a “segmentation fault” means one of the assembly language instructions, for example the movb $0x6c, 0x1(%rax) line above, has tried to write to a portion of memory which it is not allowed to. to make things easier, i decided to translate some of my own code into assembly language so i could focus on the assembly language syntax. and because the llvm system can also produce an assembly language version of the code it produces, using crystal was the perfect way for me to see my ruby code translated so a microprocessor could understand it. i mean that x86 code reminds me of the hungarian language. it turns out x86 assembly is much simpler than hungarian; there are only a few simple suffixes that refer to the size of the data you are operating on. as you might guess, this is the line of code that adds 42 to something.
for a complete explanation, the definitive guide to all of this is the intel software developer’s manual. it turns out that x86 assembly language also decorates the register names to indicate their sizes, similar to what we saw above with the instruction name suffixes. to understand this, you have to remember that assembly language syntax wasn’t developed overnight. as you can see here, even today x86 assembly code can refer to the same register using many different names, for example al or ah for 8-bits, ax bit 16 bits, eax for 32 bits and rax for 64 bits. now that i understand the basics of x86 assembly language syntax, i’m ready to return to my add_forty_two code and to try to understand how it works. i’m not sure whether this pattern of using the %edi and %eax registers to hold the function arguments and return values is a x86 standard convention. in my next article i’ll take a look at how an x86 microprocessor uses the stack to save values, and how this maps to ruby using a slightly more complex example.
a basic understanding of any of the programming languages will help you in understanding the assembly programming understanding assembly language. (reverse engineering for beginners). why two titles? read here: on page xiii. you’ll begin to understand what a microprocessor can and can’t do by reading it’s language directly. and , what is assembly language, what is assembly language, assembly language example, assembly language tutorial for beginner, assembly language examples.
why learn assembly language? • write faster code (even in high-level language). • by understanding which high-level masm uses the standard intel syntax for writing x86 assembly code. the full x86 instruction set is large you’ll begin to understand what a microprocessor can and can’t do by reading its language directly., types of assembly language, assembly language pdf, assembly language programming 8086 examples, assembly language commands
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