Introduce a few helpers to allocate/map/unmap several pages, which wrap around the MMU functionality

AFAIK, this is the proper naming scheme. "Pages" are virtual, and "frames" physical.

kernel/src/arch/x86_64/CPU.cpp

@@ -199,8 +199,8 @@ static IDTEntry idt[256];
 
 struct IDTR
 {
-    uint16_t limit;
+    u16 limit;
-    uint64_t offset;
+    u64 offset;
 } __attribute__((packed));
 
 static void idt_add_handler(short num, void* handler, u8 type_attr)

kernel/src/arch/x86_64/MMU.cpp

@@ -196,7 +196,7 @@ namespace MMU
         auto& l4 = l4_entry(virt);
         if (!l4.present)
         {
-            u64 addr = TRY(MemoryManager::alloc_physical_page());
+            u64 addr = TRY(MemoryManager::alloc_frame());
             l4.present = true;
             l4.set_address(addr);
             memset(l3_table(virt), 0, PAGE_SIZE);
@@ -208,7 +208,7 @@ namespace MMU
         auto& l3 = l3_entry(virt);
         if (!l3.present)
         {
-            u64 addr = TRY(MemoryManager::alloc_physical_page());
+            u64 addr = TRY(MemoryManager::alloc_frame());
             l3.present = true;
             l3.set_address(addr);
             memset(l2_table(virt), 0, PAGE_SIZE);
@@ -222,7 +222,7 @@ namespace MMU
         auto& l2 = l2_entry(virt);
         if (!l2.present)
         {
-            u64 addr = TRY(MemoryManager::alloc_physical_page());
+            u64 addr = TRY(MemoryManager::alloc_frame());
             l2.present = true;
             l2.set_address(addr);
             memset(l1_table(virt), 0, PAGE_SIZE);

kernel/src/arch/x86_64/Timer.cpp

@@ -8,9 +8,9 @@ const usize ARCH_TIMER_FREQ = 10;
 
 void Timer::arch_init()
 {
-    constexpr u16 divisor = (uint16_t)(base_frequency / (ARCH_TIMER_FREQ * 1000));
+    constexpr u16 divisor = (u16)(base_frequency / (ARCH_TIMER_FREQ * 1000));
     static_assert(divisor >= 100);
-    IO::outb(PIT_CHANNEL_0, (uint8_t)(divisor & 0xFF));
+    IO::outb(PIT_CHANNEL_0, (u8)(divisor & 0xFF));
     IO::outb(0x80, 0); // short delay
-    IO::outb(PIT_CHANNEL_0, (uint8_t)((divisor & 0xFF00) >> 8));
+    IO::outb(PIT_CHANNEL_0, (u8)((divisor & 0xFF00) >> 8));
 }

kernel/src/main.cpp

@@ -29,7 +29,7 @@ extern "C" [[noreturn]] void _start()
 
     Serial::printf("Mapping address 0x%lx\n", address);
 
-    u64 physical = MemoryManager::alloc_physical_page().release_value();
+    u64 physical = MemoryManager::alloc_frame().release_value();
 
     Serial::printf("Allocated physical frame %#lx\n", physical);
 

kernel/src/memory/MemoryManager.cpp

@@ -33,20 +33,24 @@ static bool page_bitmap_read(u64 index)
 
 static void page_bitmap_set(u64 index, bool value)
 {
-    uint64_t byteIndex = index / 8;
+    u64 byte_index = index / 8;
-    uint8_t bitIndexer = 0b10000000 >> (index % 8);
+    u8 mask = 0b10000000 >> (index % 8);
-    page_virtual_bitmap_addr[byteIndex] &= (uint8_t)(~bitIndexer);
+    page_virtual_bitmap_addr[byte_index] &= (u8)(~mask);
-    if (value) { page_virtual_bitmap_addr[byteIndex] |= bitIndexer; }
+    if (value) { page_virtual_bitmap_addr[byte_index] |= mask; }
 }
 
