Didn't read the article (I find the topic rather bland), but debugging on x86-64 is quite simple: you have your debugging registers (DR0-DR4) which set trigger

Didn't read the article (I find the topic rather bland), but debugging on x86-64 is quite simple: you have your debugging registers (DR0-DR4) which set trigger addresses and conditions (execute, read, write) and then call a system interrupt when the condition is satisfied. This approach is limited to 3 breakpoints. Most moder debuggers do software breakpoints, that is when you set a break point for a particular line or instruction, the debuggrr replaces the first byte of the instruction with an int3 instruction (usually interrupt instructions are two byte wide, so technically int3 and "int 3" are different) but regardless the debugger slusually stores the actual instruction byte in a table to replace the int3 when it is actually hit. I suppose one could do this differently by causing a page fault (a simple bit switch from present to not present in the page table) and then monitoring the CR2 register to get the address of the executing code or the daya that is being accesed. One point I forgot to mention is that the x86 has hardware support for single-stepping instructions (a simple flag). But all of these methods require operating system support.