Stack in Memory and Registers

Register review

We know the following general-purpose CPU registers:

• %RAX (among its specific uses is to contain function return values)
• %RBX
• %RCX
• %RDX

We also have special purpose registers:

• %RIP (Instruction Pointer)
• %RSP (Stack Pointer)

AMD64 and Intel EM64T architectures introduced additional general-purpose registers—%R8, %R9, %R10, %R11, %R12, %R13, %R14, %R15.

These additional registers are used a lot in x$64$ code. More general-purpose registers allow faster code execution because temporary computation results can be stored there instead of in-memory locations. Here is a disassembly of the read function:

(gdb) disass read

The dump of the read function is given below: