New heap allocator!

Cargo.lock

@@ -373,7 +373,6 @@ version = "0.2.0"
 dependencies = [
  "crossbeam-queue",
  "limine",
- "linked_list_allocator",
  "log",
  "slab",
  "spin",
@@ -401,15 +400,6 @@ version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eac64618e505bab2387986e5b1014f5d344130d609685bbd8b71a10af3ee599d"
 
-[[package]]
-name = "linked_list_allocator"
-version = "0.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "549ce1740e46b291953c4340adcd74c59bcf4308f4cac050fd33ba91b7168f4a"
-dependencies = [
- "spinning_top",
-]
-
 [[package]]
 name = "lock_api"
 version = "0.4.7"
@@ -755,15 +745,6 @@ dependencies = [
  "lock_api",
 ]
 
-[[package]]
-name = "spinning_top"
-version = "0.2.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "75adad84ee84b521fb2cca2d4fd0f1dab1d8d026bda3c5bea4ca63b5f9f9293c"
-dependencies = [
- "lock_api",
-]
-
 [[package]]
 name = "static_assertions"
 version = "1.1.0"

kernel/Cargo.toml

@@ -4,7 +4,6 @@ name = "kernel"
 version = "0.2.0"
 
 [dependencies]
-linked_list_allocator = "0.9"
 slab = { version = "0.4", default-features = false }
 spin = "0.9"
 versioning = { git = "https://git.ablecorp.us/able/aos_userland" }

kernel/lds/x86_64.ld

@@ -26,15 +26,15 @@ SECTIONS
         *(.text .text.*)
     } :text
 
-    /* Move to the next memory page for .rodata */
+    /* Align .rodata to page boundary */
-    . += CONSTANT(MAXPAGESIZE);
+    . = ALIGN(4K);
 
     .rodata : {
         *(.rodata .rodata.*)
     } :rodata
 
-    /* Move to the next memory page for .data */
+    /* Align .data to page boundary */
-    . += CONSTANT(MAXPAGESIZE);
+    . = ALIGN(4K);
 
     .data : {
         *(.data .data.*)
@@ -43,5 +43,11 @@ SECTIONS
     .bss : {
         *(COMMON)
         *(.bss .bss.*)
+
+        /* Align initial kernel heap to page boundary */
+        . = ALIGN(4K);
+        PROVIDE(_initial_kernel_heap_start = .);
+        PROVIDE(_initial_kernel_heap_size = 1024 * 1024);
+        . += _initial_kernel_heap_size;
     } :data
 }

kernel/src/allocator.rs

@@ -1,16 +1,342 @@
 //! Memory allocator
+/*
+ * This file incorporates work covered by the following license notice:
+ *
+ *    Copyright (c) 2020, the SerenityOS developers.
+ *    All rights reserved.
+ *
+ *    Redistribution and use in source and binary forms, with or without
+ *    modification, are permitted provided that the following conditions are met:
+ *
+ *    1. Redistributions of source code must retain the above copyright notice, this
+ *       list of conditions and the following disclaimer.
+ *
+ *    2. Redistributions in binary form must reproduce the above copyright notice,
+ *       this list of conditions and the following disclaimer in the documentation
+ *       and/or other materials provided with the distribution.
+ *
+ *    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ *    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ *    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ *    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ *    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ *    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ *    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 
-///
+use core::{
-pub const HEAP_START: usize = 0x_4444_4444_0000;
+    alloc::{GlobalAlloc, Layout},
+    mem,
+    ptr::{self, NonNull},
+};
 
-///
+use spin::Mutex;
-pub const HEAP_MULTIPLIER: usize = 100000;
 
-///
+extern "C" {
-pub const HEAP_BASE: usize = 100;
+    fn _initial_kernel_heap_start();
+    fn _initial_kernel_heap_size();
+}
 
