build: fix alloc

src/allocation.rs

@@ -36,6 +36,7 @@ pub fn init() {
         unsafe {
             sys::init_heap();
             MAIN_SECTOR = sys::alloc(PAGE_SIZE) as usize;
+            core::ptr::write_bytes(MAIN_SECTOR as *mut u8, 0, PAGE_SIZE); // make sector table start clean
         }
     }
 }
@@ -47,14 +48,14 @@ pub fn malloc(size: usize) -> *mut u8 {
 
             if (addr as usize) != 0 {
                 let sec = addr;
-                let mut hdr = *(addr as *const SectorHeader);
+                let hdr = &mut *(addr as *mut SectorHeader);
                 let sec_start_blocks = (sec as usize) + size_of::<SectorHeader>();
                 if hdr.size_left >= size {
                     let mut j = sec_start_blocks;
                     let mut first_found_block_addr = 0;
 
                     while j <= sec_start_blocks + hdr.size {
-                        let mut block = *(j as *const BlockHeader);
+                        let block = &mut *(j as *mut BlockHeader);
                         match block.sign {
                             Sign::Active => {
                                 // If block is occupated - pass
@@ -63,7 +64,7 @@ pub fn malloc(size: usize) -> *mut u8 {
                             }
 
                             Sign::Free => {
-                                if first_found_block_addr != 0 {
+                                if first_found_block_addr == 0 {
                                     first_found_block_addr = j;
                                 }
 
@@ -73,26 +74,32 @@ pub fn malloc(size: usize) -> *mut u8 {
                                     j += (size_of::<BlockHeader>()) + block.size;
                                 } else if size - sum_size < size_of::<BlockHeader>() {
                                     // Create 2 blocks
-                                    let mut main_block =
-                                        *(first_found_block_addr as *const BlockHeader);
+                                    let main_block =
+                                        &mut *(first_found_block_addr as *mut BlockHeader);
                                     main_block.sign = Sign::Active;
                                     main_block.size = size;
 
-                                    let mut secondary_block = *(first_found_block_addr
-                                        as *const BlockHeader)
-                                        .add(size_of::<BlockHeader>() + size);
-                                    secondary_block.sign = Sign::Free;
-                                    secondary_block.size =
+                                    let secondary_block = (first_found_block_addr
+                                        + size_of::<BlockHeader>()
+                                        + size)
+                                        as *mut BlockHeader;
+                                    (*secondary_block).sign = Sign::Free;
+                                    (*secondary_block).size =
                                         sum_size - size - size_of::<BlockHeader>();
 
+                                    hdr.size_left -= size + size_of::<BlockHeader>();
+
                                     return (first_found_block_addr as *mut u8)
                                         .add(size_of::<BlockHeader>());
                                 } else {
                                     // Create 1 block
-                                    let mut main_block =
-                                        *(first_found_block_addr as *const BlockHeader);
+                                    let main_block =
+                                        &mut *(first_found_block_addr as *mut BlockHeader);
                                     main_block.sign = Sign::Active;
                                     main_block.size = sum_size - size_of::<BlockHeader>();
+
+                                    hdr.size_left -= main_block.size + size_of::<BlockHeader>();
+
                                     return (first_found_block_addr as *mut u8)
                                         .add(size_of::<BlockHeader>());
                                 }
@@ -117,9 +124,11 @@ pub fn malloc(size: usize) -> *mut u8 {
                     }
                 }
             } else {
-                let sec_size = size + PAGE_SIZE - size % PAGE_SIZE;
+                // round requested size up to whole pages
+                let sec_size = (size + PAGE_SIZE - 1) & !(PAGE_SIZE - 1);
                 let new_sec = sys::alloc(sec_size);
                 let sec_hdr = new_sec as *mut SectorHeader;
+                *((MAIN_SECTOR + i * 4) as *mut u32) = new_sec as u32; // remember this sector in the table
                 *sec_hdr = SectorHeader {
                     size: sec_size,
                     size_left: sec_size - size_of::<SectorHeader>(),
@@ -138,26 +147,26 @@ pub fn malloc(size: usize) -> *mut u8 {
 
 fn free(block: *const u8) {
     unsafe {
-        let mut block_hdr = *(block.sub(size_of::<BlockHeader>()) as *mut BlockHeader);
+        let block_hdr = &mut *(block.sub(size_of::<BlockHeader>()) as *mut BlockHeader);
 
         for i in 0..PAGE_SIZE / 4 {
             let addr = *((MAIN_SECTOR + i * 4) as *const u32) as *const u8;
-            let mut hdr = *(addr as *const SectorHeader);
+            if addr.is_null() {
+                continue;
+            }
+            let hdr = &mut *(addr as *mut SectorHeader);
 
             if addr < block && (block as usize) < (addr as usize) + hdr.size {
-                hdr.size_left += block_hdr.size;
+                hdr.size_left += block_hdr.size + size_of::<BlockHeader>();
                 if hdr.size_left == hdr.size - size_of::<SectorHeader>() {
-                    free(addr)
+                    sys::free(addr); // whole sector is free, hand it back to OS
+                    *((MAIN_SECTOR + i * 4) as *mut u32) = 0; // and drop from the table
                 } else {
                     block_hdr.sign = Sign::Free;
                 }
                 break;
             }
         }
-
-        if !sys::free(block) {
-            panic!("Free failed");
-        }
     }
 }
 
@@ -181,4 +190,4 @@ unsafe impl alloc::alloc::GlobalAlloc for GlobalAlloc {
 }
 
 #[global_allocator]
-static ALLOC: GlobalAlloc = GlobalAlloc;
+static ALLOC: GlobalAlloc = GlobalAlloc;