#include	"u.h"
#include	"../port/lib.h"
#include	"mem.h"
#include	"dat.h"
#include	"fns.h"
#include	"io.h"

/*
 *  segment descriptor initializers
 */
#define	DATASEGM(p) (Segdesc){	0xFFFF,\
				SEGG|SEGB|(0xF<<16)|SEGP|SEGPL(p)|SEGDATA|SEGW }
#define	EXECSEGM(p) (Segdesc){	0xFFFF,\
				SEGG|SEGD|(0xF<<16)|SEGP|SEGPL(p)|SEGEXEC|SEGR }
#define CALLGATE(s,o,p) (Segdesc){	((o)&0xFFFF)|((s)<<16),\
					(o)&0xFFFF0000|SEGP|SEGPL(p)|SEGCG }
#define	D16SEGM(p) (Segdesc){	0xFFFF,\
				(0x0<<16)|SEGP|SEGPL(p)|SEGDATA|SEGW }
#define	E16SEGM(p) (Segdesc){	0xFFFF,\
				(0x0<<16)|SEGP|SEGPL(p)|SEGEXEC|SEGR }
#define	TSSSEGM(b,p) (Segdesc){	((b)<<16)|sizeof(Tss),\
				((b)&0xFF000000)|(((b)>>16)&0xFF)|SEGTSS|SEGPL(p)|SEGP }

static Page	ktoppg;		/* prototype top level page table
				 * containing kernel mappings  */
static ulong	*kpt;		/* 2nd level page tables for kernel mem */
static ulong	*upt;		/* 2nd level page table for struct User */

#define ROUNDUP(s,v)	(((s)+(v-1))&~(v-1))
/*
 *  offset of virtual address into
 *  top level page table
 */
#define TOPOFF(v)	(((ulong)(v))>>(2*PGSHIFT-2))

/*
 *  offset of virtual address into
 *  bottom level page table
 */
#define BTMOFF(v)	((((ulong)(v))>>(PGSHIFT))&(WD2PG-1))

#define MAXUMEG 64	/* maximum memory per user process in megabytes */
#define ONEMEG (1024*1024)

enum {
	Nisa=	256,
};
struct
{
	Lock;
	ulong s[Nisa];
	ulong e[Nisa];
} isaalloc;

/*
 *  setup mmu for a cpu assuming we've already created the kernel
 *  page tables.
 */
void
setupmmu(void)
{
	ulong x;

	/*
	 *  set up the global descriptor table. we make the tss entry here
	 *  since it requires arithmetic on an address and hence cannot
	 *  be a compile or link time constant.
	 */
	x = (ulong)&m->tss;
	m->gdt[NULLSEG] = (Segdesc){0, 0};
	m->gdt[TSSSEG] = TSSSEGM(x, 0);
	m->gdt[KDSEG] = DATASEGM(0);		/* kernel data/stack */
	m->gdt[KESEG] = EXECSEGM(0);		/* kernel code */
	m->gdt[UDSEG] = DATASEGM(3);		/* user data/stack */
	m->gdt[UESEG] = EXECSEGM(3);		/* user code */
	putgdt(m->gdt, sizeof(m->gdt));

	/*
	 *  point to kernel page table
	 */
	putcr3(ktoppg.pa);

	/*
	 *  set up the task segment
	 */
	memset(&m->tss, 0, sizeof(m->tss));
	m->tss.sp0 = USERADDR+BY2PG;
	m->tss.ss0 = KDSEL;
	m->tss.cr3 = ktoppg.pa;
	puttr(TSSSEL);
}

/*
 *  Create a prototype page map that maps all of memory into
 *  kernel (KZERO) space.  This is the default map.  It is used
 *  whenever the processor not running a process or whenever running
 *  a process which does not yet have its own map.
 */
void
mmuinit(void)
{
	int i, nkpt, npage, nbytes;
	ulong x;
	ulong y;
	ulong *top;

	/*
	 *  set up system page tables.
	 *  map all of physical memory to start at KZERO.
	 *  leave a map entry for a user area.
	 */

