
@@ -26,8 +36,10 @@ unsafe extern "C" fn _kernel_start() -> ! {
             .offset,
     ));
 
+    allocator::init(INITIAL_KERNEL_HEAP_START, INITIAL_KERNEL_HEAP_SIZE as _);
+
     static MMAP_REQ: LimineMemmapRequest = LimineMemmapRequest::new(0);
-    memory::init_falloc(
+    memory::initialize(
         MMAP_REQ
             .get_response()
             .get()
@@ -35,10 +47,25 @@ unsafe extern "C" fn _kernel_start() -> ! {
             .memmap(),
     );
 
-    allocator::init();
     gdt::init();
     interrupts::init();
 
+    {
+        let mut mm = MEMORY_MANAGER.get().unwrap().lock();
+        let alloc_0 = mm.allocate_pages(0).unwrap();
+        log::debug!("Addr: {alloc_0}");
+        let alloc_1 = mm.allocate_pages(0).unwrap();
+        log::debug!("Addr: {alloc_1}");
+        mm.deallocate_pages(alloc_0, 0);
+        let alloc_2 = mm.allocate_pages(1).unwrap();
+        log::debug!("Addr: {alloc_2}");
+        mm.deallocate_pages(alloc_1, 0);
+        mm.deallocate_pages(alloc_2, 1);
+        let alloc_3 = mm.allocate_pages(1).unwrap();
+        log::debug!("Addr: {alloc_3}");
+        mm.deallocate_pages(alloc_3, 1);
+    }
+
     static KFILE_REQ: LimineKernelFileRequest = LimineKernelFileRequest::new(0);
     static MOD_REQ: LimineModuleRequest = LimineModuleRequest::new(0);
     crate::kmain::kmain(

kernel/src/lib.rs

@@ -3,6 +3,7 @@
 #![feature(
     abi_x86_interrupt,
     alloc_error_handler,
+    inline_const,
     panic_info_message,
     pointer_is_aligned,
     prelude_import,
@@ -16,6 +17,7 @@ mod allocator;
 mod arch;
 mod kmain;
 mod logger;
+mod memory;
 mod task;
 
 use versioning::Version;
@@ -30,9 +32,9 @@ pub const VERSION: Version = Version {
 #[panic_handler]
 fn panic(info: &core::panic::PanicInfo) -> ! {
     // TODO: Better panic handler
-    let _ = crate::arch::log(format_args!(
+    // let _ = crate::arch::log(format_args!(
-        "\r\n\x1b[1m\x1b[4m\x1b[38;5;125mKernel Panic\x1b[0m\r\n",
+    //     "\r\n\x1b[1m\x1b[4m\x1b[38;5;125mKernel Panic\x1b[0m\r\n",
-    ));
+    // ));
 
     if let Some(loc) = info.location() {
         let _ = crate::arch::log(format_args!(

