Assembly, often abbreviated asm, is a low-level programming language for a computer, or other programmable device, in which there is a very strong (generally one-to-one) correspondence between the language and the architecture's machine code instructions.
x64 is a generic name for the 64-bit extensions to Intel's and AMD's 32-bit x86 instruction set architecture.
Registers rbp, rbx and r12 through r15 "belong" to the calling function and the called function is required to preserve their values. In other words, a called function must preserve these registers’ values for its caller. Remaining registers "belong" to the called function. If a calling function wants to preserve such a register value across a function call, it must save the value in its local stack frame.
[rsp]- top of stack will contain arguments count.[rsp + 8]- will contain argv[0][rsp + 16]- will contain argv[1]- and so on...
rdi- used to pass 1st argument to functionsrsi- used to pass 2nd argument to functionsrdx- used to pass 3rd argument to functionsrcx- used to pass 4th argument to functionsr8- used to pass 5th argument to functionsr9- used to pass 6th argument to functions- (the kernel destroys
rcxandr11after syscalls)
jmp <LABEL>- jump tocall <LABEL>- push next instruction address onto stack and jump toret- pop value from stack and jump to address (combines withcall)
NASM is an assembler, there are others. Its syntax is designed to be simple and easy to understand, similar to Intel's but less complex.
- https://software.intel.com/en-us/articles/introduction-to-x64-assembly
- https://www.cs.uaf.edu/2006/fall/cs301/support/x86_64/
- https://0xax.github.io/archive.html (series of posts on asm)
- https://cs.brown.edu/courses/cs033/docs/guides/x64_cheatsheet.pdf
- http://myweb.lmu.edu/dondi/share/sp/nasm64.pdf
- https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf