cs350/kern/arch/mips/vm/dumbvm.c

/*
 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
 *	The President and Fellows of Harvard College.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <types.h>
#include <kern/errno.h>
#include <lib.h>
#include <spl.h>
#include <spinlock.h>
#include <proc.h>
#include <current.h>
#include <mips/tlb.h>
#include <addrspace.h>
#include <vm.h>

/*
 * Dumb MIPS-only "VM system" that is intended to only be just barely
 * enough to struggle off the ground.
 */

/* under dumbvm, always have 48k of user stack */
#define DUMBVM_STACKPAGES    12

/*
 * Wrap rma_stealmem in a spinlock.
 */
static struct spinlock stealmem_lock = SPINLOCK_INITIALIZER;

typedef struct coremap
{
  paddr_t start;
  int framecount;
  int next;
  int * num;
} coremap;

static coremap map;
static bool init = false;

void vm_bootstrap(void)
{
  paddr_t min;
  paddr_t max;
  // size of ram available
  ram_getsize(&min, &max);
  // # of frames if we start here
  map.framecount = (max - min) / PAGE_SIZE;
  // start of the coremap array
  map.num = (int *) PADDR_TO_KVADDR(min);
  // min should start at a page start address (roundup), and be after the space for the array
  min += ROUNDUP(map.framecount * sizeof(int), PAGE_SIZE);
  // framecount needs to reflect the frames we took for the array of frames
  map.framecount = (max - min) / PAGE_SIZE;
  // set the start of actual virtual memory
  map.start = min;
  // set next frame to the start
  map.next = 0;
  
  // set all frames to empty
  for (int i = 0; i < map.framecount; ++i)
  {
    map.num[i] = -1;
  }
  
  init = true;
}

// get physical pages
static paddr_t getppages(int n)
{
	paddr_t addr;
	spinlock_acquire(&stealmem_lock);
	addr = ram_stealmem(n);
	spinlock_release(&stealmem_lock);
	return addr;
}

static paddr_t getvpages(int n)
{
  bool first = true;
	spinlock_acquire(&stealmem_lock);

	for (int i = map.next; i < map.framecount; ++i)
	{
		// may have a block starting here
		if ((map.num[i]) == -1)
		{
			int temp = n - 1;
			
			// see if we have a full block
			while (temp)
			{
				// frame is available
				if (map.num[i + temp] == -1)
				{
					--temp;
					continue;
				}
				// don't have enough contiguous space
				goto skip1;
			}
			
			// we have enough frames
			for (int j = 0; j < n; ++j)
			{
				map.num[i + j] = j;
			}
		
			if ((map.next + n) < map.framecount) map.next += n;
			else map.next = 0;
			spinlock_release(&stealmem_lock);
			return map.start + PAGE_SIZE * i;
		}
		
    skip1:
		// start searching at 0 if we are at max
    // block won't fit before end, and we didn't start between here and the end
    if (i + n >= map.framecount && map.next < i)
    {
      // reset i
      i = -1;
      first = false;
      continue;
    }
    
    // increment i as much as possible
    int temp = i;
    while (temp < map.framecount && map.num[temp] != -1)
    {
      // looping around
      if (temp == map.framecount - 1)
      {
        temp = 0;
        break;
      }
      
      // we came back to the start
      if (temp == map.next && !first)
      {
        spinlock_release(&stealmem_lock);
        return 0;
      }
      ++temp;
    }
    
    // if we came back to the start
    if ((i == map.next || temp == map.next) && !first)
    {
      spinlock_release(&stealmem_lock);
      return 0;
    }
    
    // increment i as needed from above
    if (i != temp) i = temp - 1;
    first = false;
	}
	
	spinlock_release(&stealmem_lock);
	return 0;
}

/* Allocate/free some kernel-space virtual pages */
vaddr_t alloc_kpages(int npages)
{
	paddr_t pa;
	if (init) pa = getvpages(npages);
	else pa = getppages(npages);
	if (!(pa)) return 0;
	return PADDR_TO_KVADDR(pa);
}

void free_kpages(vaddr_t addr)
{
  if (!(init))
  {
    (void)addr;
    return;
  }

  spinlock_acquire(&stealmem_lock);
	paddr_t a = addr - MIPS_KSEG0;
  int start = (a - map.start) / PAGE_SIZE;
  KASSERT(map.num[start] == 0);
  int lockstep = 0;
  
  while (map.num[start] == lockstep)
  {
    if (start == map.framecount) break;
    map.num[start] = -1;
    ++start;
    ++lockstep;
  }
  spinlock_release(&stealmem_lock);
}

void
vm_tlbshootdown_all(void)
{
	panic("dumbvm tried to do tlb shootdown?!\n");
}

void
vm_tlbshootdown(const struct tlbshootdown *ts)
{
	(void)ts;
	panic("dumbvm tried to do tlb shootdown?!\n");
}

int vm_fault(int faulttype, vaddr_t faultaddress)
{
	vaddr_t vbase1, vtop1, vbase2, vtop2, stackbase, stacktop;
	paddr_t paddr;
	int i;
	uint32_t ehi, elo;
	struct addrspace *as;
	int spl;
	bool readonly = false;

	faultaddress &= PAGE_FRAME;

