From b55887a95d71fcb62992d21edd19c871dd00403c Mon Sep 17 00:00:00 2001
From: Steffen Vogel <post@steffenvogel.de>
Date: Mon, 30 Jun 2014 00:05:56 +0200
Subject: [PATCH] added bitmap allocator

---
 include/eduos/memory.h |  48 ++++++++++++++++++++
 mm/memory.c            | 101 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 149 insertions(+)
 create mode 100644 include/eduos/memory.h

diff --git a/include/eduos/memory.h b/include/eduos/memory.h
new file mode 100644
index 0000000..9a5766a
--- /dev/null
+++ b/include/eduos/memory.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *    * Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *    * Neither the name of the University nor the names of its contributors
+ *      may be used to endorse or promote products derived from this
+ *      software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @author Steffen Vogel
+ * @file include/memory.h
+ * @brief Memory related functions
+ *
+ * This file contains platform independent memory functions
+ */
+
+#ifndef __MEMORY_H__
+#define __MEMORY_H__
+
+/** @brief Initialize the memory subsystem */
+int memory_init();
+
+/** @brief Request physical page frames */
+size_t get_pages(size_t npages);
+
+/** @brief release physical page frames */
+int put_pages(size_t phyaddr, size_t npages);
+
+#endif
diff --git a/mm/memory.c b/mm/memory.c
index 9b32356..6c40471 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -27,8 +27,21 @@
 
 #include <eduos/stddef.h>
 #include <eduos/stdlib.h>
+#include <eduos/spinlock.h>
+
+#include <asm/atomic.h>
+#include <asm/multiboot.h>
+#include <asm/page.h>
+
 
 static char stack[MAX_TASKS-1][KERNEL_STACK_SIZE];
+static char bitmap[BITMAP_SIZE];
+
+static spinlock_t bitmap_lock = SPINLOCK_INIT;
+
+atomic_int32_t total_pages = ATOMIC_INIT(0);
+atomic_int32_t total_allocated_pages = ATOMIC_INIT(0);
+atomic_int32_t total_available_pages = ATOMIC_INIT(0);
 
 void* create_stack(tid_t id)
 {
@@ -41,3 +54,91 @@ void* create_stack(tid_t id)
 
 	return (void*) stack[id-1];
 }
+
+inline static int page_marked(size_t i)
+{
+	size_t index = i >> 3;
+	size_t mod = i & 0x7;
+
+	return  (bitmap[index] & (1 << mod));
+}
+
+inline static void page_set_mark(size_t i)
+{
+	size_t index = i >> 3;
+	size_t mod = i & 0x7;
+
+	bitmap[index] = bitmap[index] | (1 << mod);
+}
+
+inline static void page_clear_mark(size_t i)
+{
+	size_t index = i / 8;
+	size_t mod = i % 8;
+
+	bitmap[index] = bitmap[index] & ~(1 << mod);
+}
+
+size_t get_pages(size_t npages)
+{
+	size_t cnt, off;
+
+	if (BUILTIN_EXPECT(!npages, 0))
+		return 0;
+	if (BUILTIN_EXPECT(npages > atomic_int32_read(&total_available_pages), 0))
+		return 0;
+
+	spinlock_lock(&bitmap_lock);
+
+	off = 1;
+	while (off <= BITMAP_SIZE*8 - npages) {
+		for (cnt=0; cnt<npages; cnt++) {
+			if (page_marked(off+cnt))
+				goto next;
+		}
+
+		for (cnt=0; cnt<npages; cnt++) {
+			page_set_mark(off+cnt);
+		}
+
+		spinlock_unlock(&bitmap_lock);
+
+		atomic_int32_add(&total_allocated_pages, npages);
+		atomic_int32_sub(&total_available_pages, npages);
+
+		return off << PAGE_BITS;
+
+next:		off += cnt+1;
+	}
+
+	spinlock_unlock(&bitmap_lock);
+
+	return 0;
+}
+
+int put_pages(size_t phyaddr, size_t npages)
+{
+	size_t i, ret = 0;
+	size_t base = phyaddr >> PAGE_BITS;
+
+	if (BUILTIN_EXPECT(!phyaddr, 0))
+		return -EINVAL;
+	if (BUILTIN_EXPECT(!npages, 0))
+		return -EINVAL;
+
+	spinlock_lock(&bitmap_lock);
+
+	for (i=0; i<npages; i++) {
+		if (page_marked(base+i)) {
+			page_clear_mark(base+i);
+			ret++;
+		}
+	}
+
+	spinlock_unlock(&bitmap_lock);
+
+	atomic_int32_sub(&total_allocated_pages, ret);
+	atomic_int32_add(&total_available_pages, ret);
+
+	return ret;
+}