Question

我正在从头开始在C中开发内核。我遇到了键盘问题。在Qemu中，当我按下键盘上的按键时，按键正常处理。当我在VirtualBox或实际计算机上运行它时，它工作正常，直到我按下一个键。在virtualbox中，当它崩溃时，它会给我错误代码VINF_EM_TRIPLE_FAULT。这是我的（重要部分）代码：

大会：

bits 32
section .text
        ;multiboot spec
        align 4
        dd 0x1BADB002              ;magic
        dd 0x00                    ;flags
        dd - (0x1BADB002 + 0x00)

global start
global keyboard_handler
global read_port
global write_port
global load_idt

extern main         ;this is defined in the c file
extern keyboard_handler_main

read_port:
    mov edx, [esp + 4]
            ;al is the lower 8 bits of eax
    in al, dx   ;dx is the lower 16 bits of edx
    ret

write_port:
    mov   edx, [esp + 4]    
    mov   al, [esp + 4 + 4]  
    out   dx, al  
    ret

load_idt:
    mov edx, [esp + 4]
    lidt [edx]
    sti                 ;turn on interrupts
    ret

keyboard_handler:                 
    call    keyboard_handler_main
    iretd

start:
    cli                 ;block interrupts
    mov esp, stack_space
    call main
    hlt                 ;halt the CPU

section .bss
resb 8192; 8KB for stack
stack_space:

C（重要的部分，我省略了不涉及键盘的部分）：

struct IDT_entry{
    unsigned short int offset_lowerbits;
    unsigned short int selector;
    unsigned char zero;
    unsigned char type_attr;
    unsigned short int offset_higherbits;
};

struct IDT_entry IDT[IDT_SIZE];
void idt_init(void)
{
    unsigned long keyboard_address;
    unsigned long idt_address;
    unsigned long idt_ptr[2];

    /* populate IDT entry of keyboard's interrupt */
    keyboard_address = (unsigned long)keyboard_handler;
    IDT[0x21].offset_lowerbits = keyboard_address & 0xffff;
    IDT[0x21].selector = KERNEL_CODE_SEGMENT_OFFSET;
    IDT[0x21].zero = 0;
    IDT[0x21].type_attr = INTERRUPT_GATE;
    IDT[0x21].offset_higherbits = (keyboard_address & 0xffff0000) >> 16;

    /*     Ports
    *    PIC1   PIC2
    *Command 0x20   0xA0
    *Data    0x21   0xA1
    */

    /* ICW1 - begin initialization */
    write_port(0x20 , 0x11);
    write_port(0xA0 , 0x11);

    /* ICW2 - remap offset address of IDT */
    /*
    * In x86 protected mode, we have to remap the PICs beyond 0x20 because
    * Intel have designated the first 32 interrupts as "reserved" for cpu exceptions
    */
    write_port(0x21 , 0x20);
    write_port(0xA1 , 0x28);

    /* ICW3 - setup cascading */
    write_port(0x21 , 0x00);
    write_port(0xA1 , 0x00);

    /* ICW4 - environment info */
    write_port(0x21 , 0x01);
    write_port(0xA1 , 0x01);
    /* Initialization finished */

    /* mask interrupts */
    write_port(0x21 , 0xff);
    write_port(0xA1 , 0xff);

    /* fill the IDT descriptor */
    idt_address = (unsigned long)IDT ;
    idt_ptr[0] = (sizeof (struct IDT_entry) * IDT_SIZE) + ((idt_address & 0xffff) << 16);
    idt_ptr[1] = idt_address >> 16 ;

    load_idt(idt_ptr);
}

void kb_init(void)
{
    /* 0xFD is 11111101 - enables only IRQ1 (keyboard)*/
    write_port(0x21 , 0xFD);
}
void keyboard_handler_main(void) {
    unsigned char status;
    char keycode;

    /* write EOI */
    write_port(0x20, 0x20);

    status = read_port(KEYBOARD_STATUS_PORT);
    /* Lowest bit of status will be set if buffer is not empty */
    if (status & 0x01) {
        keycode = read_port(KEYBOARD_DATA_PORT);
        if(keycode < 0){
            return;
        }
            char c = keyboard_map[(unsigned char) keycode]; //keyboard_map converts key codes to ASCII
            (prints the char)
        }
    }
}
void main(void)
{
    idt_init();
    kb_init();
    while(1);
    print("Welcome to Code OS");
}

当然，它们是用链接器编译的。那么为什么这在qemu工作但不是真正的计算机呢？（在实际的计算机上，它可以正常工作，直到我按任意键。）

C内核 - 在Qemu中运行良好但在VM中运行不正常

0 个答案: