在我努力了解如何使用 GNU binutils 使用 gas构建一个简单的引导加载程序时,我遇到了一个问题,你如何告诉链接器将你的数据放在哪里,在一个使用 .org 来推进位置计数器的文件中同时将文件大小保持在 512 字节。我似乎找不到办法做到这一点。
试图做到这一点的汇编程序是:
# Author: Matthew Hoggan
# Date Created: Tuesday, Mar 6, 2012
.code16 # Tell assembler to work in 16 bit mode
.section .data
msg: # Message to be printed to the screen
.asciz "hello, world"
.section .text
.globl _start # Help linker find start of program
_start:
xor %ax, %ax # Zero out ax register (ah used to specify bios function to Video Services)
movw %ax, %ds # Since ax is 0x00 0x00 use it to set data segment to 0
mov $msg, %si # Use source index as pointer to string
loop:
movb %ds:(%si), %al # Pass data to BIOS function in low nibble of ax
inc %si # Advance the pointer
or %al, %al # If byte stored in al is equal to zero then...
jz _hang # Zero signifies end of string
call print_char # Print current char in al
jmp loop # Repeat
#
# Function that uses bios function calls
# to print char to screen
#
print_char:
movb $0x0e, %ah # Function to print a character to the screen
movb $0x07, %bl # color/style to use for the character
int $0x10 # Video Service Request to Bios
ret
#
# Function used as infinite loop
#
_hang:
jmp _hang
.org 510
.byte 0x55, 0xAA
.end
更新 使用以下命令,我收到以下错误:
mehoggan@mehoggan-laptop:~/Code/svn_scripts/assembly/bootloader/gas$ ld --oformat binary -o string string.o
string.o: In function `_start':
(.text+0x5): relocation truncated to fit: R_X86_64_16 against `.data'