精彩代码linux/include/asm/system.h

00001 #define move_to_user_mode() 
00002 __asm__ ("movl %%esp,%%eax
	" 
00003     "pushl $0x17
	" 
00004     "pushl %%eax
	" 
00005     "pushfl
	" 
00006     "pushl $0x0f
	" 
00007     "pushl $1f
	" 
00008     "iret
" 
//特权变换iret
00009     "1:	movl $0x17,%%eax
	" 
00010     "movw %%ax,%%ds
	" 
00011     "movw %%ax,%%es
	" 
00012     "movw %%ax,%%fs
	" 
00013     "movw %%ax,%%gs" 
00014     :::"ax")
//以上比较精彩部分2013-08-13
00015 
00016 #define sti() __asm__ ("sti"::)
00017 #define cli() __asm__ ("cli"::)
00018 #define nop() __asm__ ("nop"::)
00019 
00020 #define iret() __asm__ ("iret"::)
00021 
00022 #define _set_gate(gate_addr,type,dpl,addr) 
00023 __asm__ ("movw %%dx,%%ax
	" 
00024     "movw %0,%%dx
	" 
00025     "movl %%eax,%1
	" 
00026     "movl %%edx,%2" 
00027     : 
00028     : "i" ((short) (0x8000+(dpl<<13)+(type<<8))), 
00029     "o" (*((char *) (gate_addr))), 
00030     "o" (*(4+(char *) (gate_addr))), 
00031     "d" ((char *) (addr)),"a" (0x00080000))
00032 
00033 #define set_intr_gate(n,addr) 
00034     _set_gate(&idt[n],14,0,addr)
//idt[] gdt[] 在汇编中有定义,c中是head.h(linux/include/linux/head.h)
00035 
00036 #define set_trap_gate(n,addr) 
00037     _set_gate(&idt[n],15,0,addr)
00038 
00039 #define set_system_gate(n,addr) 
00040     _set_gate(&idt[n],15,3,addr)
//以上4个#define  连着看
00041 
00042 #define _set_seg_desc(gate_addr,type,dpl,base,limit) {
00043     *(gate_addr) = ((base) & 0xff000000) | 
00044         (((base) & 0x00ff0000)>>16) | 
00045         ((limit) & 0xf0000) | 
00046         ((dpl)<<13) | 
00047         (0x00408000) | 
00048         ((type)<<8); 
00049     *((gate_addr)+1) = (((base) & 0x0000ffff)<<16) | 
00050         ((limit) & 0x0ffff); }
00051 
00052 #define _set_tssldt_desc(n,addr,type) 
00053 __asm__ ("movw $104,%1
	" 
00054     "movw %%ax,%2
	" 
00055     "rorl $16,%%eax
	" 
00056     "movb %%al,%3
	" 
00057     "movb $" type ",%4
	" 
00058     "movb $0x00,%5
	" 
00059     "movb %%ah,%6
	" 
00060     "rorl $16,%%eax" 
00061     ::"a" (addr), "m" (*(n)), "m" (*(n+2)), "m" (*(n+4)), 
00062      "m" (*(n+5)), "m" (*(n+6)), "m" (*(n+7)) 
00063     )
00064 
00065 #define set_tss_desc(n,addr) _set_tssldt_desc(((char *) (n)),((int)(addr)),"0x89")
00066 #define set_ldt_desc(n,addr) _set_tssldt_desc(((char *) (n)),((int)(addr)),"0x82")
00067 

//代码出自linux 0.11  linux/include/asm/system.h