assembly - 有关 VGA 和 putpixel intel x86 asm AT&T 语法的帮助

Question

我想在asm中画一条彩色线。我必须在 x86 intel linux 单元上使用 AT&T 语法。 我已经了解了很多，但我想知道如何进入 VGA 模式或 X 模式，以及如何在屏幕上放置像素。标准 C 库中是否有相应的函数(如 printf)？

非常感谢您的帮助。 :)

<p>.bss    # Declaring uninitialized variables</p>

<p>.data   # Declaring initialized variables</p>

<p>.text   # Actual assembly code and constants</p>

<pre><code>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)
</code></pre>

<p>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</p>

<pre><code>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
</code></pre>

<p>red:    #... still working on this</p>

<pre><code>    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
</code></pre>

<p>draw:<br/>
        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  </p>

<p>putpxl: #has to put a pixel at (%ebx, %ecx) and return to draw
        # should use the color from the main routine</p>

<p>end:    movl %ebp, %esp                 # Remove local variables
        popl %ebp                       # Remove base pointer
        ret                             # return to main routine
</p>

Answer 1

您能做的最好的事情就是使用更高级别的库，例如 SDL 或 Allegro。这样，您的程序将在 X11 和非 VGA 帧缓冲区上运行(例如:基于 ARM 的嵌入式设备上的显示)。

Svgalib 允许对 VGA 和所谓的 SVGA 显卡进行编程。它的开发几年前就停止了。

访问 VGA 硬件有两种方法:

• 使用寄存器
• 使用 VGA BIOS:这是您尝试过的。 VGA BIOS 被编写为在实模式下运行。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(interface)，与 DPMI 相反)所做的。