爲什麼我的中斷處理程序不能觸發？

Question

我想在Bochs上安裝一箇中斷處理程序，但由於某種原因，我的中斷處理程序沒有觸發。

首先，我設置斷點：

00036440222i[CPU0 ] [36440222] Stopped on MAGIC BREAKPOINT 
(0) [0x0000000000703044] 0008:00000000c0003044 (unk. ctxt): int3 

然後我嘗試執行int 3。

當我這樣做，但是，錯誤說int_trap_gate(): selector null，這似乎是在告訴我一些表選擇爲空。

然而，GDT如下：

<bochs:2> info gdt 
Global Descriptor Table (base=0x0000000000007c08, limit=23): 
GDT[0x00]=??? descriptor hi=0x00000000, lo=0x00000000 
GDT[0x01]=Code segment, base=0x00000000, limit=0xffffffff, Execute/Read, Accessed, 32-bit 
GDT[0x02]=Data segment, base=0x00000000, limit=0xffffffff, Read/Write, Accessed 

等特點，是IDT：

<bochs:3> info idt 
Interrupt Descriptor Table (base=0x00000000c0101020, limit=2047): 
IDT[0x00]=32-Bit Interrupt Gate target=0x0001:0xc0004148, DPL=0 
IDT[0x01]=32-Bit Interrupt Gate target=0x0001:0xc0004154, DPL=0 
IDT[0x02]=32-Bit Interrupt Gate target=0x0001:0xc0004160, DPL=0 
IDT[0x03]=32-Bit Interrupt Gate target=0x0001:0xc000416c, DPL=0 
IDT[0x04]=32-Bit Interrupt Gate target=0x0001:0xc0004178, DPL=0 
IDT[0x05]=32-Bit Interrupt Gate target=0x0001:0xc0004184, DPL=0 
IDT[0x06]=32-Bit Interrupt Gate target=0x0001:0xc0004190, DPL=0 
IDT[0x07]=32-Bit Interrupt Gate target=0x0001:0xc000419c, DPL=0 
IDT[0x08]=32-Bit Interrupt Gate target=0x0001:0xc00041a8, DPL=0 
IDT[0x09]=32-Bit Interrupt Gate target=0x0001:0xc00041b0, DPL=0 
IDT[0x0a]=32-Bit Interrupt Gate target=0x0001:0xc00041bc, DPL=0 
IDT[0x0b]=32-Bit Interrupt Gate target=0x0001:0xc00041c4, DPL=0 
IDT[0x0c]=32-Bit Interrupt Gate target=0x0001:0xc00041cc, DPL=0 
IDT[0x0d]=32-Bit Interrupt Gate target=0x0001:0xc00041d4, DPL=0 
IDT[0x0e]=32-Bit Interrupt Gate target=0x0001:0xc00041dc, DPL=0 
IDT[0x0f]=32-Bit Interrupt Gate target=0x0001:0xc00041e4, DPL=0 
IDT[0x10]=32-Bit Interrupt Gate target=0x0001:0xc00041f0, DPL=0 
IDT[0x11]=32-Bit Interrupt Gate target=0x0001:0xc00041fc, DPL=0 
IDT[0x12]=32-Bit Interrupt Gate target=0x0001:0xc0004208, DPL=0 
IDT[0x13]=32-Bit Interrupt Gate target=0x0001:0xc0004214, DPL=0 
IDT[0x14]=32-Bit Interrupt Gate target=0x0001:0xc0004220, DPL=0 
IDT[0x15]=32-Bit Interrupt Gate target=0x0001:0xc000422c, DPL=0 
IDT[0x16]=32-Bit Interrupt Gate target=0x0001:0xc0004238, DPL=0 
IDT[0x17]=32-Bit Interrupt Gate target=0x0001:0xc0004244, DPL=0 
IDT[0x18]=32-Bit Interrupt Gate target=0x0001:0xc0004250, DPL=0 
IDT[0x19]=32-Bit Interrupt Gate target=0x0001:0xc000425c, DPL=0 
IDT[0x1a]=32-Bit Interrupt Gate target=0x0001:0xc0004268, DPL=0 
IDT[0x1b]=32-Bit Interrupt Gate target=0x0001:0xc0004274, DPL=0 
IDT[0x1c]=32-Bit Interrupt Gate target=0x0001:0xc0004280, DPL=0 
IDT[0x1d]=32-Bit Interrupt Gate target=0x0001:0xc000428c, DPL=0 
IDT[0x1e]=32-Bit Interrupt Gate target=0x0001:0xc0004298, DPL=0 
IDT[0x1f]=??? descriptor hi=0x00000000, lo=0x00000000 
<...> 
IDT[0xff]=??? descriptor hi=0x00000000, lo=0x00000000 

在我看來，該IDT條目具有有效的GDT選擇，所以我不知道了解是什麼原因導致的問題，當我執行中斷：

<bochs:5> s     ; step 
(0).[36440222] [0x0000000000703044] 0008:00000000c0003044 (unk. ctxt): int3 
CPU 0: Interrupt 0x03 occured (error_code=0x0000) 
00036440222e[CPU0 ] int_trap_gate(): selector null 
CPU 0: Exception 0x0d - (#GP) general protection fault occured (error_code=0x0000) 
CPU 0: Interrupt 0x0d occured (error_code=0x0000) 
00036440222e[CPU0 ] int_trap_gate(): selector null 
CPU 0: Exception 0x0d - (#GP) general protection fault occured (error_code=0x0000) 
CPU 0: Exception 0x08 - (#DF) double fault occured (error_code=0x0000) 
CPU 0: Interrupt 0x08 occured (error_code=0x0000) 
00036440222e[CPU0 ] int_trap_gate(): selector null 
CPU 0: Exception 0x0d - (#GP) general protection fault occured (error_code=0x0000) 

問題是什麼？

Answer 1

這裏：

IDT[0x03]=32-Bit Interrupt Gate target=0x0001:0xc000416c, DPL=0 

0×0001是一個選擇器值。它的2個最低有效位是RPL位。餘下的位用作段描述符表（GDT或LDT）的索引。這些位是0.對於所有意圖和目的，這是一個NULL選擇器。

你可能要8中，而不是1

參見選擇器究竟是如何使用的CPU的文檔。