-///
+const INITIAL_KERNEL_HEAP_START: *mut u8 = _initial_kernel_heap_start as _;
-pub const HEAP_SIZE: usize = HEAP_BASE * HEAP_MULTIPLIER;
+const INITIAL_KERNEL_HEAP_SIZE: *const () = _initial_kernel_heap_size as _;
+
+struct Allocator(Mutex<Option<Heap>>);
+
+unsafe impl GlobalAlloc for Allocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut lock = self.0.lock();
+        let allocator = lock.as_mut().expect("heap allocator should be initialized");
+
+        match allocator.allocate(layout.size(), layout.align()) {
+            Some(ptr) => ptr.as_ptr(),
+            None => ptr::null_mut(),
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, _: Layout) {
+        let mut lock = self.0.lock();
+        let allocator = lock.as_mut().expect("heap allocator should be initialized");
+        allocator.deallocate(ptr);
+    }
+}
+
+#[global_allocator]
+static ALLOCATOR: Allocator = Allocator(Mutex::new(None));
+
+pub fn init() {
+    log::info!("Initialising kernel heap allocator");
+    let memory_size = unsafe { mem::transmute(INITIAL_KERNEL_HEAP_SIZE) };
+    *ALLOCATOR.0.lock() = Some(unsafe { Heap::new(INITIAL_KERNEL_HEAP_START, memory_size) });
+}
+
+// FIXME: these are arch-specific
+const CHUNK_SIZE: usize = 16;
+const MINIMUM_ALIGNMENT: usize = 8;
+
+struct Header {
+    size_in_chunks: usize,
+}
+
+// compile-time assertions to make sure that AllocationHeader's size is a power of two
+// and CHUNK_SIZE is bigger than AllocationHeader's size
+const _: () = {
+    assert!(mem::size_of::<Header>().is_power_of_two());
+    assert!(CHUNK_SIZE >= mem::size_of::<Header>());
+};
+
+/// A first-fit heap allocator, with CHUNK_SIZE chunks and a set size
+/// In the future these will become subheaps and the actual heap allocator will create more
+/// subheaps as needed
+struct Heap {
+    total_chunks: usize,
+    allocated_chunks: usize,
+    chunks: *mut u8,
+    bitmap: *mut u8,
+}
+
+impl Heap {
+    /// # Safety
+    /// This function assumes that the pointer given points at a valid memory address
+    unsafe fn new(memory: *mut u8, memory_size: usize) -> Self {
+        let total_chunks = Self::calculate_chunks(memory_size);
+        assert!(total_chunks * CHUNK_SIZE + (total_chunks + 7) / 8 <= memory_size);
+        Self {
+            total_chunks,
+            allocated_chunks: 0,
+            chunks: memory,
+            bitmap: unsafe { memory.add(total_chunks * CHUNK_SIZE) },
+        }
+    }
+
+    fn allocate(&mut self, size: usize, alignment: usize) -> Option<NonNull<u8>> {
+        assert!(alignment.is_power_of_two());
+        let alignment = if alignment < MINIMUM_ALIGNMENT {
+            MINIMUM_ALIGNMENT
+        } else {
+            alignment
+        };
+
+        // We need space for the header as well
+        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::info!("size: {size} chunks: {chunks_needed} align: {chunk_alignment}");
+
+        if chunks_needed + chunk_alignment > self.free_chunks() {
+            return None;
+        }
+
+        // FIXME: should utilize the alignment directly instead of trying to allocate `size + alignment`
+        let first_chunk = self.find_first_fit(chunks_needed + chunk_alignment)?;
+        let chunks_addr = self.chunks as usize;
+        let addr_unaligned = chunks_addr + first_chunk * CHUNK_SIZE;
+
+        // 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::info!(
+            "Addr unaligned: 0x{addr_unaligned:x} (offset: 0x{:x})",
+            addr_unaligned - chunks_addr
+        );
+        log::info!("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!(
+            aligned_first_chunk + chunks_needed <= first_chunk + chunks_needed + chunk_alignment
+        );
+
+        let header: *mut Header = unsafe { mem::transmute(addr) };
+        unsafe {
+            (*header).size_in_chunks = chunks_needed;
+        }
+
+        self.bitmap_set_range(aligned_first_chunk, chunks_needed, true);
+
+        self.allocated_chunks += chunks_needed;
+
+        let ptr: *mut u8 = unsafe { mem::transmute(header.add(1)) };
+        log::info!("{ptr:p}");
+        // FIXME: zero or scrub memory?
+        assert!(ptr.is_aligned_to(alignment));
+        NonNull::new(ptr)
+    }
+
+    fn deallocate(&mut self, ptr: *mut u8) {
+        let header = Self::allocation_header(ptr);
+        let start = (header as usize - self.chunks as usize) / CHUNK_SIZE;
+        assert!(self.bitmap_get(start));
+        let size = unsafe { (*header).size_in_chunks };
+        self.bitmap_set_range(start, size, false);
+        self.allocated_chunks -= size;
+        // FIXME: zero or scrub memory?
+    }
+
+    /// Finds first hole that can fit an allocation of `size` chunks, returns the start of the
+    /// found free chunks
+    fn find_first_fit(&self, size: usize) -> Option<usize> {
+        let mut start_of_free_chunks = 0;
+        let mut free_chunks = 0;
+        for i in 0..self.total_chunks / usize::BITS as usize {
+            if free_chunks >= size {
