Add HIPPO module and starting tracking free physical pages

src/hulk/hippo.d

@@ -0,0 +1,106 @@
+/**
+ * HIPPO, the HOS In-place Physical Page Organizer.
+ */
+module hulk.hippo;
+
+import hulk.header;
+import hulk.bootinfo;
+import hulk.klog;
+
+extern extern(C) ubyte * _hulk_bss_size;
+
+struct hippo
+{
+    /**
+     * Linked list node entry for a physical page.
+     */
+    private struct PhysicalPage
+    {
+        PhysicalPage * next;
+    }
+
+    /**
+     * Linked list of free physical pages.
+     */
+    private static __gshared PhysicalPage * free_pages;
+
+    /**
+     * Number of free physical pages.
+     */
+    private static __gshared size_t n_free_pages;
+
+    /**
+     * Initialize HIPPO.
+     *
+     * Ok, what we do here is iterate through all of the memory map regions in
+     * the bootinfo memory_map array, and create a linked list of all free
+     * physical pages that are available. Within the available memory regions,
+     * we have to watch out for the following items:
+     *   1) HULK binary (text + data)
+     *     - This includes the HULK header and bootinfo structures
+     *   2) HULK bss
+     *   3) HULK stack
+     *   4) Framebuffer
+     *   5) Page tables
+     *
+     * @param bootinfo HULK boot information structure.
+     */
+    public static void initialize(HulkHeader * header)
+    {
+        size_t usable_memory;
+        ulong[2][5] reserved = [
+            [header.bootinfo.hulk_phys, cast(ulong)header.total_size],
+            [header.bootinfo.bss_phys, cast(ulong)&_hulk_bss_size],
+            [header.bootinfo.stack_phys, header.stack_size],
+            [cast(ulong)header.bootinfo.fb.buffer, header.bootinfo.fb.height * header.bootinfo.fb.stride],
+            [header.bootinfo.pt_phys, header.bootinfo.pt_size],
+        ];
+        for (size_t ri = 0u; ri < reserved.length; ri++)
+        {
+            reserved[ri][1] += reserved[ri][0];
+        }
+        for (size_t bii = 0u; bii < header.bootinfo.memory_map_count; bii++)
+        {
+            if (header.bootinfo.memory_map[bii].type == BootInfo.MemoryRegion.Type.Conventional)
+            {
+                ulong phys = header.bootinfo.memory_map[bii].base;
+                ulong phys_end = phys + header.bootinfo.memory_map[bii].size;
+                usable_memory += header.bootinfo.memory_map[bii].size;
+                phys_loop: while (phys < phys_end)
+                {
+                    bool is_reserved = false;
+                    for (size_t ri = 0u; ri < reserved.length; ri++)
+                    {
+                        if ((reserved[ri][0] <= phys) && (phys < reserved[ri][1]))
+                        {
+                            is_reserved = true;
+                            break;
+                        }
+                    }
+                    if (!is_reserved)
+                    {
+                        free_page(phys);
+                    }
+                    phys += 4096u;
+                }
+            }
+        }
+        size_t usable_kb = usable_memory >> 10u;
+        size_t usable_mb = usable_kb >> 10u;
+        size_t frac_mb = ((1000u * (usable_kb & 0x3FFu)) + 512u) >> 10u;
+        klog.writefln("Found %u.%03uMB of usable RAM", usable_mb, frac_mb);
+    }
+
+    /**
+     * Free a physical page.
+     *
+     * @param phys Physical page address.
+     */
+    private static void free_page(ulong phys)
+    {
+        PhysicalPage * pp = cast(PhysicalPage *)phys;
+        pp.next = free_pages;
+        free_pages = pp;
+        n_free_pages++;
+    }
+}

src/hulk/hulk.d

@@ -11,6 +11,7 @@ import ldc.attributes;
 import hulk.kfont;
 import hulk.klog;
 import hulk.hurl;
+import hulk.hippo;
 
 extern extern(C) __gshared ubyte _hulk_total_size;
 
@@ -36,6 +37,8 @@ void hulk_start()
 
     klog.writefln("Welcome to HULK, the HOS UltraLight Kernel!");
 
+    hippo.initialize(&hulk_header);
+
     for (;;)
     {
     }

src/hulk/hulk.ld

@@ -26,9 +26,11 @@ SECTIONS
 
     .bss BLOCK(4K) : ALIGN(4K)
     {
+        _hulk_bss_start = .;
         *(COMMON)
         *(.bss)
     }
+    _hulk_bss_size = . - _hulk_bss_start;
 
     . = ALIGN(4K);