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初始化GDT和IDT

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This commit is contained in:
Yourtion
2014-09-10 18:51:19 +08:00
parent 76c2755631
commit 8ab05adb43
2 changed files with 80 additions and 1 deletions
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68
05_day/bootpack.c
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@@ -38,6 +38,24 @@ struct BOOTINFO {
char *vram;
};
struct SEGMENT_DESCRIPTOR {
short limit_low, base_low;
char base_mid, access_right;
char limit_high, base_high;
};
struct GATE_DESCRIPTOR {
short offset_low, selector;
char dw_count, access_right;
short offset_high;
};
void init_gdtidt(void);
void set_segmdesc(struct SEGMENT_DESCRIPTOR *sd, unsigned int limit, int base, int ar);
void set_gatedesc(struct GATE_DESCRIPTOR *gd, int offset, int selector, int ar);
void load_gdtr(int limit, int addr);
void load_idtr(int limit, int addr);
void HariMain(void)
{
struct BOOTINFO *binfo = (struct BOOTINFO *) 0x0ff0;
@@ -217,4 +235,52 @@ void putblock8_8(char *vram, int vxsize, int pxsize,
}
}
return;
}
}
void init_gdtidt(void)
{
struct SEGMENT_DESCRIPTOR *gdt = (struct SEGMENT_DESCRIPTOR *) 0x00270000;
struct GATE_DESCRIPTOR *idt = (struct GATE_DESCRIPTOR *) 0x0026f800;
int i;
/* GDT初始化 */
for (i = 0; i < 8192; i++) {
set_segmdesc(gdt + i, 0, 0, 0);
}
set_segmdesc(gdt + 1, 0xffffffff, 0x00000000, 0x4092);
set_segmdesc(gdt + 2, 0x0007ffff, 0x00280000, 0x409a);
load_gdtr(0xffff, 0x00270000);
/* IDT初始化 */
for (i = 0; i < 256; i++) {
set_gatedesc(idt + i, 0, 0, 0);
}
load_idtr(0x7ff, 0x0026f800);
return;
}
void set_segmdesc(struct SEGMENT_DESCRIPTOR *sd, unsigned int limit, int base, int ar)
{
if (limit > 0xfffff) {
ar |= 0x8000; /* G_bit = 1 */
limit /= 0x1000;
}
sd->limit_low = limit & 0xffff;
sd->base_low = base & 0xffff;
sd->base_mid = (base >> 16) & 0xff;
sd->access_right = ar & 0xff;
sd->limit_high = ((limit >> 16) & 0x0f) | ((ar >> 8) & 0xf0);
sd->base_high = (base >> 24) & 0xff;
return;
}
void set_gatedesc(struct GATE_DESCRIPTOR *gd, int offset, int selector, int ar)
{
gd->offset_low = offset & 0xffff;
gd->selector = selector;
gd->dw_count = (ar >> 8) & 0xff;
gd->access_right = ar & 0xff;
gd->offset_high = (offset >> 16) & 0xffff;
return;
}

13
05_day/naskfunc.nas
View File

@@ -10,6 +10,7 @@
GLOBAL _io_in8, _io_in16, _io_in32
GLOBAL _io_out8, _io_out16, _io_out32
GLOBAL _io_load_eflags, _io_store_eflags
GLOBAL _load_gdtr, _load_idtr
[SECTION .text]
@@ -75,3 +76,15 @@ _io_store_eflags: ; void io_store_eflags(int eflags);
PUSH EAX
POPFD ; POP EFLAGS
RET
_load_gdtr: ; void load_gdtr(int limit, int addr);
MOV AX,[ESP+4] ; limit
MOV [ESP+6],AX
LGDT [ESP+6]
RET
_load_idtr: ; void load_idtr(int limit, int addr);
MOV AX,[ESP+4] ; limit
MOV [ESP+6],AX
LIDT [ESP+6]
RET