kernel/src/memory.rs

@@ -0,0 +1,231 @@
+//! The Memory Manager
+
+use alloc::collections::VecDeque;
+use derive_more::*;
+
+pub use crate::arch::PAGE_SIZE;
+pub const MAX_ORDER: usize = 10;
+
+#[repr(transparent)]
+#[derive(
+    Add,
+    AddAssign,
+    Binary,
+    BitAnd,
+    BitAndAssign,
+    BitOr,
+    BitOrAssign,
+    BitXor,
+    BitXorAssign,
+    Clone,
+    Constructor,
+    Copy,
+    Display,
+    Div,
+    DivAssign,
+    Eq,
+    From,
+    LowerHex,
+    Mul,
+    MulAssign,
+    Not,
+    Octal,
+    Ord,
+    PartialEq,
+    PartialOrd,
+    Rem,
+    RemAssign,
+    Shl,
+    ShlAssign,
+    Shr,
+    ShrAssign,
+    Sub,
+    SubAssign,
+    Sum,
+    UpperHex,
+)]
+#[display(fmt = "0x{:x}", _0)]
+#[from(forward)]
+pub struct VirtualAddress(usize);
+
+impl VirtualAddress {
+    #[cfg(target_arch = "riscv64")]
+    /// Returns an array of Virtual Page Numbers
+    // FIXME: SV48 and SV57 support
+    pub fn vpns(&self) -> [usize; 3] {
+        [
+            // [20:12]
+            (self.0 >> 12) & 0x1ff,
+            // [29:21]
+            (self.0 >> 21) & 0x1ff,
+            // [38:30]
+            (self.0 >> 30) & 0x1ff,
+        ]
+    }
+
+    pub fn as_addr(&self) -> usize {
+        self.0
+    }
+
+    pub fn as_ptr<T>(&self) -> *const T {
+        self.0 as _
+    }
+
+    pub fn as_mut_ptr<T>(&mut self) -> *mut T {
+        self.0 as _
+    }
+}
+
+#[repr(transparent)]
+#[derive(
+    Add,
+    AddAssign,
+    Binary,
+    BitAnd,
+    BitAndAssign,
+    BitOr,
+    BitOrAssign,
+    BitXor,
+    BitXorAssign,
+    Clone,
+    Constructor,
+    Copy,
+    Display,
+    Div,
+    DivAssign,
+    Eq,
+    From,
+    LowerHex,
+    Mul,
+    MulAssign,
+    Not,
+    Octal,
+    Ord,
+    PartialEq,
+    PartialOrd,
+    Rem,
+    RemAssign,
+    Shl,
+    ShlAssign,
+    Shr,
+    ShrAssign,
+    Sub,
+    SubAssign,
+    Sum,
+    UpperHex,
+)]
+#[display(fmt = "0x{:x}", _0)]
+#[from(forward)]
+pub struct PhysicalAddress(usize);
+
+impl PhysicalAddress {
+    #[cfg(target_arch = "riscv64")]
+    /// Returns an array of Physical Page Numbers
+    // FIXME: SV48 and SV57 support
+    pub fn ppns(&self) -> [usize; 3] {
+        [
+            // [20:12]
+            (self.0 >> 12) & 0x1ff,
+            // [29:21]
+            (self.0 >> 21) & 0x1ff,
+            // [55:30]
+            (self.0 >> 30) & 0x3ffffff,
+        ]
+    }
+
+    pub fn as_addr(&self) -> usize {
+        self.0
+    }
+
+    pub fn as_ptr<T>(&self) -> *const T {
+        self.0 as _
+    }
+
+    pub fn as_mut_ptr<T>(&self) -> *mut T {
+        self.0 as _
+    }
+}
+
+pub struct MemoryManager {
+    free_lists: [VecDeque<PhysicalAddress>; MAX_ORDER + 1],
+}
+
+impl MemoryManager {
+    pub const fn new() -> Self {
+        Self {
+            free_lists: [const { VecDeque::new() }; MAX_ORDER + 1],
+        }
+    }
+
+    // FIXME: this method should take a length and turn that into an order
+    pub fn allocate_pages(&mut self, order: usize) -> Option<PhysicalAddress> {
+        self.get_free_pages(order)
+    }
+
+    // FIXME: this method should take a length and turn that into an order
+    pub fn zallocate_pages(&mut self, order: usize) -> Option<PhysicalAddress> {
+        let alloc = self.allocate_pages(order)?;
+        unsafe {
+            alloc.as_mut_ptr::<u8>().write_bytes(0, PAGE_SIZE << order);
+        }
+        Some(alloc)
+    }
+
+    /// # Safety
+    /// This method assumes that `address` is in range of this allocator
+    // FIXME: this method should take a length and turn that into an order
+    pub unsafe fn deallocate_pages(&mut self, address: PhysicalAddress, order: usize) {
+        self.free_lists[order].push_front(address);
+        self.merge_buddies(order, address)
+    }
+
+    /// # Safety
+    /// This method assumes that the given address range,
+    ///     a) starts and ends at an address aligned to page boundaries,
+    ///     b) are valid free pages not already added,
+    ///     FIXME: c) starts and ends at an address aligned to `PAGE_SIZE << MAX_ORDER`
+    pub unsafe fn add_range(&mut self, start_addr: PhysicalAddress, page_count: usize) {
+        for i in 0..page_count / 1024 {
+            self.free_lists[MAX_ORDER].push_back(start_addr + (i * 1024 * PAGE_SIZE).into());
+        }
+    }
+
+    fn get_free_pages(&mut self, order: usize) -> Option<PhysicalAddress> {
+        // We can't get such a page!
+        if order > MAX_ORDER {
+            return None;
+        }
+
+        if self.free_lists[order].len() > 0 {
+            return self.free_lists[order].pop_front();
+        }
+
+        self.get_free_pages(order + 1).map(|addr| {
+            self.free_lists[order].push_front(addr ^ (PAGE_SIZE << order).into());
+            addr
+        })
+    }
+
+    fn merge_buddies(&mut self, order: usize, address: PhysicalAddress) {
+        // if we can't have any higher order blocks, we can't merge
+        if order > MAX_ORDER - 1 {
+            return;
+        }
+
+        let buddy_address = address ^ (PAGE_SIZE << order).into();
+        log::debug!("merge buddy: 0x{buddy_address:x}");
+        if let Some(buddy_index) = self.free_lists[order]
+            .iter()
+            .position(|blk| *blk == buddy_address)
+        {
+            self.free_lists[order].pop_front();
+            self.free_lists[order].remove(buddy_index);
+            let new_address = address.min(buddy_address);
+            log::debug!(
+                "Merging 0x{address:x} @ {order} with 0x{buddy_address:x} at 0x{new_address:x}"
+            );
+            self.free_lists[order + 1].push_front(new_address);
+            self.merge_buddies(order + 1, new_address)
+        }
+    }
+}

