hos/kernel/mm/vmm.c

// vmm.c
// Author: Josh Holtrop
// Date: 09/30/03
// Rewritten from scratch: 12/23/03
// Modified: 07/29/04

#include "hos_defines.h"
#include "kernel.h"
#include "mm/vmm.h"
#include "asmfuncs.h"
#include "mm/mm.h"

int	vmm_map(void *virt);
int	vmm_map1(unsigned int virt, unsigned int physical);
int	vmm_mapn(unsigned int virt, unsigned int physical, unsigned int n);
void	vmm_unmap1(unsigned int virt);
void	vmm_unmapn(unsigned int virt, unsigned int n);
int	vmm_map_range(void *virt_start, void *virt_end, u32_t phys_start);
void	vmm_heb_init(HeapEntryBlock_t *heb);
void	vmm_addToQueue(u32_t queue, HeapEntry_t *preceeding, HeapEntry_t *he);
int	vmm_countHeapEntries(HeapEntry_t *he);
HeapEntry_t *vmm_followChain(HeapEntry_t *he);
HeapEntry_t *vmm_getUnusedEntry();
HeapEntry_t *vmm_stripUnusedEntry();

//void	*calloc(unsigned int number, unsigned int size);

extern	mb_info_t mb_info_block;
extern	mb_module_t mb_modules[MAX_MODULES];
extern	u32_t mm_freepages;

HeapEntryQueue_t heapEntryQueues[VMM_HE_TYPES];		// linked queue of HeapEntry objects
HeapEntry_t heapEntryHeadNodes[VMM_HE_TYPES];		// head nodes for linked queues
HeapEntry_t heapEntryTailNodes[VMM_HE_TYPES];		// tail nodes for linked queues
HeapEntryBlock_t initialHEB;				// block for initial 256 HeapEntry objects


// This is the initialization procedure for the Virtual Memory Manager
//  It sets up the heap for dynamic memory allocation and virtual page allocation
void	vmm_init()
{
	int i;
	for (i = 0; i < mb_info_block.mods_count; i++)	//page in the kernel modules
		vmm_map_range((void*)mb_modules[i].mod_start, (void*)mb_modules[i].mod_end - 1, mb_modules[i].mod_start - VIRT_OFFSET);
	for (i = 0; i < VMM_HE_TYPES; i++)
	{
		heapEntryQueues[i].head = &heapEntryHeadNodes[i];
		heapEntryHeadNodes[i].next = &heapEntryTailNodes[i];
		heapEntryTailNodes[i].prev = &heapEntryHeadNodes[i];
	}
	vmm_heb_init(&initialHEB);
	vmm_addToQueue(VMM_HE_UNUSED, &heapEntryHeadNodes[VMM_HE_UNUSED], &initialHEB.entry[0]);
	HeapEntry_t *wilderness = vmm_stripUnusedEntry();
	wilderness->base = (void *) HEAP_START;
	wilderness->length = HEAP_LENGTH;
	vmm_addToQueue(VMM_HE_HOLE, &heapEntryHeadNodes[VMM_HE_HOLE], wilderness);
}


/* Allocate a physical page and map the virtual address to it, return physical address allocated or NULL */
int	vmm_map(void *virt)
{
	if (mm_freepages < 10);
		return -1;
	vmm_map1((u32_t)virt, mm_palloc());
	return 0;
}


// This function maps a virtual address to a physical address using the page directory / page table
int	vmm_map1(u32_t virt, u32_t physical)
{
	u32_t pde = virt >> 22;
	u32_t pte = (virt & 0x003FF000) >> 12;
	u32_t *pageTables = (u32_t *)0xFFFFF000;	//this is the location of the page directory
	if (!(pageTables[pde] & 0x01))		//the page directory entry is not present, we must allocate a page table
	{
		u32_t newpagetable;
		if (!(newpagetable = mm_palloc()))
			return 1;		//out of physical memory
		pageTables[pde] = newpagetable | 0x03;
		invlpg_(virt);		//in case it was cached, so we can fill page table safely
		memsetd((void*)(0xFFC00000 | (pde << 12)), 0, 1024);	//zero out new page table
	}
	*(u32_t *)(0xFFC00000 | (pde << 12) | (pte << 2)) = (physical & 0xFFFFF000) | 0x03;
	invlpg_(virt);
	return 0;
}


// This function maps a variable number of pages in a row
int	vmm_mapn(u32_t virt, u32_t physical, u32_t n)
{
	while (n > 0)
	{
		if (vmm_map1(virt, physical))
			return 1;	// error mapping page
		virt += 4096;
		physical += 4096;
		n--;
	}
	return 0;
}


// This function removes the virtual address's entry in the page directory / page table
void	vmm_unmap1(u32_t virt)
{
	*(u32_t *)(0xFFC00000 | ((virt & 0xFFC00000) >> 10) | ((virt & 0x003FF000) >> 10)) = 0;
 	invlpg_(virt);
}


// This function removes multiple pages' entries
void	vmm_unmapn(u32_t virt, u32_t n)
{
	while (n > 0)
	{
		vmm_unmap1(virt);
		virt += 4096;
		n--;
	}
}


// This function maps an entire address range into memory
int	vmm_map_range(void *virt_start, void *virt_end, u32_t phys_start)
{
	if (virt_end < virt_start)
		return -1;	// invalid region
	while (virt_start < virt_end)
	{
		if (vmm_map1((u32_t)virt_start, phys_start))
			return -2;	// out of memory
		virt_start += 4096;
		phys_start += 4096;
	}
	return 0;
}



