Inject a scalable buddy system allocator to OSTD

Co-authored-by: Zhe Tang <tangzh@stu.pku.edu.cn>

Cargo.lock

@@ -211,6 +211,7 @@ dependencies = [
  "libflate",
  "log",
  "lru",
+ "osdk-frame-allocator",
  "ostd",
  "paste",
  "rand",
@@ -1254,6 +1255,14 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08d65885ee38876c4f86fa503fb49d7b507c2b62552df7c70b2fce627e06381"
 
+[[package]]
+name = "osdk-frame-allocator"
+version = "0.1.0"
+dependencies = [
+ "log",
+ "ostd",
+]
+
 [[package]]
 name = "osdk-test-kernel"
 version = "0.11.3"

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 resolver = "2"
 members = [
+    "osdk/deps/frame-allocator",
     "osdk/deps/test-kernel",
     "ostd",
     "ostd/libs/align_ext",

Makefile

@@ -144,6 +144,7 @@ NON_OSDK_CRATES := \
 # In contrast, OSDK crates depend on OSTD (or being `ostd` itself)
 # and need to be built or tested with OSDK.
 OSDK_CRATES := \
+	osdk/deps/frame-allocator \
 	osdk/deps/test-kernel \
 	ostd \
 	ostd/libs/linux-bzimage/setup \

kernel/Cargo.toml

@@ -19,6 +19,7 @@ aster-virtio = { path = "comps/virtio" }
 aster-rights = { path = "libs/aster-rights" }
 component = { path = "libs/comp-sys/component" }
 controlled = { path = "libs/comp-sys/controlled" }
+osdk-frame-allocator = { path = "../osdk/deps/frame-allocator" }
 ostd = { path = "../ostd" }
 typeflags = { path = "libs/typeflags" }
 typeflags-util = { path = "libs/typeflags-util" }

kernel/src/fs/procfs/meminfo.rs

@@ -8,8 +8,6 @@
 
 use alloc::format;
 
-use ostd::mm::stat;
-
 use crate::{
     fs::{
         procfs::template::{FileOps, ProcFileBuilder},
@@ -27,21 +25,17 @@ impl MemInfoFileOps {
     }
 }
 
-/// Total memory in the entire system in bytes.
-fn mem_total() -> usize {
-    stat::mem_total()
-}
-
-/// An estimation of how much memory is available for starting new
-/// applications, without disk operations.
-fn mem_available() -> usize {
-    stat::mem_available()
-}
-
 impl FileOps for MemInfoFileOps {
     fn data(&self) -> Result<Vec<u8>> {
-        let total = mem_total() / 1024;
+        // The total amount of physical memory available to the system.
-        let available = mem_available() / 1024;
+        let total = crate::vm::mem_total();
+        // An estimation of how much memory is available for starting new
+        // applications, without disk operations.
+        let available = osdk_frame_allocator::load_total_free_size();
+
+        // Convert the values to KiB.
+        let total = total / 1024;
+        let available = available / 1024;
         let free = total - available;
         let output = format!(
             "MemTotal:\t{} kB\nMemFree:\t{} kB\nMemAvailable:\t{} kB\n",

kernel/src/syscall/sysinfo.rs

@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 
 use aster_time::read_monotonic_time;
-use ostd::mm::stat::{mem_available, mem_total};
 
 use super::SyscallReturn;
 use crate::prelude::*;
@@ -26,8 +25,8 @@ pub struct sysinfo {
 pub fn sys_sysinfo(sysinfo_addr: Vaddr, ctx: &Context) -> Result<SyscallReturn> {
     let info = sysinfo {
         uptime: read_monotonic_time().as_secs() as i64,
-        totalram: mem_total() as u64,
+        totalram: crate::vm::mem_total() as u64,
-        freeram: mem_available() as u64,
+        freeram: osdk_frame_allocator::load_total_free_size() as u64,
         ..Default::default() // TODO: add other system information
     };
     ctx.user_space().write_val(sysinfo_addr, &info)?;

kernel/src/vm/mod.rs

@@ -16,8 +16,27 @@
 //! In Asterinas, VMARs and VMOs, as well as other capabilities, are implemented
 //! as zero-cost capabilities.
 
+use osdk_frame_allocator::FrameAllocator;
+
 pub mod page_fault_handler;
 pub mod perms;
 pub mod util;
 pub mod vmar;
 pub mod vmo;
+
+#[ostd::global_frame_allocator]
+static FRAME_ALLOCATOR: FrameAllocator = FrameAllocator;
+
+/// Total physical memory in the entire system in bytes.
+pub fn mem_total() -> usize {
+    use ostd::boot::{boot_info, memory_region::MemoryRegionType};
+
+    let regions = &boot_info().memory_regions;
+    let total = regions
+        .iter()
+        .filter(|region| region.typ() == MemoryRegionType::Usable)
+        .map(|region| region.len())
+        .sum::<usize>();
+
+    total
+}

osdk/deps/frame-allocator/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "osdk-frame-allocator"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+log = "0.4"
+ostd = { version = "0.11.1", path = "../../../ostd" }
+
+[lints]
+workspace = true

