seg.h

来自「Murphy 大俠 GPL 的 C++/x86 RTOS, 支持 MMU, 用戶」· C头文件 代码 · 共 178 行

/* 
 * Mach Operating System
 * Copyright (c) 1991,1990 Carnegie Mellon University
 * Copyright (c) 1991 IBM Corporation 
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation,
 * and that the name IBM not be used in advertising or publicity 
 * pertaining to distribution of the software without specific, written
 * prior permission.
 * 
 * CARNEGIE MELLON AND IBM ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON AND IBM DISCLAIM ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  [e-mail]
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 * 
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */

#ifndef	_EKERNEL_SEG_H_
#define	_EKERNEL_SEG_H_


#include "Types.h"

// x86 segmentation.

// Real segment descriptor.
struct x86_desc {
	DWORD	limit_low:16,	// limit 0..15
		base_low:16,	// base  0..15
		base_med:8,	// base  16..23
		access:8,	// access BYTE
		limit_high:4,	// limit 16..19
		granularity:4,	// granularity
		base_high:8;	// base 24..31
};

// Trap, interrupt, or call gate.
struct x86_gate {
	DWORD	offset_low:16,	// offset 0..15
		selector:16,
		WORD_count:8,
		access:8,
		offset_high:16;	// offset 16..31
};

#define	SZ_32		0x4			/* 32-bit segment */
#define SZ_16		0x0			/* 16-bit segment */
#define	SZ_G		0x8			/* 4K limit field */

#define	ACC_A		0x01			/* accessed */
#define	ACC_TYPE	0x1e			/* type field: */

#define	ACC_TYPE_SYSTEM	0x00			/* system descriptors: */

#define	ACC_LDT		0x02			    /* LDT */
#define	ACC_CALL_GATE_16 0x04			    /* 16-bit call gate */
#define	ACC_TASK_GATE	0x05			    /* task gate */
#define	ACC_TSS		0x09			    /* task segment */
#define	ACC_CALL_GATE	0x0c			    /* call gate */
#define	ACC_INTR_GATE	0x0e			    /* interrupt gate */
#define	ACC_TRAP_GATE	0x0f			    /* trap gate */

#define	ACC_TSS_BUSY	0x02			    /* task busy */

#define	ACC_TYPE_USER	0x10			/* user descriptors */

#define	ACC_DATA	0x10			    /* data */
#define	ACC_DATA_W	0x12			    /* data, writable */
#define	ACC_DATA_E	0x14			    /* data, expand-down */
#define	ACC_DATA_EW	0x16			    /* data, expand-down,
							     writable */
#define	ACC_CODE	0x18			    /* code */
#define	ACC_CODE_R	0x1a			    /* code, readable */
#define	ACC_CODE_C	0x1c			    /* code, conforming */
#define	ACC_CODE_CR	0x1e			    /* code, conforming,
						       readable */
#define	ACC_PL		0x60			/* access rights: */
#define	ACC_PL_K	0x00			/* kernel access only */
#define	ACC_PL_U	0x60			/* user access */
#define	ACC_P		0x80			/* segment present */

//
// Components of a selector
//
#define	SEL_LDT		0x04			/* local selector */
#define	SEL_PL		0x03			/* privilege level: */
#define	SEL_PL_K	0x00			    /* kernel selector */
#define	SEL_PL_U	0x03			    /* user selector */

//
// Convert selector to descriptor table index.
//
#define	sel_idx(sel)	((sel)>>3)


/* Return the privilege level of a segment selector */
#define ISPL(s)         ((s) & SEL_PL) 

#define USERMODE(s, f)          (ISPL(s) == SEL_PL_U || ((f) & EFL_VM) != 0)
#define KERNELMODE(s, f)        (ISPL(s) == SEL_PL_K && ((f) & EFL_VM) == 0)


/* Format of a "pseudo-descriptor", used for loading the IDT and GDT.  */
struct pseudo_descriptor
{
	short pad __attribute__ ((packed));
	unsigned short limit __attribute__ ((packed));
	unsigned long linear_base __attribute__ ((packed));
};


// Fill a segment descriptor.
extern inline void fill_descriptor(struct x86_desc *desc, unsigned base, unsigned limit,
		unsigned char access, unsigned char sizebits)
{
	if (limit > 0xfffff)
	{
		limit >>= 12;
		sizebits |= SZ_G;
	}
	desc->limit_low = limit & 0xffff;
	desc->base_low = base & 0xffff;
	desc->base_med = (base >> 16) & 0xff;
	desc->access = access | ACC_P;
	desc->limit_high = limit >> 16;
	desc->granularity = sizebits;
	desc->base_high = base >> 24;
}

// Set the base address in a segment descriptor.
extern inline void fill_descriptor_base(struct x86_desc *desc, unsigned base)
{
	desc->base_low = base & 0xffff;
	desc->base_med = (base >> 16) & 0xff;
	desc->base_high = base >> 24;
}

/* Set the limit in a segment descriptor.  */
extern inline void fill_descriptor_limit(struct x86_desc *desc, unsigned limit)
{
	if (limit > 0xfffff)
	{
		limit >>= 12;
		desc->granularity |= SZ_G;
	}
	else
		desc->granularity &= ~SZ_G;
	desc->limit_low = limit & 0xffff;
	desc->limit_high = limit >> 16;
}

/* Fill a gate with particular values.  */
extern inline void fill_gate(struct x86_gate *gate, DWORD offset, unsigned short selector,
	  unsigned char access, unsigned char WORD_count)
{
	gate->offset_low = offset & 0xffff;
	gate->selector = selector;
	gate->WORD_count = WORD_count;
	gate->access = access | ACC_P;
	gate->offset_high = (offset >> 16) & 0xffff;
}


#endif	/* _EKERNEL_SEG_H_ */