+                return Some(start_of_free_chunks);
+            }
+
+            let mut bucket = unsafe { *self.bitmap.cast::<usize>().add(i) };
+            if bucket == usize::MAX {
+                // Skip over completely full bucket
+                free_chunks = 0;
+                continue;
+            }
+            if bucket == 0 {
+                // Skip over completely empty bucket
+                if free_chunks == 0 {
+                    start_of_free_chunks = i * usize::BITS as usize;
+                }
+
+                free_chunks += usize::BITS as usize;
+                continue;
+            }
+
+            let mut viewed_bits = 0;
+            while viewed_bits < usize::BITS as usize {
+                if bucket == 0 {
+                    if free_chunks == 0 {
+                        start_of_free_chunks = i * usize::BITS as usize + viewed_bits;
+                    }
+
+                    free_chunks += usize::BITS as usize - viewed_bits;
+                    viewed_bits = usize::BITS as usize;
+                } else {
+                    let trailing_zeros = bucket.trailing_zeros() as usize;
+                    bucket >>= trailing_zeros;
+
+                    if free_chunks == 0 {
+                        start_of_free_chunks = i * usize::BITS as usize + viewed_bits;
+                    }
+
+                    free_chunks += trailing_zeros;
+                    viewed_bits += trailing_zeros;
+
+                    if free_chunks >= size {
+                        return Some(start_of_free_chunks);
+                    }
+
+                    let trailing_ones = bucket.trailing_ones() as usize;
+                    bucket >>= trailing_ones;
+                    viewed_bits += trailing_ones;
+                    free_chunks = 0;
+                }
+            }
+        }
+
+        if free_chunks >= size {
+            return Some(start_of_free_chunks);
+        }
+
+        let first_trailing_bit = (self.total_chunks / usize::BITS as usize) * usize::BITS as usize;
+        let trailing_bits = self.total_chunks % usize::BITS as usize;
+        for i in 0..trailing_bits {
+            if self.bitmap_get(first_trailing_bit + i) {
+                free_chunks = 0;
+                continue;
+            }
+
+            if free_chunks == 0 {
+                start_of_free_chunks = first_trailing_bit + i;
+            }
+
+            free_chunks += 1;
+            if free_chunks >= size {
+                return Some(start_of_free_chunks);
+            }
+        }
+
+        None
+    }
+
+    fn bitmap_set_range(&mut self, start: usize, length: usize, value: bool) {
+        assert!(start + length <= self.total_chunks);
+        if length == 0 {
+            return;
+        }
+
+        const BITMASK_FIRST_BYTE: [u8; 8] = [0xFF, 0xFE, 0xFC, 0xF8, 0xF0, 0xE0, 0xC0, 0x80];
+        const BITMASK_LAST_BYTE: [u8; 8] = [0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F];
+        let first = unsafe { self.bitmap.add(start / 8) };
+        let last = unsafe { self.bitmap.add((start + length) / 8) };
+        let mut byte_mask = BITMASK_FIRST_BYTE[start % 8];
+        if first == last {
+            byte_mask &= BITMASK_LAST_BYTE[(start + length) % 8];
+            if value {
+                unsafe {
+                    *first |= byte_mask;
+                }
+            } else {
+                unsafe {
+                    *first &= !byte_mask;
+                }
+            }
+        } else {
+            if value {
+                unsafe {
+                    *first |= byte_mask;
+                }
+            } else {
+                unsafe {
+                    *first &= !byte_mask;
+                }
+            }
+
+            byte_mask = BITMASK_LAST_BYTE[(start + length) % 8];
+            if value {
+                unsafe {
+                    *last |= byte_mask;
+                }
+            } else {
+                unsafe {
+                    *last &= !byte_mask;
+                }
+            }
+
+            let first = unsafe { first.add(1) };
+            if first >= last {
+                return;
+            }
+
+            if value {
+                unsafe {
+                    first.write_bytes(0xFF, last.sub_ptr(first));
+                }
+            } else {
+                unsafe {
+                    first.write_bytes(0, last.sub_ptr(first));
+                }
+            }
+        }
+    }
+
+    fn bitmap_get(&self, index: usize) -> bool {
+        assert!(index < self.total_chunks);
+        (unsafe { *self.bitmap.add(index / 8) } & (1 << (index % 8))) != 0
+    }
+
+    const fn free_chunks(&self) -> usize {
+        self.total_chunks - self.allocated_chunks
+    }
+
+    fn allocation_header(ptr: *mut u8) -> *mut Header {
+        unsafe { mem::transmute::<_, *mut Header>(ptr).sub(1) }
+    }
+
+    const fn calculate_chunks(memory_size: usize) -> usize {
+        memory_size / (CHUNK_SIZE + 1)
+    }
+}
+
+unsafe impl Send for Heap {}
 
