path: root/kernel/vmem.c

// http://www.brokenthorn.com/Resources/OSDev18.html

#include "kernel.h"
#include "x86.h"
#include "mem.h"
#include "lib/logger/log.h"	// logger facilities
#define FOOLOS_MODULE_NAME "vmem"


// TODO : why is the frame not 0xfffff??
enum PAGE_PTE_FLAGS 
{
 
    I86_PTE_PRESENT		=	1,		//0000000000000000000000000000001
    I86_PTE_WRITABLE		=	2,		//0000000000000000000000000000010
    I86_PTE_USER		=	4,		//0000000000000000000000000000100
    I86_PTE_WRITETHOUGH		=	8,		//0000000000000000000000000001000
    I86_PTE_NOT_CACHEABLE	=	0x10,		//0000000000000000000000000010000
    I86_PTE_ACCESSED		=	0x20,		//0000000000000000000000000100000
    I86_PTE_DIRTY		=	0x40,		//0000000000000000000000001000000
    I86_PTE_PAT			=	0x80,		//0000000000000000000000010000000
    I86_PTE_CPU_GLOBAL		=	0x100,		//0000000000000000000000100000000
    I86_PTE_LV4_GLOBAL		=	0x200,		//0000000000000000000001000000000
    I86_PTE_FRAME		=	0xFFFFF000 	//1111111111111111111000000000000
};

enum PAGE_PDE_FLAGS 
{
 
    I86_PDE_PRESENT		=	1,		//0000000000000000000000000000001
    I86_PDE_WRITABLE		=	2,		//0000000000000000000000000000010
    I86_PDE_USER		=	4,		//0000000000000000000000000000100
    I86_PDE_PWT			=	8,		//0000000000000000000000000001000
    I86_PDE_PCD			=	0x10,		//0000000000000000000000000010000
    I86_PDE_ACCESSED		=	0x20,		//0000000000000000000000000100000
    I86_PDE_DIRTY		=	0x40,		//0000000000000000000000001000000
    I86_PDE_4MB			=	0x80,		//0000000000000000000000010000000
    I86_PDE_CPU_GLOBAL		=	0x100,		//0000000000000000000000100000000
    I86_PDE_LV4_GLOBAL		=	0x200,		//0000000000000000000001000000000
    I86_PDE_FRAME		=	0xFFFFF000 	//1111111111111111111000000000000
};

//! page table entry
typedef uint32_t pt_entry;

//! a page directery entry
typedef uint32_t pd_entry;

////

//! virtual address
typedef uint32_t virtual_addr;
typedef uint32_t physical_addr;

typedef uint8_t bool;
 
//! i86 architecture defines 1024 entries per table--do not change
#define PAGES_PER_TABLE 1024
#define PAGES_PER_DIR	1024

#define PAGE_DIRECTORY_INDEX(x) (((x) >> 22) & 0x3ff)
#define PAGE_TABLE_INDEX(x) (((x) >> 12) & 0x3ff)
#define PAGE_GET_PHYSICAL_ADDRESS(x) (*x & ~0xfff)

//! page table represents 4mb address space
#define PTABLE_ADDR_SPACE_SIZE 0x400000

//! directory table represents 4gb address space
#define DTABLE_ADDR_SPACE_SIZE 0x100000000

//! page sizes are 4k
#define PAGE_SIZE 4096
 
//! page table
typedef struct ptable_struct {
 
    pt_entry m_entries[PAGES_PER_TABLE];
}ptable ;
 
//! page directory
typedef struct pdirectory_struct {
 
    pd_entry m_entries[PAGES_PER_DIR];
}pdirectory;

#define MAX_PAGEDIRS 10
pdirectory *page_dirs[MAX_PAGEDIRS];
int next_page_dir=0;
int current_dir=0;

////

void pt_entry_add_attrib (pt_entry* e, uint32_t attrib)
{
    *e|=attrib;
}
void pt_entry_del_attrib (pt_entry* e, uint32_t attrib)
{
    *e&=~attrib;
}
void pt_entry_set_frame (pt_entry* e , physical_addr addr)
{
     //          *e = (*e & ~I86_PTE_FRAME) | addr;                               

    *e|=I86_PTE_FRAME&addr;

}
physical_addr pt_entry_get_frame (pt_entry* e)
{
    return *e&I86_PTE_FRAME;