kernel/targets/riscv64-virt-ableos.json

@@ -0,0 +1,22 @@
+{
+    "arch": "riscv64",
+    "code-model": "medium",
+    "cpu": "generic-rv64",
+    "data-layout": "e-m:e-p:64:64-i64:64-i128:128-n32:64-S128",
+    "eh-frame-header": false,
+    "emit-debug-gdb-scripts": false,
+    "features": "+m,+a,+f,+d,+c",
+    "linker": "rust-lld",
+    "linker-flavor": "ld.lld",
+    "llvm-abiname": "lp64d",
+    "llvm-target": "riscv64",
+    "max-atomic-width": 64,
+    "panic-strategy": "abort",
+    "relocation-model": "static",
+    "target-pointer-width": "64",
+    "pre-link-args": {
+        "ld.lld": [
+            "--script=kernel/lds/riscv64-virt.ld"
+        ]
+    }
+}

repbuild/src/main.rs

@@ -8,19 +8,34 @@ fn main() -> Result<(), Error> {
     args.next();
 
     match args.next().as_deref() {
-        Some("build" | "b") => build(
+        Some("build" | "b") => {
-            args.next()
+            let mut release = false;
-                .map(|x| x == "-r" || x == "--release")
+            let mut target = Target::X86_64;
-                .unwrap_or_default(),
+            for arg in args {
-        )
+                if arg == "-r" || arg == "--release" {
-        .change_context(Error::Build),
+                    release = true;
+                }
+                if arg == "rv64" || arg == "riscv64" || arg == "riscv64-virt" {
+                    target = Target::Riscv64Virt;
+                }
+            }
+
+            build(release, target).change_context(Error::Build)
+        }
         Some("run" | "r") => {
-            build(
+            let mut release = false;
-                args.next()
+            let mut target = Target::X86_64;
-                    .map(|x| x == "-r" || x == "--release")
+            for arg in args {
-                    .unwrap_or_default(),
+                if arg == "-r" || arg == "--release" {
-            )?;
+                    release = true;
-            run()
+                }
+                if arg == "rv64" || arg == "riscv64" || arg == "riscv64-virt" {
+                    target = Target::Riscv64Virt;
+                }
+            }
+
+            build(release, target)?;
+            run(release, target)
         }
         Some("help" | "h") => {
             println!(concat!(
@@ -31,6 +46,7 @@ fn main() -> Result<(), Error> {
                 "    run (r): Build and run AbleOS in QEMU\n\n",
                 "Options for build and run:\n",
                 "        -r: build in release mode",
+                "  [target]: sets target"
             ),);
             Ok(())
         }
@@ -87,7 +103,7 @@ fn get_fs() -> Result<FileSystem<impl ReadWriteSeek>, io::Error> {
     Ok(fs)
 }
 
-fn build(release: bool) -> Result<(), Error> {
+fn build(release: bool, target: Target) -> Result<(), Error> {
     let fs = get_fs().change_context(Error::Io)?;
     let mut com = Command::new("cargo");
     com.current_dir("kernel");
@@ -96,12 +112,23 @@ fn build(release: bool) -> Result<(), Error> {
         com.arg("-r");
     }
 
+    match target {
+        Target::Riscv64Virt => {
+            com.args(["--target", "targets/riscv64-virt-ableos.json"]);
+        }
+        _ => {}
+    }
+
     match com.status() {
         Ok(s) if s.code() != Some(0) => bail!(Error::Build),
         Err(e) => bail!(report!(e).change_context(Error::Build)),
         _ => (),
     }
 
+    if target != Target::X86_64 {
+        return Ok(());
+    }
+
     (|| -> std::io::Result<_> {
         io::copy(
             &mut File::open(
@@ -117,9 +144,13 @@ fn build(release: bool) -> Result<(), Error> {
     .change_context(Error::Io)
 }
 
-fn run() -> Result<(), Error> {
+fn run(release: bool, target: Target) -> Result<(), Error> {
-    let mut com = Command::new("qemu-system-x86_64");
+    let mut com = match target {
+        Target::X86_64 => Command::new("qemu-system-x86_64"),
+        Target::Riscv64Virt => Command::new("qemu-system-riscv64"),
+    };
 
+    if target == Target::X86_64 {
         #[rustfmt::skip]
         com.args([
             "-bios",
@@ -136,6 +167,22 @@ fn run() -> Result<(), Error> {
         {
             com.args(["-enable-kvm", "-cpu", "host"]);
         }
+    }
+
+    if target == Target::Riscv64Virt {
+        #[rustfmt::skip]
+        com.args([
+            "-M", "virt",
+            "-m", "128M",
+            "-serial", "stdio",
+            "-kernel",
+            if release {
+                "target/riscv64-virt-ableos/release/kernel"
+            } else {
+                "target/riscv64-virt-ableos/debug/kernel"
+            }
+        ]);
+    }
 
     match com
         .status()
@@ -147,6 +194,12 @@ fn run() -> Result<(), Error> {
     }
 }
 
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum Target {
+    X86_64,
+    Riscv64Virt,
+}
+
 #[derive(Debug)]
 enum Error {
     Build,