+#define CHECK_PAGE_ALIGNED(address) check(is_aligned(address, ARCH_PAGE_SIZE))
+
 namespace MemoryManager
 {
     Result<void> protect_kernel_sections()
     {
-        u64 rodata_pages = get_blocks_from_size((u64)(end_of_kernel_rodata - start_of_kernel_rodata), ARCH_PAGE_SIZE);
+        const u64 rodata_size = (u64)(end_of_kernel_rodata - start_of_kernel_rodata);
+        const u64 rodata_pages = get_blocks_from_size(rodata_size, ARCH_PAGE_SIZE);
         TRY(remap((u64)start_of_kernel_rodata, rodata_pages, MMU::NoExecute));
 
-        u64 data_pages = get_blocks_from_size((u64)(end_of_kernel_data - start_of_kernel_data), ARCH_PAGE_SIZE);
+        const u64 data_size = (u64)(end_of_kernel_data - start_of_kernel_data);
+        const u64 data_pages = get_blocks_from_size(data_size, ARCH_PAGE_SIZE);
         TRY(remap((u64)start_of_kernel_data, data_pages, MMU::NoExecute | MMU::ReadWrite));
 
         return {};
@@ -61,7 +65,7 @@ namespace MemoryManager
 
         // walk the memory map
         MMapEnt* ptr = &bootboot.mmap;
-        uint64_t mmap_entries = (bootboot.size - 128) / 16;
+        u64 mmap_entries = (bootboot.size - 128) / 16;
         for (u64 i = 0; i < mmap_entries; i++)
         {
             u64 size = MMapEnt_Size(ptr);
@@ -92,22 +96,19 @@ namespace MemoryManager
         memset(page_bitmap_addr, 0xFF, page_bitmap_size);
 
         ptr = &bootboot.mmap;
-        for (uint64_t i = 0; i < mmap_entries; i++)
+        for (u64 i = 0; i < mmap_entries; i++)
         {
-            uint64_t index = MMapEnt_Ptr(ptr) / ARCH_PAGE_SIZE;
+            u64 index = MMapEnt_Ptr(ptr) / ARCH_PAGE_SIZE;
             if (!MMapEnt_IsFree(ptr)) { reserved_mem += MMapEnt_Size(ptr); }
             else
             {
                 free_mem += MMapEnt_Size(ptr);
-                for (uint64_t j = 0; j < (MMapEnt_Size(ptr) / ARCH_PAGE_SIZE); j++)
+                for (u64 j = 0; j < (MMapEnt_Size(ptr) / ARCH_PAGE_SIZE); j++) { page_bitmap_set(index + j, false); }
-                {
-                    page_bitmap_set(index + j, false);
-                }
             }
             ptr++;
         }
 
-        lock_pages((u64)page_bitmap_addr, page_bitmap_size / ARCH_PAGE_SIZE + 1);
+        lock_frames((u64)page_bitmap_addr, page_bitmap_size / ARCH_PAGE_SIZE + 1);
     }
 
     void init()
@@ -116,21 +117,21 @@ namespace MemoryManager
         MMU::setup_initial_page_directory();
     }
 
-    void lock_page(u64 page)
+    void lock_frame(u64 frame)
     {
-        uint64_t index = ((uint64_t)page) / ARCH_PAGE_SIZE;
+        const u64 index = ((u64)frame) / ARCH_PAGE_SIZE;
         if (page_bitmap_read(index)) return;
         page_bitmap_set(index, true);
         used_mem += ARCH_PAGE_SIZE;
         free_mem -= ARCH_PAGE_SIZE;
     }
 
-    void lock_pages(u64 pages, u64 count)
+    void lock_frames(u64 frames, u64 count)
     {
-        for (u64 index = 0; index < count; index++) { lock_page(pages + (index * ARCH_PAGE_SIZE)); }
+        for (u64 index = 0; index < count; index++) { lock_frame(frames + (index * ARCH_PAGE_SIZE)); }
     }
 