// kernel virtual memory allocator
void *kmalloc(u32_t size)
{
	k_enter_critical();
	
	k_leave_critical();
	return NULL;
}


// kernel virtual memory de-allocator
int kfree(void *addr)
{
	k_enter_critical();
	
	k_leave_critical();
	return 0;
}


// This function allocates a virtual page and maps it to a physical page
void *vmm_palloc()
{
	k_enter_critical();
	HeapEntry_t *he = heapEntryQueues[VMM_HE_HOLE].head->next;
	HeapEntry_t *wilderness = he;
	while (he)
	{
		if (he->length == 4096)
		{
			((HeapEntry_t *)he->prev)->next = he->next;
			((HeapEntry_t *)he->next)->prev = he->prev;
			heapEntryQueues[VMM_HE_HOLE].count--;
			he->next = NULL;
			he->prev = NULL;
			vmm_addToQueue(VMM_HE_USED, &heapEntryHeadNodes[VMM_HE_USED], he);
			vmm_map(he->base);
			k_leave_critical();
			return he->base;
		}
		if (he->length > wilderness->length)
			wilderness = he;
		he = (HeapEntry_t *)he->next;
	}
	if (wilderness->length < 0x00010000)		//leave 16 pages free
	{
		k_leave_critical();
		return NULL;
	}
	wilderness->length -= 4096;			//strip 4k from the top
	he = vmm_getUnusedEntry();
	he->base = wilderness->base + wilderness->length;
	he->length = 4096;
	vmm_addToQueue(VMM_HE_USED, &heapEntryHeadNodes[VMM_HE_USED], he);
	vmm_map(he->base);
	k_leave_critical();
	return he->base;
}


// This function frees a previously-allocated virtual page
int vmm_pfree(void *addr)
{
	k_enter_critical();
	HeapEntry_t *he = heapEntryQueues[VMM_HE_USED].head->next;
	while (he)
	{
		if (he->base == addr)		//found the page to free
		{
			((HeapEntry_t *)he->prev)->next = he->next;
			((HeapEntry_t *)he->next)->prev = he->prev;
			heapEntryQueues[VMM_HE_USED].count--;
			he->next = NULL;
			he->prev = NULL;
			vmm_unmap1((u32_t)he->base);
			vmm_addToQueue(VMM_HE_HOLE, &heapEntryHeadNodes[VMM_HE_HOLE], he);
			k_leave_critical();
			return 0;
		}
		he = he->next;
	}
	k_leave_critical();
	return -1;	// page not found
}


// This function allocates and zeros memory for the given number of objects,
//  given the size of each object
/*
void	*calloc(u32_t number, u32_t size)
{
	void *mem = malloc(number * size);
	if (!mem)
		return NULL;	//could not get memory
	memset(mem, 0, number * size);
	return mem;
}*/



// This function initialzes a Heap Entry Block to entries linked together
void	vmm_heb_init(HeapEntryBlock_t *heb)
{
	int a;
	for (a = 0; a < 255; a++)
	{
		heb->entry[a].next = &heb->entry[a+1];
		heb->entry[a+1].prev = &heb->entry[a];
	}
	heb->entry[0].prev = NULL;
	heb->entry[255].next = NULL;
}


// This function adds a HeapEntry structure to the queue following 'preceeding' the queue
void vmm_addToQueue(u32_t queue, HeapEntry_t *preceeding, HeapEntry_t *he)
{
	heapEntryQueues[queue].count += vmm_countHeapEntries(he);
	HeapEntry_t *last = vmm_followChain(he);
	last->next = preceeding->next;
	he->prev = preceeding;
	((HeapEntry_t *)last->next)->prev = last;
	preceeding->next = he;
}


// This function returns how many HeapEntry objects are in a queue starting/including from the object given
int vmm_countHeapEntries(HeapEntry_t *he)
{
	int count = 0;
	while (he)
	{
		count++;
		he = (HeapEntry_t *)he->next;
	}
	return count;
}


// This function follows a chain of HeapEntry objects and returns a pointer to the last one
HeapEntry_t *vmm_followChain(HeapEntry_t *he)
{
	while (he->next)
		he = (HeapEntry_t *)he->next;
	return he;
}


// This function breaks an unused chunk from its queue and returns a pointer to it
HeapEntry_t *vmm_getUnusedEntry()
{
	if (heapEntryQueues[VMM_HE_UNUSED].count < 5)
	{
		HeapEntry_t *he = heapEntryQueues[VMM_HE_HOLE].head->next;
		HeapEntry_t *wilderness = he;
		while (he)
		{
			if ((he->length) > (wilderness->length))
				wilderness = he;
			he = (HeapEntry_t *)he->next;
		}
		wilderness->length -= 4096;			//strip 4k from the top
		HeapEntryBlock_t *newHEB = wilderness->base + wilderness->length;
		vmm_map(newHEB);
		vmm_heb_init(newHEB);
		HeapEntry_t *newDesc = vmm_stripUnusedEntry();	//descriptor for the new HEB
		newDesc->base = newHEB;
		newDesc->length = 4096;
		vmm_addToQueue(VMM_HE_USED, heapEntryTailNodes[VMM_HE_USED].prev, newDesc);
	}
	return vmm_stripUnusedEntry();
}


// Return pointer to an unused HeapEntry object, ASSUMES THERE IS ONE PRESENT IN QUEUE
HeapEntry_t *vmm_stripUnusedEntry()
{
	HeapEntry_t *he = heapEntryQueues[VMM_HE_UNUSED].head->next;
	heapEntryQueues[VMM_HE_UNUSED].head->next = he->next;
	((HeapEntry_t *)he->next)->prev = he->prev;
	heapEntryQueues[VMM_HE_UNUSED].count--;
	he->next = 0;
	he->prev = 0;
	return he;
}