path: root/include/vm.h

/**
** @file	vm.h
**
** @author	CSCI-452 class of 20245
**
** @brief	Virtual memory-related declarations.
*/

#ifndef VM_H_
#define VM_H_

#include <defs.h>
#include <types.h>

#include <procs.h>

/*
** VM layout of the system
**
** User processes use the first 4MB of the 32-bit address space; see the
** next comment for details.
**
** Kernel virtual addresses are in the "higher half" range, beginning
** at 0x80000000.  We define our mapping such that virtual address
** 0x8nnnnnnn maps to physical address 0x0nnnnnnn, so converting between
** the two is trivial.
*/

/*
** VM layout of process' address space
**
** Processes are limited to the first 4MB of the 32-bit address space:
**
**  Address Range            Contents
**  =======================  ================================
**  0x00000000 - 0x00000fff  page 0 is inaccessible
**  0x00001000 - 0x000..fff  text occupies pages 1 - N
**  0x000..000 - 0x000..fff  data occupies pages N+1 - N+d
**  0x000..000 - 0x000..fff  bss occupies pages N+d+1 - N+d+b
**  0x000..000 - 0x003fdfff  unusable
**  0x003fe000 - 0x003fffff  stack occupies last two pages
**
** This gives us the following page table structure:
**
** Page directory:
**   Entries    Contents
**   ========   ==============================
**   0          point to PMT for address space
**   1 - 1023   invalid
**
** Page map table:
**   Entries         Contents
**   ========        ==============================
**   0               invalid
**   1 - N           text frames
**   N+1 - N+d       data frames
**   N+d+1 - N+d+b   bss frames
**   N+d+b+1 - 1021  invalid
**   1022 - 1023     stack frames
*/

/*
** General (C and/or assembly) definitions
*/

// user virtual addresses
#define USER_TEXT 0x00001000
#define USER_STACK 0x003fe000
#define USER_STK_END 0x00400000

// how to find the addresses of the stack pages in the VM hierarchy
// user address space is the first 4MB of virtual memory
#define USER_PDE 0
// the stack occupies the last two pages of the address space
#define USER_STK_PTE1 1022
#define USER_STK_PTE2 1023

// some important memory addresses
#define KERN_BASE 0x80000000 // start of "kernel" memory
#define EXT_BASE 0x00100000 // start of "extended" memory (1MB)
#define DEV_BASE 0xfe000000 // "device" memory
#define PHYS_TOP 0x3fffffff // last usable physical address (1GB - 1)

// where the kernel actually lives
#define KERN_PLINK 0x00010000
#define KERN_VLINK (KERN_BASE + KERN_PLINK)

// number of entries in a page directory or page table
#define N_PDE 1024
#define N_PTE 1024

// index field shift counts and masks
#define PDIX_SHIFT 22
#define PTIX_SHIFT 12
#define PIX2I_MASK 0x3ff

// physical/virtual converters that don't use casting
// (usable from anywhere)
#define V2PNC(a) ((a) - KERN_BASE)
#define P2VNC(a) ((a) + KERN_BASE)

// page-size address rounding macros
#define SZ_PG_M1 MOD4K_BITS
#define SZ_PG_MASK MOD4K_MASK
#define PGUP(a) (((a) + SZ_PG_M1) & SZ_PG_MASK)
#define PGDOWN(a) ((a) & SZ_PG_MASK)

// page directory entry bit fields
#define PDE_P 0x00000001 // 1 = present
#define PDE_RW 0x00000002 // 1 = writable
#define PDE_US 0x00000004 // 1 = user and system usable
#define PDE_PWT 0x00000008 // cache: 1 = write-through
#define PDE_PCD 0x00000010 // cache: 1 = disabled
#define PDE_A 0x00000020 // accessed
#define PDE_D 0x00000040 // dirty (4MB pages)
#define PDE_AVL1 0x00000040 // ignored (4KB pages)
#define PDE_PS 0x00000080 // 1 = 4MB page size
#define PDE_G 0x00000100 // global
#define PDE_AVL2 0x00000e00 // ignored
#define PDE_PAT 0x00001000 // (4MB pages) use page attribute table
#define PDE_PTA 0xfffff000 // page table address field (4KB pages)
#define PDE_FA 0xffc00000 // frame address field (4MB pages)

// page table entry bit fields
#define PTE_P 0x00000001 // present
#define PTE_RW 0x00000002 // 1 = writable
#define PTE_US 0x00000004 // 1 = user and system usable
#define PTE_PWT 0x00000008 // cache: 1 = write-through
#define PTE_PCD 0x00000010 // cache: 1 = disabled
#define PTE_A 0x00000020 // accessed
#define PTE_D 0x00000040 // dirty
#define PTE_PAT 0x00000080 // use page attribute table
#define PTE_G 0x00000100 // global
#define PTE_AVL2 0x00000e00 // ignored
#define PTE_FA 0xfffff000 // frame address field

