我想在asm中绘制一条彩色线条 . 我必须在x86 intel linux上使用AT&T语法 . 我已经相当远了,但我想知道如何进入VGA模式或模式X,以及如何在屏幕上放置一个像素 . 在标准C库(如printf)中是否有这样的功能?
非常感谢你的帮助 . :)
``
.bss # Declaring uninitialized variables
.data # Declaring initialized variables
.text # Actual assembly code and constants
intro: .asciz "Draw a line in VGA\n\n"
clr: .asciz "Give a color \n"
optns: .asciz "red (1), blue (2), white (3)\n"
res .asciz "%d"
ent: .asciz "\n"
.global main # Tell kernel where to start (visible from outside)
main: pushl %ebp # Push base pointer
movl %esp, %ebp # Initialize base pointer
pushl $intro # Push the string address
call printf # Call the printf routine from C library
addl $8, %esp
pushl $clr # push color question on the stack
call printf # Print it
subl $4, %esp # Reserve stack space for variable
leal -4(%ebp), %eax # Load address of stack var in eax
pushl %eax # Push second argument of scanf
pushl $rets # Push first argument of scanf
call scanf # Call scanf
movl 4(%ebp), %ecx # mov the result in ecx
cmpl $1, %ecx
je red
cmpl $2, %ecx
je blue
jne white
red: #... still working on this
movl 0013h, %eax # enter 320x200x256 mode
int 10h # IS THIS CORRECT?
movl $0, %ebx # set X to 0
movl $0, %ecx # set Y to 0
call draw # Call line routine
movl 0003h, %eax # IS THIS CORRECT?
int 10h # return to text mode
movl $0, (%esp) # Make esp 0, indicating succesful termination
call exit # Exit the program
draw:
call putpixel
# pushl %ebp # Push the base pointer
# movl %esp, %ebp # Initialize base pointer
inc %ebx # increment X
inc %ecx # increment Y
cmpl $200, %ecx # check if Y => 200
jge end # if Y=> 200, jump to end
jmp draw # loop
putpxl: #has to put a pixel at (%ebx, %ecx) and return to draw
# should use the color from the main routine
end: movl %ebp, %esp # Remove local variables
popl %ebp # Remove base pointer
ret # return to main routine
2 回答
您可以做的最好的事情是使用更高级别的库,如SDL或Allegro . 这样,您的程序将在X11和非VGA帧缓冲区之上工作(例如:在基于ARM的嵌入式设备上显示) .
Svgalib允许为VGA和所谓的SVGA图形卡编程 . 它的发展在几年前停止了 .
有两种方法可以访问VGA硬件:
使用寄存器
使用VGA BIOS:这是您尝试过的 . VGA BIOS编写为以实模式运行 . 要从保护模式调用它们,您需要切换到vm86模式 . 这就是LRMI(Linux实模式接口,与DPMI相反)的作用 .
您不能在linux(受保护的操作系统)中执行直接视频(图形模式)输出 . 它只能在dos(实模式操作系统)中使用 .
您可以使用帧缓冲设备或SDL或libX11 . 但是没有理由与asm的高级库一起工作 .
直接在linux中不允许使用Int 10(在用户模式下;内核必须进行低级访问) .
例如这是5岁完全相同的讨论http://www.gamedev.net/topic/368196-linux-assembler-int-10h/