将 [symbol + constant] Intel 语法寻址模式转换为 AT&T 语法? [英] Converting [symbol + constant] Intel syntax addressing mode to AT&T syntax?

问题描述

我只是不知道如何在移动值时向目的地添加偏移量，特别是在我拥有的英特尔语法中:

I just cant figure out how to add an offset to my destination when moving a value, specifically in Intel syntax I have:

MOV   [gdtr + 2], EAX

对于 AT&T 语法，我尝试将其转换为:

and for AT&T syntax I have tried converting it to:

movl %eax, gdtr(2,1)

在表达式之后编译 junk '(2,1)' 时出错 但仅使用 gdtr(,1) 工作正常.

which gives an error when compiling junk '(2,1)' after expression but using just gdtr(,1) works fine.

我不明白为什么我不能使用基本偏移量，而只能使用比例因子.

I don't understand why I cant use base offset, and only the scale factor.

推荐答案

简单写

movl %eax, gdtr+2

基址偏移寻址仅在偏移为寄存器时才有效.使用寻址模式将两个常量相加是没有意义的；其工作方式(无论语法如何)是汇编器/链接器将 symbol+constant 解析为指令编码的位移字段的单个数字.

Base-offset addressing only works when the offset is a register. There's no point in having an addressing mode to add two constants together; the way this works (regardless of syntax) is that the assembler / linker resolve symbol+constant into a a single number for the displacement field of the instruction encoding.

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