	/*  allocate top level table */
	top = xspanalloc(BY2PG, BY2PG, 0);
	ktoppg.va = (ulong)top;
	ktoppg.pa = ktoppg.va & ~KZERO;

	/*  map all memory to KZERO */
	npage = 128*MB/BY2PG;
	nbytes = PGROUND(npage*BY2WD);		/* words of page map */
	nkpt = nbytes/BY2PG;			/* pages of page map */
	kpt = xspanalloc(nbytes, BY2PG, 0);
	for(i = 0; i < npage; i++)
		kpt[i] = (0+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE;
	x = TOPOFF(KZERO);
	y = ((ulong)kpt)&~KZERO;
	for(i = 0; i < nkpt; i++)
		top[x+i] = (y+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE;

	/*  page table for u-> */
	upt = xspanalloc(BY2PG, BY2PG, 0);
	x = TOPOFF(USERADDR);
	y = ((ulong)upt)&~KZERO;
	top[x] = y | PTEVALID | PTEKERNEL | PTEWRITE;

	setupmmu();
}

/*
 *  Mark the mmu and tlb as inconsistent and call mapstack to fix it up.
 */
void
flushmmu(void)
{
	int s;

	s = splhi();
	if(u){
		u->p->newtlb = 1;
		mapstack(u->p);
	} else
		putcr3(ktoppg.pa);
	splx(s);
}

/*
 *  Switch to a process's memory map.  If the process doesn't
 *  have a map yet, just use the prototype one that contains
 *  mappings for only the kernel and the User struct.
 */
void
mapstack(Proc *p)
{
	Page *pg;
	ulong *top;

	if(p->upage->va != (USERADDR|(p->pid&0xFFFF)) && p->pid != 0)
		panic("mapstack %d 0x%lux 0x%lux", p->pid, p->upage->pa, p->upage->va);

	if(p->newtlb){
		/*
		 *  newtlb set means that they are inconsistent
		 *  with the segment.c data structures.
		 *
		 *  bin the current second level page tables and
		 *  the pointers to them in the top level page.
		 *  pg->daddr is used by putmmu to save the offset into
		 *  the top level page.
		 */
		if(p->mmutop && p->mmuused){
			top = (ulong*)p->mmutop->va;
			for(pg = p->mmuused; pg->next; pg = pg->next)
				ilputl(&top[pg->daddr], 0);
			ilputl(&top[pg->daddr], 0);
			pg->next = p->mmufree;
			p->mmufree = p->mmuused;
			p->mmuused = 0;
		}
		p->newtlb = 0;
	}

	/* map in u area */
	upt[0] = PPN(p->upage->pa) | PTEVALID | PTEKERNEL | PTEWRITE;

	/* tell processor about new page table (flushes cached entries) */
	if(p->mmutop)
		pg = p->mmutop;
	else
		pg = &ktoppg;
	putcr3(pg->pa);

	u = (User*)USERADDR;
}

/*
 *  give all page table pages back to the free pool.  This is called in sched()
 *  with palloc locked.
 */
void
mmurelease(Proc *p)
{
	Page *pg;
	Page *next;

	/* point 386 to protoype page map */
	putcr3(ktoppg.pa);

	/* give away page table pages */
	for(pg = p->mmufree; pg; pg = next){
		next = pg->next;
		simpleputpage(pg);
	}
	p->mmufree = 0;
	for(pg = p->mmuused; pg; pg = next){
		next = pg->next;
		simpleputpage(pg);
	}
	p->mmuused = 0;
	if(p->mmutop)
		simpleputpage(p->mmutop);
	p->mmutop = 0;
}

/*
 *  Add an entry into the mmu.
 */
void
putmmu(ulong va, ulong pa, Page *pg)
{
	int topoff;
	ulong *top;
	ulong *pt;
	Proc *p;
	int s;

	if(u==0)
		panic("putmmu");
	p = u->p;

