/* 
 * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM.
 */

/**
 * @file arch/x86/include/asm/page.h
 * @brief Definitions and functions related to paging
 * @author Stefan Lankes
 *
 * This file defines the interface for paging as like structures related to paging.
 */

#ifndef __ARCH_PAGE_H__
#define __ARCH_PAGE_H__

#include <metalsvm/stddef.h>
#include <metalsvm/stdlib.h>

#define _PAGE_BIT_PRESENT	0	/* is present */
#define _PAGE_BIT_RW		1	/* writeable */
#define _PAGE_BIT_USER		2	/* userspace addressable */
#define _PAGE_BIT_PWT		3	/* page write through */
#define _PAGE_BIT_PCD		4	/* page cache disabled */
#define _PAGE_BIT_ACCESSED	5	/* was accessed (raised by CPU) */
#define _PAGE_BIT_DIRTY		6	/* was written to (raised by CPU) */
#define _PAGE_BIT_PSE		7	/* 4 MB (or 2MB) page */
#define _PAGE_BIT_PAT		7	/* on 4KB pages */
#define _PAGE_BIT_GLOBAL	8	/* Global TLB entry PPro+ */
#define _PAGE_BIT_SVM_STRONG	9	/* mark a virtual address range as used by the SVM system */
#define _PAGE_BIT_SVM_LAZYRELEASE	10 /* mark a virtual address range as used by the SVM system */
#define _PAGE_BIT_SVM_INIT	11	/* mark if the MBP proxy is used  */

/// Page is present
#define PG_PRESENT	(1 << _PAGE_BIT_PRESENT)
/// Page is read- and writable
#define PG_RW		(1 << _PAGE_BIT_RW)
/// Page is addressable from userspace
#define PG_USER		(1 << _PAGE_BIT_USER)
/// Page write through is activated
#define PG_PWT		(1 << _PAGE_BIT_PWT)
/// Page cache is disabled
#define PG_PCD		(1 << _PAGE_BIT_PCD)
/// Page was recently accessed (set by CPU)
#define PG_ACCESSED	(1 << _PAGE_BIT_ACCESSED)
/// Page is dirty due to recentwrite-access (set by CPU)
#define PG_DIRTY	(1 << _PAGE_BIT_DIRTY)
/// Big page: 4MB (or 2MB)
#define PG_PSE		(1 << _PAGE_BIT_PSE)
/// Page is part of the MPB (SCC specific entry)
#define PG_MPE		PG_PSE
/// Global TLB entry (Pentium Pro and later)
#define PG_GLOBAL	(1 << _PAGE_BIT_GLOBAL)
/// Pattern flag
#define PG_PAT		(1 << _PAGE_BIT_PAT)
/// This virtual address range is used by SVM system as marked
#define PG_SVM PG_SVM_STRONG
#define PG_SVM_STRONG		(1 << _PAGE_BIT_SVM_STRONG)
/// This virtual address range is used by SVM system as marked
#define PG_SVM_LAZYRELEASE	(1 << _PAGE_BIT_SVM_LAZYRELEASE)
/// Currently, no page frame is behind this page (only the MBP proxy)
#define PG_SVM_INIT		(1 << _PAGE_BIT_SVM_INIT)

/// This is a whole set of flags (PRESENT,RW,ACCESSED,DIRTY) for kernelspace tables
#define KERN_TABLE	(PG_PRESENT|PG_RW|PG_ACCESSED|PG_DIRTY)
/// This is a whole set of flags (PRESENT,RW,ACCESSED,DIRTY,USER) for userspace tables
#define USER_TABLE	(PG_PRESENT|PG_RW|PG_ACCESSED|PG_DIRTY|PG_USER)
/// This is a whole set of flags (PRESENT,RW,GLOBAL) for kernelspace pages
#define KERN_PAGE	(PG_PRESENT|PG_RW|PG_GLOBAL)
/// This is a whole set of flags (PRESENT,RW,USER) for userspace pages
#define USER_PAGE	(PG_PRESENT|PG_RW|PG_USER)