	DEBUG(DB_VM, "dumbvm: fault: 0x%x\n", faultaddress);

	switch (faulttype)
	{
	  case VM_FAULT_READONLY:
	    return EINVAL;
	 case VM_FAULT_READ:
	 case VM_FAULT_WRITE:
		break;
	    default:
		return EINVAL;
	}

	if (curproc == NULL) {
		/*
		 * No process. This is probably a kernel fault early
		 * in boot. Return EFAULT so as to panic instead of
		 * getting into an infinite faulting loop.
		 */
		return EFAULT;
	}

	as = curproc_getas();
	if (as == NULL) {
		/*
		 * No address space set up. This is probably also a
		 * kernel fault early in boot.
		 */
		return EFAULT;
	}

	/* Assert that the address space has been set up properly. */
	KASSERT(as->as_vbase1 != 0);
	KASSERT(as->as_pbase1 != 0);
	KASSERT(as->as_npages1 != 0);
	KASSERT(as->as_vbase2 != 0);
	KASSERT(as->as_pbase2 != 0);
	KASSERT(as->as_npages2 != 0);
	KASSERT(as->as_stackpbase != 0);
	KASSERT((as->as_vbase1 & PAGE_FRAME) == as->as_vbase1);
	KASSERT((as->as_pbase1 & PAGE_FRAME) == as->as_pbase1);
	KASSERT((as->as_vbase2 & PAGE_FRAME) == as->as_vbase2);
	KASSERT((as->as_pbase2 & PAGE_FRAME) == as->as_pbase2);
	KASSERT((as->as_stackpbase & PAGE_FRAME) == as->as_stackpbase);

	vbase1 = as->as_vbase1;
	vtop1 = vbase1 + as->as_npages1 * PAGE_SIZE;
	vbase2 = as->as_vbase2;
	vtop2 = vbase2 + as->as_npages2 * PAGE_SIZE;
	stackbase = USERSTACK - DUMBVM_STACKPAGES * PAGE_SIZE;
	stacktop = USERSTACK;

  // text
	if (faultaddress >= vbase1 && faultaddress < vtop1)
	{
		paddr = (faultaddress - vbase1) + as->as_pbase1;
		readonly = true;
	}
	// heap
	else if (faultaddress >= vbase2 && faultaddress < vtop2)
	{
		paddr = (faultaddress - vbase2) + as->as_pbase2;
	}
	// stack
	else if (faultaddress >= stackbase && faultaddress < stacktop)
	{
		paddr = (faultaddress - stackbase) + as->as_stackpbase;
	}
	else return EFAULT;

	/* make sure it's page-aligned */
	KASSERT((paddr & PAGE_FRAME) == paddr);

	/* Disable interrupts on this CPU while frobbing the TLB. */
	spl = splhigh();

	for (i = 0; i < NUM_TLB; ++i)
	{
		tlb_read(&ehi, &elo, i);
		if (elo & TLBLO_VALID)
		{
			continue;
		}
		ehi = faultaddress;
		elo = paddr | TLBLO_DIRTY | TLBLO_VALID;
		if (readonly && !(as->loading)) elo &= ~TLBLO_DIRTY;
		DEBUG(DB_VM, "dumbvm: 0x%x -> 0x%x\n", faultaddress, paddr);
		tlb_write(ehi, elo, i);
		splx(spl);
		return 0;
	}

  ehi = faultaddress;
	elo = paddr | TLBLO_DIRTY | TLBLO_VALID;
	if (readonly && !(as->loading)) elo &= ~TLBLO_DIRTY;
	tlb_random(ehi, elo);
	splx(spl);
	return 0;
}

struct addrspace * as_create(void)
{
	struct addrspace *as = kmalloc(sizeof(struct addrspace));
	if (as==NULL) {
		return NULL;
	}

	as->as_vbase1 = 0;
	as->as_pbase1 = 0;
	as->as_npages1 = 0;
	as->as_vbase2 = 0;
	as->as_pbase2 = 0;
	as->as_npages2 = 0;
	as->as_stackpbase = 0;
	as->loading = true;

	return as;
}

void
as_destroy(struct addrspace *as)
{
  free_kpages(as->as_pbase1 - MIPS_KSEG0);
  free_kpages(as->as_pbase2 - MIPS_KSEG0);
  free_kpages(as->as_stackpbase - MIPS_KSEG0);
	kfree(as);
}

void
as_activate(void)
{
	int i, spl;
	struct addrspace *as;

	as = curproc_getas();
#ifdef UW
        /* Kernel threads don't have an address spaces to activate */
#endif
	if (as == NULL) {
		return;
	}

