From e9751585fe0e12dc3d140ad7dfb60be7470db551 Mon Sep 17 00:00:00 2001
From: Paul Pan <i@0x7f.app>
Date: Sun, 7 Apr 2024 00:21:13 +0800
Subject: [PATCH] fix: allocator: freelist: reserve is not handling overlapped
 situations

---
 kernel/src/vspace/addr.rs               | 16 ++++++-
 kernel/src/vspace/allocator/freelist.rs | 56 ++++++++++++++++---------
 2 files changed, 50 insertions(+), 22 deletions(-)

diff --git a/kernel/src/vspace/addr.rs b/kernel/src/vspace/addr.rs
index fddc366..dd586cf 100644
--- a/kernel/src/vspace/addr.rs
+++ b/kernel/src/vspace/addr.rs
@@ -13,10 +13,10 @@ pub fn align_down(addr: usize, align: usize) -> usize {
     addr & !(align - 1)
 }
 
-#[derive(Copy, Clone, Default, PartialOrd, PartialEq)]
+#[derive(Copy, Clone, Default, Eq, Ord, PartialOrd, PartialEq)]
 pub struct PhysAddr(pub usize);
 
-#[derive(Copy, Clone, Default, PartialOrd, PartialEq)]
+#[derive(Copy, Clone, Default, Eq, Ord, PartialOrd, PartialEq)]
 pub struct VirtAddr(pub usize);
 
 pub trait AddressOps {
@@ -227,6 +227,12 @@ impl<T> From<*mut T> for PhysAddr {
     }
 }
 
+impl<T> From<*const T> for PhysAddr {
+    fn from(addr: *const T) -> Self {
+        PhysAddr(addr as usize)
+    }
+}
+
 impl From<PhysAddr> for usize {
     fn from(addr: PhysAddr) -> Self {
         addr.0
@@ -263,6 +269,12 @@ impl<T> From<*mut T> for VirtAddr {
     }
 }
 
+impl<T> From<*const T> for VirtAddr {
+    fn from(addr: *const T) -> Self {
+        VirtAddr(addr as usize)
+    }
+}
+
 impl From<VirtAddr> for usize {
     fn from(addr: VirtAddr) -> Self {
         addr.0
diff --git a/kernel/src/vspace/allocator/freelist.rs b/kernel/src/vspace/allocator/freelist.rs
index 5c20d84..76d52c7 100644
--- a/kernel/src/vspace/allocator/freelist.rs
+++ b/kernel/src/vspace/allocator/freelist.rs
@@ -3,6 +3,8 @@
 use crate::utils::then::Then;
 use crate::vspace::addr::{AddressOps, PhysAddr};
 use core::alloc::{GlobalAlloc, Layout};
+use core::cmp::{max, min};
+use core::fmt::Debug;
 use spin::Mutex;
 
 struct ListNode {
@@ -42,12 +44,21 @@ impl ListNode {
     }
 }
 
-struct FreeList {
+impl Debug for ListNode {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        f.debug_struct("ListNode")
+            .field("begin", &self.start_addr())
+            .field("end", &self.end_addr())
+            .finish()
+    }
+}
+
+pub struct FreeList {
     head: ListNode,
 }
 
 impl FreeList {
-    const fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             head: ListNode::new(0),
         }
@@ -78,7 +89,7 @@ impl FreeList {
         (size, layout.align())
     }
 
-    unsafe fn alloc(&mut self, layout: Layout) -> *mut u8 {
+    pub unsafe fn alloc(&mut self, layout: Layout) -> *mut u8 {
         let (size, align) = Self::align_layout(layout);
 
         if let Some((region, alloc_start)) = self.alloc_node(|region| region.fit(size, align)) {
@@ -93,7 +104,7 @@ impl FreeList {
         }
     }
 
-    unsafe fn dealloc(&mut self, start: PhysAddr, size: usize) {
+    pub unsafe fn dealloc(&mut self, start: PhysAddr, size: usize) {
         assert_eq!(start.align_up(core::mem::align_of::<ListNode>()), start);
         assert!(size >= core::mem::size_of::<ListNode>());
 
@@ -105,33 +116,38 @@ impl FreeList {
     }
 
     pub fn reserve(&mut self, start: PhysAddr, size: usize) {
-        if let Some((region, _)) =
-            self.alloc_node(|region| (region.start_addr() <= start).and(|| region.fit(size, 1), ()))
-        {
-            /* layout
-             * region: | before | [start +: size] | after |
-             *         ^        ^                 ^       ^ region.end_addr()
-             *         |        | alloc_start     |
-             *         |                          | alloc_end
-             *         | region.start_addr()
-             */
-
+        if let Some((region, _)) = self.alloc_node(|region| {
+            let left = max(region.start_addr(), start);
+            let right = min(region.end_addr(), start + size);
+            (left < right).some(|| (), ())
+        }) {
             let region_start = region.start_addr();
             let region_end = region.end_addr();
 
-            let before_size = (start - region_start).as_usize();
-            if before_size > 0 {
-                unsafe { self.dealloc(region_start, before_size) }
-            }
-
             let after_size = (region_end - (start + size)).as_usize();
             if after_size > 0 {
                 unsafe { self.dealloc(start + size, after_size) }
             }
+
+            let before_size = (start - region_start).as_usize();
+            if before_size > 0 {
+                unsafe { self.dealloc(region_start, before_size) }
+            }
         }
     }
 }
 
+impl Debug for FreeList {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        let mut current = &self.head;
+        while let Some(ref region) = current.next {
+            write!(f, "{:?} -> ", region)?;
+            current = region;
+        }
+        write!(f, "None")
+    }
+}
+
 pub struct FreeListAllocator {
     list: Mutex<FreeList>,
 }