system.h

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#ifndef __ASM_SYSTEM_H
#define __ASM_SYSTEM_H

#include <linux/segment.h>

#define move_to_user_mode() \
__asm__ __volatile__ ("movl %%esp,%%eax\n\t" \
        "pushl %0\n\t" \
        "pushl %%eax\n\t" \
        "pushfl\n\t" \
        "pushl %1\n\t" \
        "pushl $1f\n\t" \
        "iret\n" \
        "1:\tmovl %0,%%eax\n\t" \
        "mov %%ax,%%ds\n\t" \
        "mov %%ax,%%es\n\t" \
        "mov %%ax,%%fs\n\t" \
        "mov %%ax,%%gs" \


*/ :"i" (USER_DS), "i" (USER_CS):"ax")

#define sti() __asm__ __volatile__ ("sti": : :"memory")
#define cli() __asm__ __volatile__ ("cli": : :"memory")
#define nop() __asm__ __volatile__ ("nop")

/**
*

 * Clear and set 'TS' bit respectively


*/
#define clts() __asm__ __volatile__ ("clts")
#define stts() \
__asm__ __volatile__ ( \
        "movl %%cr0,%%eax\n\t" \
        "orl $8,%%eax\n\t" \
        "movl %%eax,%%cr0" \


*/ \


*/ \
        :"ax")


extern inline int tas(char * m)
{
        char res;

        __asm__("xchgb %0,%1":"=q" (res),"=m" (*m):"0" (0x1));
        return res;
}

#define save_flags(x) \


*/ :"memory")

#define restore_flags(x) \


*/ :"r" (x):"memory")

#define iret() __asm__ __volatile__ ("iret": : :"memory")

#define _set_gate(gate_addr,type,dpl,addr) \
__asm__ __volatile__ ("movw %%dx,%%ax\n\t" \
        "movw %2,%%dx\n\t" \
        "movl %%eax,%0\n\t" \
        "movl %%edx,%1" \
        :"=m" (*((long *) (gate_addr))), \
         "=m" (*(1+(long *) (gate_addr))) \
        :"i" ((short) (0x8000+(dpl<<13)+(type<<8))), \
         "d" ((char *) (addr)),"a" (KERNEL_CS << 16) \
        :"ax","dx")

#define set_intr_gate(n,addr) \
        _set_gate(&idt[n],14,0,addr)

#define set_trap_gate(n,addr) \
        _set_gate(&idt[n],15,0,addr)

#define set_system_gate(n,addr) \
        _set_gate(&idt[n],15,3,addr)

#define set_call_gate(a,addr) \
        _set_gate(a,12,3,addr)

#define _set_seg_desc(gate_addr,type,dpl,base,limit) {\
        *((gate_addr)+1) = ((base) & 0xff000000) | \
                (((base) & 0x00ff0000)>>16) | \
                ((limit) & 0xf0000) | \
                ((dpl)<<13) | \
                (0x00408000) | \
                ((type)<<8); \
        *(gate_addr) = (((base) & 0x0000ffff)<<16) | \
                ((limit) & 0x0ffff); }

#define _set_tssldt_desc(n,addr,limit,type) \
__asm__ __volatile__ ("movw $" #limit ",%1\n\t" \
        "movw %%ax,%2\n\t" \
        "rorl $16,%%eax\n\t" \
        "movb %%al,%3\n\t" \
        "movb $" type ",%4\n\t" \
        "movb $0x00,%5\n\t" \
        "movb %%ah,%6\n\t" \
        "rorl $16,%%eax" \


*/ \
        :"a" (addr+0xc0000000), "m" (*(n)), "m" (*(n+2)), "m" (*(n+4)), \
         "m" (*(n+5)), "m" (*(n+6)), "m" (*(n+7)) \
        )

#define set_tss_desc(n,addr) _set_tssldt_desc(((char *) (n)),((int)(addr)),235,"0x89")
#define set_ldt_desc(n,addr,size) \
        _set_tssldt_desc(((char *) (n)),((int)(addr)),((size << 3) - 1),"0x82")


#endif

---