	/* Disable interrupts on this CPU while frobbing the TLB. */
	spl = splhigh();

	for (i=0; i<NUM_TLB; i++) {
		tlb_write(TLBHI_INVALID(i), TLBLO_INVALID(), i);
	}

	splx(spl);
}

void
as_deactivate(void)
{
	/* nothing */
}

int
as_define_region(struct addrspace *as, vaddr_t vaddr, size_t sz,
		 int readable, int writeable, int executable)
{
	size_t npages;

	/* Align the region. First, the base... */
	sz += vaddr & ~(vaddr_t)PAGE_FRAME;
	vaddr &= PAGE_FRAME;

	/* ...and now the length. */
	sz = (sz + PAGE_SIZE - 1) & PAGE_FRAME;

	npages = sz / PAGE_SIZE;

	/* We don't use these - all pages are read-write */
	(void)readable;
	(void)writeable;
	(void)executable;

	if (as->as_vbase1 == 0) {
		as->as_vbase1 = vaddr;
		as->as_npages1 = npages;
		return 0;
	}

	if (as->as_vbase2 == 0) {
		as->as_vbase2 = vaddr;
		as->as_npages2 = npages;
		return 0;
	}

	/*
	 * Support for more than two regions is not available.
	 */
	kprintf("dumbvm: Warning: too many regions\n");
	return EUNIMP;
}

static
void
as_zero_region(paddr_t paddr, unsigned npages)
{
	bzero((void *)PADDR_TO_KVADDR(paddr), npages * PAGE_SIZE);
}

int
as_prepare_load(struct addrspace *as)
{
	KASSERT(as->as_pbase1 == 0);
	KASSERT(as->as_pbase2 == 0);
	KASSERT(as->as_stackpbase == 0);

	as->as_pbase1 = alloc_kpages(as->as_npages1) - MIPS_KSEG0;
	if (as->as_pbase1 == 0) {
		return ENOMEM;
	}

	as->as_pbase2 = alloc_kpages(as->as_npages2) - MIPS_KSEG0;
	if (as->as_pbase2 == 0) {
		return ENOMEM;
	}

	as->as_stackpbase = alloc_kpages(DUMBVM_STACKPAGES) - MIPS_KSEG0;
	if (as->as_stackpbase == 0) {
		return ENOMEM;
	}
	
	as_zero_region(as->as_pbase1, as->as_npages1);
	as_zero_region(as->as_pbase2, as->as_npages2);
	as_zero_region(as->as_stackpbase, DUMBVM_STACKPAGES);

	return 0;
}

int
as_complete_load(struct addrspace *as)
{
	(void)as;
	return 0;
}

int
as_define_stack(struct addrspace *as, vaddr_t *stackptr)
{
	KASSERT(as->as_stackpbase != 0);

	*stackptr = USERSTACK;
	return 0;
}

int
as_copy(struct addrspace *old, struct addrspace **ret)
{
	struct addrspace *new;

	new = as_create();
	if (new==NULL) {
		return ENOMEM;
	}

	new->as_vbase1 = old->as_vbase1;
	new->as_npages1 = old->as_npages1;
	new->as_vbase2 = old->as_vbase2;
	new->as_npages2 = old->as_npages2;

	/* (Mis)use as_prepare_load to allocate some physical memory. */
	if (as_prepare_load(new)) {
		as_destroy(new);
		return ENOMEM;
	}

	KASSERT(new->as_pbase1 != 0);
	KASSERT(new->as_pbase2 != 0);
	KASSERT(new->as_stackpbase != 0);

	memmove((void *)PADDR_TO_KVADDR(new->as_pbase1),
		(const void *)PADDR_TO_KVADDR(old->as_pbase1),
		old->as_npages1*PAGE_SIZE);

	memmove((void *)PADDR_TO_KVADDR(new->as_pbase2),
		(const void *)PADDR_TO_KVADDR(old->as_pbase2),
		old->as_npages2*PAGE_SIZE);

	memmove((void *)PADDR_TO_KVADDR(new->as_stackpbase),
		(const void *)PADDR_TO_KVADDR(old->as_stackpbase),
		DUMBVM_STACKPAGES*PAGE_SIZE);
	
	*ret = new;
	return 0;
}