osdk/deps/frame-allocator/src/allocator.rs

@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use core::{
+    alloc::Layout,
+    cell::RefCell,
+    ops::DerefMut,
+    sync::atomic::{AtomicUsize, Ordering},
+};
+
+use ostd::{
+    cpu::{all_cpus, PinCurrentCpu},
+    cpu_local,
+    mm::{frame::GlobalFrameAllocator, Paddr, PAGE_SIZE},
+    sync::{LocalIrqDisabled, SpinLock},
+    trap,
+};
+
+use crate::chunk::{size_of_order, BuddyOrder};
+
+use super::set::BuddySet;
+
+/// The global free buddies.
+static GLOBAL_POOL: SpinLock<BuddySet<MAX_BUDDY_ORDER>, LocalIrqDisabled> =
+    SpinLock::new(BuddySet::new_empty());
+static GLOBAL_POOL_SIZE: AtomicUsize = AtomicUsize::new(0);
+
+// CPU-local free buddies.
+cpu_local! {
+    static LOCAL_POOL: RefCell<BuddySet<MAX_LOCAL_BUDDY_ORDER>> = RefCell::new(BuddySet::new_empty());
+    static LOCAL_POOL_SIZE: AtomicUsize = AtomicUsize::new(0);
+}
+
+/// Maximum supported order of the buddy system.
+///
+/// i.e., it is the number of classes of free blocks. It determines the
+/// maximum size of each allocation.
+///
+/// A maximum buddy order of 32 supports up to 4KiB*2^31 = 8 TiB of chunks.
+const MAX_BUDDY_ORDER: BuddyOrder = 32;
+
+/// Maximum supported order of the buddy system for CPU-local buddy system.
+///
+/// Since large blocks are rarely allocated, caching such blocks will lead
+/// to much fragmentation.
+///
+/// Lock guards are also allocated on stack. We can limit the stack usage
+/// for common paths in this way.
+///
+/// A maximum local buddy order of 18 supports up to 4KiB*2^17 = 512 MiB of
+/// chunks.
+const MAX_LOCAL_BUDDY_ORDER: BuddyOrder = 18;
+
+/// The global frame allocator provided by OSDK.
+///
+/// It is a singleton that provides frame allocation for the kernel. If
+/// multiple instances of this struct are created, all the member functions
+/// will eventually access the same allocator.
+pub struct FrameAllocator;
+
+impl GlobalFrameAllocator for FrameAllocator {
+    fn alloc(&self, layout: Layout) -> Option<Paddr> {
+        let irq_guard = trap::disable_local();
+        let local_pool_cell = LOCAL_POOL.get_with(&irq_guard);
+        let mut local_pool = local_pool_cell.borrow_mut();
+
+        let size_order = greater_order_of(layout.size());
+        let align_order = greater_order_of(layout.align());
+
+        let order = size_order.max(align_order);
+        let mut chunk_addr = None;
+
+        if order < MAX_LOCAL_BUDDY_ORDER {
+            chunk_addr = local_pool.alloc_chunk(order);
+        }
+
+        // Fall back to the global free lists if the local free lists are empty.
+        if chunk_addr.is_none() {
+            chunk_addr = alloc_from_global_pool(order);
+        }
+        // TODO: On memory pressure the global pool may be not enough. We may need
+        // to merge all buddy chunks from the local pools to the global pool and
+        // try again.
+
+        // If the alignment order is larger than the size order, we need to split
+        // the chunk and return the rest part back to the free lists.
+        if align_order > size_order {
+            if let Some(chunk_addr) = chunk_addr {
+                let addr = chunk_addr + size_of_order(size_order);
+                let size = size_of_order(align_order) - size_of_order(size_order);
+                self.add_free_memory(addr, size);
+            }
+        } else {
+            balancing::balance(local_pool.deref_mut());
+        }
+
+        LOCAL_POOL_SIZE
+            .get_on_cpu(irq_guard.current_cpu())
+            .store(local_pool.total_size(), Ordering::Relaxed);
+
+        chunk_addr
+    }
+
+    fn add_free_memory(&self, mut addr: Paddr, mut size: usize) {
+        let irq_guard = trap::disable_local();
+        let local_pool_cell = LOCAL_POOL.get_with(&irq_guard);
+        let mut local_pool = local_pool_cell.borrow_mut();
+
+        // Split the range into chunks and return them to the local free lists
+        // respectively.
+        while size > 0 {
+            let next_chunk_order = max_order_from(addr).min(lesser_order_of(size));
+
+            if next_chunk_order >= MAX_LOCAL_BUDDY_ORDER {
+                dealloc_to_global_pool(addr, next_chunk_order);
+            } else {
+                local_pool.insert_chunk(addr, next_chunk_order);
+            }
+
+            size -= size_of_order(next_chunk_order);
+            addr += size_of_order(next_chunk_order);
+        }
+
+        balancing::balance(local_pool.deref_mut());
+        LOCAL_POOL_SIZE
+            .get_on_cpu(irq_guard.current_cpu())
+            .store(local_pool.total_size(), Ordering::Relaxed);
+    }
+}
+
+fn alloc_from_global_pool(order: BuddyOrder) -> Option<Paddr> {
+    let mut lock_guard = GLOBAL_POOL.lock();
+    let res = lock_guard.alloc_chunk(order);
+    GLOBAL_POOL_SIZE.store(lock_guard.total_size(), Ordering::Relaxed);
+    res
+}
+
+fn dealloc_to_global_pool(addr: Paddr, order: BuddyOrder) {
+    let mut lock_guard = GLOBAL_POOL.lock();
+    lock_guard.insert_chunk(addr, order);
+    GLOBAL_POOL_SIZE.store(lock_guard.total_size(), Ordering::Relaxed);
+}
+
+/// Loads the total size (in bytes) of free memory in the allocator.
+pub fn load_total_free_size() -> usize {
+    let mut total = 0;
+    total += GLOBAL_POOL_SIZE.load(Ordering::Relaxed);
+    for cpu in all_cpus() {
+        total += LOCAL_POOL_SIZE.get_on_cpu(cpu).load(Ordering::Relaxed);
+    }
+    total
+}
+
+/// Returns an order that covers at least the given size.
+fn greater_order_of(size: usize) -> BuddyOrder {
+    let size = size / PAGE_SIZE;
+    size.next_power_of_two().trailing_zeros() as BuddyOrder
+}
+
+/// Returns a order that covers at most the given size.
+fn lesser_order_of(size: usize) -> BuddyOrder {
+    let size = size / PAGE_SIZE;
+    (usize::BITS - size.leading_zeros() - 1) as BuddyOrder
+}
+
+/// Returns the maximum order starting from the address.
+///
+/// If the start address is not aligned to the order, the address/order pair
+/// cannot form a buddy chunk.
+///
+/// # Panics
+///
+/// Panics if the address is not page-aligned in debug mode.
+fn max_order_from(addr: Paddr) -> BuddyOrder {
+    (addr.trailing_zeros() - PAGE_SIZE.trailing_zeros()) as BuddyOrder
+}
+
+pub mod balancing {
+    //! Controlling the balancing between CPU-local free pools and the global free pool.
+
+    use core::sync::atomic::Ordering;
+
+    use ostd::cpu::num_cpus;
+
+    use super::{
+        lesser_order_of, BuddyOrder, BuddySet, GLOBAL_POOL, GLOBAL_POOL_SIZE, MAX_LOCAL_BUDDY_ORDER,
+    };
+
+    use crate::chunk::size_of_order;
+
+    /// Controls the expected size of cache for each CPU-local free pool.
+    ///
+    /// The expected size will be the size of `GLOBAL_POOL` divided by the number
+    /// of the CPUs, and then divided by this constant.
+    const CACHE_EXPECTED_PORTION: usize = 2;
+
+    /// Returns the expected size of cache for each CPU-local free pool.
+    ///
+    /// It depends on the size of the global free pool.
+    fn cache_expected_size(global_size: usize) -> usize {
+        global_size / num_cpus() / CACHE_EXPECTED_PORTION
+    }
+
+    /// Controls the minimal size of cache for each CPU-local free pool.
+    ///
+    /// The minimal will be the expected size divided by this constant.
+    const CACHE_MINIMAL_PORTION: usize = 8;
+
+    /// Returns the minimal size of cache for each CPU-local free pool.
+    ///
+    /// It depends on the size of the global free pool.
+    fn cache_minimal_size(global_size: usize) -> usize {
+        cache_expected_size(global_size) / CACHE_MINIMAL_PORTION
+    }
+
+    /// Controls the maximal size of cache for each CPU-local free pool.
+    ///
+    /// The maximal will be the expected size multiplied by this constant.
+    const CACHE_MAXIMAL_MULTIPLIER: usize = 2;
+
+    /// Returns the maximal size of cache for each CPU-local free pool.
+    ///
+    /// It depends on the size of the global free pool.
+    fn cache_maximal_size(global_size: usize) -> usize {
+        cache_expected_size(global_size) * CACHE_MAXIMAL_MULTIPLIER
+    }
+
+    /// Balances a local cache and the global free pool.
+    pub fn balance(local: &mut BuddySet<MAX_LOCAL_BUDDY_ORDER>) {
+        let global_size = GLOBAL_POOL_SIZE.load(Ordering::Relaxed);
+
+        let minimal_local_size = cache_minimal_size(global_size);
+        let expected_local_size = cache_expected_size(global_size);
+        let maximal_local_size = cache_maximal_size(global_size);
+
+        let local_size = local.total_size();
+
+        if local_size >= maximal_local_size {
+            // Move local frames to the global pool.
+            if local_size == 0 {
+                return;
+            }
+
+            let expected_removal = local_size - expected_local_size;
+            let lesser_order = lesser_order_of(expected_removal);
+            let mut global_pool_lock = GLOBAL_POOL.lock();
+
+            balance_to(local, &mut *global_pool_lock, lesser_order);
+
+            GLOBAL_POOL_SIZE.store(global_pool_lock.total_size(), Ordering::Relaxed);
+        } else if local_size < minimal_local_size {
+            // Move global frames to the local pool.
+            if global_size == 0 {
+                return;
+            }
+
+            let expected_allocation = expected_local_size - local_size;
+            let lesser_order = lesser_order_of(expected_allocation);
+            let mut global_pool_lock = GLOBAL_POOL.lock();
+
+            balance_to(&mut *global_pool_lock, local, lesser_order);
+
+            GLOBAL_POOL_SIZE.store(global_pool_lock.total_size(), Ordering::Relaxed);
+        }
+    }
+
+    /// Balances from `a` to `b`.
+    fn balance_to<const MAX_ORDER1: BuddyOrder, const MAX_ORDER2: BuddyOrder>(
+        a: &mut BuddySet<MAX_ORDER1>,
+        b: &mut BuddySet<MAX_ORDER2>,
+        order: BuddyOrder,
+    ) {
+        let allocated_from_a = a.alloc_chunk(order);
+
+        if let Some(addr) = allocated_from_a {
+            if order >= MAX_ORDER2 {
+                let inserted_order = MAX_ORDER2 - 1;
+                for i in 0..(1 << (order - inserted_order)) as usize {
+                    let split_addr = addr + size_of_order(inserted_order) * i;
+                    b.insert_chunk(split_addr, inserted_order);
+                }
+            } else {
+                b.insert_chunk(addr, order);
+            }
+        } else {
+            // Maybe the chunk size is too large.
+            // Try to reduce the order and balance again.
+            if order > 1 {
+                balance_to(a, b, order - 1);
+                balance_to(a, b, order - 1);
+            }
+        }
+    }
+}

