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

typedef struct Tss	Tss;
struct Tss
{
	ulong	backlink;	/* unused */
	ulong	sp0;		/* pl0 stack pointer */
	ulong	ss0;		/* pl0 stack selector */
	ulong	sp1;		/* pl1 stack pointer */
	ulong	ss1;		/* pl1 stack selector */
	ulong	sp2;		/* pl2 stack pointer */
	ulong	ss2;		/* pl2 stack selector */
	ulong	cr3;		/* page table descriptor */
	ulong	eip;		/* instruction pointer */
	ulong	eflags;		/* processor flags */
	ulong	eax;		/* general (hah?) registers */
	ulong 	ecx;
	ulong	edx;
	ulong	ebx;
	ulong	esp;
	ulong	ebp;
	ulong	esi;
	ulong	edi;
	ulong	es;		/* segment selectors */
	ulong	cs;
	ulong	ss;
	ulong	ds;
	ulong	fs;
	ulong	gs;
	ulong	ldt;		/* local descriptor table */
	ulong	iomap;		/* io map base */
};
Tss tss;

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

/*
 *  global descriptor table describing all segments
 */
Segdesc gdt[] =
{
[NULLSEG]	{ 0, 0},		/* null descriptor */
[KDSEG]		DATASEGM(0),		/* kernel data/stack */
[KESEG]		EXECSEGM(0),		/* kernel code */
[UDSEG]		DATASEGM(3),		/* user data/stack */
[UESEG]		EXECSEGM(3),		/* user code */
[TSSSEG]	TSSSEGM(0,0),		/* tss segment */
};

static ulong	ktoppa;		/* prototype top level page table
				 * containing kernel mappings  */
static ulong	*kpt;		/* 2nd level page tables for kernel mem */

#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)

/* unallocated ISA space */
enum {
	Nisa=	256,
};
struct
{
	Lock;
	ulong s[Nisa];
	ulong e[Nisa];
} isaalloc;

/* unallocated space */
struct
{
	Lock;
	ulong s;
	ulong e;
} msalloc;

/*
 *  Change current page table and the stack to use for exceptions
 *  (traps & interrupts).  The exception stack comes from the tss.
 *  Since we use only one tss, (we hope) there's no need for a
 *  puttr().
 */
static void
taskswitch(ulong pagetbl, ulong stack)
{
	tss.ss0 = KDSEL;
	tss.sp0 = stack;
tss.ss1 = KDSEL;
tss.sp1 = stack;
tss.ss2 = KDSEL;
tss.sp2 = stack;
	tss.cr3 = pagetbl;
	putcr3(pagetbl);
}

/*
 *  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 is 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 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)&tss;
	gdt[TSSSEG].d0 = (x<<16)|sizeof(Tss);
	gdt[TSSSEG].d1 = (x&0xFF000000)|((x>>16)&0xFF)|SEGTSS|SEGPL(0)|SEGP;
	putgdt(gdt, sizeof gdt);

	/*
	 *  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);
	ktoppa = PADDR(top);

	/*  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;
	for(i = 0xa0000/BY2PG; i < 0xC0000/BY2PG; i++)
		kpt[i] = (0+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE | PTEWT;
	for(i = 0xC0000/BY2PG; i < MB/BY2PG; i++)
		kpt[i] = (0+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE | PTEUNCACHED;
	for(i = conf.topofmem/BY2PG; i < 128*MB/BY2PG; i++)
		kpt[i] = (0+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE | PTEUNCACHED;
	x = TOPOFF(KZERO);
	y = ((ulong)kpt)&~KZERO;
	for(i = 0; i < nkpt; i++)
		top[x+i] = (y+i*BY2PG) | PTEVALID | PTEKERNEL | PTEWRITE;

	/*
	 *  set up the task segment
	 */
	memset(&tss, 0, sizeof(tss));
	taskswitch(ktoppa, BY2PG + (ulong)m);
	puttr(TSSSEL);/**/

	/*
	 *  allocatable, non ISA memory
	 */
	if(conf.topofmem > 16*1024*1024)
		msalloc.s = conf.topofmem;
	else
		msalloc.s = 16*1024*1024;
	msalloc.e = 128*1024*1024;
}

/*
 *  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;
}

/*
 *  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);
}

/*
 *  get non-ISA memory space
 */
ulong
getspace(int len, int span)
{
	ulong x;

	lock(&msalloc);
	x = msalloc.s;
	if(span)
		x = ROUND(x, span);
	if(len > msalloc.e - x){
		unlock(&msalloc);
		return 0;
	}
	msalloc.s = x + len;
	unlock(&msalloc);

	return x | KZERO;
}