Feature: Page Frame Allocator

include/nanvix/mm.h

@@ -116,4 +116,128 @@
 
 /**@}*/
 
+/*============================================================================*
+ * Page Frame Allocator                                                       *
+ *============================================================================*/
+
+/**
+ * @addtogroup kernel-mm-frame Frame Allocator
+ * @ingroup kernel-mm
+ *
+ * @brief Page Frame Allocator
+ */
+/**@{*/
+
+	/**
+	 * @brief Number of page frames for user use.
+	 */
+	#define NUM_UFRAMES (UMEM_SIZE/PAGE_SIZE)
+
+	/**
+	 * @param Null frame.
+	 */
+	#define FRAME_NULL ((frame_t) -1)
+
+	/**
+	 * @brief Asserts if a frame ID is valid.
+	 *
+	 * The frame_is_valid_id() function asserts whether or not the
+	 * frame @p ID is valid.
+	 *
+	 * @returns If @p id is valid, non zero is returned. Otherwise,
+	 * zero is returned instead.
+	 *
+	 * @author Pedro Henrique Penna
+	 */
+	static inline int frame_is_valid_id(int id)
+	{
+		return ((id >= 0) && (id < NUM_UFRAMES));
+	}
+
+	/**
+	 * @brief Converts an ID of a user page frame to a page frame number.
+	 *
+	 * @param id ID of target user page frame.
+	 *
+	 * @returns Frame number of target user page frame.
+	 *
+	 * @author Pedro Henrique Penna
+	 */
+	static inline frame_t frame_id_to_num(int id)
+	{
+		/* Invalid ID. */
+		if (!frame_is_valid_id(id))
+			return (FRAME_NULL);
+
+		return ((UBASE_PHYS >> PAGE_SHIFT) + id);
+	}
+
+	/**
+	 * @brief Asserts if a frame number is valid.
+	 *
+	 * The frame_is_valid_num() function asserts whether or not the
+	 * frame number @p frame is valid.
+	 *
+	 * @returns If @p frame is valid, non zero is returned. Otherwise,
+	 * zero is returned instead.
+	 *
+	 * @author Pedro Henrique Penna
+	 */
+	static inline int frame_is_valid_num(frame_t frame)
+	{
+		return (
+			(frame >= (UBASE_PHYS >> PAGE_SHIFT)) &&
+			(frame < ((UBASE_PHYS >> PAGE_SHIFT) + NUM_UFRAMES))
+		);
+	}
+
+	/**
+	 * @brief Converts a page frame number to an ID of a user page frame.
+	 *
+	 * @param frame Number of the target page frame.
+	 *
+	 * @returns ID of target user page frame.
+	 *
+	 * @author Pedro Henrique Penna
+	 */
+	static inline int frame_num_to_id(frame_t frame)
+	{
+		/* Invalid frame. */
+		if (!frame_is_valid_num(frame))
+			return (-1);
+
+		return (frame - (UBASE_PHYS >> PAGE_SHIFT));
+	}
+
+	/**
+	 * @brief Allocates a page frame.
+	 *
+	 * @returns Upon successful completion, the number of the
+	 * allocated page frame is returned. Upon failure, @p FRAME_NULL
+	 * is returned instead.
+	 */
+	EXTERN frame_t frame_alloc(void);
+
+	/**
+	 * @brief Frees a page frame.
+	 *
+	 * @param frame Number of the target page frame.
+	 *
+	 * @returns Upon successful completion, zero is returned. Upon
+	 * failure, a negative error code is returned instead.
+	 */
+	EXTERN int frame_free(frame_t frame);
+
+	/**
+	 * @brief Runs unit tests on the frame allocator.
+	 */
+	EXTERN void frame_test_driver(void);
+
+	/**
+	 * @brief Initializes the frame allocator.
+	 */
+	EXTERN void frame_init(void);
+
+/**@}*/
+
 #endif /** NANVIX_MM_H_ */

src/kernel/mm/frame.c

@@ -0,0 +1,113 @@
+/*
+ * MIT License
+ *
+ * Copyright(c) 2011-2018 Pedro Henrique Penna <pedrohenriquepenna@gmail.com>
+ *              2015-2016 Davidson Francis     <davidsondfgl@gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <nanvix/hal/hal.h>
+#include <nanvix/const.h>
+#include <nanvix/mm.h>
+#include <nanvix/klib.h>
+#include <errno.h>
+
+/**
+ * @brief Reference count for page frames.
+ */
+PRIVATE int frames[NUM_UFRAMES] = {0, };
+
+/*============================================================================*
+ * frame_alloc()                                                              *
+ *============================================================================*/
+
+/**
+ * The frame_alloc() function searches sequentially, for a free frame
+ * to be allocated. The first free frame is allocated (if any) and its
+ * number is returned.
+ */
+PUBLIC frame_t frame_alloc(void)
+{
+	/* Search for a free frame. */
+	for (int i = 0; i < NUM_UFRAMES; i++)
+	{
+		/* Found it. */
+		if (frames[i] == 0)
+		{
+			frames[i] = 1;
+			hal_dcache_invalidate();
+
+			return (frame_id_to_num(i));
+		}
+	}
+
+	kprintf("mm: page frame overflow");
+
+	return (FRAME_NULL);
+}
+
+/*============================================================================*
+ * frame_free()                                                               *
+ *============================================================================*/
+
+/**
+ * The frame_free() function frees a previously allocated page frame
+ * whose number equals to @p frame.
+ */
+PUBLIC int frame_free(frame_t frame)
+{
+	if (!frame_is_valid_num(frame))
+		return (-EINVAL);
+
+	if (frames[frame_num_to_id(frame)] == 0)
+	{
+		kprintf("mm: double free on page frame");
+		return (-EFAULT);
+	}
+
+	frames[frame_num_to_id(frame)]--;
+	hal_dcache_invalidate();
+
+	return (0);
+}
+
+/*============================================================================*
+ * frame_init()                                                               *
+ *============================================================================*/
+
+/**
+ * The frame_init() function initializes internal structures of the
+ * page frame allocator. Additionally, if the kernel is compiled
+ * without the @p NDEBUG build option, unit tests on the page frame
+ * allocator are launched once its initialization is completed.
+ */
+PUBLIC void frame_init(void)
+{
+	kprintf("initializing the page frame allocator");
+
+#ifndef __NANVIX_FAST_BOOT
+	for (int i = 0; i < NUM_UFRAMES; i++)
+		frames[i] = 0;
+#endif
+
+#ifndef NDEBUG
+	frame_test_driver();
+#endif
+}