osdk/deps/frame-allocator/src/chunk.rs

@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use ostd::{
+    impl_frame_meta_for,
+    mm::{frame::linked_list::Link, Paddr, UniqueFrame, PAGE_SIZE},
+};
+
+/// The order of a buddy chunk.
+///
+/// The size of a buddy chunk is `(1 << order) * PAGE_SIZE`.
+pub(crate) type BuddyOrder = usize;
+
+/// Returns the size of a buddy chunk of the given order.
+pub(crate) const fn size_of_order(order: BuddyOrder) -> usize {
+    (1 << order) * PAGE_SIZE
+}
+
+/// The metadata of the head frame in a free buddy chunk.
+#[derive(Debug)]
+pub(crate) struct FreeHeadMeta {
+    /// The order of the buddy chunk.
+    order: BuddyOrder,
+}
+
+impl_frame_meta_for!(FreeHeadMeta);
+
+impl FreeHeadMeta {
+    /// Returns the order of the buddy chunk.
+    pub(crate) fn order(&self) -> BuddyOrder {
+        self.order
+    }
+}
+
+/// A free buddy chunk.
+#[derive(Debug)]
+pub(crate) struct FreeChunk {
+    head: UniqueFrame<Link<FreeHeadMeta>>,
+}
+
+impl FreeChunk {
+    /// Gets a buddy chunk from the head frame.
+    ///
+    /// The caller must ensure that the head frame should be uniquely free.
+    /// Otherwise it waits indefinitely.
+    ///
+    /// We need a unique ownership of this chunk. Other threads may be
+    /// deallocating it's buddy and inspecting this chunk (see
+    /// [`Self::buddy`]). So we may spuriously fail to acquire it. But
+    /// they will soon release it so we can acquire it ultimately.
+    pub(crate) fn from_free_head(head: UniqueFrame<Link<FreeHeadMeta>>) -> FreeChunk {
+        FreeChunk { head }
+    }
+
+    /// Gets a buddy chunk from unused frames.
+    ///
+    /// # Panics
+    ///
+    /// Panics if:
+    ///  - the range is not actually unused;
+    ///  - the address is not aligned to the order.
+    pub(crate) fn from_unused(addr: Paddr, order: BuddyOrder) -> FreeChunk {
+        assert!(addr % size_of_order(order) == 0);
+
+        let head = UniqueFrame::from_unused(addr, Link::new(FreeHeadMeta { order }))
+            .expect("The head frame is not unused");
+
+        #[cfg(debug_assertions)]
+        {
+            use ostd::mm::{
+                frame::meta::{AnyFrameMeta, GetFrameError},
+                Frame,
+            };
+
+            let end = addr + size_of_order(order);
+            for paddr in (addr + PAGE_SIZE..end).step_by(PAGE_SIZE) {
+                let Err(GetFrameError::Unused) = Frame::<dyn AnyFrameMeta>::from_in_use(paddr)
+                else {
+                    panic!("The range is not actually unused");
+                };
+            }
+        }
+
+        FreeChunk { head }
+    }
+
+    /// Turns the free chunk into a pointer to the head frame.
+    pub(crate) fn into_unique_head(self) -> UniqueFrame<Link<FreeHeadMeta>> {
+        self.head
+    }
+
+    /// Returns the order of the buddy chunk.
+    pub(crate) fn order(&self) -> BuddyOrder {
+        self.head.meta().order()
+    }
+
+    /// Returns the address of the buddy chunk.
+    pub(crate) fn addr(&self) -> Paddr {
+        self.head.start_paddr()
+    }
+
+    /// Gets the address of the buddy of this chunk.
+    pub(crate) fn buddy(&self) -> Paddr {
+        let addr = self.addr();
+        let order = self.order();
+        addr ^ size_of_order(order)
+    }
+
+    /// Splits the buddy chunk into two smaller buddies.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the buddy chunk is not uniquely free.
+    pub(crate) fn split_free(self) -> (FreeChunk, FreeChunk) {
+        let order = self.order();
+        let addr = self.addr();
+        let new_order = order - 1;
+        let left_child_addr = addr;
+        let right_child_addr = addr ^ size_of_order(new_order);
+
+        let mut unique_head = self.into_unique_head();
+        debug_assert_eq!(unique_head.start_paddr(), left_child_addr);
+        unique_head.meta_mut().order = new_order;
+
+        let left_child = FreeChunk { head: unique_head };
+        let right_child = FreeChunk {
+            head: UniqueFrame::from_unused(
+                right_child_addr,
+                Link::new(FreeHeadMeta { order: new_order }),
+            )
+            .expect("Tail frames are not unused"),
+        };
+        (left_child, right_child)
+    }
+
+    /// Merges the buddy chunk with the sibling buddy.
+    ///
+    /// # Panics
+    ///
+    /// Panics if either the buddy chunks are not free or not buddies.
+    pub(crate) fn merge_free(mut self, mut buddy: FreeChunk) -> FreeChunk {
+        if self.addr() > buddy.addr() {
+            core::mem::swap(&mut self, &mut buddy);
+        }
+
+        let order = self.order();
+        let addr = self.addr();
+        let buddy_order = buddy.order();
+        let buddy_addr = buddy.addr();
+
+        buddy.into_unique_head().reset_as_unused(); // This will "drop" the frame without up-calling us.
+
+        assert_eq!(order, buddy_order);
+        assert_eq!(addr ^ size_of_order(order), buddy_addr);
+        let new_order = order + 1;
+        let mut unique_head = self.into_unique_head();
+        unique_head.meta_mut().order = new_order;
+        FreeChunk { head: unique_head }
+    }
+}
+
+#[cfg(ktest)]
+mod test {
+    use super::*;
+    use crate::test::MockMemoryRegion;
+    use ostd::prelude::ktest;
+
+    #[ktest]
+    fn test_free_chunk_ops() {
+        let order = 3;
+        let size = size_of_order(order);
+        let region = MockMemoryRegion::alloc(size);
+        let addr1 = region.start_paddr();
+        let addr2 = addr1 + size_of_order(order - 2);
+        let addr3 = addr1 + size_of_order(order - 2) * 2;
+
+        let chunk = FreeChunk::from_unused(addr1, order);
+        assert_eq!(chunk.order(), order);
+        assert_eq!(chunk.addr(), addr1);
+        assert_eq!(chunk.buddy(), addr1 ^ size);
+
+        let (left, right) = chunk.split_free();
+
+        assert_eq!(left.order(), order - 1);
+        assert_eq!(left.addr(), addr1);
+        assert_eq!(left.buddy(), addr3);
+
+        assert_eq!(right.order(), order - 1);
+        assert_eq!(right.addr(), addr3);
+        assert_eq!(right.buddy(), addr1);
+
+        let (r1, r2) = left.split_free();
+
+        assert_eq!(r1.order(), order - 2);
+        assert_eq!(r1.addr(), addr1);
+        assert_eq!(r1.buddy(), addr2);
+
+        assert_eq!(r2.order(), order - 2);
+        assert_eq!(r2.addr(), addr2);
+        assert_eq!(r2.buddy(), addr1);
+
+        let left = r1.merge_free(r2);
+        let chunk = left.merge_free(right);
+        assert_eq!(chunk.order(), order);
+        assert_eq!(chunk.addr(), addr1);
+
+        chunk.into_unique_head().reset_as_unused();
+    }
+}

osdk/deps/frame-allocator/src/lib.rs

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: MPL-2.0
+
+#![no_std]
+#![deny(unsafe_code)]
+
+//! An implementation of the global physical memory frame allocator for
+//! [OSTD](https://crates.io/crates/ostd) based kernels.
+//!
+//! # Background
+//!
+//! `OSTD` has provided a page allocator interface, namely [`GlobalFrameAllocator`]
+//! and [`global_frame_allocator`] procedure macro, allowing users to plug in
+//! their own frame allocator into the kernel safely. You can refer to the
+//! [`ostd::mm::frame::allocator`] module for detailed introduction.
+//!
+//! # Introduction
+//!
+//! This crate is an implementation of a scalable and efficient global frame
+//! allocator based on the buddy system. It is by default shipped with OSDK
+//! for users that don't have special requirements on the frame allocator.
+//!
+//! [`GlobalFrameAllocator`]: ostd::mm::GlobalFrameAllocator
+//! [`global_frame_allocator`]: ostd::global_frame_allocator
+
+mod allocator;
+mod chunk;
+mod set;
+
+#[cfg(ktest)]
+mod test;
+
+pub use allocator::{load_total_free_size, FrameAllocator};

osdk/deps/frame-allocator/src/set.rs

@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use ostd::mm::{frame::linked_list::LinkedList, Paddr};
+
+use crate::chunk::{size_of_order, BuddyOrder, FreeChunk, FreeHeadMeta};
+
+/// A set of free buddy chunks.
+pub(crate) struct BuddySet<const MAX_ORDER: BuddyOrder> {
+    /// The sum of the sizes of all free chunks.
+    total_size: usize,
+    /// The lists of free buddy chunks for each orders.
+    lists: [LinkedList<FreeHeadMeta>; MAX_ORDER],
+}
+
+impl<const MAX_ORDER: BuddyOrder> BuddySet<MAX_ORDER> {
+    /// Creates a new empty set of free lists.
+    pub(crate) const fn new_empty() -> Self {
+        Self {
+            total_size: 0,
+            lists: [const { LinkedList::new() }; MAX_ORDER],
+        }
+    }
+
+    /// Gets the total size of free chunks.
+    pub(crate) fn total_size(&self) -> usize {
+        self.total_size
+    }
+
+    /// Inserts a free chunk into the set.
+    pub(crate) fn insert_chunk(&mut self, addr: Paddr, order: BuddyOrder) {
+        debug_assert!(order < MAX_ORDER);
+
+        let inserted_size = size_of_order(order);
+        let mut chunk = FreeChunk::from_unused(addr, order);
+
+        let order = chunk.order();
+        // Coalesce the chunk with its buddy whenever possible.
+        for (i, list) in self.lists.iter_mut().enumerate().skip(order) {
+            if i + 1 >= MAX_ORDER {
+                // The chunk is already the largest one.
+                break;
+            }
+            let buddy_addr = chunk.buddy();
+            let Some(mut cursor) = list.cursor_mut_at(buddy_addr) else {
+                // The buddy is not in this free list, so we can't coalesce.
+                break;
+            };
+            let taken = cursor.take_current().unwrap();
+            debug_assert_eq!(buddy_addr, taken.start_paddr());
+            chunk = chunk.merge_free(FreeChunk::from_free_head(taken));
+        }
+        // Insert the coalesced chunk into the free lists.
+        let order = chunk.order();
+        self.lists[order].push_front(chunk.into_unique_head());
+
+        self.total_size += inserted_size;
+    }
+
+    /// Allocates a chunk from the set.
+    ///
+    /// The function will choose and remove a buddy chunk of the given order
+    /// from the set. The address of the chunk will be returned.
+    pub(crate) fn alloc_chunk(&mut self, order: BuddyOrder) -> Option<Paddr> {
+        // Find the first non-empty size class larger than the requested order.
+        let mut non_empty = None;
+        for (i, list) in self.lists.iter_mut().enumerate().skip(order) {
+            if !list.is_empty() {
+                non_empty = Some(i);
+                break;
+            }
+        }
+        let non_empty = non_empty?;
+        let mut chunk = {
+            let head = self.lists[non_empty].pop_front().unwrap();
+            debug_assert_eq!(head.meta().order(), non_empty as BuddyOrder);
+
+            Some(FreeChunk::from_free_head(head))
+        };
+
+        // Split the chunk.
+        for i in (order + 1..=non_empty).rev() {
+            let (left_sub, right_sub) = chunk.take().unwrap().split_free();
+            // Push the right sub-chunk back to the free lists.
+            let right_sub = right_sub.into_unique_head();
+            debug_assert_eq!(right_sub.meta().order(), (i - 1) as BuddyOrder);
+            self.lists[i - 1].push_front(right_sub);
+            // Pass the left sub-chunk to the next iteration.
+            chunk = Some(left_sub);
+        }
+
+        let allocated_size = size_of_order(order);
+
+        self.total_size -= allocated_size;
+
+        // The remaining chunk is the one we want.
+        let head_frame = chunk.take().unwrap().into_unique_head();
+        let paddr = head_frame.start_paddr();
+        head_frame.reset_as_unused(); // It will "drop" the frame without up-calling us.
+        Some(paddr)
+    }
+}
+
+#[cfg(ktest)]
+mod test {
+    use super::*;
+    use crate::test::MockMemoryRegion;
+    use ostd::prelude::ktest;
+
+    #[ktest]
+    fn test_buddy_set_insert_alloc() {
+        let region_order = 4;
+        let region_size = size_of_order(region_order);
+        let region = MockMemoryRegion::alloc(region_size);
+        let region_start = region.start_paddr();
+
+        let mut set = BuddySet::<5>::new_empty();
+        set.insert_chunk(region_start, region_order);
+        assert!(set.total_size() == region_size);
+
+        // Allocating chunks of orders of 0, 0, 1, 2, 3 should be okay.
+        let chunk1 = set.alloc_chunk(0).unwrap();
+        assert!(set.total_size() == region_size - size_of_order(0));
+        let chunk2 = set.alloc_chunk(0).unwrap();
+        assert!(set.total_size() == region_size - size_of_order(1));
+        let chunk3 = set.alloc_chunk(1).unwrap();
+        assert!(set.total_size() == region_size - size_of_order(2));
+        let chunk4 = set.alloc_chunk(2).unwrap();
+        assert!(set.total_size() == region_size - size_of_order(3));
+        let chunk5 = set.alloc_chunk(3).unwrap();
+        assert!(set.total_size() == 0);
+
+        // Putting them back should enable us to allocate the original region.
+        set.insert_chunk(chunk3, 1);
+        assert!(set.total_size() == size_of_order(1));
+        set.insert_chunk(chunk1, 0);
+        assert!(set.total_size() == size_of_order(0) + size_of_order(1));
+        set.insert_chunk(chunk5, 3);
+        assert!(set.total_size() == size_of_order(0) + size_of_order(1) + size_of_order(3));
+        set.insert_chunk(chunk2, 0);
+        assert!(set.total_size() == size_of_order(2) + size_of_order(3));
+        set.insert_chunk(chunk4, 2);
+        assert!(set.total_size() == size_of_order(4));
+
+        let chunk = set.alloc_chunk(region_order).unwrap();
+        assert!(chunk == region_start);
+        assert!(set.total_size() == 0);
+    }
+}

