Mastering Assembly Programming

Microsoft x64 (64-bit)

Microsoft uses its own calling convention in the 64-bit mode (long mode) using a mixed register/stack paradigm for passing procedure parameters. This means that only the first four parameters may be passed via registers and the rest (if any) should be pushed onto the stack. The following table illustrates which registers are used and in what manner:

Parameter index (zero based)	Integer/pointer	Floating point
0	RCX	XMM0
1	RDX	XMM1
2	R8	XMM2
3	R9	XMM3

 

All of this looks quite clear, yet there are two things that we need to pay special attention to:

• The stack must be aligned on a 16-bytes boundary
• A 32-bytes shadow space on the stack is required--32 bytes between the last pushed ...