#if __SIZEOF_POINTER__ == 4
#define PGT_ENTRIES	1024
#elif __SIZEOF_POINTER__ == 8
#define PGT_ENTRIES	512
#endif
 
/** @brief Page table structure
 *
 * This structure keeps page table entries.\n
 * On a 32bit system, a page table consists normally of 1024 entries.
 */
typedef struct page_table
{
	/// Page table entries are unsigned 32bit integers.
	size_t entries[PGT_ENTRIES];
} page_table_t __attribute__ ((aligned (4096)));

/** @brief Page directory structure
 *
 * This structure keeps page directory entries.\
 * On a 32bit system, a page directory consists normally of 1024 entries.
 */
typedef struct page_dir
{
	/// Page dir entries are unsigned 32bit integers.
	size_t entries[PGT_ENTRIES];
} page_dir_t __attribute__ ((aligned (4096)));

/** @brief Converts a virtual address to a physical
 *
 * @param viraddr Virtual address to convert
 * @return physical address
 */
size_t virt_to_phys(size_t viraddr);

/** @brief Allocates a virtual address space range of npages
 *
 * The address range with special flags (if given) will have the size of n pages.
 *
 * @param npages The range in page-granularity
 * @param flags further page flags
 *
 * @return The new range's address
 */
size_t vm_alloc(uint32_t npages, uint32_t flags);

/** @brief Frees a range in the virtual address space
 *
 * @param addr Address of the range
 * @param npages Size of the range in pages
 *
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure.
 */
int vm_free(size_t addr, uint32_t npages);

/** @brief Unmap the physical memory at a specific virtual address
 *
 * All Page table entries within this range will be marked as not present
 * and (in the case of userspace memory) the page usage of the task will be decremented.
 *
 * @param viraddr The range's virtual address
 * @param npages The range's size in pages
 *
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure.
 */
int unmap_region(size_t viraddr, uint32_t npages);

/** @brief Mapping a physical mem-region to a virtual address
 *
 * Maps a physical memory region to a specific virtual address.
 * If the virtual address is zero, this functions allocates a valid virtual address on demand.
 *
 * @param viraddr Desired virtual address
 * @param phyaddr Physical address to map from
 * @param npages The region's size in number of pages
 * @param flags Further page flags
 *
 * @return
 * - A virtual address on success
 * - 0 on failure.
 */
size_t map_region(size_t viraddr, size_t phyaddr, uint32_t npages, uint32_t flags);

/** @brief Sets up the environment and enables paging.
 *
 * - Installs the page handler IRQ
 * - sets up the whole page directory and page tables for the kernel space (virt adr = phys adr)
 * - maps VGA, multi boot info and initrd into kernel space
 * - writes to cr0 and cr3 register
 * - marks 'paging_enabled' var = 1
 * - Registers kernel thread for task state switching
 *
 * @return returns
 * - 0 on success
 * - -ENOMEM (-12) on failure
 */
int arch_paging_init(void);

/** @brief Returns the page directory of the boot task
 *
 * The boot task's page directory is a static array of page_dir_t type vars.
 *
 * @return Returns the address of the boot task's page dir array.
 */
page_dir_t* get_boot_pgd(void);

/** @brief Setup a new page directory for a new user-level task
 *
 * @param task Pointer to the task-specific task_t structure
 * @param copy If true: PGD will be a copy of the kernel's address space PGD
 *
 * @return
 * - counter of allocated page tables
 * - -ENOMEM (-12) on failure
 */
int create_pgd(task_t* task, int copy);

/** @brief Delete page directory and its page tables
 *
 * Puts page tables and page directory back to buffer and
 * sets the task's page directory pointer to NULL
 *
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure (in case PGD is still the boot-pgd).
 */
int drop_pgd(void);

/** @brief Change the page permission in the page tables of the current task
 *
 * Applies given flags noted in the 'flags' parameter to
 * the range denoted by virtual start and end addresses.
 *
 * @param start Range's virtual start address
 * @param end Range's virtual end address
 * @param flags flags to apply
 *
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure.
 */
int change_page_permissions(size_t start, size_t end, uint32_t flags);

#endif