osdk/deps/frame-allocator/src/test.rs

@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! Providing test utilities and high-level test cases for the frame allocator.
+
+use core::alloc::Layout;
+
+use ostd::{
+    mm::{frame::GlobalFrameAllocator, FrameAllocOptions, Paddr, Segment, UniqueFrame, PAGE_SIZE},
+    prelude::ktest,
+};
+
+use super::FrameAllocator;
+
+#[ktest]
+fn frame_allocator_alloc_layout_match() {
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 2, PAGE_SIZE).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 3, PAGE_SIZE).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 4, PAGE_SIZE).unwrap());
+
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 2, PAGE_SIZE * 2).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 4, PAGE_SIZE * 4).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 8, PAGE_SIZE * 8).unwrap());
+    assert_allocation_well_formed(Layout::from_size_align(PAGE_SIZE * 16, PAGE_SIZE * 16).unwrap());
+}
+
+#[track_caller]
+fn assert_allocation_well_formed(layout: Layout) {
+    let instance = FrameAllocator;
+
+    let allocated = instance.alloc(layout).unwrap();
+    assert_eq!(
+        allocated % layout.align(),
+        0,
+        "Allocation alignment mismatch"
+    );
+
+    for offset in (0..layout.size()).step_by(PAGE_SIZE) {
+        let frame = allocated + offset;
+        let frame = UniqueFrame::from_unused(frame, ()).unwrap_or_else(|e| {
+            panic!(
+                "Metadata not well-formed after allocation at offset {:#x}: {:#?}",
+                offset, e
+            )
+        });
+        frame.reset_as_unused();
+    }
+
+    instance.add_free_memory(allocated, layout.size());
+}
+
+/// A mocked memory region for testing.
+///
+/// All the frames in the returned memory region will be marked as used.
+/// When the region is dropped, all the frames will be returned to the global
+/// frame allocator. If any frame is not unused by that time, the drop will panic.
+pub(crate) struct MockMemoryRegion {
+    addr: Paddr,
+    size: usize,
+}
+
+impl MockMemoryRegion {
+    /// Gets a memory region for testing.
+    pub(crate) fn alloc(size: usize) -> Self {
+        let seg = FrameAllocOptions::new()
+            .alloc_segment(size / PAGE_SIZE)
+            .unwrap();
+        let addr = seg.start_paddr();
+        for frame in seg {
+            UniqueFrame::try_from(frame).unwrap().reset_as_unused();
+        }
+        Self { addr, size }
+    }
+
+    /// Gets the start address of the memory region.
+    pub(crate) fn start_paddr(&self) -> Paddr {
+        self.addr
+    }
+}
+
+impl Drop for MockMemoryRegion {
+    fn drop(&mut self) {
+        let seg = Segment::from_unused(self.addr..self.addr + self.size, |_| ()).unwrap();
+        drop(seg);
+    }
+}

osdk/src/base_crate/main.rs.template

@@ -1,6 +1,8 @@
 #![no_std]
 #![no_main]
 
+#![feature(linkage)]
+
 extern crate #TARGET_NAME#;
 
 #[panic_handler]
@@ -10,3 +12,12 @@ fn panic(info: &core::panic::PanicInfo) -> ! {
     }
     unsafe { __ostd_panic_handler(info); }
 }
+
+use ostd::mm::frame::GlobalFrameAllocator;
+
+use osdk_frame_allocator::FrameAllocator;
+static FRAME_ALLOCATOR: FrameAllocator = FrameAllocator;
+
+#[no_mangle]
+#[linkage = "weak"]
+static __GLOBAL_FRAME_ALLOCATOR_REF: &'static dyn GlobalFrameAllocator = &FRAME_ALLOCATOR;

osdk/src/base_crate/mod.rs

@@ -57,8 +57,8 @@ pub enum BaseCrateType {
 /// Create a new base crate that will be built by cargo.
 ///
 /// The dependencies of the base crate will be the target crate. If
-/// `link_unit_test_runner` is set to true, the base crate will also depend on
+/// `link_unit_test_kernel` is set to true, the base crate will also depend on
-/// the `ostd-test-runner` crate.
+/// the `ostd-test-kernel` crate.
 ///
 /// It returns the path to the base crate.
 pub fn new_base_crate(
@@ -66,7 +66,7 @@ pub fn new_base_crate(
     base_crate_path_stem: impl AsRef<Path>,
     dep_crate_name: &str,
     dep_crate_path: impl AsRef<Path>,
-    link_unit_test_runner: bool,
+    link_unit_test_kernel: bool,
 ) -> PathBuf {
     let base_crate_path: PathBuf = PathBuf::from(
         (base_crate_path_stem.as_ref().as_os_str().to_string_lossy()
@@ -85,7 +85,7 @@ pub fn new_base_crate(
             &base_crate_tmp_path,
             dep_crate_name,
             &dep_crate_path,
-            link_unit_test_runner,
+            link_unit_test_kernel,
         );
         let cargo_result = are_files_identical(
             &base_crate_path.join("Cargo.toml"),
@@ -105,7 +105,7 @@ pub fn new_base_crate(
         &base_crate_path,
         dep_crate_name,
         dep_crate_path,
-        link_unit_test_runner,
+        link_unit_test_kernel,
     );
 
     base_crate_path
@@ -115,7 +115,7 @@ fn do_new_base_crate(
     base_crate_path: impl AsRef<Path>,
     dep_crate_name: &str,
     dep_crate_path: impl AsRef<Path>,
-    link_unit_test_runner: bool,
+    link_unit_test_kernel: bool,
 ) {
     let workspace_root = {
         let meta = get_cargo_metadata(None::<&str>, None::<&[&str]>).unwrap();
@@ -182,7 +182,7 @@ fn do_new_base_crate(
     fs::write("src/main.rs", main_rs).unwrap();
 
     // Add dependencies to the Cargo.toml
-    add_manifest_dependency(dep_crate_name, dep_crate_path, link_unit_test_runner);
+    add_manifest_dependency(dep_crate_name, dep_crate_path, link_unit_test_kernel);
 
     // Copy the manifest configurations from the target crate to the base crate
     copy_profile_configurations(workspace_root);
@@ -197,7 +197,7 @@ fn do_new_base_crate(
 fn add_manifest_dependency(
     crate_name: &str,
     crate_path: impl AsRef<Path>,
-    link_unit_test_runner: bool,
+    link_unit_test_kernel: bool,
 ) {
     let manifest_path = "Cargo.toml";
 
@@ -224,31 +224,47 @@ fn add_manifest_dependency(
     .unwrap();
     dependencies.as_table_mut().unwrap().extend(target_dep);
 
-    if link_unit_test_runner {
+    if link_unit_test_kernel {
-        let dep_str = match option_env!("OSDK_LOCAL_DEV") {
+        add_manifest_dependency_to(
-            Some("1") => {
+            dependencies,
-                let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+            "osdk-test-kernel",
-                let test_kernel_dir = crate_dir.join("deps").join("test-kernel");
+            Path::new("deps").join("test-kernel"),
-                format!(
+        );
-                    "osdk-test-kernel = {{ path = \"{}\" }}",
-                    test_kernel_dir.display()
-                )
-            }
-            _ => concat!(
-                "osdk-test-kernel = { version = \"",
-                env!("CARGO_PKG_VERSION"),
-                "\" }"
-            )
-            .to_owned(),
-        };
-        let test_runner_dep = toml::Table::from_str(&dep_str).unwrap();
-        dependencies.as_table_mut().unwrap().extend(test_runner_dep);
     }
 
+    add_manifest_dependency_to(
+        dependencies,
+        "osdk-frame-allocator",
+        Path::new("deps").join("frame-allocator"),
+    );
+
+    add_manifest_dependency_to(dependencies, "ostd", Path::new("..").join("ostd"));
+
     let content = toml::to_string(&manifest).unwrap();
     fs::write(manifest_path, content).unwrap();
 }
 