// error code bit assignments for page faults
#define PFLT_P 0x00000001
#define PFLT_W 0x00000002
#define PFLT_US 0x00000004
#define PFLT_RSVD 0x00000008
#define PFLT_ID 0x00000010
#define PFLT_PK 0x00000020
#define PFLT_SS 0x00000040
#define PFLT_HLAT 0x00000080
#define PFLT_SGX 0x00008000
#define PFLT_UNUSED 0xffff7f00

#ifndef ASM_SRC

/*
** Start of C-only definitions
*/

// physical/virtual converters that do use casting
// (not usable from assembly)
#define V2P(a) (((uint32_t)(a)) - KERN_BASE)
#define P2V(a) (((uint32_t)(a)) + KERN_BASE)

// create a pde/pte from an integer frame number and permission bits
#define MKPDE(f, p) ((pde_t)(TO_FRAME((f)) | (p)))
#define MKPTE(f, p) ((pte_t)(TO_FRAME((f)) | (p)))

// is a PDE/PTE present?
// (P bit is in the same place in both)
#define IS_PRESENT(entry) (((entry) & PDE_P) != 0)

// is a PDE a 4MB page entry?
#define IS_LARGE(pde) (((pde) & PDE_PS) != 0)

// is this entry "system only" or "system and user"?
#define IS_SYSTEM(entry) (((entry) & PDE_US) == 0)
#define IS_USER(entry) (((entry) & PDE_US) != 0)

// low-order nine bits of PDEs and PTEs hold "permission" flag bits
#define PERMS_MASK MOD4K_MASK

// 4KB frame numbers are 20 bits wide
#define FRAME_4K_SHIFT 12
#define FRAME2I_4K_MASK 0x000fffff
#define TO_4KFRAME(n) (((n) & FRAME2I_4K_MASK) << FRAME_4K_SHIFT)
#define GET_4KFRAME(n) (((n) >> FRAME_4K_SHIFT) & FRAME2I_4K_MASK)
#define PDE_4K_ADDR(n) ((n) & MOD4K_MASK)
#define PTE_4K_ADDR(n) ((n) & MOD4K_MASK)

// 4MB frame numbers are 10 bits wide
#define FRAME_4M_SHIFT 22
#define FRAME2I_4M_MASK 0x000003ff
#define TO_4MFRAME(n) (((n) & FRAME2I_4M_MASK) << FRAME_4M_SHIFT)
#define GET_4MFRAME(n) (((n) >> FRAME_4M_SHIFT) & FRAME2I_4M_MASK)
#define PDE_4M_ADDR(n) ((n) & MOD4M_MASK)
#define PTE_4M_ADDR(n) ((n) & MOD4M_MASK)

// extract the PMT address or frame address from a table entry
// PDEs could point to 4MB pages, or 4KB PMTs
#define PDE_ADDR(p) \
	(IS_LARGE(p) ? (((uint32_t)p) & PDE_FA) : (((uint32_t)p) & PDE_PTA))
// PTEs always point to 4KB pages
#define PTE_ADDR(p) (((uint32_t)(p)) & PTE_FA)
// everything has nine bits of permission flags
#define PERMS(p) (((uint32_t)(p)) & PERMS_MASK)

// extract the table indices from a 32-bit address
#define PDIX(v) ((((uint32_t)(v)) >> PDIX_SHIFT) & PIX2I_MASK)
#define PTIX(v) ((((uint32_t)(v)) >> PTIX_SHIFT) & PIX2I_MASK)

/*
** Types
*/

// page directory entries

// as a 32-bit word, in types.h
// typedef uint32_t pde_t;

// PDE for 4KB pages
typedef struct pdek_s {
	uint_t p : 1; // present
	uint_t rw : 1; // writable
	uint_t us : 1; // user/supervisor
	uint_t pwt : 1; // cache write-through
	uint_t pcd : 1; // cache disable
	uint_t a : 1; // accessed
	uint_t avl1 : 1; // ignored (available)
	uint_t ps : 1; // page size (must be 0)
	uint_t avl2 : 4; // ignored (available)
	uint_t fa : 20; // frame address
} pdek_f_t;

// PDE for 4MB pages
typedef struct pdem_s {
	uint_t p : 1; // present
	uint_t rw : 1; // writable
	uint_t us : 1; // user/supervisor
	uint_t pwt : 1; // cache write-through
	uint_t pcd : 1; // cache disable
	uint_t a : 1; // accessed
	uint_t d : 1; // dirty
	uint_t ps : 1; // page size (must be 1)
	uint_t g : 1; // global
	uint_t avl : 3; // ignored (available)
	uint_t fa : 20; // frame address
} pdem_f_t;

// page table entries

// as a 32-bit word, in types.h
// typedef uint32_t pte_t;

// broken out into fields
typedef struct pte_s {
	uint_t p : 1; // present
	uint_t rw : 1; // writable
	uint_t us : 1; // user/supervisor
	uint_t pwt : 1; // cache write-through
	uint_t pcd : 1; // cache disable
	uint_t a : 1; // accessed
	uint_t d : 1; // dirty
	uint_t pat : 1; // page attribute table in use
	uint_t g : 1; // global
	uint_t avl : 3; // ignored (available)
	uint_t fa : 20; // frame address
} ptef_t;

