Question

我最近开始在NASM汇编中进行编码，我的问题是我不知道如何正确地访问struct元素。我已经在该网站和google上搜索了解决方案，但是到处都是人们说不同的话。我的程序崩溃了，我感到问题出在访问结构上。

查看示例代码时：

STRUC Test
    .normalValue RESD 1
    .address RESD 1
ENDSTRUC

TestStruct:    
    istruc Test
        at Test.normalValue dd ffff0000h
        at Test.address dd 01234567h
    iend

;Example:
mov eax, TestStruct ; moves pointer to first element to eax

mov eax, [TestStruct] ; moves content of the dereferenced pointer to eax (same as mov eax, ffff0000h)

mov eax, TestStruct
add eax, 4
mov ebx, eax ; moves pointer to the second element (4 because RESD 1)

mov eax, [TestStruct+4] ; moves content of the dereferenced pointer to eax (same as mov eax, 01234567h)

mov ebx, [eax] ; moves content at the address 01234567h to ebx

对吗？

感谢您的帮助

Answer 1

我不知道您是否知道，但是这是我们的代码，做了一些小的修改即可。除了最后一个try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) { Pipe pipe = new Pipe(image.getInputStream(), outputStream); convertCmd.setInputProvider( pipe ); convertCmd.setOutputConsumer( pipe ); return outputStream.toByteArray(); }以外，所有指令都是正确的，这是您试图访问地址mov ebx, [eax]导致内容0x1234567

的预期原因

SIGSEGV

使用section .bss struc Test normalValue RESD 1 address RESD 1 endstruc section .data TestStruct: istruc Test at normalValue, dd 0xffff0000 at address, dd 0x01234567 iend section .text global _start _start: mov eax, TestStruct ; moves pointer to first element to eax mov eax, [TestStruct] ; moves content of the dereferenced pointer to eax same as mov eax, ffff0000h mov eax, TestStruct add eax, 4 mov ebx, eax ; moves pointer to the second element 4 because RESD 1 mov eax, [TestStruct+4] ; moves content of the dereferenced pointer to eax same as mov eax, 01234567h mov ebx, [eax] ; moves content at the address 01234567h to ebx编译，链接和逐步运行

nasm-按值和地址访问结构元素

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