Allocate space for a frame bitmap

Basically there, but still some kinks to work out...

src/memory/FrameAllocator.cc

@@ -10,6 +10,7 @@
 #include "kstd/Memory.hh"
 #include "kstd/PrintFormat.hh"
 #include "memory/FrameAllocator.hh"
+#include "memory/Memory.hh"
 
 namespace kernel {
 
@@ -23,16 +24,68 @@ void
 FrameAllocator::initialize(const StartupInformation& startupInformation)
 {
     // Page frame bitmap starts immediately after the kernel.
-    mBitmap = reinterpret_cast<u8*>(startupInformation.kernelEnd);
+    mBitmap = reinterpret_cast<Bitmap*>(startupInformation.kernelEnd);
 
-    const u32 pageSize = startupInformation.pageSize;
+    const u32 numberOfPages = startupInformation.memorySize() / memory::pageSize;
-    const u32 numberOfPages = startupInformation.multibootInformation->memoryKB() * 1024 / pageSize;
+    const u32 pagesPerBitmap = Bitmap::length;
-    mBitmapSize = numberOfPages / (sizeof(FrameBitmap) * 8);
+
+    mBitmapSize = numberOfPages / pagesPerBitmap;
+    if ((numberOfPages % pagesPerBitmap) != 0) {
+        // Add an extra bitmap for the last few pages.
+        mBitmapSize++;
+    }
 
     kstd::printFormat("Allocated bitmap of %ld bytes for %ld pages at 0x%08lX\n", mBitmapSize, numberOfPages, u32(mBitmap));
 
     // TODO: Before modifying this memory, maybe make sure none of the multiboot information is hanging out there?
+
     kstd::Memory::zero(mBitmap, mBitmapSize);
+
+    // Lower 1 MB is always allocated.
+    reserveRange(0, 0x100000);
+    // Kernel image (including this frame bitmap) is always allocated.
+    reserveRange(startupInformation.kernelStart, startupInformation.kernelSize() + mBitmapSize);
+}
+
+void
+FrameAllocator::reserveRange(u32 start,
+                             u32 length)
+{
+    // TODO: `start` and `length` validation.
+    const u32 pagesPerBitmap = Bitmap::length;
+
+    const u32 startPage = memory::pageAlignDown(start) / memory::pageSize;
+    const u32 endPage = memory::pageAlignUp(start + length) / memory::pageSize;
+
+    // Iterators
+    u32 page = startPage;
+    u32 bitmapIndex = start / pagesPerBitmap;
+    u8 bitmapOffset = start % pagesPerBitmap;
+
+    kstd::printFormat("Reserving %ld pages for memory addresses between 0x%08lX and 0x%08lX\n", endPage - startPage, start, start + length);
+
+    // Fill in any entries that aren't aligned to pagesPerBitmap at the beginning.
+    while (bitmapOffset != 0) {
+        mBitmap[bitmapIndex].set(bitmapOffset);
+        bitmapOffset = (bitmapOffset + 1) % 8;
+        page++;
+        if (bitmapOffset == 0) {
+            bitmapIndex++;
+        }
+    }
+
+    // Fill in entries in `pagesPerBitmap` sized chunks.
+    while ((endPage - page) > pagesPerBitmap) {
+        mBitmap[bitmapIndex++].fill();
+        page += pagesPerBitmap;
+    }
+
+    // Fill in any entries that aren't aligned to `pagesPerBitmap` at the end of the range.
+    while ((endPage - page) > 0) {
+        mBitmap[bitmapIndex].set(bitmapOffset);
+        bitmapOffset = (bitmapOffset + 1) % 8;
+        page++;
+    }
 }
 
 } /* namespace kernel */

src/memory/FrameAllocator.hh

@@ -10,9 +10,9 @@
 #define __MEMORY_FRAMEALLOCATOR_HH__
 
 #include "StartupInformation.hh"
+#include "kstd/Bitmap.hh"
 #include "kstd/Types.hh"
 
-
 namespace kernel {
 
 struct FrameAllocator
@@ -22,12 +22,15 @@ struct FrameAllocator
     void initialize(const StartupInformation& startupInformation);
 
 private:
-    typedef u8 FrameBitmap;
+    typedef kstd::Bitmap<u8> Bitmap;
 
     /** Starting address of the frame allocation bitmap. */
-    FrameBitmap* mBitmap;
+    Bitmap* mBitmap;
-    /** Size of the bitmap in bytes. */
+    /** Size of the bitmap in `sizeof(Bitmap)` units. */
     u32 mBitmapSize;
+
+    /** Reserve a range of memory. */
+    void reserveRange(u32 start, u32 length);
 };
 
 } /* namespace  */