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//
// seg.h
//
// Segment descriptors
//
// Copyright (C) 2002 Michael Ringgaard. All rights reserved.
//
// 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 project 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
//
#ifndef SEG_H
#define SEG_H
// Each descriptor should have exactly one of next 8 codes to define the type of descriptor
#define D_LDT 0x02 // LDT segment
#define D_TASK 0x05 // Task gate
#define D_TSS 0x09 // TSS
#define D_CALL 0x0C // 386 call gate
#define D_INT 0x0E // 386 interrupt gate
#define D_TRAP 0x0F // 386 trap gate
#define D_DATA 0x10 // Data segment
#define D_CODE 0x18 // Code segment
// Descriptors may include the following as appropriate:
#define D_DPL3 0x60 // DPL3 or mask for DPL
#define D_DPL2 0x40 // DPL2 or mask for DPL
#define D_DPL1 0x20 // DPL1 or mask for DPL
#define D_DPL0 0x00 // DPL0 or mask for DPL
#define D_PRESENT 0x80 // Present
// Segment descriptors (not gates) may include:
#define D_ACCESSED 0x1 // Accessed (data or code)
#define D_WRITE 0x2 // Writable (data segments only)
#define D_EXDOWN 0x4 // Expand down (data segments only)
#define D_READ 0x2 // Readable (code segments only)
#define D_CONFORM 0x4 // Conforming (code segments only)
#define D_BUSY 0x2 // Busy (TSS only)
// Granularity flags
#define D_BIG 0x4 // Default to 32 bit mode
#define D_BIG_LIM 0x8 // Limit is in 4K units
// Structures for descriptors and gates
#pragma pack(push, 1)
struct segment {
unsigned short limit_low; // Limit 0..15
unsigned short base_low; // Base 0..15
unsigned char base_med; // Base 16..23
unsigned char access; // Access byte
unsigned char limit_high; // Limit 16..19 + Granularity << 4
unsigned char base_high; // Base 24..31
};
struct gate {
unsigned short offset_low; // Offset 0..15
unsigned short selector; // Selector
unsigned char notused;
unsigned char access; // Access flags
unsigned short offset_high; // Offset 16..31
};
struct desc {
unsigned long low;
unsigned long high;
};
union dte {
struct segment segment;
struct gate gate;
struct desc desc;
};
struct selector {
unsigned short limit;
void *dt;
};
struct fullptr {
unsigned long offset;
unsigned short segment;
};
void __inline seginit(struct segment *seg, unsigned long addr, unsigned long size, int access, int granularity) {
seg->base_low = (unsigned short) (addr & 0xFFFF);
seg->base_med = (unsigned char) ((addr >> 16) & 0xFF);
seg->base_high = (unsigned char) ((addr >> 24) & 0xFF);
seg->limit_low = (unsigned short) ((size - 1) & 0xFFFF);
seg->limit_high = (unsigned char) ((((size - 1) >> 16) & 0xF) | (granularity << 4));
seg->access = access;
}
#pragma pack(pop)
#endif