+fn add_manifest_dependency_to(manifest: &mut toml::Value, dep_name: &str, path: PathBuf) {
+    let dep_str = match option_env!("OSDK_LOCAL_DEV") {
+        Some("1") => {
+            let crate_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+            let dep_crate_dir = crate_dir.join(path);
+            format!(
+                "{} = {{ path = \"{}\" }}",
+                dep_name,
+                dep_crate_dir.display()
+            )
+        }
+        _ => format!(
+            "{} = {{ version = \"{}\" }}",
+            dep_name,
+            env!("CARGO_PKG_VERSION"),
+        ),
+    };
+    let dep_val = toml::Table::from_str(&dep_str).unwrap();
+    manifest.as_table_mut().unwrap().extend(dep_val);
+}
+
 fn copy_profile_configurations(workspace_root: impl AsRef<Path>) {
     let target_manifest_path = workspace_root.as_ref().join("Cargo.toml");
     let manifest_path = "Cargo.toml";

ostd/libs/ostd-macros/src/lib.rs

@@ -65,6 +65,43 @@ pub fn test_main(_attr: TokenStream, item: TokenStream) -> TokenStream {
     .into()
 }
 
+/// A macro attribute for the global frame allocator.
+///
+/// The attributed static variable will be used to provide frame allocation
+/// for the kernel. The variable should have type `ostd::mm::GlobalFrameAllocator`.
+///
+/// # Example
+///
+/// ```ignore
+/// use ostd::{mm::{frame::GlobalFrameAllocator, Paddr}, global_frame_allocator};
+///
+/// // Of course it won't work because all allocations will fail.
+/// // It's just an example.
+/// #[global_frame_allocator]
+/// static ALLOCATOR: MyFrameAllocator = MyFrameAllocator;
+///
+/// struct MyFrameAllocator;
+///
+/// impl GlobalFrameAllocator for MyFrameAllocator {
+///     fn alloc(&self, _layout: Layout) -> Option<Paddr> { None }
+///     fn dealloc(&self, _paddr: Paddr, _size: usize) {}
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn global_frame_allocator(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    // Make a `static __GLOBAL_FRAME_ALLOCATOR_REF: &'static dyn GlobalFrameAllocator`
+    // That points to the annotated static variable.
+    let item = parse_macro_input!(item as syn::ItemStatic);
+    let static_name = &item.ident;
+
+    quote!(
+        #[no_mangle]
+        static __GLOBAL_FRAME_ALLOCATOR_REF: &'static dyn ostd::mm::frame::GlobalFrameAllocator = &#static_name;
+        #item
+    )
+    .into()
+}
+
 /// A macro attribute for the panic handler.
 ///
 /// The attributed function will be used to override OSTD's default

ostd/src/lib.rs

@@ -67,6 +67,13 @@ pub use self::{error::Error, prelude::Result};
 #[doc(hidden)]
 unsafe fn init() {
     arch::enable_cpu_features();
+
+    // SAFETY: This function is called only once, before `allocator::init`
+    // and after memory regions are initialized.
+    unsafe {
+        mm::frame::allocator::init_early_allocator();
+    }
+
     arch::serial::init();
 
     #[cfg(feature = "cvm_guest")]

ostd/src/mm/frame/allocator.rs

@@ -2,18 +2,18 @@
 
 //! The physical memory allocator.
 
+use core::{alloc::Layout, ops::Range};
+
 use align_ext::AlignExt;
-use buddy_system_allocator::FrameAllocator;
-use log::info;
-use spin::Once;
 
 use super::{meta::AnyFrameMeta, segment::Segment, Frame};
 use crate::{
     boot::memory_region::MemoryRegionType,
     error::Error,
+    impl_frame_meta_for,
     mm::{paddr_to_vaddr, Paddr, PAGE_SIZE},
     prelude::*,
-    sync::SpinLock,
+    util::range_difference,
 };
 
 /// Options for allocating physical memory frames.
@@ -52,16 +52,9 @@ impl FrameAllocOptions {
 
     /// Allocates a single frame with additional metadata.
     pub fn alloc_frame_with<M: AnyFrameMeta>(&self, metadata: M) -> Result<Frame<M>> {
-        let frame = FRAME_ALLOCATOR
+        let single_layout = Layout::from_size_align(PAGE_SIZE, PAGE_SIZE).unwrap();
-            .get()
+        let frame = alloc_upcall(single_layout)
-            .unwrap()
+            .map(|paddr| Frame::from_unused(paddr, metadata).unwrap())
-            .disable_irq()
-            .lock()
-            .alloc(1)
-            .map(|idx| {
-                let paddr = idx * PAGE_SIZE;
-                Frame::from_unused(paddr, metadata).unwrap()
-            })
             .ok_or(Error::NoMemory)?;
 
         if self.zeroed {
@@ -93,18 +86,10 @@ impl FrameAllocOptions {
         if nframes == 0 {
             return Err(Error::InvalidArgs);
         }
-        let segment = FRAME_ALLOCATOR
+        let layout = Layout::from_size_align(nframes * PAGE_SIZE, PAGE_SIZE).unwrap();
-            .get()
+        let segment = alloc_upcall(layout)
-            .unwrap()
-            .disable_irq()
-            .lock()
-            .alloc(nframes)
             .map(|start| {
-                Segment::from_unused(
+                Segment::from_unused(start..start + nframes * PAGE_SIZE, metadata_fn).unwrap()
-                    start * PAGE_SIZE..start * PAGE_SIZE + nframes * PAGE_SIZE,
-                    metadata_fn,
-                )
-                .unwrap()
             })
             .ok_or(Error::NoMemory)?;
 
@@ -140,73 +125,236 @@ fn test_alloc_dealloc() {
     }
 }
 
-/// FrameAllocator with a counter for allocated memory
+/// The trait for the global frame allocator.
-pub(in crate::mm) struct CountingFrameAllocator {
+///
-    allocator: FrameAllocator,
+/// OSTD allows a customized frame allocator by the [`global_frame_allocator`]
-    total: usize,
+/// attribute, which marks a static variable of this type.
-    allocated: usize,
+///
+/// The API mimics the standard Rust allocator API ([`GlobalAlloc`] and
+/// [`global_allocator`]). However, this trait is much safer. Double free
+/// or freeing in-use memory through this trait only mess up the allocator's
+/// state rather than causing undefined behavior.
+///
+/// Whenever OSTD or other modules need to allocate or deallocate frames via
+/// [`FrameAllocOptions`], they are forwarded to the global frame allocator.
+/// It is not encoraged to call the global allocator directly.
+///
+/// [`global_frame_allocator`]: crate::global_frame_allocator
+/// [`GlobalAlloc`]: core::alloc::GlobalAlloc
+pub trait GlobalFrameAllocator: Sync {
+    /// Allocates a contiguous range of frames.
+    ///
+    /// The caller guarantees that `layout.size()` is aligned to [`PAGE_SIZE`].
+    ///
+    /// When the allocated memory is not in use, OSTD return them by calling
+    /// [`GlobalFrameAllocator::add_free_memory`].
+    fn alloc(&self, layout: Layout) -> Option<Paddr>;
+
+    /// Adds a contiguous range of frames to the allocator.
+    ///
+    /// The caller guarantees that `addr` and `size` are both aligned to
+    /// [`PAGE_SIZE`]. The added memory can be uninitialized.
+    ///
+    /// The memory being added would never overlap with any memory that is
+    /// already added, i.e., a frame cannot be added twice without being
+    /// allocated in between.
+    ///
+    /// However, if [`GlobalFrameAllocator::alloc`] returns multiple frames,
+    /// it is possible that some of them are added back before others.
+    fn add_free_memory(&self, addr: Paddr, size: usize);
 }
 
-impl CountingFrameAllocator {
+extern "Rust" {
-    pub fn new(allocator: FrameAllocator, total: usize) -> Self {
+    /// The global frame allocator's reference exported by
-        CountingFrameAllocator {
+    /// [`crate::global_frame_allocator`].
-            allocator,
+    static __GLOBAL_FRAME_ALLOCATOR_REF: &'static dyn GlobalFrameAllocator;
-            total,
-            allocated: 0,
-        }
-    }
-
-    pub fn alloc(&mut self, count: usize) -> Option<usize> {
-        match self.allocator.alloc(count) {
-            Some(value) => {
-                self.allocated += count * PAGE_SIZE;
-                Some(value)
-            }
-            None => None,
-        }
-    }
-
-    // TODO: this method should be marked unsafe as invalid arguments will mess
-    // up the underlying allocator.
-    pub fn dealloc(&mut self, start_frame: usize, count: usize) {
-        self.allocator.dealloc(start_frame, count);
-        self.allocated -= count * PAGE_SIZE;
-    }
-
-    pub fn mem_total(&self) -> usize {
-        self.total
-    }
-
-    pub fn mem_available(&self) -> usize {
-        self.total - self.allocated
-    }
 }
 
-pub(in crate::mm) static FRAME_ALLOCATOR: Once<SpinLock<CountingFrameAllocator>> = Once::new();
+/// Directly allocates a contiguous range of frames.
+fn alloc_upcall(layout: core::alloc::Layout) -> Option<Paddr> {
+    // SAFETY: We believe that the global frame allocator is set up correctly
+    // with the `global_frame_allocator` attribute. If they use safe code only
+    // then the up-call is safe.
+    unsafe { __GLOBAL_FRAME_ALLOCATOR_REF.alloc(layout) }
+}
 
