1 files changed, 280 insertions, 0 deletions
diff --git a/kernel/libk/liballoc.cc b/kernel/libk/liballoc.cc
new file mode 100644
index 0000000..6f48557
--- /dev/null
+++ b/kernel/libk/liballoc.cc
@@ -0,0 +1,280 @@
+/*
+
+ * bubbl
+ * Copyright (C) 2025  Raghuram Subramani <raghus2247@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <kernel/spinlock.h>
+#include <libk/liballoc.h>
+#include <libk/stdio.h>
+#include <mm/virtual_mm.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* TODO: Kmalloc must have space for a page table *at all times*. */
+
+#define LIBALLOC_MAGIC 0xc001c0de
+#define MAXCOMPLETE 5
+#define MAXEXP 32
+#define MINEXP 8
+
+#define MODE_BEST 0
+#define MODE_INSTANT 1
+
+#define MODE MODE_BEST
+
+namespace LibAlloc
+{
+
+struct boundary_tag *l_freePages[MAXEXP]; //< Allowing for 2^MAXEXP blocks
+int l_completePages[MAXEXP];              //< Allowing for 2^MAXEXP blocks
+
+static unsigned int l_initialized = 0; //< Flag to indicate initialization.
+static unsigned int l_pageSize = 4096; //< Individual page size
+static unsigned int l_pageCount = 1;   //< Minimum number of pages to allocate.
+
+spinlock_t lock;
+bool kmalloc_initialized;
+
+#define liballoc_alloc VirtualMM::alloc_pages
+#define liballoc_free VirtualMM::free_pages
+
+inline int
+liballoc_lock(void)
+{
+  Spinlock::acquire(&lock);
+  return 0;
+}
+
+inline int
+liballoc_unlock(void)
+{
+  Spinlock::release(&lock);
+  return 0;
+}
+
+bool
+initialized(void)
+{
+  return kmalloc_initialized;
+}
+
+void
+initialize(void)
+{
+  // void *x =
+  kmalloc(1);
+  kmalloc_initialized = true;
+  // kfree(x);
+}
+
+static inline int
+getexp(int size)
+{
+  if (size < (1 << MINEXP)) {
+    return -1; // Smaller than the quantum.
+  }
+
+  int shift = MINEXP;
+
+  while (shift < MAXEXP) {
+    if ((1 << shift) > size)
+      break;
+    shift += 1;
+  }
+
+  return shift - 1;
+}
+
+static inline void
+insert_tag(struct boundary_tag *tag, int index)
+{
+  int realIndex;
+
+  if (index < 0) {
+    realIndex = getexp(tag->real_size - sizeof(struct boundary_tag));
+    if (realIndex < MINEXP)
+      realIndex = MINEXP;
+  } else
+    realIndex = index;
+
+  tag->index = realIndex;
+
+  if (l_freePages[realIndex] != NULL) {
+    l_freePages[realIndex]->prev = tag;
+    tag->next = l_freePages[realIndex];
+  }
+
+  l_freePages[realIndex] = tag;
+}
+
+static inline void
+remove_tag(struct boundary_tag *tag)
+{
+  if (l_freePages[tag->index] == tag)
+    l_freePages[tag->index] = tag->next;
+
+  if (tag->prev != NULL)
+    tag->prev->next = tag->next;
+  if (tag->next != NULL)
+    tag->next->prev = tag->prev;
+
+  tag->next = NULL;
+  tag->prev = NULL;
+  tag->index = -1;
+}
+
+static inline struct boundary_tag *
+split_tag(struct boundary_tag *tag)
+{
+  unsigned int remainder
+      = tag->real_size - sizeof(struct boundary_tag) - tag->size;
+
+  struct boundary_tag *new_tag
+      = (struct boundary_tag *) ((unsigned int) tag
+                                 + sizeof(struct boundary_tag) + tag->size);
+
+  new_tag->magic = LIBALLOC_MAGIC;
+  new_tag->real_size = remainder;
+
+  new_tag->next = NULL;
+  new_tag->prev = NULL;
+
+  new_tag->split_left = tag;
+  new_tag->split_right = tag->split_right;
+
+  if (new_tag->split_right != NULL)
+    new_tag->split_right->split_left = new_tag;
+  tag->split_right = new_tag;
+
+  tag->real_size -= new_tag->real_size;
+
+  insert_tag(new_tag, -1);
+
+  return new_tag;
+}
+
+static struct boundary_tag *
+allocate_new_tag(unsigned int size)
+{
+  unsigned int pages;
+  unsigned int usage;
+  struct boundary_tag *tag;
+
+  // This is how much space is required.
+  usage = size + sizeof(struct boundary_tag);
+
+  // Perfect amount of space
+  pages = usage / l_pageSize;
+  if ((usage % l_pageSize) != 0)
+    pages += 1;
+
+  // Make sure it's >= the minimum size.
+  if (pages < l_pageCount)
+    pages = l_pageCount;
+
+  tag = (struct boundary_tag *) liballoc_alloc(pages);
+
+  if (tag == NULL)
+    return NULL; // uh oh, we ran out of memory.
+
+  tag->magic = LIBALLOC_MAGIC;
+  tag->size = size;
+  tag->real_size = pages * l_pageSize;
+  tag->index = -1;
+
+  tag->next = NULL;
+  tag->prev = NULL;
+  tag->split_left = NULL;
+  tag->split_right = NULL;
+
+  return tag;
+}
+
+void *
+kmalloc(size_t size)
+{
+  int index;
+  void *ptr;
+  struct boundary_tag *tag = NULL;
+
+  liballoc_lock();
+
+  if (l_initialized == 0) {
+    for (index = 0; index < MAXEXP; index++) {
+      l_freePages[index] = NULL;
+      l_completePages[index] = 0;
+    }
+    l_initialized = 1;
+  }
+
+  index = getexp(size) + MODE;
+  if (index < MINEXP)
+    index = MINEXP;
+
+  // Find one big enough.
+  tag = l_freePages[index]; // Start at the front of the list.
+  while (tag != NULL) {
+    // If there's enough space in this tag.
+    if ((tag->real_size - sizeof(struct boundary_tag))
+        >= (size + sizeof(struct boundary_tag))) {
+      break;
+    }
+
+    tag = tag->next;
+  }
+
+  // No page found. Make one.
+  if (tag == NULL) {
+    if ((tag = allocate_new_tag(size)) == NULL) {
+      liballoc_unlock();
+      return NULL;
+    }
+
+    index = getexp(tag->real_size - sizeof(struct boundary_tag));
+  } else {
+    remove_tag(tag);
+
+    if ((tag->split_left == NULL) && (tag->split_right == NULL))
+      l_completePages[index] -= 1;
+  }
+
+  // We have a free page.  Remove it from the free pages list.
+
+  tag->size = size;
+
+  // Removed... see if we can re-use the excess space.
+
+  unsigned int remainder
+      = tag->real_size - size
+        - sizeof(struct boundary_tag) * 2; // Support a new tag + remainder
+
+  if (((int) (remainder)
+       > 0) /*&& ( (tag->real_size - remainder) >= (1<<MINEXP))*/) {
+    int childIndex = getexp(remainder);
+
+    if (childIndex >= 0) {
+      struct boundary_tag *new_tag = split_tag(tag);
+      (void) new_tag;
+    }
+  }
+
+  ptr = (void *) ((unsigned int) tag + sizeof(struct boundary_tag));
+  liballoc_unlock();
+  return ptr;
+}
+
+}