 #[alloc_error_handler]
 fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {

kernel/src/arch/x86_64/allocator.rs

@@ -1,46 +0,0 @@
-use linked_list_allocator::LockedHeap;
-use x86_64::{
-    structures::paging::{
-        mapper::MapToError, FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB,
-    },
-    VirtAddr,
-};
-
-use crate::allocator::{HEAP_SIZE, HEAP_START};
-
-#[global_allocator]
-static ALLOCATOR: LockedHeap = LockedHeap::empty();
-
-pub unsafe fn init_alloc() -> Result<(), MapToError<Size4KiB>> {
-    log::info!("Initialising kernel heap allocator");
-    let page_range = Page::range_inclusive(
-        Page::containing_address(VirtAddr::new(HEAP_START as u64)),
-        Page::containing_address(VirtAddr::new(HEAP_START as u64) + HEAP_SIZE - 1u64),
-    );
-
-    let mut frame_allocator = super::memory::FRAME_ALLOC
-        .get()
-        .expect("frame allocator is not initialised")
-        .lock();
-
-    let mut mapper = super::memory::PAGE_TABLE
-        .get()
-        .expect("page table is not initialised")
-        .lock();
-
-    for page in page_range {
-        let frame = frame_allocator
-            .allocate_frame()
-            .ok_or(MapToError::FrameAllocationFailed)?;
-        let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
-        mapper
-            .map_to(page, frame, flags, &mut *frame_allocator)?
-            .flush();
-    }
-
-    ALLOCATOR
-        .lock()
-        .init(crate::allocator::HEAP_START, crate::allocator::HEAP_SIZE);
-
-    Ok(())
-}

kernel/src/arch/x86_64/mod.rs

@@ -3,7 +3,8 @@ use spin::Mutex;
 use uart_16550::SerialPort;
 use x86_64::VirtAddr;
 
-mod allocator;
+use crate::allocator;
+
 mod gdt;
 mod interrupts;
 mod memory;
@@ -37,7 +38,7 @@ unsafe extern "C" fn _kernel_start() -> ! {
             .expect("tried to get memory map from Limine"),
     );
 
-    allocator::init_alloc().expect("tried to initialise allocator");
+    allocator::init();
     gdt::init();
     interrupts::init();
 

kernel/src/lib.rs

@@ -4,7 +4,9 @@
     abi_x86_interrupt,
     alloc_error_handler,
     panic_info_message,
-    prelude_import
+    pointer_is_aligned,
+    prelude_import,
+    ptr_sub_ptr
 )]
 #![no_std]
 

repbuild/src/main.rs

@@ -108,7 +108,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                     let dbus_conn = zbus::blocking::Connection::system()?;
 
                     // Setup loop device
-                    let disk_img = File::options().read(true).write(true).open("./target/disk.img")?;
+                    let disk_img = File::options()
+                        .read(true)
+                        .write(true)
+                        .open("./target/disk.img")?;
                     let loopdev = udisks::manager::UDisks2ManagerProxyBlocking::new(&dbus_conn)?
                         .loop_setup(
                             disk_img.as_raw_fd().into(),
@@ -261,7 +264,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
                     // Setup loopback device for disk.img, with partitions
                     // FIXME: don't do ths if running without changes
                     // Setup loop device
-                    let disk_img = File::options().read(true).write(true).open("./target/disk.img")?;
+                    let disk_img = File::options()
+                        .read(true)
+                        .write(true)
+                        .open("./target/disk.img")?;
                     let dbus_conn = zbus::blocking::Connection::system()?;
                     let loopdev = udisks::manager::UDisks2ManagerProxyBlocking::new(&dbus_conn)?
                         .loop_setup(
@@ -339,7 +345,10 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
                     // Setup loopback device for disk.img, with partitions
                     // FIXME: don't do ths if running without changes
-                    let disk_img = File::options().read(true).write(true).open("./target/disk.img")?;
+                    let disk_img = File::options()
+                        .read(true)
+                        .write(true)
+                        .open("./target/disk.img")?;
                     let dbus_conn = zbus::blocking::Connection::system()?;
                     let loopdev = udisks::manager::UDisks2ManagerProxyBlocking::new(&dbus_conn)?
                         .loop_setup(