/*----------------------------------------------------------------------------
PAGING.C: DJGPP program to dump the CPU page tables.
Chris Giese	<ChrisGiese@SisAndHappy.com>
http://SisAndHappy.com/ChrisGiese
This code is public domain (no copyright).
You can do whatever you want with it.

Build with CWSDPR0.EXE instead of CWSDPMI.EXE:
	gcc -o paging.exe -O2 -Wall -W -g paging.c
	stubedit paging.exe dpmi=cwsdpr0.exe

Run under plain DOS (no Windows or EMM386.EXE).

			page directory entry			    unused PDE
page table entry (PTE)	(PDE) for 4MB page	normal PDE	    or PTE
----------------------	--------------------	----------------    ----------
b31-22	=page addr	=b31-22 of page addr	=page table addr    =AVAILABLE
b21	=page addr	=RESERVED=0		=page table addr    =AVAILABLE
b20-13	=page addr	=b39-32 of page addr	=page table addr    =AVAILABLE
b12	=page addr	=PAT			=page table addr    =AVAILABLE
b11-9	=AVAILABLE	=AVAILABLE		=AVAILABLE	    =AVAILABLE
b8	G=global	G=global		=AVAILABLE	    =AVAILABLE
b7	=PAT		=page size=1		=page size=0	    =AVAILABLE
b6	D=dirty		D=dirty			=AVAILABLE	    =AVAILABLE
b5	A=accessed	A=accessed		A=accessed	    =AVAILABLE
b4	=cache disable	=cache disable		=cache disable	    =AVAILABLE
b3	=write-through	=write-through		=write-through	    =AVAILABLE
b2	U=user		U=user			U=user		    =AVAILABLE
b1	W=writable	W=writable		W=writable	    =AVAILABLE
b0	P=present=1	P=present=1		P=present=1	    present=0

PAT:		page attribute table (?)(Pentium III CPU or newer)
page size:	0=4K page, 1=4M page (? CPU or newer).
			b39-b32 valid only if PAE enabled
global:		page mapping not invalidated by reloading register CR3
			(P6 CPU or newer)
dirty:		page was modified (written to)
accessed:	page was read from or written to
cache disable:	page is uncached (486 CPU or newer)
write-through:	"write-through" caching is enabled (486 CPU or newer)
user:		page can be accessed by code running at ring 3
writable:	page can be written to
present:	other bits are valid

PAE: Physical Address Extension (>4 GB memory). Pentium Pro CPU or newer.
INVLPG addr: This instruction invalidates one page table entry
	corresponding to memory location addr (486 CPU or newer)
Reloading CR3 register invalidates all page table entries except
	for those with the G bit set
----------------------------------------------------------------------------*/
#include <stdio.h> /* printf() */

#if defined(__DJGPP__)
#include <sys/nearptr.h> /* __djgpp_conventional_base */
#include <crt0.h> /* _CRT0_FLAG_NEARPTR, _crt0_startup_flags */
#define	PTR2LINEAR(P)	((uint32_t)(P) - __djgpp_conventional_base)
#define	LINEAR2PTR(L)	(void *)((L) + __djgpp_conventional_base)

/* Doesn't work with Watcom C, sorry. I tried. */
#elif defined(__WATCOMC__) && defined(__386__)
#define	PTR2LINEAR(P)	((uint32_t)(P))
#define	LINEAR2PTR(L)	(void *)(L)

unsigned get_cr3(void);
#pragma aux get_cr3 =	\
"mov eax,cr3"		\
value [ eax ];

#else
#error Sorry, unsupported compiler
#endif

#define	HIBITS(N)	((N) & 0xFFFFF000L)

typedef unsigned long	uint32_t;
/****************************************************************************/
int main(void)
{
/* PD=Page Directory, PDE=PD Entry, PT=Page Table, PTE=PT Entry,
v=virtual address, p=physical address, v2p=virtual-to-physical
conversion value, pv2p=previous V2P */
	uint32_t cr3, *pd, pde, *pt, pte, v, p, v2p, pv2p;
/* Page Directory Index, Page Table Index */
	unsigned pdi, pti;

#if defined(__DJGPP__)
/* turn off data segment limit, for nearptr access */
	if(!(_crt0_startup_flags & _CRT0_FLAG_NEARPTR))
	{
		if(!__djgpp_nearptr_enable())
		{
			printf("Error: can not enable near pointer "
				"access (WinNT/2k/XP?)\n");
			return 1;
		}
	}
/* get pointer to page directory */
	__asm__("mov %%cr3,%%eax\n"
		: "=a"(cr3));
#else /* defined(__WATCOMC__) */
	cr3 = get_cr3();
#endif
	pd = LINEAR2PTR(HIBITS(cr3));
/* virtaddr of main() is different because of segmentation; not paging */
	printf(	"address of main()=0x%p, virtaddr of main()=0x%lX\n"
		"CR3 (page directory pointer)=0x%lX\n"
		"PDI=Page Directory Index, PTI=Page Table Index\n"
		"D=Dirty, A=Accessed, U=User (Ring 3), W=Writable\n"
		"PDI  PTI  D A U W virtaddr physaddr virt2phys\n"
		"---- ---- - - - - -------- -------- --------\n",
			main, PTR2LINEAR(main), cr3);
	pv2p = -1uL;
/* Walk page directory. PDI = bits 31-22 of virtual address. */
	for(pdi = 0; pdi < 1024; pdi++)
	{
		if(((pde = pd[pdi]) & 1) == 0) /* Present bit = 0 */
			continue;
		pt = LINEAR2PTR(HIBITS(pde));
/* Walk page table. PTI = bits 21-12 of virtual address. */
		for(pti = 0; pti < 1024; pti++)
		{
			if(((pte = pt[pti]) & 1) == 0)
				continue;
			v = ((pdi << 10L) | pti) << 12L;
			p = HIBITS(pte);
			printf("%4u %4u %c %c %c %c %8lX %8lX", pdi, pti,
				(pte & 0x40) ? 'D' : ' ',
				(pte & 0x20) ? 'A' : ' ',
				(pte & 0x04) ? 'U' : ' ',
				(pte & 0x02) ? 'W' : ' ',
				v, p);
			if((v2p = v - p) != pv2p)
			{
				printf(" %8lX", v2p);
				pv2p = v2p;
			}
			printf("\n");

		}
	}
	return 0;
}