	/*
	 *  create a top level page if we don't already have one.
	 *  copy the kernel top level page into it for kernel mappings.
	 */
	if(p->mmutop == 0){
		pg = newpage(0, 0, 0);
		pg->va = VA(kmap(pg));
		memmove((void*)pg->va, (void*)ktoppg.va, BY2PG);
		p->mmutop = pg;
	}
	top = (ulong*)p->mmutop->va;
	topoff = TOPOFF(va);

	/*
	 *  if bottom level page table missing, allocate one 
	 *  and point the top level page at it.
	 */
	s = splhi();
	if(PPN(top[topoff]) == 0){
		if(p->mmufree == 0){
			spllo();
			pg = newpage(1, 0, 0);
			pg->va = VA(kmap(pg));
			splhi();
		} else {
			pg = p->mmufree;
			p->mmufree = pg->next;
			memset((void*)pg->va, 0, BY2PG);
		}
		ilputl(&top[topoff], PPN(pg->pa) | PTEVALID | PTEUSER | PTEWRITE);
		pg->daddr = topoff;
		pg->next = p->mmuused;
		p->mmuused = pg;
	}

	/*
	 *  put in new mmu entry
	 */
	pt = (ulong*)(PPN(top[topoff])|KZERO);
	ilputl(&pt[BTMOFF(va)], pa | PTEUSER);

	/* flush cached mmu entries */
	putcr3(p->mmutop->pa);
	splx(s);
}

void
invalidateu(void)
{
	/* unmap u area */
	upt[0] = 0;

	/* flush cached mmu entries */
	putcr3(ktoppg.pa);
}

/*
 *  used to map a page into 16 meg - BY2PG for confinit(). tpt is the temporary
 *  page table set up by l.s.
 */
long*
mapaddr(ulong addr)
{
	ulong base;
	ulong off;
	static ulong *pte, top;
	extern ulong tpt[];

	if(pte == 0){
		top = (((ulong)tpt)+(BY2PG-1))&~(BY2PG-1);
		pte = (ulong*)top;
		top &= ~KZERO;
		top += BY2PG;
		pte += (4*1024*1024-BY2PG)>>PGSHIFT;
	}

	base = off = addr;
	base &= ~(KZERO|(BY2PG-1));
	off &= BY2PG-1;

	*pte = base|PTEVALID|PTEKERNEL|PTEWRITE; /**/
	putcr3((ulong)top);

	return (long*)(KZERO | 4*1024*1024-BY2PG | off);
}

/*
 *  make isa address space available
 */
void
putisa(ulong addr, int len)
{
	ulong e;
	int i, hole;

	addr &= ~KZERO;

	e = addr + len;
	lock(&isaalloc);
	hole = -1;
	for(i = 0; i < Nisa; i++){
		if(isaalloc.s[i] == e){
			isaalloc.s[i] = addr;
			break;
		}
		if(isaalloc.e[i] == addr){
			isaalloc.e[i] = e;
			break;
		}
		if(isaalloc.s[i] == 0)
			hole = i;
	}
	if(i >= Nisa && hole >= 0){
		isaalloc.s[hole] = addr;
		isaalloc.e[hole] = e;
	}
	unlock(&isaalloc);
}

/*
 *  allocate some address space (already mapped into the kernel)
 *  for ISA bus memory.
 */
ulong
getisa(ulong addr, int len, int align)
{
	int i;
	long os, s, e;

	lock(&isaalloc);
	os = s = e = 0;
	for(i = 0; i < Nisa; i++){
		s = os = isaalloc.s[i];
		if(s == 0)
			continue;
		e = isaalloc.e[i];
		if(addr && addr >= s && addr < e)
			break;
		if(align > 0)
			s = ((s + align - 1)/align)*align;
		if(e - s >= len)
			break;
	}
	if(i >= Nisa){
		unlock(&isaalloc);
		return 0;
	}

	/* remove */
	isaalloc.s[i] = 0;
	unlock(&isaalloc);

	/* give back edges */
	if(s != os)
		putisa(os, s - os);
	os = s + len;
	if(os != e)
		putisa(os, e - os);

	return KZERO|s;
}