}
bool pt_entry_is_present (pt_entry e)
{
    return e&I86_PTE_PRESENT;
}

bool pt_entry_is_writable (pt_entry e)
{
    return e&I86_PTE_WRITABLE;
}

physical_addr pt_entry_pfn (pt_entry e)
{
    return e&I86_PTE_FRAME;
}

void		pd_entry_add_attrib (pd_entry* e, uint32_t attrib)
{
    *e|=attrib;
}

void		pd_entry_del_attrib (pd_entry* e, uint32_t attrib)
{
    *e&=~attrib;
}
void		pd_entry_set_frame (pd_entry* e, physical_addr add)
{
    *e|=I86_PDE_FRAME&add;
}
physical_addr pd_entry_get_frame (pd_entry* e)
{
    return *e&I86_PDE_FRAME;

}

bool		pd_entry_is_present (pd_entry e)
{
    return e&I86_PDE_PRESENT;
}
/*
bool		pd_entry_is_user (pd_entry e)
{
    return 1;
}

bool		pd_entry_is_4mb (pd_entry e)
{
    return 1;
}
*/

bool		pd_entry_is_writable (pd_entry e)
{
    return e&I86_PDE_WRITABLE;
}

physical_addr	pd_entry_pfn (pd_entry e)
{
    return e&I86_PDE_FRAME;
}

/*
void		pd_entry_enable_global (pd_entry e)
{
}
*/


uint8_t vmmngr_alloc_page (pt_entry* e) 
{
 
	//! allocate a free physical frame
	void* p = pmmngr_alloc_block ();
	if (!p)
		return 0;
 
	//! map it to the page
	pt_entry_set_frame (e, (physical_addr)p);
	pt_entry_add_attrib (e, I86_PTE_PRESENT);

	return 1;
}

void vmmngr_free_page (pt_entry* e) 
{
    void* p = (void*)pt_entry_pfn (*e);
    if (p)
	pmmngr_free_block (p);
 
    pt_entry_del_attrib (e, I86_PTE_PRESENT);
}

pt_entry* vmmngr_ptable_lookup_entry (ptable* p, virtual_addr addr) 
{
 
    if (p)
	return &p->m_entries[ PAGE_TABLE_INDEX (addr) ];

    return 0;
}


// TODO !?  http://www.brokenthorn.com/Resources/OSDev18.html
/*
void vmmngr_map_page (void* phys, void* virt) 
{

}

void show_cr()
{

    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_DEBUG,"cr0: 0x%08x",x86_get_cr0());
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_DEBUG,"cr1: 0x%08x",x86_get_cr1());
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_DEBUG,"cr2: 0x%08x",x86_get_cr2());
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_DEBUG,"cr3: 0x%08x",x86_get_cr3());
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_DEBUG,"cr4: 0x%08x",x86_get_cr4());

}

uint32_t vmem_alloc_block_at(uint32_t virt_addr)
{

    uint32_t phys_addr=pmmngr_alloc_block();   // get free space from the memory manager
    if (!phys_addr)panic(FOOLOS_MODULE_NAME,"unable to alloc spce");
    pdirectory*	dir = page_dirs[current_dir];
    pd_entry* entry = &dir->m_entries [PAGE_DIRECTORY_INDEX (virt_addr) ];
    if(entry==0)panic(FOOLOS_MODULE_NAME,"no table present at requested addr :(");
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"found entry at %08X",entry);

    //! create a new page
    pt_entry page=0;
    pt_entry_add_attrib (&page, I86_PTE_PRESENT);
    pt_entry_add_attrib (&page, I86_PTE_WRITABLE);
    pt_entry_set_frame (&page, phys_addr);

    //! ...and add it to the page table
    ptable *table=pt_entry_get_frame(entry);
    table->m_entries [PAGE_TABLE_INDEX (virt_addr) ] = page;
    return phys_addr;

}
*/

// vmem init and also copies all the shit for FORK 
volatile int vmem_new_space_dir(int copy_dir)
{
    x86_paging_disable();
    
    pdirectory*	dir = (pdirectory*) pmmngr_alloc_block ();
    if (!dir)panic(FOOLOS_MODULE_NAME,"unable to alloc pdirectory");
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"pdirectory: 0x%X",dir);

    for(int i=0;i<1024;i++)dir->m_entries [i]=0;

    uint32_t phys_addr=0;
    uint32_t virt_addr=0;

