Question

我有一个用C编写的函数，该函数从键盘读取一个字符，并返回按下的字符。

kmain.c

#include <stdint.h>

char getch()
{
   uint16_t inchar;

   __asm__ __volatile__ ("int $0x16\n\t"
                        : "=a"(inchar)
                        : "0"(0x0));

   return ((char)inchar);
}


void println(char *str)
{
    while (*str) 
    {
        // AH=0x0e, AL=char to print, BH=page, BL=fg color
        __asm__ __volatile__ ("int $0x10"
                              :
                              : "a" ((0x0e<<8) | *str++),
                                "b" (0x0000));

    }

}


void kernelmain()
{
    println("Println called from C code");
    char c;
    c = getch();
    println(c);
}

boot.asm

extern println
extern kernelmain
global start
bits 16

section .text
start:
    xor ax, ax            
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov esp, 0x7C00
    jmp 0x0000:setcs     
setcs:
    cld                   

    push dword msg1
    call dword println
    ; If you use call instead of jmp, it gonna throw a nice error :)
    jmp kernelmain
    cli
    hlt ; halt the processor


section .data
    msg1 db 'Println called from NASM code', 0x0A, 0x0D, 0

但是当我要打印获得的密钥时，它会抛出此无用的错误：

qemu: fatal: Trying to execute code outside RAM or ROM at 0xd08ec08e

EAX=00002d78 EBX=00000000 ECX=00000000 EDX=00000000
ESI=00000000 EDI=00000000 EBP=d88ec031 ESP=00007c08
EIP=d08ec08e EFL=00000206 [-----P-] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =0000 00000000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300
DS =0000 00000000 0000ffff 00009300
FS =0000 00000000 0000ffff 00009300
GS =0000 00000000 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     000f6c00 00000037
IDT=     00000000 000003ff
CR0=00000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000
DR6=ffff0ff0 DR7=00000400
CCS=00000004 CCD=0000fe9c CCO=EFLAGS
EFER=0000000000000000
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
Aborted (core dumped)

编译kernel.bin：

gcc -fno-PIC -ffreestanding -m16 -c kmain.c -o kmain.o
nasm -f elf32 boot.asm -o boot.o
ld -melf_i386 -T link.ld kmain.o boot.o -o kernel.elf
objcopy -O binary kernel.elf kernel.bin
qemu-system-i386 -fda kernel.bin

我发现了与此错误相同的问题，但它们并没有帮助我。另外，我知道最好用OpenWatcom进行编译，但这太复杂了。

qemu：致命的：试图在0xd08ec08e的RAM或ROM外部执行代码

0 个答案: