assembly - 如何处理实模式下的int中断？（16 位）

Question

从今年夏天开始，我正在创建一个操作系统，它是一个在保护模式下工作的 32 位操作系统。我需要创建一种方法来使 BIOS 中断，所以我需要在实模式下传递，在 16 位之前，我成功地传递到 16 位，但我不确定我在代码末尾是否以实模式传递。我尝试通过示例切换视频模式，但我的模拟器 Boch 写道：

00012417016e[CPU0 ] interrupt(real mode) vector > idtr.limit
00012417016e[CPU0 ] interrupt(real mode) vector > idtr.limit
00012417016e[CPU0 ] interrupt(real mode) vector > idtr.limit
00012417016i[CPU0 ] real mode
00012417016i[CPU0 ] CS.d_b = 16 bit
00012417016i[CPU0 ] SS.d_b = 16 bit
00012417016i[CPU0 ] | EAX=00004c00  EBX=00000123  ECX=00000000  EDX=00001034
00012417016i[CPU0 ] | ESP=0009f000  EBP=0009effc  ESI=00000123  EDI=0000ffde
00012417016i[CPU0 ] | IOPL=0 id vip codec vm RF nt of df IF tf sf zf af pf cf
00012417016i[CPU0 ] | SEG selector     base    limit G D
00012417016i[CPU0 ] | SEG sltr(index|ti|rpl)     base    limit G D
00012417016i[CPU0 ] |  CS:0000( 0004| 0|  0) 00000000 0000ffff 0 0
00012417016i[CPU0 ] |  DS:07c0( 0005| 0|  0) 00007c00 0000ffff 0 0
00012417016i[CPU0 ] |  SS:8000( 0005| 0|  0) 00080000 0000ffff 0 0
00012417016i[CPU0 ] |  ES:07c0( 0005| 0|  0) 00007c00 0000ffff 0 0
00012417016i[CPU0 ] |  FS:0000( 0005| 0|  0) 00000000 0000ffff 0 0
00012417016i[CPU0 ] |  GS:0000( 0005| 0|  0) 00000000 0000ffff 0 0
00012417016i[CPU0 ] | EIP=00001d63 (00001d63 )
00012417016i[CPU0 ] | CR0=0x00000010 CR1=0 CR2=0x00000000
00012417016i[CPU0 ] | CR3=0x00000000 CR4=0x00000000
00012417016i[CPU0 ] >> int 0x21 : CD21
00012417016e[CPU0 ] exception(): 3rd (13) exception with no resolution, shutdown status is 00h, resetting
00012417016i[SYS  ] bx_pc_system_c::Reset(SOFTWARE) called

我在实模式下切换的汇编代码是：

global go16
;______________________________________________________________________________________________________
;Switch to 16-bit real Mode
;IN/OUT:  nothing

go16:
    [BITS 32]
    ;cli                 ;Clear interrupts    
    pop edx             ;save return location in edx
    jmp 0x20:PM16       ;Load CS with selector 0x20
;For go to 16-bit real mode, first we have to go to 16-bit protected mode
    [BITS 16]
PM16:
    mov ax, 0x28            ;0x28 is 16-bit protected mode selector.
    mov ss, ax  
    mov ds, ax
    mov es, ax
    mov gs, ax
    mov fs, ax
    mov sp, 0x7c00+0x200    ;Stack hase base at 0x7c00+0x200    

    mov eax, cr0
    mov [savcr0], eax
    and eax, 0xfffffffe     ;Clear protected enable bit in cr0
    mov cr0, eax  
    jmp 0:realMode          ;Load CS and IP

realMode:
;Load segment registers with 16-bit Values.
    mov ax, 0   
    mov ds, ax
    mov es, ax
    mov fs, ax
    mov gs, ax
    mov ss, ax
    mov sp, 0x7c00+0x200    
    mov ax, 0x07c0
    mov ds, ax
    mov es, ax
    mov ax, 0x8000
    mov ss, ax
    mov sp, 0xf000
    lidt [idt_real]     ;Load real mode interrupt vector table
    sti
    mov ax,4c00h
    int 10h
    cli
    hlt


;Real mode interrupt vector table
idt_real:
    dw 0x3ff        ; 256 entries, 4b each = 1K
    dd 0            ; Real Mode IVT @ 0x0000
 
savcr0:
    dd 0

感谢您的帮助，如果您需要其他元素，请在评论中向我询问

标签： assemblyoperating-systemx86-16biosreal-mode