-    Result<u64> alloc_physical_page()
+    Result<u64> alloc_frame()
     {
         for (u64 index = start_index; index < (page_bitmap_size * 8); index++)
         {
@@ -145,9 +146,9 @@ namespace MemoryManager
         return err; // FIXME: ENOMEM.
     }
 
-    Result<void> free_physical_page(u64 page)
+    Result<void> free_frame(u64 frame)
     {
-        u64 index = page / ARCH_PAGE_SIZE;
+        const u64 index = frame / ARCH_PAGE_SIZE;
         if (index > (page_bitmap_size * 8)) return err;
         if (!page_bitmap_read(index)) return err;
         page_bitmap_set(index, false);
@@ -159,7 +160,7 @@ namespace MemoryManager
 
     Result<void> remap(u64 address, usize count, int flags)
     {
-        check(is_aligned(address, ARCH_PAGE_SIZE));
+        CHECK_PAGE_ALIGNED(address);
 
         while (count--)
         {
@@ -170,6 +171,62 @@ namespace MemoryManager
         return {};
     }
 
+    Result<void> map(u64 virt, u64 phys, usize count, int flags)
+    {
+        CHECK_PAGE_ALIGNED(virt);
+        CHECK_PAGE_ALIGNED(phys);
+
+        while (count--)
+        {
+            TRY(MMU::map(virt, phys, flags));
+            virt += ARCH_PAGE_SIZE;
+            phys += ARCH_PAGE_SIZE;
+        }
+
+        return {};
+    }
+
+    Result<u64> alloc_at(u64 virt, usize count, int flags)
+    {
+        CHECK_PAGE_ALIGNED(virt);
+
+        while (count--)
+        {
+            u64 frame = TRY(alloc_frame());
+            TRY(MMU::map(virt, frame, flags));
+            virt += ARCH_PAGE_SIZE;
+        }
+
+        return virt;
+    }
+
+    Result<void> unmap_owned(u64 virt, usize count)
+    {
+        CHECK_PAGE_ALIGNED(virt);
+
+        while (count--)
+        {
+            u64 frame = TRY(MMU::unmap(virt));
+            TRY(free_frame(frame));
+            virt += ARCH_PAGE_SIZE;
+        }
+
+        return {};
+    }
+
+    Result<void> unmap_weak(u64 virt, usize count)
+    {
+        CHECK_PAGE_ALIGNED(virt);
+
+        while (count--)
+        {
+            TRY(MMU::unmap(virt));
+            virt += ARCH_PAGE_SIZE;
+        }
+
+        return {};
+    }
+
     Result<void> remap_unaligned(u64 address, usize count, int flags)
     {
         if (!is_aligned(address, ARCH_PAGE_SIZE)) count++;

kernel/src/memory/MemoryManager.h

@@ -8,11 +8,11 @@ namespace MemoryManager
 
     Result<void> protect_kernel_sections();
 
-    Result<u64> alloc_physical_page();
+    Result<u64> alloc_frame();
-    Result<void> free_physical_page(u64 page);
+    Result<void> free_frame(u64 frame);
 
-    void lock_page(u64 page);
+    void lock_frame(u64 frame);
-    void lock_pages(u64 pages, u64 count);
+    void lock_frames(u64 frames, u64 count);
 
     Result<void> remap(u64 address, usize count, int flags);
     Result<void> remap_unaligned(u64 address, usize count, int flags);
@@ -20,6 +20,13 @@ namespace MemoryManager
     bool validate_readable_page(u64 address);
     bool validate_writable_page(u64 address);
 
+    Result<void> map(u64 virt, u64 phys, usize count, int flags);
+
+    Result<u64> alloc_at(u64 virt, usize count, int flags);
+
+    Result<void> unmap_owned(u64 virt, usize count);
+    Result<void> unmap_weak(u64 virt, usize count);
+
     u64 free();
     u64 used();
     u64 reserved();