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Let's Learn x86-64 Assembly (2020)
! Part 0 - Setup and First Steps published on Apr 18 2020 The way I was taught x86 assembly at the university had been completely outdated for many years by the time I had my first class. It was around 2008 or 2009, and 64-bit processors had already started becoming a thing even in my neck of the woods.
RegisterLower byteLower wordLower dword raxalaxeaxrbxblbxebxrcxclcxecxrdxdldxedxrspsplspesprsisilsiesirdidildiedirbpbplbpebpr8r8br8wr8dr9r9br9wr9dr10r10br10wr10dr11r11br11wr11dr12r12br12wr12dr13r13br13wr13dr14r14br14wr14dr15r15br15wr15dAdditionally, the higher 8 bits of rax, rbx, rcx and rdx can be referred to as ah, bh, ch and dh. While it is true that on 64-bit Windows your programs see memory as a flat contiguous array of bytes with addresses starting at 0, it is actually an elaborate illusion maintained by the OS and CPU working together. Fire it up in WinDbg again, run until our hardcoded breakpoint, then single-step to see how we eventually call ExitProcess, making note of how the rsp and rcx registers change.
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