-pub(crate) fn init() {
+/// Up-call to add a range of frames to the global frame allocator.
+///
+/// It would return the frame to the allocator for further use. This would like
+/// to be done after the release of the metadata to avoid re-allocation before
+/// the metadata is reset.
+pub(super) fn add_free_memory_upcall(addr: Paddr, size: usize) {
+    // SAFETY: We believe that the global frame allocator is set up correctly
+    // with the `global_frame_allocator` attribute. If they use safe code only
+    // then the up-call is safe.
+    unsafe { __GLOBAL_FRAME_ALLOCATOR_REF.add_free_memory(addr, size) }
+}
+
+/// Initializes the global frame allocator.
+///
+/// It just does adds the frames to the global frame allocator. Calling it
+/// multiple times would be not safe.
+///
+/// # Safety
+///
+/// This function should be called only once.
+pub(crate) unsafe fn init() {
     let regions = &crate::boot::EARLY_INFO.get().unwrap().memory_regions;
-    let mut total: usize = 0;
+
-    let mut allocator = FrameAllocator::<32>::new();
+    // Retire the early allocator.
+    let early_allocator = EARLY_ALLOCATOR.lock().take().unwrap();
+    let (range_1, range_2) = early_allocator.allocated_regions();
+
     for region in regions.iter() {
         if region.typ() == MemoryRegionType::Usable {
-            // Make the memory region page-aligned, and skip if it is too small.
+            debug_assert!(region.base() % PAGE_SIZE == 0);
-            let start = region.base().align_up(PAGE_SIZE) / PAGE_SIZE;
+            debug_assert!(region.len() % PAGE_SIZE == 0);
-            let region_end = region.base().checked_add(region.len()).unwrap();
+
-            let end = region_end.align_down(PAGE_SIZE) / PAGE_SIZE;
-            if end <= start {
-                continue;
-            }
             // Add global free pages to the frame allocator.
-            allocator.add_frame(start, end);
+            // Truncate the early allocated frames if there is an overlap.
-            total += (end - start) * PAGE_SIZE;
+            for r1 in range_difference(&(region.base()..region.end()), &range_1) {
-            info!(
+                for r2 in range_difference(&r1, &range_2) {
-                "Found usable region, start:{:x}, end:{:x}",
+                    log::info!("Adding free frames to the allocator: {:x?}", r2);
-                region.base(),
+                    add_free_memory_upcall(r2.start, r2.len());
-                region.base() + region.len()
+                }
-            );
+            }
         }
     }
-    let counting_allocator = CountingFrameAllocator::new(allocator, total);
+}
-    FRAME_ALLOCATOR.call_once(|| SpinLock::new(counting_allocator));
+
+/// An allocator in the early boot phase when frame metadata is not available.
+pub(super) struct EarlyFrameAllocator {
+    // We need to allocate from under 4G first since the linear mapping for
+    // the higher region is not constructed yet.
+    under_4g_range: Range<Paddr>,
+    under_4g_end: Paddr,
+
+    // And also sometimes 4G is not enough for early phase. This, if not `0..0`,
+    // is the largest region above 4G.
+    max_range: Range<Paddr>,
+    max_end: Paddr,
+}
+
+/// The global frame allocator in the early boot phase.
+///
+/// It is used to allocate frames before the frame metadata is initialized.
+/// The allocated frames are not tracked by the frame metadata. After the
+/// metadata is initialized with [`super::meta::init`], the frames are tracked
+/// with metadata and the early allocator is no longer used.
+///
+/// This is protected by the [`spin::Mutex`] rather than [`crate::sync::SpinLock`]
+/// since the latter uses CPU-local storage, which isn't available in the early
+/// boot phase. So we must make sure that no interrupts are enabled when using
+/// this allocator.
+pub(super) static EARLY_ALLOCATOR: spin::Mutex<Option<EarlyFrameAllocator>> =
+    spin::Mutex::new(None);
+
+impl EarlyFrameAllocator {
+    /// Creates a new early frame allocator.
+    ///
+    /// It uses at most 2 regions, the first is the maximum usable region below
+    /// 4 GiB. The other is the maximum usable region above 4 GiB and is only
+    /// usable when linear mapping is constructed.
+    pub fn new() -> Self {
+        let regions = &crate::boot::EARLY_INFO.get().unwrap().memory_regions;
+
+        let mut under_4g_range = 0..0;
+        let mut max_range = 0..0;
+        for region in regions.iter() {
+            if region.typ() != MemoryRegionType::Usable {
+                continue;
+            }
+            const PADDR4G: Paddr = 0x1_0000_0000;
+            if region.base() < PADDR4G {
+                let range = region.base()..region.end().min(PADDR4G);
+                if range.len() > under_4g_range.len() {
+                    under_4g_range = range;
+                }
+            }
+            if region.end() >= PADDR4G {
+                let range = region.base().max(PADDR4G)..region.end();
+                if range.len() > max_range.len() {
+                    max_range = range;
+                }
+            }
+        }
+
+        log::debug!(
+            "Early frame allocator (below 4G) at: {:#x?}",
+            under_4g_range
+        );
+        if !max_range.is_empty() {
+            log::debug!("Early frame allocator (above 4G) at: {:#x?}", max_range);
+        }
+
+        Self {
+            under_4g_range: under_4g_range.clone(),
+            under_4g_end: under_4g_range.start,
+            max_range: max_range.clone(),
+            max_end: max_range.start,
+        }
+    }
+
+    /// Allocates a contiguous range of frames.
+    pub fn alloc(&mut self, layout: Layout) -> Option<Paddr> {
+        let size = layout.size().align_up(PAGE_SIZE);
+        let allocated = self.under_4g_end.align_up(layout.align());
+        if allocated + size <= self.under_4g_range.end {
+            // Allocated below 4G.
+            self.under_4g_end = allocated + size;
+            Some(allocated)
+        } else {
+            // Try above 4G.
+            let allocated = self.max_end.align_up(layout.align());
+            if allocated + size <= self.max_range.end {
+                self.max_end = allocated + size;
+            }
+            Some(allocated)
+        }
+    }
+
+    pub(super) fn allocated_regions(&self) -> (Range<Paddr>, Range<Paddr>) {
+        (
+            self.under_4g_range.start..self.under_4g_end,
+            self.max_range.start..self.max_end,
+        )
+    }
+}
+
+/// Metadata for frames allocated in the early boot phase.
+///
+/// Frames allocated with [`early_alloc`] are not immediately tracked with
+/// frame metadata. But [`super::meta::init`] will track them later.
+#[derive(Debug)]
+pub(crate) struct EarlyAllocatedFrameMeta;
+
+impl_frame_meta_for!(EarlyAllocatedFrameMeta);
+
+/// Allocates a contiguous range of frames in the early boot phase.
+///
+/// The early allocated frames will not be reclaimable, until the metadata is
+/// initialized by [`super::meta::init`]. Then we can use [`Frame::from_raw`]
+/// to free the frames.
+///
+/// # Panics
+///
+/// This function panics if:
+///  - it is called before [`init_early_allocator`],
+///  - or if is called after [`init`].
+pub(crate) fn early_alloc(layout: Layout) -> Option<Paddr> {
+    let mut early_allocator = EARLY_ALLOCATOR.lock();
+    early_allocator.as_mut().unwrap().alloc(layout)
+}
+
+/// Initializes the early frame allocator.
+///
+/// [`early_alloc`] should be used after this initialization. After [`init`], the
+/// early allocator.
+///
+/// # Safety
+///
+/// This function should be called only once after the memory regions are ready.
+pub(crate) unsafe fn init_early_allocator() {
+    let mut early_allocator = EARLY_ALLOCATOR.lock();
+    *early_allocator = Some(EarlyFrameAllocator::new());
 }

ostd/src/mm/frame/meta.rs

@@ -39,10 +39,11 @@ pub(crate) mod mapping {
 }
 
 use core::{
+    alloc::Layout,
     any::Any,
     cell::UnsafeCell,
     fmt::Debug,
-    mem::{size_of, MaybeUninit},
+    mem::{size_of, ManuallyDrop, MaybeUninit},
     result::Result,
     sync::atomic::{AtomicU64, Ordering},
 };
@@ -50,16 +51,19 @@ use core::{
 use align_ext::AlignExt;
 use log::info;
 
-use super::{allocator, Segment};
 use crate::{
     arch::mm::PagingConsts,
     const_assert,
     mm::{
-        kspace::LINEAR_MAPPING_BASE_VADDR, paddr_to_vaddr, page_size, page_table::boot_pt,
+        frame::allocator::{self, EarlyAllocatedFrameMeta},
-        CachePolicy, Infallible, Paddr, PageFlags, PageProperty, PrivilegedPageFlags, Vaddr,
+        kspace::LINEAR_MAPPING_BASE_VADDR,
-        VmReader, PAGE_SIZE,
+        paddr_to_vaddr, page_size,
+        page_table::boot_pt,
+        CachePolicy, Infallible, Paddr, PageFlags, PageProperty, PrivilegedPageFlags, Segment,
+        Vaddr, VmReader, PAGE_SIZE,
     },
     panic::abort,
+    util::range_difference,
 };
 
 /// The maximum number of bytes of the metadata of a frame.
@@ -383,16 +387,6 @@ impl MetaSlot {
         // `Release` pairs with the `Acquire` in `Frame::from_unused` and ensures
         // `drop_meta_in_place` won't be reordered after this memory store.
         self.ref_count.store(REF_COUNT_UNUSED, Ordering::Release);
-
-        // Deallocate the frame.
-        // It would return the frame to the allocator for further use. This would be done
-        // after the release of the metadata to avoid re-allocation before the metadata
-        // is reset.
-        allocator::FRAME_ALLOCATOR
-            .get()
-            .unwrap()
-            .lock()
-            .dealloc(self.frame_paddr() / PAGE_SIZE, 1);
     }
 
     /// Drops the metadata of a slot in place.
@@ -460,8 +454,6 @@ pub(crate) unsafe fn init() -> Segment<MetaPageMeta> {
 
     add_temp_linear_mapping(max_paddr);
 
