FreeBSD/Linux Kernel Cross Reference
sys/kernel/protect.h

     /* Constants for protected mode. */
     
     /* Table sizes. */
     #define GDT_SIZE (FIRST_LDT_INDEX + NR_TASKS + NR_PROCS) 
                                             /* spec. and LDT's */
     #define IDT_SIZE (IRQ8_VECTOR + 8)      /* only up to the highest vector */
     #define LDT_SIZE (2 + NR_REMOTE_SEGS)   /* CS, DS and remote segments */
     
     /* Fixed global descriptors.  1 to 7 are prescribed by the BIOS. */
    #define GDT_INDEX            1  /* GDT descriptor */
    #define IDT_INDEX            2  /* IDT descriptor */
    #define DS_INDEX             3  /* kernel DS */
    #define ES_INDEX             4  /* kernel ES (386: flag 4 Gb at startup) */
    #define SS_INDEX             5  /* kernel SS (386: monitor SS at startup) */
    #define CS_INDEX             6  /* kernel CS */
    #define MON_CS_INDEX         7  /* temp for BIOS (386: monitor CS at startup) */
    #define TSS_INDEX            8  /* kernel TSS */
    #define DS_286_INDEX         9  /* scratch 16-bit source segment */
    #define ES_286_INDEX        10  /* scratch 16-bit destination segment */
    #define A_INDEX             11  /* 64K memory segment at A0000 */
    #define B_INDEX             12  /* 64K memory segment at B0000 */
    #define C_INDEX             13  /* 64K memory segment at C0000 */
    #define D_INDEX             14  /* 64K memory segment at D0000 */
    #define FIRST_LDT_INDEX     15  /* rest of descriptors are LDT's */
    
    #define GDT_SELECTOR      0x08  /* (GDT_INDEX * DESC_SIZE) bad for asld */
    #define IDT_SELECTOR      0x10  /* (IDT_INDEX * DESC_SIZE) */
    #define DS_SELECTOR       0x18  /* (DS_INDEX * DESC_SIZE) */
    #define ES_SELECTOR       0x20  /* (ES_INDEX * DESC_SIZE) */
    #define FLAT_DS_SELECTOR  0x21  /* less privileged ES */
    #define SS_SELECTOR       0x28  /* (SS_INDEX * DESC_SIZE) */
    #define CS_SELECTOR       0x30  /* (CS_INDEX * DESC_SIZE) */
    #define MON_CS_SELECTOR   0x38  /* (MON_CS_INDEX * DESC_SIZE) */
    #define TSS_SELECTOR      0x40  /* (TSS_INDEX * DESC_SIZE) */
    #define DS_286_SELECTOR   0x49  /* (DS_286_INDEX*DESC_SIZE+TASK_PRIVILEGE) */
    #define ES_286_SELECTOR   0x51  /* (ES_286_INDEX*DESC_SIZE+TASK_PRIVILEGE) */
    
    /* Fixed local descriptors. */
    #define CS_LDT_INDEX         0  /* process CS */
    #define DS_LDT_INDEX         1  /* process DS=ES=FS=GS=SS */
    #define EXTRA_LDT_INDEX      2  /* first of the extra LDT entries */
    
    /* Privileges. */
    #define INTR_PRIVILEGE       0  /* kernel and interrupt handlers */
    #define TASK_PRIVILEGE       1  /* kernel tasks */
    #define USER_PRIVILEGE       3  /* servers and user processes */
    
    /* 286 hardware constants. */
    
    /* Exception vector numbers. */
    #define BOUNDS_VECTOR        5  /* bounds check failed */
    #define INVAL_OP_VECTOR      6  /* invalid opcode */
    #define COPROC_NOT_VECTOR    7  /* coprocessor not available */
    #define DOUBLE_FAULT_VECTOR  8
    #define COPROC_SEG_VECTOR    9  /* coprocessor segment overrun */
    #define INVAL_TSS_VECTOR    10  /* invalid TSS */
    #define SEG_NOT_VECTOR      11  /* segment not present */
    #define STACK_FAULT_VECTOR  12  /* stack exception */
    #define PROTECTION_VECTOR   13  /* general protection */
    
    /* Selector bits. */
    #define TI                0x04  /* table indicator */
    #define RPL               0x03  /* requester privilege level */
    
    /* Descriptor structure offsets. */
    #define DESC_BASE            2  /* to base_low */
    #define DESC_BASE_MIDDLE     4  /* to base_middle */
    #define DESC_ACCESS          5  /* to access byte */
    #define DESC_SIZE            8  /* sizeof (struct segdesc_s) */
    
    /* Base and limit sizes and shifts. */
    #define BASE_MIDDLE_SHIFT   16  /* shift for base --> base_middle */
    
    /* Access-byte and type-byte bits. */
    #define PRESENT           0x80  /* set for descriptor present */
    #define DPL               0x60  /* descriptor privilege level mask */
    #define DPL_SHIFT            5
    #define SEGMENT           0x10  /* set for segment-type descriptors */
    
    /* Access-byte bits. */
    #define EXECUTABLE        0x08  /* set for executable segment */
    #define CONFORMING        0x04  /* set for conforming segment if executable */
    #define EXPAND_DOWN       0x04  /* set for expand-down segment if !executable*/
    #define READABLE          0x02  /* set for readable segment if executable */
    #define WRITEABLE         0x02  /* set for writeable segment if !executable */
    #define TSS_BUSY          0x02  /* set if TSS descriptor is busy */
    #define ACCESSED          0x01  /* set if segment accessed */
    
    /* Special descriptor types. */
    #define AVL_286_TSS          1  /* available 286 TSS */
    #define LDT                  2  /* local descriptor table */
    #define BUSY_286_TSS         3  /* set transparently to the software */
    #define CALL_286_GATE        4  /* not used */
    #define TASK_GATE            5  /* only used by debugger */
    #define INT_286_GATE         6  /* interrupt gate, used for all vectors */
    #define TRAP_286_GATE        7  /* not used */
    
    /* Extra 386 hardware constants. */
    
   /* Exception vector numbers. */
   #define PAGE_FAULT_VECTOR   14
   #define COPROC_ERR_VECTOR   16  /* coprocessor error */
   
   /* Descriptor structure offsets. */
   #define DESC_GRANULARITY     6  /* to granularity byte */
   #define DESC_BASE_HIGH       7  /* to base_high */
   
   /* Base and limit sizes and shifts. */
   #define BASE_HIGH_SHIFT     24  /* shift for base --> base_high */
   #define BYTE_GRAN_MAX   0xFFFFFL   /* maximum size for byte granular segment */
   #define GRANULARITY_SHIFT   16  /* shift for limit --> granularity */
   #define OFFSET_HIGH_SHIFT   16  /* shift for (gate) offset --> offset_high */
   #define PAGE_GRAN_SHIFT     12  /* extra shift for page granular limits */
   
   /* Type-byte bits. */
   #define DESC_386_BIT  0x08 /* 386 types are obtained by ORing with this */
                                   /* LDT's and TASK_GATE's don't need it */
   
   /* Granularity byte. */
   #define GRANULAR          0x80  /* set for 4K granularilty */
   #define DEFAULT           0x40  /* set for 32-bit defaults (executable seg) */
   #define BIG               0x40  /* set for "BIG" (expand-down seg) */
   #define AVL               0x10  /* 0 for available */
   #define LIMIT_HIGH        0x0F  /* mask for high bits of limit */

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