// page fault error code bits
// comment: meaning when 1 / meaning when 0
struct pfec_s {
	uint_t p : 1; // page-level protection violation / !present
	uint_t w : 1; // write / read
	uint_t us : 1; // user-mode access / supervisor-mode access
	uint_t rsvd : 1; // reserved bit violation / not
	uint_t id : 1; // instruction fetch / data fetch
	uint_t pk : 1; // protection-key violation / !pk
	uint_t ss : 1; // shadow stack access / !ss
	uint_t hlat : 1; // HLAT paging / ordinary paging or access rights
	uint_t xtr1 : 7; // unused
	uint_t sgz : 1; // SGX-specific access control violation / !SGX
	uint_t xtr2 : 16; // more unused
};

typedef union pfec_u {
	uint32_t u;
	struct pfec_s s;
} pfec_t;

// Mapping descriptor for VA::PA mappings
typedef struct mapping_t {
	uint32_t va_start; // starting virtual address for this range
	uint32_t pa_start; // first physical address in the range
	uint32_t pa_end; // last physical address in the range
	uint32_t perm; // access control
} mapping_t;

/*
** Globals
*/

// created page directory for the kernel
extern pde_t *kpdir;

/*
** Prototypes
*/

/**
** Name:	vm_init
**
** Initialize the VM module
**
** Note: should not be called until after the memory free list has
** been set up.
*/
void vm_init(void);

/**
** Name:    vm_pagedup
**
** Duplicate a page of memory
**
** @param old  Pointer to the first byte of a page
**
** @return a pointer to the new, duplicate page, or NULL
*/
void *vm_pagedup(void *old);

/**
** Name:    vm_ptdup
**
** Duplicate a page directory entry
**
** @param dst   Pointer to where the duplicate should go
** @param curr  Pointer to the entry to be duplicated
**
** @return true on success, else false
*/
bool_t vm_ptdup(pde_t *dst, pde_t *curr);

/**
** Name:	vm_getpte
**
** Return the address of the PTE corresponding to the virtual address
** 'va' within the address space controlled by 'pgdir'. If there is no
** page table for that VA and 'alloc' is true, create the necessary
** page table entries.
**
** @param pdir   Pointer to the page directory to be searched
** @param va     The virtual address we're looking for
** @param alloc  Should we allocate a page table if there isn't one?
**
** @return A pointer to the page table entry for this VA, or NULL
*/
pte_t *vm_getpte(pde_t *pdir, const void *va, bool_t alloc);

/**
** Name:	vm_mkkvm
**
** Create the kernel's page table hierarchy
*/
pde_t *vm_mkkvm(void);

/**
** Name:	vm_mkuvm
**
** Create the page table hierarchy for a user process
*/
pde_t *vm_mkuvm(void);

/**
** Name:	vm_set_kvm
**
** Switch the page table register to the kernel's page directory
*/
void vm_set_kvm(void);

/**
** Name:	vm_set_uvm
**
** Switch the page table register to the page directory for a user process.
**
** @param p   The PCB of the user process
*/
void vm_set_uvm(pcb_t *p);

/**
** Name:    vm_add
**
** Add pages to the page hierarchy for a process, copying data into
** them if necessary.
**
** @param pdir   Pointer to the page directory to modify
** @param wr     "Writable" flag for the PTE
** @param sys    "System" flag for the PTE
** @param va     Starting VA of the range
** @param size   Amount of physical memory to allocate
** @param data   Pointer to data to copy, or NULL
** @param bytes  Number of bytes to copy
**
** @return status of the allocation attempt
*/
int vm_add(pde_t *pdir, bool_t wr, bool_t sys, void *va, uint32_t size,
		   char *data, uint32_t bytes);

/**
** Name:	vm_free
**
** Deallocate a page table hierarchy and all physical memory frames
** in the user portion.
**
** @param pdir  Pointer to the page directory
*/
void vm_free(pde_t *pdir);

/*
** Name:	vm_map
**
** Create PTEs for virtual addresses starting at 'va' that refer to
** physical addresses in the range [pa, pa+size-1]. We aren't guaranteed
** that va is page-aligned.
**
** @param pdir  Page directory for this address space
** @param va    The starting virtual address
** @param pa    The starting physical address
** @param size  Length of the range to be mapped
** @param perm  Permission bits for the PTEs
*/
int vm_map(pde_t *pdir, void *va, uint32_t pa, uint32_t size, int perm);

/**
** Name:    vm_uvmdup
**
** Create a duplicate of the user portio of an existing page table
** hierarchy. We assume that the "new" page directory exists and
** the system portions of it should not be touched.
**
** @param new  New page directory
** @param old  Existing page directory
**
** @return status of the duplication attempt
*/
int vm_uvmdup(pde_t *new, pde_t *old);

#endif /* !ASM_SRC */

#endif