-    super::MAX_PADDR.store(max_paddr, Ordering::Relaxed);
-
     let tot_nr_frames = max_paddr / page_size::<PagingConsts>(1);
     let (nr_meta_pages, meta_pages) = alloc_meta_frames(tot_nr_frames);
 
@@ -482,10 +474,33 @@ pub(crate) unsafe fn init() -> Segment<MetaPageMeta> {
     .unwrap();
 
     // Now the metadata frames are mapped, we can initialize the metadata.
-    Segment::from_unused(meta_pages..meta_pages + nr_meta_pages * PAGE_SIZE, |_| {
+    super::MAX_PADDR.store(max_paddr, Ordering::Relaxed);
-        MetaPageMeta {}
+
-    })
+    let meta_page_range = meta_pages..meta_pages + nr_meta_pages * PAGE_SIZE;
-    .unwrap()
+
+    let (range_1, range_2) = allocator::EARLY_ALLOCATOR
+        .lock()
+        .as_ref()
+        .unwrap()
+        .allocated_regions();
+    for r in range_difference(&range_1, &meta_page_range) {
+        let early_seg = Segment::from_unused(r, |_| EarlyAllocatedFrameMeta).unwrap();
+        let _ = ManuallyDrop::new(early_seg);
+    }
+    for r in range_difference(&range_2, &meta_page_range) {
+        let early_seg = Segment::from_unused(r, |_| EarlyAllocatedFrameMeta).unwrap();
+        let _ = ManuallyDrop::new(early_seg);
+    }
+
+    Segment::from_unused(meta_page_range, |_| MetaPageMeta {}).unwrap()
+}
+
+/// Returns whether the global frame allocator is initialized.
+pub(in crate::mm) fn is_initialized() -> bool {
+    // `init` sets it with relaxed ordering somewhere in the middle. But due
+    // to the safety requirement of the `init` function, we can assume that
+    // there is no race conditions.
+    super::MAX_PADDR.load(Ordering::Relaxed) != 0
 }
 
 fn alloc_meta_frames(tot_nr_frames: usize) -> (usize, Paddr) {
@@ -493,13 +508,10 @@ fn alloc_meta_frames(tot_nr_frames: usize) -> (usize, Paddr) {
         .checked_mul(size_of::<MetaSlot>())
         .unwrap()
         .div_ceil(PAGE_SIZE);
-    let start_paddr = allocator::FRAME_ALLOCATOR
+    let start_paddr = allocator::early_alloc(
-        .get()
+        Layout::from_size_align(nr_meta_pages * PAGE_SIZE, PAGE_SIZE).unwrap(),
-        .unwrap()
+    )
-        .lock()
+    .unwrap();
-        .alloc(nr_meta_pages)
-        .unwrap()
-        * PAGE_SIZE;
 
     let slots = paddr_to_vaddr(start_paddr) as *mut MetaSlot;
 
@@ -523,14 +535,6 @@ fn alloc_meta_frames(tot_nr_frames: usize) -> (usize, Paddr) {
     (nr_meta_pages, start_paddr)
 }
 
-/// Returns whether the global frame allocator is initialized.
-pub(in crate::mm) fn is_initialized() -> bool {
-    // `init` sets it somewhere in the middle. But due to the safety
-    // requirement of the `init` function, we can assume that there
-    // is no race condition.
-    super::MAX_PADDR.load(Ordering::Relaxed) != 0
-}
-
 /// Adds a temporary linear mapping for the metadata frames.
 ///
 /// We only assume boot page table to contain 4G linear mapping. Thus if the

ostd/src/mm/frame/mod.rs

@@ -44,6 +44,7 @@ use core::{
     sync::atomic::{AtomicUsize, Ordering},
 };
 
+pub use allocator::GlobalFrameAllocator;
 use meta::{mapping, AnyFrameMeta, GetFrameError, MetaSlot, REF_COUNT_UNUSED};
 pub use segment::Segment;
 use untyped::{AnyUFrameMeta, UFrame};
@@ -220,6 +221,8 @@ impl<M: AnyFrameMeta + ?Sized> Drop for Frame<M> {
 
             // SAFETY: this is the last reference and is about to be dropped.
             unsafe { self.slot().drop_last_in_place() };
+
+            allocator::add_free_memory_upcall(self.start_paddr(), PAGE_SIZE);
         }
     }
 }

ostd/src/mm/frame/unique.rs

@@ -99,6 +99,26 @@ impl<M: AnyFrameMeta + ?Sized> UniqueFrame<M> {
         unsafe { &mut *self.slot().dyn_meta_ptr() }
     }
 
+    /// Resets the frame to unused without up-calling the allocator.
+    ///
+    /// This is solely useful for the allocator implementation/testing and
+    /// is highly experimental. Usage of this function is discouraged.
+    ///
+    /// Usage of this function other than the allocator would actually leak
+    /// the frame since the allocator would not be aware of the frame.
+    //
+    // FIXME: We may have a better `Segment` and `UniqueSegment` design to
+    // allow the allocator hold the ownership of all the frames in a chunk
+    // instead of the head. Then this weird public API can be `#[cfg(ktest)]`.
+    pub fn reset_as_unused(self) {
+        let this = ManuallyDrop::new(self);
+
+        this.slot().ref_count.store(0, Ordering::Release);
+        // SAFETY: We are the sole owner and the reference count is 0.
+        // The slot is initialized.
+        unsafe { this.slot().drop_last_in_place() };
+    }
+
     /// Converts this frame into a raw physical address.
     pub(crate) fn into_raw(self) -> Paddr {
         let this = ManuallyDrop::new(self);
@@ -134,6 +154,8 @@ impl<M: AnyFrameMeta + ?Sized> Drop for UniqueFrame<M> {
         // SAFETY: We are the sole owner and the reference count is 0.
         // The slot is initialized.
         unsafe { self.slot().drop_last_in_place() };
+
+        super::allocator::add_free_memory_upcall(self.start_paddr(), PAGE_SIZE);
     }
 }
 

ostd/src/mm/heap_allocator/mod.rs

@@ -2,7 +2,10 @@
 
 mod slab_allocator;
 
-use core::alloc::{GlobalAlloc, Layout};
+use core::{
+    alloc::{GlobalAlloc, Layout},
+    mem::ManuallyDrop,
+};
 
 use align_ext::AlignExt;
 use log::debug;
@@ -11,11 +14,11 @@ use spin::Once;
 
 use super::paddr_to_vaddr;
 use crate::{
-    mm::{frame::allocator::FRAME_ALLOCATOR, PAGE_SIZE},
+    impl_frame_meta_for,
+    mm::{FrameAllocOptions, PAGE_SIZE},
     prelude::*,
     sync::SpinLock,
     trap::disable_local,
-    Error,
 };
 
 #[global_allocator]
@@ -49,6 +52,12 @@ struct LockedHeapWithRescue {
     heap: Once<SpinLock<Heap>>,
 }
 
+/// The metadata for the kernel heap frames.
+#[derive(Debug)]
+pub struct KernelHeapMeta;
+
+impl_frame_meta_for!(KernelHeapMeta);
+
 impl LockedHeapWithRescue {
     /// Creates an new heap
     pub const fn new() -> Self {
@@ -94,22 +103,26 @@ impl LockedHeapWithRescue {
         };
 
         let allocation_start = {
-            let mut page_allocator = FRAME_ALLOCATOR.get().unwrap().lock();
+            let mut options = FrameAllocOptions::new();
-            if num_frames >= MIN_NUM_FRAMES {
+            options.zeroed(false);
-                page_allocator.alloc(num_frames).ok_or(Error::NoMemory)?
+            let segment = if num_frames >= MIN_NUM_FRAMES {
+                options
+                    .alloc_segment_with(num_frames, |_| KernelHeapMeta)
+                    .unwrap()
             } else {
-                match page_allocator.alloc(MIN_NUM_FRAMES) {
+                match options.alloc_segment_with(MIN_NUM_FRAMES, |_| KernelHeapMeta) {
-                    None => page_allocator.alloc(num_frames).ok_or(Error::NoMemory)?,
+                    Ok(seg) => {
-                    Some(start) => {
                         num_frames = MIN_NUM_FRAMES;
-                        start
+                        seg
                     }
+                    Err(_) => options.alloc_segment_with(num_frames, |_| KernelHeapMeta)?,
                 }
-            }
+            };
+            let paddr = segment.start_paddr();
+            let _ = ManuallyDrop::new(segment);
+            paddr
         };
-        // FIXME: the alloc function internally allocates heap memory(inside FrameAllocator).
+        let vaddr = paddr_to_vaddr(allocation_start);
-        // So if the heap is nearly run out, allocating frame will fail too.
-        let vaddr = paddr_to_vaddr(allocation_start * PAGE_SIZE);
 
         // SAFETY: the frame is allocated from FrameAllocator and never be deallocated,
         // so the addr is always valid.

ostd/src/mm/mod.rs

@@ -16,7 +16,6 @@ pub(crate) mod kspace;
 mod offset;
 pub(crate) mod page_prop;
 pub(crate) mod page_table;
-pub mod stat;
 pub mod tlb;
 pub mod vm_space;
 

ostd/src/mm/page_table/boot_pt.rs

@@ -5,6 +5,7 @@
 //! in order to initialize the running phase page tables.
 