    // first pages are identity mapped
    for(int j=0;j<3;j++)
    {

	// this is the table for our page directory. It maps 1024*4096 bytes
	ptable* table;

	// create new tables on init
	if(next_page_dir==0)
	{
	    // alloc space for our new table
	    table = (ptable*) pmmngr_alloc_block ();
	    if (!table)panic(FOOLOS_MODULE_NAME,"unable to alloc table");

	    //! idenitity mapping
	    for (int i=0, frame=phys_addr, virt=virt_addr; i<1024; i++, frame+=4096, virt+=4096) 
	    {
		//! create a new page
		pt_entry page=0;
		pt_entry_add_attrib (&page, I86_PTE_PRESENT);
		pt_entry_add_attrib (&page, I86_PTE_WRITABLE);
		pt_entry_set_frame (&page, frame);

		//! ...and add it to the page table
		table->m_entries [PAGE_TABLE_INDEX (virt) ] = page;
	    }

	    pd_entry* entry = &dir->m_entries [PAGE_DIRECTORY_INDEX (virt_addr) ];
	    *entry=0;
	    pd_entry_add_attrib (entry, I86_PDE_PRESENT);
	    pd_entry_add_attrib (entry, I86_PDE_WRITABLE);
	    pd_entry_set_frame (entry, (physical_addr)table);

	}
	// otherwise simply take existing stuff from pdir 0
	else
	{
	    dir->m_entries[PAGE_DIRECTORY_INDEX(virt_addr)]=
		page_dirs[0]->m_entries[PAGE_DIRECTORY_INDEX(virt_addr)];

	}

	phys_addr+=1024*4096;
	virt_addr+=1024*4096;
    }

    // programm space 
    virt_addr=0x8048000;
    for(int j=0;j<2;j++)
    {

	ptable* table = (ptable*) pmmngr_alloc_block ();
	pd_entry *oldentry= &(page_dirs[copy_dir]->m_entries[PAGE_DIRECTORY_INDEX(virt_addr)]);
	ptable* oldtable=pd_entry_get_frame(oldentry);
	log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"oldtable at: 0x%08X",oldtable);

	if (!table)panic(FOOLOS_MODULE_NAME,"unable to alloc table");
	log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"alloc table: %08X",table);
    
	for (int i=0, virt=virt_addr; i<1024; i++, virt+=4096) 
	{
	    phys_addr=pmmngr_alloc_block();   // get free space from the memory manager
	    if (!phys_addr)panic(FOOLOS_MODULE_NAME,"unable to alloc spce for frame");

	    // if this is not init , copy contents from current space!
	    if(next_page_dir!=0)
	    {
		uint32_t addr_old=pt_entry_get_frame(&oldtable->m_entries[PAGE_TABLE_INDEX(virt)]);
		log(FOOLOS_MODULE_NAME,FOOLOS_LOG_FINE,"physical memcpy(0x%08X,0x%08X,4096)",phys_addr, addr_old);
		memcpy(phys_addr,addr_old,4096);

	    }


	    int frame=phys_addr;

	    //! create a new page
	    pt_entry page=0;
	    pt_entry_add_attrib (&page, I86_PTE_PRESENT);
	    pt_entry_add_attrib (&page, I86_PTE_WRITABLE);
	    pt_entry_set_frame (&page, frame);

	    //! ...and add it to the page table
	    table->m_entries [PAGE_TABLE_INDEX (virt) ] = page;
	}
	
	pd_entry* entry = &dir->m_entries [PAGE_DIRECTORY_INDEX (virt_addr) ];
	*entry=0;
	pd_entry_add_attrib (entry, I86_PDE_PRESENT);
	pd_entry_add_attrib (entry, I86_PDE_WRITABLE);
	pd_entry_set_frame (entry, (physical_addr)table);

	virt_addr+=1024*4096;

    }

    page_dirs[next_page_dir]=dir;
    if(next_page_dir!=0)x86_paging_enable();
    return next_page_dir++;

}

void vmem_set_dir(int dir)
{
    x86_set_pdbr(page_dirs[dir]);
    current_dir=dir;
}



void vmem_init()
{
    //log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"init paging (vesa base: 0x%08x)",vesa_physbase);
    log(FOOLOS_MODULE_NAME,FOOLOS_LOG_INFO,"init paging");
    vmem_set_dir(vmem_new_space_dir(0));
    x86_paging_enable();

}