/* 
 * 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
 * @author Steffen Vogel <steffen.vogel@rwth-aachen.de>
 *
 * 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>

/// Page offset bits
#define PAGE_BITS		12

#ifdef CONFIG_X86_32
 /// Number of page map indirections
 #define PAGE_MAP_LEVELS	2
 /// Page map bits
 #define PAGE_MAP_BITS		10
 /// Total operand width in bits
 #define BITS			32
 /// Linear/virtual address width
 #define VIRT_BITS		BITS
 /// Physical address width (we dont support PAE)
 #define PHYS_BITS		BITS
#elif defined(CONFIG_X86_64)
 /// Number of page map indirections
 #define PAGE_MAP_LEVELS	4
 /// Page map bits
 #define PAGE_MAP_BITS		9
 /// Total operand width in bits
 #define BITS			64
 /// Linear/virtual address width
 #define VIRT_BITS		48
 /// Physical address width (maximum value)
 #define PHYS_BITS		52
#endif

/// The size of a single page in bytes
#define PAGE_SIZE		( 1L << PAGE_BITS)
/// The number of entries in a page map table
#define PAGE_MAP_ENTRIES	( 1L << PAGE_MAP_BITS)
/// Mask the page address
#define PAGE_MASK		(-1L << PAGE_BITS)
/// Mask the entry in a page table
#define PAGE_ENTRY_MASK		(-1L << (PAGE_BITS-PAGE_MAP_BITS))
/// Mask for all flag bits in a page map entry (including ignored bits)
#define PAGE_FLAGS_MASK		(~(-1L << PAGE_BITS) | (-1L << VIRT_BITS))

/// Align to next page
#define PAGE_FLOOR(addr)	(((addr) + PAGE_SIZE - 1) & PAGE_MASK)
/// Align to page
#define PAGE_CEIL(addr)		( (addr)                  & PAGE_MASK)
/// Sign extension to get a valid canonical address (hack: by using aritmethic shifts)
#define VIRT_SEXT(addr)		((ssize_t) addr << (BITS-VIRT_BITS) >> (BITS-VIRT_BITS))

// base addresses of page map tables
#ifdef CONFIG_X86_32
 #define PAGE_MAP_PGD			0xFFFFF000
 #define PAGE_MAP_PGT			0xFFC00000
#elif defined(CONFIG_X86_64)
 #define PAGE_MAP_PML4		0xFFFFFFFFFFFFF000
 #define PAGE_MAP_PDPT		0xFFFFFFFFFFE00000
 #define PAGE_MAP_PGD		0xFFFFFFFFC0000000
 #define PAGE_MAP_PGT		0xFFFFFF8000000000
#endif

/// Page is present
#define PG_PRESENT		(1 << 0)
/// Page is read- and writable
#define PG_RW			(1 << 1)
/// Page is addressable from userspace
#define PG_USER			(1 << 2)
/// Page write through is activated
#define PG_PWT			(1 << 3)
/// Page cache is disabled
#define PG_PCD			(1 << 4)
/// Page was recently accessed (set by CPU)
#define PG_ACCESSED		(1 << 5)
/// Page is dirty due to recentwrite-access (set by CPU)
#define PG_DIRTY		(1 << 6)
/// Huge page: 4MB (or 2MB, 1GB)
#define PG_PSE			(1 << 7)
/// Page is part of the MPB (SCC specific entry)
#define PG_MPE			PG_PSE
/// Page attribute table
#define PG_PAT			PG_PSE
/// Global TLB entry (Pentium Pro and later)
#define PG_GLOBAL		(1 << 8)
/// This virtual address range is used by SVM system as marked
#define PG_SVM			(1 << 9)
#define PG_SVM_STRONG		PG_SVM
/// This virtual address range is used by SVM system as marked
#define PG_SVM_LAZYRELEASE	(1 << 10)
/// Currently, no page frame is behind this page (only the MBP proxy)
#define PG_SVM_INIT		(1 << 11)
/// Disable execution for this page
#define PG_XD			(1L << 63)

/// This is a whole set of flags (PRESENT,RW,ACCESSED,DIRTY) for kernelspace tables
#define PG_TABLE		(PG_PRESENT|PG_RW|PG_XD)
/// This is a whole set of flags (PRESENT,RW,GLOBAL) for kernelspace pages
#define PG_PAGE			(PG_PRESENT|PG_RW|PG_GLOBAL|PG_XD)

/** @brief A single entry in a page map */
typedef size_t page_entry_t;

/** @brief General page map structure
 *
 * This page map structure is a general type for all indirecton levels.
 * As all page map levels containing the same amount of entries.
 * All page maps must be page aligned!
 */
typedef struct page_map {
	page_entry_t entries[PAGE_MAP_ENTRIES];
} __attribute__ ((aligned (PAGE_SIZE))) page_map_t;

/** @brief A callback type for the page map iterator
 *
 * @param entry A pointer to the current page map entry
 * @return
 * - 0 if we want to skip underlying page tables
 * - >0 if want to recurse into underlying page tables
 */
typedef int (*page_cb_t)(page_entry_t* entry, int level);

/** @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_map_t* get_boot_page_map(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: copy userspace pages and tables
 *
 * @return
 * - counter of allocated page tables
 * - -ENOMEM (-12) on failure
 */
int copy_page_map(struct task* task, int copy);

/** @brief Delete all page map structures of the current task
 *
 * Puts PML4, PDPT, PGD, PGT tables back to buffer and
 * sets the task's page map pointer to NULL
 *
 * @return
 * - 0 on success
 * - -EINVAL (-22) on failure (in case PGD is still the boot-pgd).
 */
int drop_page_map(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);

/** @brief Dump mapped memory */
void page_dump(size_t start, size_t end);

/** @brief Print stats about page flags
 *
 * @param reset Reset accessed and dirty bits in page tables
 */
void page_stats(size_t start, size_t end, int reset);

#endif