 use core::{
+    alloc::Layout,
     result::Result,
     sync::atomic::{AtomicU32, Ordering},
 };
@@ -15,7 +16,11 @@ use crate::{
     cpu::num_cpus,
     cpu_local_cell,
     mm::{
-        frame::allocator::FRAME_ALLOCATOR, nr_subpage_per_huge, paddr_to_vaddr, Paddr, PageFlags,
+        frame::{
+            self,
+            allocator::{self, EarlyAllocatedFrameMeta},
+        },
+        nr_subpage_per_huge, paddr_to_vaddr, Frame, FrameAllocOptions, Paddr, PageFlags,
         PageProperty, PagingConstsTrait, PagingLevel, Vaddr, PAGE_SIZE,
     },
     sync::SpinLock,
@@ -62,13 +67,27 @@ where
 /// The caller should ensure that:
 ///  - another legitimate page table is activated on this CPU;
 ///  - this function should be called only once per CPU;
-///  - no [`with`] calls are performed on this CPU after this dismissal;
+///  - no [`with_borrow`] calls are performed on this CPU after this dismissal;
-///  - no [`with`] calls are performed on this CPU after the activation of
+///  - no [`with_borrow`] calls are performed on this CPU after the activation
-///    another page table and before this dismissal.
+///    of another page table and before this dismissal.
 pub(crate) unsafe fn dismiss() {
     IS_DISMISSED.store(true);
     if DISMISS_COUNT.fetch_add(1, Ordering::SeqCst) as usize == num_cpus() - 1 {
-        BOOT_PAGE_TABLE.lock().take();
+        let boot_pt = BOOT_PAGE_TABLE.lock().take().unwrap();
+
+        dfs_walk_on_leave::<PageTableEntry, PagingConsts>(
+            boot_pt.root_pt,
+            PagingConsts::NR_LEVELS,
+            &mut |pte| {
+                if !pte.prop().flags.contains(PTE_POINTS_TO_FIRMWARE_PT) {
+                    // SAFETY: The pointed frame is allocated and forgotten with `into_raw`.
+                    drop(unsafe { Frame::<EarlyAllocatedFrameMeta>::from_raw(pte.paddr()) })
+                }
+                // Firmware provided page tables may be a DAG instead of a tree.
+                // Clear it to avoid double-free when we meet it the second time.
+                *pte = PageTableEntry::new_absent();
+            },
+        );
     }
 }
 
@@ -97,6 +116,13 @@ pub(crate) struct BootPageTable<
     _pretend_to_use: core::marker::PhantomData<(E, C)>,
 }
 
+// We use extra two available bits in the boot PT for memory management.
+//
+// The first available bit is used to differentiate firmware page tables from
+// the page tables allocated here. The second is for identifying double-visits
+// when walking the page tables since the PT can be a DAG.
+const PTE_POINTS_TO_FIRMWARE_PT: PageFlags = PageFlags::AVAIL1;
+
 impl<E: PageTableEntryTrait, C: PagingConstsTrait> BootPageTable<E, C> {
     /// Creates a new boot page table from the current page table root
     /// physical address.
@@ -108,15 +134,13 @@ impl<E: PageTableEntryTrait, C: PagingConstsTrait> BootPageTable<E, C> {
     /// by the firmware, loader or the setup code.
     unsafe fn from_current_pt() -> Self {
         let root_pt = crate::arch::mm::current_page_table_paddr() / C::BASE_PAGE_SIZE;
-        // Make sure the first available bit is not set for firmware page tables.
+        // Make sure the 2 available bits are not set for firmware page tables.
         dfs_walk_on_leave::<E, C>(root_pt, C::NR_LEVELS, &mut |pte: &mut E| {
             let prop = pte.prop();
-            if prop.flags.contains(PageFlags::AVAIL1) {
+            pte.set_prop(PageProperty::new(
-                pte.set_prop(PageProperty::new(
+                prop.flags | PTE_POINTS_TO_FIRMWARE_PT,
-                    prop.flags - PageFlags::AVAIL1,
+                prop.cache,
-                    prop.cache,
+            ));
-                ));
-            }
         });
         Self {
             root_pt,
@@ -230,17 +254,26 @@ impl<E: PageTableEntryTrait, C: PagingConstsTrait> BootPageTable<E, C> {
     }
 
     fn alloc_child(&mut self) -> E {
-        let frame = FRAME_ALLOCATOR.get().unwrap().lock().alloc(1).unwrap();
+        let frame_paddr = if frame::meta::is_initialized() {
+            let frame = FrameAllocOptions::new()
+                .zeroed(false)
+                .alloc_frame_with(EarlyAllocatedFrameMeta)
+                .unwrap();
+            frame.into_raw()
+        } else {
+            allocator::early_alloc(
+                Layout::from_size_align(C::BASE_PAGE_SIZE, C::BASE_PAGE_SIZE).unwrap(),
+            )
+            .unwrap()
+        };
+
         // Zero it out.
-        let vaddr = paddr_to_vaddr(frame * PAGE_SIZE) as *mut u8;
+        let vaddr = paddr_to_vaddr(frame_paddr) as *mut u8;
         unsafe { core::ptr::write_bytes(vaddr, 0, PAGE_SIZE) };
 
-        let mut pte = E::new_pt(frame * C::BASE_PAGE_SIZE);
+        let mut pte = E::new_pt(frame_paddr);
         let prop = pte.prop();
-        pte.set_prop(PageProperty::new(
+        pte.set_prop(PageProperty::new(prop.flags, prop.cache));
-            prop.flags | PageFlags::AVAIL1,
-            prop.cache,
-        ));
 
         pte
     }
@@ -267,20 +300,6 @@ fn dfs_walk_on_leave<E: PageTableEntryTrait, C: PagingConstsTrait>(
     }
 }
 
-impl<E: PageTableEntryTrait, C: PagingConstsTrait> Drop for BootPageTable<E, C> {
-    fn drop(&mut self) {
-        dfs_walk_on_leave::<E, C>(self.root_pt, C::NR_LEVELS, &mut |pte| {
-            if pte.prop().flags.contains(PageFlags::AVAIL1) {
-                let pt = pte.paddr() / C::BASE_PAGE_SIZE;
-                FRAME_ALLOCATOR.get().unwrap().lock().dealloc(pt, 1);
-            }
-            // Firmware provided page tables may be a DAG instead of a tree.
-            // Clear it to avoid double-free when we meet it the second time.
-            *pte = E::new_absent();
-        });
-    }
-}
-
 #[cfg(ktest)]
 use crate::prelude::*;
 

ostd/src/mm/stat/mod.rs

@@ -1,21 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-
-//! APIs for memory statistics.
-
-use crate::mm::frame::allocator::FRAME_ALLOCATOR;
-
-/// Total memory available for any usages in the system (in bytes).
-///
-/// It would be only a slightly less than total physical memory of the system
-/// in most occasions. For example, bad memory, kernel statically-allocated
-/// memory or firmware reserved memories do not count.
-pub fn mem_total() -> usize {
-    FRAME_ALLOCATOR.get().unwrap().lock().mem_total()
-}
-
-/// Current readily available memory (in bytes).
-///
-/// Such memory can be directly used for allocation without reclaiming.
-pub fn mem_available() -> usize {
-    FRAME_ALLOCATOR.get().unwrap().lock().mem_available()
-}

tools/bump_version.sh

@@ -111,6 +111,7 @@ LINUX_BZIMAGE_BUILDER_CARGO_TOML_PATH=${ASTER_SRC_DIR}/ostd/libs/linux-bzimage/b
 LINUX_BZIMAGE_SETUP_CARGO_TOML_PATH=${ASTER_SRC_DIR}/ostd/libs/linux-bzimage/setup/Cargo.toml
 OSDK_CARGO_TOML_PATH=${ASTER_SRC_DIR}/osdk/Cargo.toml
 OSDK_TEST_RUNNER_CARGO_TOML_PATH=${ASTER_SRC_DIR}/osdk/deps/test-kernel/Cargo.toml
+OSDK_FRAME_ALLOCATOR_CARGO_TOML_PATH=${ASTER_SRC_DIR}/osdk/deps/frame-allocator/Cargo.toml
 VERSION_PATH=${ASTER_SRC_DIR}/VERSION
 
 current_version=$(cat ${VERSION_PATH})
@@ -131,13 +132,16 @@ update_package_version ${OSTD_CARGO_TOML_PATH}
 update_package_version ${LINUX_BOOT_PARAMS_CARGO_TOML_PATH}
 update_package_version ${LINUX_BZIMAGE_BUILDER_CARGO_TOML_PATH}
 update_package_version ${LINUX_BZIMAGE_SETUP_CARGO_TOML_PATH}
+update_package_version ${OSDK_CARGO_TOML_PATH}
+update_package_version ${OSDK_TEST_RUNNER_CARGO_TOML_PATH}
+update_package_version ${OSDK_FRAME_ALLOCATOR_CARGO_TOML_PATH}
+
+update_dep_version ${OSDK_TEST_RUNNER_CARGO_TOML_PATH} ostd
+update_dep_version ${OSDK_FRAME_ALLOCATOR_CARGO_TOML_PATH} ostd
 update_dep_version ${OSTD_CARGO_TOML_PATH} ostd-test
 update_dep_version ${OSTD_CARGO_TOML_PATH} linux-boot-params
 update_dep_version ${OSTD_CARGO_TOML_PATH} ostd-macros
 update_dep_version ${LINUX_BZIMAGE_SETUP_CARGO_TOML_PATH} linux-boot-params
-update_package_version ${OSDK_CARGO_TOML_PATH}
-update_package_version ${OSDK_TEST_RUNNER_CARGO_TOML_PATH}
-update_dep_version ${OSDK_TEST_RUNNER_CARGO_TOML_PATH} ostd
 update_dep_version ${OSDK_CARGO_TOML_PATH} linux-bzimage-builder
 
 # Automatically bump Cargo.lock files

tools/github_workflows/publish_osdk_and_ostd.sh

@@ -83,6 +83,7 @@ for TARGET in $TARGETS; do
     do_publish_for ostd/libs/ostd-test $TARGET
     do_publish_for ostd/libs/linux-bzimage/setup $TARGET
     do_publish_for ostd $TARGET
+    do_publish_for osdk/deps/frame-allocator $TARGET
     do_publish_for osdk/deps/test-kernel $TARGET
 
     # For actual publishing, we should only publish once. Using any target that